RU2409003C1 - Selection of coding table with alternate length based on type of video unit for improvement of coefficients coding - Google Patents

Abstract

FIELD: information technologies.

SUBSTANCE: information is sent from coder device to coder device, which identifies the coding tables with alternate length to be used for decoding of two or more different types of video units. Information may be sent once per frame (or other coded unit) and may identify the first table to be used for intra-coded units, and the second table to be used for inter-coded units of appropriate frame; decoder selects table on the basis of this information and decodes various types of video units, using selected table for each type of unit.

EFFECT: improved efficiency of coding of transformation ratios, in particular in coding with alternate length of coefficients of SVC circuit expansion level detailing.

25 cl, 8 dwg

Description

[0001] This application claims the priority of the following provisional US patent applications, all of which are incorporated herein by reference:

provisional application for US patent No. 60 / 829,274, filed October 12, 2006,

U.S. Patent Application Serial No. 60 / 883,741, filed January 5, 2007, and

provisional application for US patent No. 60 / 829,276, filed October 12, 2006.

FIELD OF THE INVENTION

[0002] This disclosure relates to digital video coding and, more specifically, variable length coding (VLC) of transform coefficients in extension levels of a scalable video coding (SVC) scheme.

State of the art

[0003] Digital video capabilities can be incorporated into a wide range of devices, including digital TVs, digital direct broadcast systems, wireless communication devices, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, digital cameras, digital recorders, video game devices, game consoles, cellular or satellite radiotelephones, etc. Digital video devices implement video compression techniques such as MPEG-2, MPEG-4 or H.264 / MPEG-4, part 10, Advanced Video Encoding (AVC) to transmit and receive digital video more efficiently. Video compression techniques perform spatial and temporal prediction to reduce or remove redundancy inherent in video sequences.

[0004] In video encoding, video compression often includes spatial prediction, motion estimation, and motion compensation. Intra-coding relies on spatial prediction to reduce or remove spatial redundancy between video blocks within a given video frame. Intercoding relies on temporal prediction to reduce or remove temporal redundancy between video blocks of sequential video frames of a video sequence. For intercoding, a video encoder performs motion estimation to track the movement of matching video blocks between two or more adjacent frames. The motion estimation generates motion vectors that indicate the offset of the video blocks relative to the corresponding video prediction blocks in one or more reference frames. Motion compensation uses motion vectors to generate video prediction blocks from a reference frame. After motion compensation, a residual video block is formed by subtracting the video prediction block from the original video block to be encoded.

[0005] A video encoder typically employs variable length transform, quantization and coding (VLC) processes to further reduce the bit rate associated with transmitting the residual block. VLC residual blocks includes the use of variable-length codes to further compress residual coefficients generated by quantization and transform operations. For example, a VLC table can be used to match different sets of coefficients with a variable-length codeword in a way that promotes coding efficiency. Different VLC tables can be used for different video content. The video decoder performs the inverse VLC operations to recover the coefficients, and then performs the inverse transform of these coefficients. A video decoder may decode video information based on motion information and residual information associated with the video blocks.

[0006] Some video coding uses scalable techniques. For example, scalable video encoding (SVC) refers to video encoding that uses a base layer and one or more scalable extension layers. For SVC, the base layer usually carries video data with a base level of quality. One or more extension layers carry additional video data to support higher spatial, temporal, and / or SNR levels. The base layer may be transmitted in a manner that is more reliable than transmitting extension layers. Extension levels can add spatial resolution to base-level frames, or they can add additional frames to increase the overall frame rate. In one example, the most reliable portions of the modulated signal can be used to transmit the base layer, while the less reliable portions of the modulated signal can be used to transmit extension layers. Extension levels can define different types of coefficients, called essential coefficients and improvement (refinement) coefficients.

SUMMARY OF THE INVENTION

[0007] Generally, this disclosure describes extension level encoding methods in a scalable video encoding (SVC) scheme. These methods include selecting variable length coding tables (VLCs) in a decoder in a manner that facilitates simplification of calculations. These methods can be used in coding transform coefficients and are particularly useful in VLC expansion level detail coefficients in the SVC scheme. Coefficients of detail relate to the coefficients of the level of expansion, for which the corresponding coefficients of the previous level in the SVC scheme had nonzero values. Variable-length coding of detail coefficients can be performed separately from variable-length coding of significant coefficients, which relate to expansion level coefficients for which the corresponding coefficients of the previous level in the SVC scheme had values of zero.

[0008] According to the methods of this disclosure, information is transmitted from an encoder device to a decoder device that identifies which VLC tables should be used to decode two or more different types of video blocks. Information can be transmitted once per frame (or another coded unit, such as a slice or FGS level of a frame) and can identify the first table that should be used for intra-coded (intra-coded) blocks, and the second table that should be used for inter-coded blocks corresponding frame. The decoder selects the VLC table based on this information and decodes the video blocks using the selected VLC tables. In addition, in some cases, the encoder and decoder have an agreement regarding tables to be used for different types of blocks. In this case, the tables that are used are dependent on the type of block, but no additional information should be transmitted from the encoder to the decoder, since the encoder and decoder have an agreement.

[0009] In one example, this disclosure provides a method for encoding an extension level in an SVC scheme, the method comprising the steps of: encoding coefficients associated with video blocks of an extension level based on variable length encoding tables, generating information identifying a first variable length encoding table, which should be used by the decoding device to decode the first type of video blocks, and the second variable length coding table, which should be used by devices a decoding ohm to decode a second type of video blocks, transmitting information representing encoded coefficients to a decoding device and transmitting information identifying a first variable length encoding table to be used by a decoding device to decode the first type of video blocks, and a second variable length encoding table to be used by the decoding device to decode the second type of video blocks.

[0010] In another example, this disclosure provides a method for encoding an extension level for an SVC scheme, the method comprising the steps of: receiving information representing encoded coefficients associated with the video blocks of the extension level, receiving information identifying the first variable length encoding table to be used for decoding the first type of video blocks, and the second variable length coding table, which should be used to decode the second type of video blocks, select the tab persons for decoding information representing encoded coefficients based on information identifying the first and second variable length coding table to be used, and decoding information representing encoded coefficients based on selected tables.

[0011] In another example, this disclosure provides a device that encodes an extension level in an SVC scheme, the device comprising: an encoder that encodes coefficients associated with extension level video blocks based on variable length encoding tables and generates information identifying the first encoding table with a variable length, which must be used by the decoding device to decode the first type of video blocks, and a second coding table with a variable length, which must be used to decode to decode the second type of video blocks, and a transmitter that transmits information representing the encoded coefficients and transmits information identifying the first variable-length coding table to be used by the decoding device to decode the first type of video blocks, and a second coding table with variable length to be used by the decoding device to decode the second type of video block.

[0012] In another example, this disclosure provides a device that encodes an extension level of an SVC scheme, the device comprising: a receiver that receives information representing encoded coefficients associated with the video blocks of the extension level, and receives information identifying a first variable length encoding table, which should be used to decode the first type of video blocks, and the second variable-length coding table, which should be used to decode orogo type of video blocks and a decoder which selects a table to decode the information representing the encoded coefficients, based on the information identifying the first and second encoding table with variable length, to be used, and decodes the information representing the encoded coefficients, based on the selected tables.

[0013] In another example, this disclosure provides a device that encodes an extension level of an SVC scheme, the device comprising: means for encoding coefficients associated with video blocks of the extension level, based on variable length encoding tables in which the encoding means generates information identifying the first variable length coding table to be used by the decoding device to decode the first type of video blocks, and the second alternating coding table the length to be used by the decoding device to decode the second type of video blocks, and means for transmitting information representing the encoded coefficients to the decoding device, the means for transmitting transmitting information identifying the first variable length encoding table to be used by the decoding device to decode the first type of video blocks, and the second variable length coding table to be used by the deco device keying to decode the second type of video blocks.

[0014] In another example, this disclosure provides a device that encodes an extension level of an SVC scheme, the device comprising means for receiving encoded coefficients associated with video blocks of an extension level, the reception means also receiving information identifying a first variable length coding table that should be used to decode the first type of video blocks, and the second variable length coding table, which should be used to decode the second of the type of video blocks, means for selecting tables for decoding information representing the encoded coefficients based on information identifying the first and second variable length coding table to be used, and means for decoding information representing encoded coefficients based on the selected tables.

[0015] The methods described in this disclosure may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the software may be executed in one or more processors, such as a microprocessor, a specialized integrated circuit (ASIC), a user programmable gate array (FPGA), or a digital signal processor (DSP). Software that performs these methods may be initially stored in a computer-readable medium and downloaded and executed on a processor.

[0016] Accordingly, this disclosure also contemplates computer-readable media containing instructions that, after executing in the video encoding device, cause the device to encode the extension level of the SVC circuit, while the instructions cause the device to encode coefficients associated with the video blocks of the extension level based on coding tables with variable length, generate information identifying the first variable length coding table to be used by the decoder code to decode the first type of video block, and a second variable length coding table to be used by the decoding device to decode the second type of video block, transmit information representing encoded coefficients to the decoding device and transmit information identifying the first variable length coding table, which should be used by the decoding device to decode the first type of video block, and the second variable length coding table, which th decoding device to be used to decode a second type of video block.

[0017] In addition, this disclosure also contemplates computer-readable media containing instructions that, after executing in the video encoding device, cause the device to encode the extension level of the SVC circuit, in which, after receiving information representing encoded coefficients associated with the video blocks of the extension level, and receiving information identifying the first variable-length coding table to be used to decode the first type of video blocks, and the second table to variable length coding, which should be used to decode the second type of video blocks, commands cause this device to select tables for decoding information representing encoded coefficients based on information identifying the first and second variable length coding table to be used, and decode the information representing encoded coefficients based on selected tables.

[0018] In some cases, the computer-readable medium may be part of a computer program product that can be sold to manufacturers and / or used in a video encoding device. A computer program product may include computer-readable media, and in some cases may also include packaging materials.

[0019] This disclosure may also refer to a circuit, such as an integrated circuit, a set of specialized integrated circuits (ASIC), a user programmable gate array (FPGA), logic, or various combinations thereof, configured to perform one or more of the methods described herein. Accordingly, this disclosure also considers a circuit configured to encode an extension level of an SVC scheme, and this circuit is configured to encode coefficients associated with video blocks of an extension level, based on variable length encoding tables, to generate information identifying a first variable length encoding table, which should be used by the decoding device to decode the first type of video blocks, and the second variable length coding table, which Must be used by a decoding device to decode a second type of video blocks, transmit information representing encoded coefficients to a decoding device, and transmit information identifying a first variable-length encoding table to be used by a decoding device to decode a first type of video blocks, and a second encoding table with a variable length, which must be used by the decoding device to decode the second type of video blocks.

[0020] This disclosure also considers a circuit configured to encode an extension level of a scalable video encoding (SVC) scheme, wherein the circuit is configured to receive information representing encoded coefficients associated with the video blocks of the extension level, to receive information identifying the first variable encoding table the length that should be used to decode the first type of video blocks, and the second variable length coding table, which should be used When decoding the second type of video blocks, select tables for decoding information representing the encoded coefficients based on information identifying the first and second variable length coding tables to be used and decoding information representing encoded coefficients based on the selected tables.

[0021] In addition, this disclosure considers a circuit configured to encode an extension level of an SVC scheme, wherein the scheme is configured to receive information representing encoded coefficients associated with extension level video blocks, select various variable length encoding tables to be used for decoding information, based on block types associated with video blocks, in accordance with an agreement established by an encoder, decode information representing coded coefficients based on selected tables.

[0022] Details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.

Brief Description of the Drawings

[0023] FIG. 1 is an exemplary block diagram illustrating a video encoding and decoding system.

[0024] FIG. 2 is a conceptual diagram illustrating video frames of a base layer and an extension layer of a scalable video bitstream.

[0025] FIG. 3 is a block diagram illustrating an example of a video encoder compatible with the present invention.

[0026] FIG. 4 is a block diagram illustrating an example of a video decoder compatible with the present invention.

[0027] FIG. 5 is an exemplary block diagram of a variable length coding (VLC) coding unit.

[0028] FIG. 6 is an exemplary block diagram of a VLC decoding module.

[0029] FIG. 7 is a flowchart illustrating a VLC technique for variable-length coding compatible with the present invention.

[0030] FIG. 8 is a flowchart illustrating a VLC technique for variable length decoding compatible with the present invention.

Detailed description

[0031] This disclosure describes techniques for coding an extension layer in a scalable video coding (SVC) scheme. These techniques involve the selection of variable length coding tables (VLCs) in a decoder in a manner that improves simplicity of computation. These techniques can be used in coding transform coefficients and are especially useful in variable length coding of detail coefficients of the level of expansion of an SVC circuit. Coefficients of detail relate to the coefficients of the level of expansion, for which the corresponding coefficients of the previous level in the SVC scheme have nonzero values. Variable length coding of detail coefficients can be performed separately from coding with variable length of significant coefficients (for example, for which the corresponding coefficients of the previous level in the SVC scheme have zero values).

[0032] According to the techniques of this disclosure, information identifying which VLC tables should be used to decode two or more different types of video blocks is transmitted from the encoder device to the decoder device. This information can be transmitted once per frame (or other coded unit) and can identify the first table that should be used for intra-coded blocks, and the second table that should be used for intercoded blocks of the corresponding frame. The decoder performs table selection based on this information and decodes the video blocks using the selected tables.

[0033] In the encoder device, the selection of a VLC table for encoding various video blocks can be made based on information collected for previously or currently encoded frames. For example, statistical analysis of previously encoded frames may be performed to facilitate table selection in the encoder device. This computationally intensive analysis, however, can be avoided in the decoder device. Instead, information identifying the tables to be selected for the first and second types of video blocks, for example, an intra-coded block and inter-coded blocks, can be transmitted from the encoder device to the decoder device. A decoder device may use this transmitted information to facilitate proper table selections. Alternatively, in some cases, the encoder and decoder may have an agreement regarding tables to be used for various types of blocks. In this case, the tables that are used are dependent on the type of block, but no additional information should be transmitted from the encoder to the decoder, since the encoder and decoder have an agreement.

[0034] The selected tables in the encoder can be very dependent on the quantization level used in the encoding process. The level of quantization used, in turn, may depend on the type of video block. Since the quantization level used in the encoder is usually unknown at the decoder, information regarding the type of video block provides a useful mechanism for selecting a table in the decoder. In particular, since the quantization level may depend on the type of video block, selecting a VLC table in the decoder based on the type of video block may be useful. VLC tables are identified for the decoder for various types of video block, and the decoder can determine the type associated with the corresponding video block and use the corresponding VLC table to decode this corresponding video block.

[0035] FIG. 1 shows a block diagram illustrating a video encoding and decoding system 10. As shown in FIG. 1, system 10 includes a source device 12 that transmits encoded video to a reception device 16 over a communication channel 15. The source device 12 may include a video source 20, a video encoder 22, and a modulator / transmitter 24. A receiving device 16 may include a receiver / demodulator 26, a video decoder 28, and a display device 30. System 10 may be configured to apply techniques for variable length coding (VLC) of video information associated with an extension level in a scalable video coding (SVC) scheme.

[0036] SVC refers to video encoding that uses a base layer and one or more scalable extension layers. For SVC, the base layer usually carries video data with a base level of quality. One or more extension layers carry additional video data to support higher spatial, temporal and / or signal-to-noise SNR levels. Extension levels can be determined relative to a previously encoded level. Levels of expansion define at least two different types of coefficients called essential coefficients and coefficients of detail (improvement). Coefficients of detail can determine the values relative to the corresponding values of the previously encoded level. Extension level frames sometimes include only part of the total number of video blocks in the base level or previous extension level, for example, only those blocks for which expansion is performed.

[0037] Material coefficients relate to coefficients for which the corresponding coefficients in the previous level had zero values. Detail factors refer to factors for which the corresponding factors in the previous level had nonzero values in the previous level. Variable-length coding of extension levels usually uses a two-pass approach. A first pass is performed to encode the lengths of a series of significant coefficients, and another pass is performed to encode the detail coefficients. The techniques of this disclosure are particularly useful for variable length coding of detail coefficients, although the present disclosure is not necessarily limited in this regard.

[0038] According to the techniques of this disclosure, information is transmitted from the source device 12 to the receiving device 16, which identifies which VLC tables should be used to decode two or more different types of video blocks. The information may be transmitted once per frame (or other coded unit), and may identify the first table to be used for intra-coded blocks, and the second table to be used for intercoded blocks of the corresponding frame. This information may contain one or more bits that identify the first VLC table for intra-encoded blocks, and one or more bits that identify the second VLC table for intra-encoded blocks. Video decoder 28 of the receiving device 16 performs table selection based on this information and decodes the video blocks using the selected tables. Again, however, in some cases, encoder 22 and decoder 28 may have agreement on tables to be used for various types of blocks. In this case, the tables that are used are dependent on the type of block, but no additional information should be transmitted from the source device 12 to the receiving device 16, since the encoder 22 and decoder 28 have an agreement.

[0039] In the example of FIG. 1, the communication channel 15 may comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines, or any combination of wireless or wired media. Communication channel 15 may be part of a packet-based network, such as a local area network, wide area network, or wide area network, such as the Internet. Communication channel 15 is typically any suitable communication medium or “collection” of various communication media for transmitting video data from source device 12 to reception device 16. Communication channel 15 may include various base stations or other components to facilitate transmission from source device 12 to reception device 16.

[0040] The source device 12 and the receiving device 16 may comprise any of a wide variety of wireless communication devices, such as wireless digital televisions, handsets of wireless communication devices, personal digital assistants (PDAs), wireless laptop or desktop computers, wireless digital cameras, wireless digital recorders, wireless video game devices, wireless computer game consoles, cellular or satellite radiotelephones, and the like.

[0041] The source device 12 generates encoded video data for transmission to the receiving device 16. In some cases, however, devices 12, 16 may operate in a substantially symmetrical manner. For example, each of the devices 12, 16 may include video encoding and decoding components. Therefore, system 10 can support one-way or two-way video transmission between video devices 12, 16, for example, for streaming video, broadcasting video, or video telephony.

[0042] The video source 20 from the source device 12 may include a video capture device, such as a video camera, a video archive containing previously captured video or video transmission from a video content provider. As another alternative, video source 20 may generate computer-based data as a source video or a combination of real-time video and computer-generated video. In some cases, if the video source 20 is a video camera, the source device 12 and the receiving device 16 may form so-called camera telephones or video telephones. In each case, captured, pre-captured or computer-generated video can be encoded by video encoder 22 for transmission from the video source device 12 to video decoder 28 of video receiving device 16 through modulator / transmitter 22, communication channel 15 and receiver / demodulator 26. Video encoding and decoding processes can implement the coding methods of the lengths of the series described here to improve these processes. The display device 30 displays the decoded video data to the user and may comprise any of a variety of display devices, such as a cathode ray tube, liquid crystal display (LCD), plasma display, organic light emitting diode (OLED) display, or other type of display device.

[0043] Video encoder 22 and video decoder 28 may be configured to support SVC for spatial, temporal, and / or signal to noise ratio (SNR) scalability. In some aspects, video encoder 22 and video decoder 28 may be configured to support fine granularity SNR scalability (FGS) encoding for SVC. Encoder 22 and decoder 28 can support varying degrees of scalability by supporting encoding, transmitting, and decoding of the base layer and one or more scalable extension layers. Again, for scalable video encoding, the base layer carries video data with a basic level of quality. One or more extension layers carry additional data to support higher spatial, temporal, and / or SNR levels. The base layer may be transmitted in a manner that is more reliable than transmitting extension layers. For example, the most reliable parts of the modulated signal can be used to transmit the base level, while the less reliable parts of the modulated signal can be used to transmit the extension levels.

[0044] In order to support SVC, video encoder 22 may include a base layer encoder 32 and one or more extension layer encoders 34 to perform encoding of the base layer and one or more extension layers, respectively. The techniques of this disclosure, which use VLC table selection, are applicable to coding video blocks of extension layers in SVC.

[0045] Video decoder 28 may include a combined base level / extension level decoder that decodes blocks of video and base level and extension level. Video decoder 28 can decode the video blocks associated with both the base and extension layers, and combine the decoded video to restore frames of the video sequence. The display device 30 receives the decoded video sequence and presents the video sequence to the user.

[0046] Video encoder 22 and video decoder 28 may operate according to a video compression standard such as MPEG-2, MPEG-4, ITU-T or ITU-T H.264 / MPEG-4 MPEG-2, Part 10, Advanced Video Encoding ( AVC). Although not shown in FIG. 1, in some aspects, video encoder 22 and video decoder 28 may each be integrated with an audio encoder and decoder and may include respective MUX-DEMUX modules or other hardware and software for encoding and audio processing and video in a shared data stream or individual data streams. If applicable, the MUX-DEMUX modules may conform to the H.223 ITU multiplexer protocol or other protocols such as user datagram protocol (UDP).

[0047] The H.264 / MPEG-4 (AVC) standard was formulated by the ITU-T Video Coding Experts Group (VCEG) together with the ISO / IEC Moving Images Experts Group (MPEG) as a collaborative partnership product known as the Combined Video Group (JVT). In some aspects, the techniques described in this disclosure may be applied to devices that typically comply with the H.264 standard. The H.264 standard is described in ITU-T Recommendation H.264, Advanced Video Coding for Universal Audiovisual Services, through the ITU-T Study Group dated March 2005, which may be referred to here as the H.264 standard or the H.264 specification or standard or H.264 / AVC specification.

[0048] The Combined Video Group (JVT) continues to work to expand the SVC on the H.264 / MPEG-4 AVC. The specification for the evolving SVC extension is in the form of a Joint Project (JD). The Joint Scalable Video Model (JSVM) created by JVT implements tools for use in scalable video, which can be used in system 10 for various coding tasks described in this disclosure. Detailed information on fine granularity SNR scalability coding (FGS) can be found in the Joint Project documents and, in particular, in Joint Project 6 (SVC JD6), Thomas Wiegand, Gary Sullivan, Julien Reichel, Heiko Schwarz, and Mathias Wien, "Joint Draft 6: Scalable Video Coding," JVT-S 201, April 2006, Geneva, and Joint Draft 9 (SVC JD9), Thomas Wiegand, Gary Sullivan, Julien Reichel, Heiko Schwarz, and Mathias Wien, "Joint Draft 9 of SVC Amendment, "JVT-V 201, January 2007, Marrakech, Morocco.

[0049] In some aspects for video broadcasting, the techniques described in this disclosure can be applied to Enhanced H.264 video encoding in order to provide real-time video services in terrestrial mobile multimedia broadcasting (TM3) systems using the Air Interface Specification Only Direct Link (FLO), "Forward Link Only Air Interface Specification for Terrestrial Mobile Multimedia Multicast," published as Technical Standard TIA-1099 ("FLO Specification"). That is, the communication channel 15 may comprise a wireless information channel used to wirelessly broadcast video information according to the FLO Specification, or the like. The FLO specification includes examples defining the syntax and semantics of the bitstream and decoding processes suitable for the FLO air interface. Alternatively, the video can be transmitted according to other standards, such as DVB-H (broadcast digital video to portable devices), ISDB-T (terrestrial digital broadcast integrated services) or DMB (broadcast digital audio-visual information). Therefore, the source device 12 may be a mobile wireless terminal, a video streaming server, or a video broadcast server. However, the techniques described in this disclosure are not limited to a particular type of broadcasting, multicasting, or point-to-point system. In the case of broadcasting, source device 12 may broadcast several video information channels to a plurality of reception devices, each of which may be similar to reception device 16 in FIG.

[0050] Video encoder 22 and video decoder 28, each, may be implemented as one or more microprocessors, digital signal processors (DSP), custom integrated circuits (ASIC), field programmable gate arrays (FPGAs), discrete logic, software, hardware , firmware or any combination thereof. Each of video encoder 22 and video decoder 28 may be included in one or more encoders or decoders, any of which may be integrated as part of a combined encoder / decoder (codec) in a corresponding mobile device, subscriber device, broadcast device, server, or the like. In addition, the source device 12 and the receiving device 16, each, may include appropriate modulation, demodulation, frequency conversion, filtering, and amplifiers components for transmitting and receiving encoded video, as appropriate, including radio frequency (RF) wireless components and antennas, sufficient to maintain wireless connectivity. For ease of illustration, however, such components are combined as being the modulator / transmitter 24 of the source device 12 and the receiver / demodulator 26 of the receiving device 16 in FIG. 1.

[0051] The video sequence includes a sequence of video frames. Video encoder 22 performs operations on blocks of pixels (or blocks of converted coefficients) in individual video frames to encode video data. Video blocks may have fixed or variable sizes and may vary in size according to a given coding standard. In some cases, each video frame is a coded unit, while in other cases each video frame can be split, and includes a sequence of “slices” that form coded units. Each slice may include a sequence of macroblocks that can be organized into subunits. As an example, the H.264 ITU-T standard supports intra prediction at various block sizes, for example 16 by 16, 8 by 8 or 4 by 4 for luminance components and 8x8 for chrominance components, as well as inter prediction in various block sizes, for example 16 16, 16 by 8, 8 by 16, 8 by 8, 8 by 4, 4 by 8 and 4 by 4 for luminance components and corresponding scaled sizes for chroma components. According to this disclosure, VLC table selection information for intra-encoded blocks and intercoded blocks can be transmitted from source device 12 to reception device 16 once to an encoded module, for example, once per frame, once per slice, or once per FGS level of a frame. This information can then be used to select a VLC table for encoding the transform coefficients of the video blocks associated with this corresponding coded module.

[0052] The form and contents of information transmitted to identify various VLC tables may vary. For example, information can be formulated as two different single-bit or multi-bit codes that identify which VLC table should be used to decode the first type of video block and which VLC table should be used to decode the second type of video block. For each frame to be decoded, one single-bit or multi-bit code can be sent for interblocks and another single-bit or multi-bit code can be sent for interblocks. Decoder 28 selects various VLC tables to decode intra- and intercoded blocks based on the tables identified in these codes.

[0053] Smaller video blocks can provide better resolution and can be used for video frame locations that include higher levels of detail. Typically, macroblocks (MBs) and various subblocks can be considered as video blocks. In addition, the slice can be considered as a sequence of video blocks, such as MB and / or sub-blocks. As noted, each slice may be an independently decoded video frame unit. After the prediction, the conversion can be performed on the 8 × 8 residual block or the 4 × 4 residual block, and an additional conversion can be applied to the 4 × 4 block DC coefficients for the color signal or luminance component components if the intra_16 × 16 prediction mode is used.

[0054] After intra- or inter-based predictive coding, additional coding methods may be applied to the transmitted bitstream. These additional encoding methods may include transform methods (such as 4 × 4 or 8 × 8 integer transform used in H.264 / AVC, or discrete cosine DCT transform) and variable length encoding. Blocks of conversion coefficients may be referred to as video blocks. In other words, the term “video block” refers to a block of video data regardless of the area of information. Thus, the video blocks may be in a pixel region or a region of transformed coefficients. The use of VLC coding is described generally in this disclosure with respect to transform coefficient blocks.

[0055] This disclosure provides methods for variable length coding of detail coefficients. Again, detail coefficients refer to coefficients that have non-zero values in the previous level, while significant coefficients refer to coefficients that have zero values in the previous level. According to this disclosure, information can be transmitted from source device 12 to reception device 16 to select a VLC table in a decoder for two or more different types of video blocks. One of many different VLC tables may be selected for each type of video block based on information sent from source device 12 to reception device 16. The receiving device then selects between the two identified VLC tables based on the type of decoded video block.

[0056] Each VLC table may include a number of code symbols having different lengths. The code symbols can be assigned corresponding characteristics within the video block, for example, a specific length of a series of zeros of detail coefficients. In some cases, tables are static, but in other cases, these tables can be generated or updated based on coding statistics so that variable-length codewords are converted into sets of coefficients in a way that improves coding efficiency. Of course, if tables are updated at the encoder, table updates must also be updated at the decoder.

[0057] Encoder 22 and decoder 28 may perform mutually inverse methods that encode the extension level in the SVC scheme. At encoder 22, a table selection for encoding various video blocks can be made based on information collected for currently or previously encoded frames. If the selection is based on previously encoded frames, single-pass encoding may be used, but if the encoding is based on currently encoded frames, this may require two-pass encoding. In some cases, statistical analysis of previously encoded frames may be performed to facilitate the selection of a table in encoder 22. This computationally intensive analysis, however, can be avoided in decoder 28. Instead, information identifying the tables for the first and second types of video blocks, for example, an intra-coded block and inter-coded blocks may be transmitted from the source device 12 to the receiving device 16. Decoder 28 can then use this transmitted information to facilitate proper table selections.

[0058] The selected tables in the encoder (for example, which can be selected based on statistics) can greatly depend on the quantization level used in the encoding process. The level of quantization used, in turn, may depend on the type of video block. Since the quantization level used in encoder 22 is generally unknown to decoder 28, information regarding the type of video block provides a useful alternative for use in decoder 28. Therefore, tables are identified for decoder 28 for various types of video block, and decoder 28 can determine the type associated with the corresponding video block, and use the corresponding VLC table to decode this corresponding video block. As used herein, the term “coding” generally refers to at least a portion of the encoding or decoding processes. Video encoder 22 encodes the data, while video decoder 28 decodes the data.

[0059] The VLC tables themselves can assign codewords to various sets of transform coefficients. Sets of coefficients with null values may be represented by series lengths of zeros, and shorter VLC codes may be assigned to more general series lengths. Shorter series lengths can be assigned longer VLC codes. Therefore, selecting codes from VLC tables can improve coding efficiency. The assignment of codes in VLC tables can also be based on statistics during the table generation process, although static VLC tables can also be used.

[0001] FIG. 2 is a diagram illustrating video frames in a base layer 17 and an extension level 18 of a scalable video bitstream. As noted above, the methods of the present disclosure are applicable to encoding these extension levels. Base layer 17 may comprise a bitstream containing encoded video data that represents a first level of spatial, temporal, or SNR scalability. Extension level 18 may comprise a bitstream containing encoded video data that represents a second level of spatial, temporal and / or SNR scalability. Although one extension level is shown, in some cases several extension levels may be used. The bitstream of the extension layer can only be decoded together with the base layer (or the previous extension layer if there are many extension layers). Extension layer 18 contains links to decoded video data in the base layer 17. Such links can be used either in the transform domain or in the pixel region to generate final decoded video data.

[0002] The base level 17 and extension level 18 may comprise intra (I), inter (P) and bi-directional (B) frames. Intra-frames may include all of the intra-encoded video blocks. I and P frames may include at least some intercoded video blocks, but may also include some intra-coded blocks. The different frames of extension level 18 do not have to include all the video blocks in base level 17. The frames P in extension level 18 rely on links to frames P in base level 17. By decoding frames in extension level 18 and base level 17, the video decoder is able to improve quality video decoded video. For example, the base layer 17 may include video encoded at a minimum frame rate, for example 15 frames per second, while the extension level 18 may include video encoded with a higher frame rate, for example 30 frames per second. In order to support coding with different quality levels, the base layer 17 and the extension layer 18 can be encoded with a higher quantization parameter (QP) and lower QP, respectively. In addition, the base layer 17 may be transmitted in a manner that is more reliable than the transmission of the extension layer 18. As an example, the most reliable parts of the modulated signal can be used to transmit the base level 17, while the less reliable parts of the modulated signal can be used to transmit the extension level 18. The illustration in FIG. 2 is merely exemplary, since the base and extension levels can be defined in many different ways.

[0060] FIG. 3 is a block diagram illustrating an example of a video encoder 50 that includes a VLC module 46 for encoding data in a compatible manner with the present invention. The video encoder 50 of FIG. 3 may correspond to an extension level encoder 34 of the source device 12 of FIG. 1. That is, the base layer encoding components are not illustrated in FIG. 3 for simplicity. Therefore, video encoder 50 can be considered as an extension level encoder. Alternatively, the illustrated components of video encoder 50 may also be implemented in combination with base layer coding modules or units, for example, in a pyramidal encoder design that supports scalable video coding of a base level and extension level.

[0061] Video encoder 50 may perform intra and inter-coding of blocks in video frames. Intra-coding relies on spatial prediction to reduce or remove spatial redundancy in a video within a given video frame. Intercoding relies on temporal prediction to reduce or remove temporal redundancy in a video within adjacent frames of a video sequence. For inter-coding, video encoder 50 performs a motion estimation to track the movement of respective video blocks between two or more adjacent frames.

[0062] As shown in FIG. 3, the video encoder 50 receives the current video block 31 (for example, an extension level video block) within the video frame to be encoded. In the example of FIG. 3, video encoder 50 includes a motion estimation module 33, a reference frame memory 35, a motion compensation module 37, a block transform module 39, a quantization module 41, a quantization module 42, a quantization module 44, and a VLC module 46. A deblocking filter (not shown) can also be included to filter block boundaries to remove blocking artifacts. Video encoder 50 also includes an adder 48 and an adder 51. FIG. 3 illustrates temporal prediction components of a video encoder 50 for inter-coding video blocks. Although not shown in FIG. 3, for ease of illustration, video encoder 50 may also include spatial prediction components for intra-coding some video blocks. Spatial prediction components, however, are typically used only for base layer coding.

[0063] Motion estimation module 33 compares video block 31 with blocks in one or more adjacent (adjacent) video frames to generate one or more motion vectors. An adjacent frame or frames may be retrieved from the reference frame memory 35, which may be any type of memory or memory device, to store video blocks reconstructed from previously encoded blocks. Motion estimation can be performed for blocks of variable sizes, for example 16 × 16, 16 × 8, 8 × 16, 8 × 8 or smaller blocks. Motion estimation module 33 identifies a block in an adjacent frame that most closely matches the current video block 31, for example, based on a transmission rate distortion model, and determines the offset between the blocks. On this basis, motion estimation module 33 generates a motion vector (MV) (or a plurality of MVs in the case of bidirectional prediction), which indicates the magnitude and trajectory of the offset between the current video block 31 and the prediction block used to encode the current video block 31.

[0064] Motion vectors can have an accuracy of half or a quarter pixel or even higher accuracy, allowing video encoder 50 to track the movement with higher accuracy than locations with integer pixels and obtain a block with a better prediction. When motion vectors with fractional pixel values are used, interpolation operations are performed in the motion compensation unit 37. Motion estimation module 33 can identify the best motion vector for a video block using a transmission rate distortion model. Using the resulting motion vector, the motion compensation module 37 generates a video prediction block by motion compensation.

[0065] Video encoder 50 generates a residual video block by subtracting the video prediction block generated by the motion compensation unit 37 from the original, current video block 31 in the adder 48. The block transform module 39 applies a transform, such as a discrete cosine transform (DCT), to the residual block, forming the coefficients of the residual transformation blocks. The quantization module 41 quantizes the coefficients of the residual transform blocks to further reduce the bit rate. Adder 49A receives base layer coefficient information, for example, from a base layer encoder (not shown) and is located between block transform unit 39 and quantization unit 41 to provide this base layer coefficient information for encoding the extension layer. In particular, the adder 49A subtracts information about the coefficients of the base level from the output signal of the module 39 conversion blocks. Similarly, adder 49B, which is located between the inverse transform unit 44 and the inverse quantization unit 42, also receives base layer coefficient information from a base layer encoder (not shown). The adder 49B summarizes the information about the coefficients of the base level with the output signal of the module 42 inverse quantization.

[0066] VLC module 46 encodes the quantized transform coefficients according to a variable length coding methodology to further reduce the bit rate of the transmitted information. In particular, VLC module 46 employs the techniques of this disclosure to encode detail level coefficients of an extension. VLC module 46 may also generate additional information to identify which tables the decoder should use for various types of video blocks. This additional information may be included in the encoded bitstream so that the decoder can determine the appropriate tables for the various types of video blocks and then select such tables based on the type of video block being decoded.

[0067] Table selection by VLC module 46 for encoding various video blocks can be made based on information collected for previously or currently encoded frames. For example, statistical analysis of previously encoded frames may be performed to facilitate table selection by VLC module 46. This computationally intensive analysis, however, can be avoided in the decoder. Instead, information identifying tables for the first and second types of video blocks, for example, an intra-coded block and inter-coded blocks, can be encoded into a bitstream. A decoder device may use this transmitted information to facilitate the selection of proper tables. Alternatively, in some cases, the encoding device and the decoding device may have an agreement - which tables to use for different types of video blocks.

[0068] After variable length encoding, the encoded video can be transferred to another device. In addition, the inverse quantization unit 42 and the inverse transform unit 44 apply inverse quantization and inverse transform, respectively, to restore the residual block. An adder 51 summarizes this reconstructed residual block with a motion compensated prediction block generated by the motion compensation unit 37 to form a reconstructed video block for storing 35 reference frames in memory. The reconstructed video block is used by the motion estimation module 33 and the motion compensation module 37 to encode the block in a subsequent video frame.

[0069] FIG. 4 is a block diagram illustrating an example of a video decoder 60, which may correspond to the video decoder 28 in FIG. 1, which performs decoding of a base layer and an extension layer. Video decoder 60 includes a VLC module 52A for extension level information that performs the corresponding function of the VLC module 46 in FIG. 3. That is, like the VLC module 46, the VLC module 52A encodes the detail level coefficients of the extension. As noted, in the encoder, the selection of a VLC table for encoding various video blocks can be made based on information collected for previously or currently encoded frames, for example, using statistical analysis of previously encoded or currently encoded frames to facilitate table selection in the encoder. This computationally intensive analysis, however, can be avoided in decoder 40. Instead, information identifying tables for the first and second types of video blocks, for example, an intra-encoded block and intercoded blocks, can be transmitted from the encoder to decoder 60. Decoder 60 can use this transmitted information to facilitate proper table selections.

[0070] Video decoder 60 may also include another VLC module 52B for base layer information. The intra prediction unit 55 may optionally perform any spatial decoding of the base layer video blocks, and the output of the intra prediction unit 55 may be directed to the adder 53. The extension layer path may include a quantization unit 58A, and the base layer path may include a quantization unit 56B . Information in the paths of the base level and extension level can be combined by an adder 57.

[0071] Video decoder 60 may perform intra- and interdecoding of blocks in video frames. In the example of FIG. 4, video decoder 60 includes VLC modules 52A and 52B (mentioned above), motion compensation module 54, inverse quantization units 56A and 56B, inverse transform unit 58, and reference frame memory 62. Video decoder 60 also includes an adder 64. Optionally, video decoder 60 may also include a deblocking filter (not shown) that filters the output of adder 64. Again adder 57 combines the information in the base layer and extension layer paths and intra prediction unit 55 and adder 53 facilitates any spatial decoding of basic level video blocks.

[0072] In accordance with the present invention, the VLC module 52A receives the extension level information of the encoded video bitstream and applies the VLC methods described in this disclosure. In particular, for video detail coefficients, a bitstream can be encoded to identify the corresponding VLC tables for two or more different types of video blocks. VLC module 52A determines the type of video block for each encoded video block and selects the corresponding VLC decoding table for the corresponding video block based on information transmitted in the bitstream that identifies such a VLC decoding table for this type of video block. The decoding process may generate quantized residual coefficients, macroblocks, and a coding mode of subunits and motion information, which may include motion and blocking vectors.

[0073] After decoding performed by the VLC module 52A, the motion compensation module 54 receives the motion vectors and one or more reconstructed reference frames from the reference frame memory 62. The inverse quantization unit 56A performs inverse quantization, that is, it quantizes the quantized block coefficients. After combining the extension level information and the base information by the adder 57, the inverse transform unit 58 applies an inverse transform, such as an inverse DCT, to these coefficients to form residual blocks. Motion compensation module 54 generates motion-compensated blocks that are summed by adder 64 with residual blocks to form decoded blocks. If desired, a deblocking filter can also be applied to filter decoded blocks to remove blocking artifacts. The filtered blocks are then placed in a reference frame memory 62, which outputs the reference blocks from motion compensation and also generates decoded video to drive a display device (such as device 30 in FIG. 1).

[0074] FIG. 5 is a block diagram illustrating an example VLC module 46, which may correspond to that shown in FIG. 3. VLC module 46 includes a coding module 72, a table selection module 74, and a VLC of a table 78. VLC of a table 78 generally refers to tables that can be stored at any location, for example locally or off-chip, in a separate memory location. VLC tables 78 may be updated periodically, as desired.

[0075] The coding unit 72 encodes detail coefficients and significant coefficients in separate coding passes. Table selection by VLC module 46 for encoding coefficients associated with various video blocks can be made based on information collected for previously encoded or currently encoded frames. For example, statistical analysis of previously encoded frames may be performed to facilitate table selection by VLC module 46. For detail coefficients (and possibly other coefficients), the VLC module 46 generates information (which is then included in the encoded bitstream) that identifies the various VLC tables to use in the decoder for various types of video blocks. A decoder device may use this information to facilitate proper table selections. The information that identifies the various VLC tables to use in the decoder for various types of video blocks can take various forms, but in one case contains two bits of information. The first bit identifies a table of two possible tables for intra-coded blocks, and the second bit identifies a table of two possible tables for inter-coded blocks. Of course, more information may be needed if there are more than two tables to select from for each block type.

[0076] The detail coefficients can have values limited to -1, 0, and 1, which can be encoded with two bits of information. The first bit (coeff_ref_flag) may indicate whether the coefficient is 0 (coeff_ref_flag = 0) or not (coeff_ref_flag = 1), and the second bit may indicate whether the sign (denoted by s _n ) of the detail coefficient is the same (coeff_ref_dir_fiag = 0) or different (coeff_ref_dir_flag = 1) from the sign (denoted as s _n-1 ) of the corresponding coefficient of the previous level. The previous level is denoted as s _n-1 . If the sign of the current coefficient is the same as the sign from the previous level, then coeff_ref_dir_fiag = 0, and if the sign of the current coefficient is different from that of the previous level, then coeff_ref_dir_flag = 1. Two drill bits can be combined into an alphabet of three drill symbols as follows in Table 1:

TABLE 1 coeff_ref_flag coeff_ref_dir_fiag ref_symbol 0 - 0 one 0 one one one 2

Alternatively, another scheme may also be used to code the detail coefficients without departing from the techniques of this disclosure.

[0077] VLC tables 78 may contain variable-length codewords that are converted to different sets of coefficients that can be defined by characters, flags, or other types of bits. VLC tables 78 may be updated as desired. Any number of tables can be included in VLC 88 tables. In some cases, two tables are used, although more can be included. In any case, coding module 72 may access various VLC tables for various types of video blocks and may transmit information regarding these tables for various types of video blocks as part of the encoded bitstream. Thus, the decoder device does not have to perform computationally intensive statistical analysis to determine which tables to use, and instead can simply identify the tables from the information in the encoded bitstream. Tables used in coding various types of video blocks can be defined once per frame, once per slice, once per FGS level of a frame or once per other type of encoded unit.

[0078] FIG. 6 is a block diagram illustrating an example VLC module 52A, which may correspond to the VLC module 52A shown in FIG. 4. The VLC module 52A performs inverse decoding functions with respect to the coding that is performed by the VLC module 46. Thus, while the VLC module 46 receives the quantized residual coefficients and generates a bitstream, the VLC module 52A receives the bitstream and generates the quantized residual coefficients. However, unlike VLC module 46, the VLC decoding module does not have to perform computationally intensive statistical analysis to determine which tables to use, and instead can simply identify the tables from the information in the encoded bitstream and select a table for a given video block based on the block type this video block.

[0079] VLC module 52A includes decoding module 82, table selection module 86, and one or more VLC tables 88. As in module 46, VLC tables 88 of module 52 typically refer to tables that can be stored at any location, such as locally or off-chip at the location of a separate memory. VLC tables 88 may be updated periodically, as desired. Any number of tables can be included in VLC tables 88. In some cases, two tables are used, although more can be included.

[0080] VLC decoding module 82 may perform separate decoding passes for significant coefficients and detail coefficients. The methods of this disclosure may be applicable to coding or granularity coefficients only, or may be used for both granularity coefficients and significant coefficients.

[0081] The encoded bit stream received by the decoding unit 82 includes information representing encoded coefficients, for example codewords, and information that identifies tables to be used in decoding various types of video blocks. Table selection module 86 determines which tables should be used for different types of video blocks for each coded module, for example, for each frame. Decoding module 82 then decodes the received information based on the corresponding VLC tables 88, as determined by table selection module 86, to generate quantized residual coefficients that have been encoded in the bitstream.

[0082] FIG. 7 is a flowchart illustrating a coding technique for variable-length coding of coefficients (eg, typically coefficients of detail) of an extension level compatible with the present invention. As shown in FIG. 7, the table selection module 76 selects suitable tables to be used for coding (91). Selected tables can improve coding efficiency and can be selected based on a statistical analysis of previously encoded or currently encoded video frames. In particular, table selection module 76 may select various VLC tables to be used in coding video blocks based on the quantization levels associated with such blocks and corresponding statistics that indicate which tables were used as similar quantization levels.

[0083] The coding unit 72 encodes the coefficients by performing searches in the VLC tables 78 (92) that were selected by the table selection unit 76. Coefficient sets (such as sets with a series length of zeros or sets of coded block patterns) can be assigned variable-length codes in VLC tables. Thus, more likely coefficient sets can be encoded with shorter length codewords and less likely coefficient sets can be encoded with shorter length codewords to improve coding efficiency.

[0084] Different VLC tables can be selected for different types of video blocks, for example, intra-coded blocks and intercoded blocks, since these different types of video blocks are usually encoded at different quantization levels. VLC module 46 generates information identifying tables that should be used to decode various types of video blocks (93). The output bitstream of VLC module 46 may include information representing encoded coefficients and information identifying tables to be used in decoding various types of video blocks.

[0085] An output bitstream may be sent to a transmitter (such as a modulator / transmitter 24 in FIG. 1) for transmission to a reception device 16 via a communication channel 15. This bitstream transmission includes transmitting information representing encoded coefficients (94), which may contain codewords selected from VLC tables 78. In addition, transmitting a bitstream includes transmitting information identifying tables to be used in decoding various types of video blocks (95). The process of FIG. 7 may be repeated for each coded unit (96), for example, for each slice or each frame to be encoded.

[0086] FIG. 8 is a flowchart illustrating a decoding technique for variable-length coding coefficients (typically detail coefficients) of an enhancement layer compatible with the present invention. As shown in FIG. 8, the VLC decoding module 82 receives information representing encoded coefficients (101) and receives information identifying various tables to be used to decode various types of video blocks (102). A receiver, such a receiver / demodulator 26 (FIG. 1), can facilitate the reception of this information from the communication channel 15.

[0087] The table selection module 86 selects tables for various types of video block based on received information identifying the various tables to be used (103). Various types of video blocks may contain intra-coded blocks and inter-coded blocks. Accordingly, intra-coded blocks and intercoded blocks can be assigned different VLC tables for each coded unit, for example, each frame or each slice. Decoding unit 82 decodes information representing encoded coefficients based on selected tables (104). For example, decoding module 82 may refer to selected VLC tables 88 and perform tabular searches to decode information to generate coefficients. The process of FIG. 8 is repeated for each coded unit (105). Alternatively, if the agreement between the encoder and the decoder has been previously established regarding tables for use for different types of blocks, step 102 can be deleted and the selection of the table in step 103 can only be based on the type of block to be decoded.

[0088] As described here, in the encoder, the selection of a table for encoding the detail coefficients associated with various types of video blocks can be made based on information collected for previously encoded or currently encoded frames. Statistical analysis of previously encoded frames can be performed, for example, to facilitate the selection of tables in the encoder. For example, detail coefficients can be encoded using the available tables, and a table that provides the least number of bits for encoding information can be selected. This computationally intensive analysis, however, can be avoided in the decoder. Instead, information identifying tables for the first and second types of video blocks, for example, an intra-coded block and inter-coded blocks, can be transmitted from the encoder to the decoder. The decoder may use this transmitted information to facilitate proper table selections based on the type of block.

[0089] The selected tables may depend on the quantization level used in the encoding process. The level of quantization used, in turn, may depend on the type of video block. Since the quantization level used in the encoder is generally unknown to the decoder, information regarding the type of video block provides a useful selection tool for use in the decoder. Therefore, tables are identified for the decoder for various types of video block, and the decoder can determine the type associated with the corresponding video block and select the corresponding VLC table to decode this corresponding video block. Tables for different types of video blocks can be changed frame-by-frame (or slice-by-slice).

[0090] The methods described herein may be implemented in hardware, software, firmware or any combination thereof. Any features described as modules or components can be implemented together in an integrated logic device or separately as discrete but interacting logic devices. If implemented in software, the methods may be implemented, at least in part, by a computer-readable medium containing instructions that, when executed, execute one or more of the methods described above. Computer-readable storage media may be part of a computer program product, which may include packaging materials. Computer-readable media may include random access memory (RAM), such as synchronous dynamic RAM (SDRAM), ROM (ROM), non-volatile RAM (NVRAM), electrically erasable ROM (EEPROM), flash memory, magnetic or optical storage media, etc. .P. The methods can additionally or alternatively be implemented, at least in part, by a computer-readable communication medium that carries or reports code in the form of instructions or data structures, and this can be accessed, read and / or executed by a computer.

[0091] The code may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, specialized integrated circuits (ASICs), user-programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuits . Accordingly, the term “processor,” as used herein, may refer to any previous structure or any other structure suitable for implementing the techniques described herein. In addition, in some aspects, the functionality described herein may be provided in dedicated software or hardware modules configured for encoding and decoding, or integrated in a combined video encoder / decoder (codec).

[0092] This disclosure may also refer to a circuit, such as an integrated circuit, ASIC, FPGA, logic circuits, or various combinations thereof, configured to perform one or more of the techniques described herein. Accordingly, this disclosure also contemplates a circuit configured to encode an extension level of an SVC scheme, where the circuit is configured to encode coefficients associated with video blocks of an extension level based on variable length encoding tables, generating information identifying a first variable length encoding table which should used by the decoding device to decode the first type of video blocks, and the second variable length coding table, which should use the decoding device to decode the second type of video blocks, transmit information representing the encoded coefficients to the decoding device and transmit information identifying the first variable length encoding table to be used by the decoding device to decode the first type of video blocks, and the second variable encoding table the length to be used by the decoding device to decode the second type of video blocks.

[0093] This disclosure also considers a circuit configured to encode an extension level of a scalable video encoding (SVC) scheme, in which the circuit is configured to receive information representing encoded coefficients associated with the video blocks of the extension level, to receive information identifying the first variable encoding table the length that should be used to decode the first type of video blocks, and the second variable length coding table, which should be used to decode the second type of video blocks, select tables for decoding information representing the encoded coefficients based on information identifying the first and second variable length coding table to be used, and decode information representing encoded coefficients based on the selected tables.

[0094] In addition, this disclosure considers a circuit configured to encode an extension level of an SVC scheme, wherein the scheme is configured to receive information representing encoded coefficients associated with extension level video blocks, select various variable length encoding tables to be used. for decoding information based on block types associated with video blocks, in accordance with an agreement established with an encoder, decode information representing encoded coefficients based on the selected tables.

[0095] Various embodiments of the invention have been described. These and other embodiments are within the scope of the following claims.

Claims (25)

1. A method of encoding an extension level of a scalable video coding (SVC) scheme, the method comprising encoding coefficients associated with video blocks of an extension level, based on variable length codebook tables for each of a plurality of encoded units; for each of the aforementioned coded units, generating information identifying a first variable-length coding table to be used by a decoding device to decode a first type of video blocks, and a second variable-length coding table to be used by a decoding device to decode a second type of video blocks and wherein the generation of said information includes performing a statistical analysis of the information collected for previously encoded x units or current coded units associated with the extension level; transmitting information representing the encoded coefficients to a decoding device; and for each of said coded units, transmitting said information identifying a first variable length code coding table to be used by a decoding device to decode the first type of video blocks, and a second variable code length encoding table to be used by a decoding device to decode a second type of video blocks, wherein the transmission of said identifying information is performed once for each of the encoded units. 2. The method according to claim 1, wherein the coefficients comprise detail coefficients for which the corresponding coefficients of one or more previous levels in the SVC scheme have non-zero values. 3. The method according to claim 1, in which the encoded units are frames, wherein the encoding of the coefficients comprises selecting a first and second encoding table with a variable code length based on information collected for previously encoded frames. 4. The method according to claim 3, in which the selection of the first and second encoding tables comprises the selection of the first and second encoding tables from two or more possible tables. 5. The method according to claim 1, in which the first type of video blocks contains an intra-encoded video block and the second type of video blocks contains an intercoded video block. 6. The method according to claim 1, in which the video blocks are arranged in frames and the encoded units are frames, the method further comprising transmitting information for each of the frames identifying the first and second coding tables with a variable code length to be used. 7. The method according to claim 1, wherein the information representing the encoded coefficients comprises codewords selected from one or more coding tables with a variable code length. 8. A method for decoding an extension level of a scalable video coding (SVC) scheme, the method comprising the steps of: receiving information representing encoded coefficients associated with video blocks of an extension level for each of a plurality of encoded units; for each of the aforementioned coded units, receiving information identifying a first coding table with a variable code length that should be used to decode the first type of video blocks, and a second coding table with a variable code length that should be used to decode the second type of video blocks; for each of said coded units, selecting tables for decoding information representing encoded coefficients based on information identifying the first and second coding table with a variable code length to be used; and decoding information representing the encoded coefficients based on the selected tables, said identification information being received once for each of the encoded units. 9. The method of claim 8, wherein the coefficients comprise detail coefficients for which the corresponding coefficients of one or more previous levels in the SVC scheme are non-zero. 10. The method of claim 8, in which the selection of the first and second encoding tables comprises the selection of the first and second encoding tables from two or more possible tables. 11. The method according to claim 8, in which the first type of video blocks contains an intra-encoded video block and the second type of video blocks contain an intercoded video block. 12. The method according to claim 8, in which the encoded units are frames, the method further comprising receiving information identifying the first and second coding tables with a variable code length that should be used once per frame. 13. The method of claim 8, wherein the information representing the encoded coefficients comprises codewords selected by the encoder from one or more coding tables with a variable code length. 14. A device that encodes an extension level of a scalable video coding (SVC) scheme, the device comprising an encoder that encodes coefficients associated with video blocks of the extension level, based on variable length codepage tables for each of the plurality of encoded units, and for each of encoded units generates information identifying a first variable-length codebook to be used by a decoding device to decode a first type of video component Cove, and a second encoding table with variable length, to be used decoding device to decode the second type of video block, and generating said information includes performing a statistical analysis of the information gathered for previously coded units or current coded units associated with an enhancement layer; and a transmitter that transmits information representing encoded coefficients for each of the plurality of coded units, and for each of the coded units, transmits said information identifying a first variable-length codebook to be used by a decoding device to decode said first type of said video blocks, and a second coding table with a variable code length, which must be used by the decoding device to decode the one mentioned in the second type of said video blocks, said identification information being transmitted once for each of the encoded units. 15. The device according to 14, in which the coefficients contain coefficients of detail for which the corresponding coefficients of one or more previous levels in the SVC scheme had non-zero values. 16. The device according to 14, in which the encoded units are frames, and in which the encoder selects the first and second encoding tables with a variable code length based on information collected for previously encoded frames. 17. The device according to 14, in which the first type of video blocks contains an intra-encoded video block, and the second type of video blocks contain an intercoded video block. 18. The device according to 14, in which the video blocks are arranged in frames and the encoded units are frames, and the transmitter transmits information identifying the first and second coding tables with a variable code length, which must be used once for each of the frames. 19. The device according to 14, in which the information representing the encoded coefficients, contains code words selected from one or more coding tables with a variable code length. 20. The device according to 14, in which the device is at least one of: an integrated circuit and a wireless communication device. 21. A device that decodes an extension level of a scalable video coding (SVC) scheme, the device comprising a receiver that receives information representing encoded coefficients associated with the video blocks of the extension level for each of a plurality of encoded units; and for each of said coded units, receives information identifying a first variable-length coding table that should be used to decode the first type of video blocks, and a second variable-length coding table that should be used to decode the second type of video blocks; and a decoder which, for each of said coded units, selects tables for decoding information representing the encoded coefficients based on information identifying the first and second codebooks with a variable code length to be used, and decodes information representing coded coefficients based on the selected tables, and said identifying information is received once for each of the encoded units. 22. The device according to item 21, in which the coefficients contain the coefficients of detail for which the corresponding coefficients of one or more previous levels in the SVC scheme have non-zero values. 23. The device according to item 21, in which the first type of video blocks contains an intra-encoded video block, and the second type of video blocks contains an intercoded video block. 24. The device according to item 21, in which the video blocks are arranged in frames, and the encoded units contain frames, and the receiver receives information identifying the first and second coding tables with a variable code length, which should be used once for each of the frames. 25. The device according to item 21, in which the device is at least one of: an integrated circuit and a wireless communication device.

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