JP3679606B2 - Encoding apparatus and method, and computer-readable recording medium on which an encoding program is recorded - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus that performs variable-length coding on image data and performs transmission coding according to a transmission path, and specifically relates to a multiplexing process of variable-length coded data and transmission synchronization information.
[0002]
[Prior art]
Recently, digital processing systems compliant with MPEG (Moving Picture Experts Group) 2 standards (ISO / IEC (International Organization for Standardization / International Electrotechnical Commission) 13818-1 to 3) are becoming the standard for video transmission systems.
[0003]
FIG. 4 is a block diagram showing a configuration of a transmission side of a general digital transmission apparatus according to ISO / IEC13818-1 to 3.
[0004]
In FIG. 4, 401 is a video encoder that compresses digital video data to comply with ISO / IEC 13818-2, 402 is an audio encoder that compresses digital audio signals to comply with ISO / IEC 13818-3, 403 is a packetizer that packetizes the video elementary stream, which is the output of the video encoder, according to PES (Packetized Elementary Stream) of ISO / IEC 13818-1, and 404 is the ISO / IEC 13818-1 packet elementary stream, which is the output of the audio encoder. / Packetizer that packetizes to comply with PES of IEC 13818-1.
[0005]
Reference numeral 405 denotes a TS (Transport Stream) multiplexer that packetizes and multiplexes the video PES and audio PES output from the packetizer into transport stream packets according to ISO / IEC 13818-1 TS (Transport Stream).
[0006]
Hereinafter, the transmission operation of the digital transmission apparatus configured as described above will be described.
[0007]
Video data and audio data are input to the video encoder 401 and the audio encoder 402, respectively. In accordance with ISO / IEC 13818-2, the video encoder 401 inspects information with high spatial and temporal correlation and converts the information into data with low redundancy to compress the amount of information.
[0008]
Also, the speech encoder 402 compresses the amount of information by examining highly correlated information in accordance with ISO / IEC 13818-3 and converting it into data with low redundancy. Of these compressed data strings, a unit that can be expanded independently is called an access unit (AU), and the data strings of video AU and audio AU are respectively referred to as video elementary stream (video ES) and audio elementary stream (audio ES). ).
[0009]
Video ES and audio ES are input to the packetizers 403 and 404, respectively, and are generally a unit based on the access unit, a stream ID representing the attribute of the ES, and time stamp information indicating a decoding time and a display time on the decoding side. Etc. and packetized (PES) into variable length packets.
[0010]
The TS multiplexer 405 receives the video PES and the audio PES, converts them into a transport stream (TS), and outputs them.
[0011]
FIG. 5 is a block diagram showing a detailed configuration of the TS multiplexer 405.
[0012]
In FIG. 5, video PES and audio PES are stored in respective buffers and packetized in units of data transmission. This packet is called a transport stream packet (TS packet). The TS packet has a size of 188 bytes according to ISO / IEC 13818-1, and includes a packet header including a sync byte necessary for decoding the TS packet on the decoding side and a PID (Packet Identification) indicating the ID of the TS packet. Attached information necessary for transmission such as PCR (Program Clock Reference) indicating the reference time that defines the reception time on the decoding side is described in the adaptation field, and video PES or audio PES is stored in other free space (payload) To do. On the other hand, comprehensive TS attached information such as PID definition is generated as PSI (Program Specific Information), stored in a buffer, and packetized into TS packets having a predefined PID.
[0013]
Since PCR must be output as a TS within a period of 100 ms, generally, a PID for PCR is defined in PSI separately from a packet for transmitting video PES and audio PES, and a packet including the PID. It is packetized as a TS packet composed only of a header and an adaptation field.
[0014]
Each TS packet is read from each buffer in TS packet units at an appropriate timing and output as a TS.
[0015]
[Problems to be solved by the invention]
In the data multiplexing method in the digital transmission apparatus as described above, the amount of data transmitted on the transmission path is greatly limited, the transmission path cannot be used effectively, and wasteful stuffing data must always be multiplexed.
[0016]
For example, when converting the video PES shown in FIG. 6 into a TS packet, an adaptation field is inserted into the last TS packet, and useless stuffing bytes (dummy data bytes for making the packet data length constant) must be multiplexed. I must.
[0017]
In addition, when an independent TS packet is transmitted for PCR transmission as shown in FIG. 7, stuffing processing is required in the TS packet. Further, even when the PCR transmission is inserted into the video data transmission TS packet as shown in FIG. 8, the stuffing amount may further increase due to the definition of the PCR transmission cycle.
[0018]
In view of the above-mentioned background, the present invention solves the above-mentioned problems in the conventional data multiplexing method, enables an effective use of the transmission path, and further provides a coding apparatus and method with strong transmission errors, and a recording medium on which a transmission program is recorded. The purpose is to provide.
[0019]
[Means for Solving the Problems]
The encoding apparatus / method according to the present invention inputs variable-length-encoded first information data, converts the first information data into variable-length packets with a plurality of data strings, and converts the first information data into the first information data. Process of generating related transmission synchronization information, multiplexing the generated transmission synchronization information into the variable-length packetized first information data into a plurality of fixed-length packets, and multiplexing the transmission synchronization information Counting time, detecting a packet length of the information string converted into a variable length packet, and controlling multiplexing processing to the fixed length packet according to the counting result and the detection result, To do.
[0020]
The encoding apparatus / method according to the present invention inputs first information data that is variable-length encoded, converts the first information data into a variable-length packet with a plurality of data strings, and outputs the first information data. Transmission synchronization information related to data is generated, and the generated transmission synchronization information is multiplexed into a plurality of fixed-length packets in the variable-length packetized first information data. The packet length of the information sequence is detected, and the multiplexing process to the fixed-length packet is controlled according to the detection result.
[0021]
In addition, a computer-readable recording medium on which an encoding program according to the present invention is recorded includes an input process code for inputting variable-length encoded first information data, and the first information data as a plurality of data strings. The first packetizing step code for variable length packetization, the generation step code for generating transmission synchronization information related to the first information data, and the variable length packetized by the first packetizing step. The second packetizing step code that multiplexes the transmission synchronization information generated by the generation step with the first information data into a plurality of fixed-length packets, and the elapsed time when the transmission synchronization information is multiplexed are counted. A code for a counting step, a code for a detecting step for detecting a packet length of the information string variable-length packetized by the first packetizing step, and the counting step According to the result of the serial detection process, and having a code of a control step of controlling the multiplexing process of the second packetization process.
[0022]
In addition, a computer-readable recording medium on which an encoding program according to the present invention is recorded includes an input process code for inputting variable-length encoded first information data, and the first information data as a plurality of data strings. The first packetizing step code for variable length packetization, the generation step code for generating transmission synchronization information related to the first information data, and the variable length packetized by the first packetizing step. The second packetizing step code for multiplexing the first information data and the transmission synchronization information generated by the generating step into a plurality of fixed length packets, and variable length packetization by the first packetizing step A control process for controlling the multiplexing process of the second packetization process in accordance with the code of the detection process for detecting the packet length of the information string and the result of the detection process And having a code.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
In this embodiment, ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) recommendation H.222.0: Video data encoded in ISO / IEC 13818-2 is ITU-T recommendation H. .222.0: A case where system encoding is performed according to ISO / IEC 13818-1 will be described as an example.
[0024]
FIG. 1 is a block diagram showing the configuration of an encoding apparatus as an embodiment of the present invention.
[0025]
In FIG. 1, video data captured by the camera unit 100 is encoded by an MPEG encoder 101 based on ITU-T recommendation H.222.0: ISO / IEC 13818-2.
[0026]
The video data encoded by the MPEG encoder 101 is output to the packetizer 102 as a video elementary stream.
[0027]
The input video elementary stream is converted into a packetized elementary stream represented by ITU-T recommendation H.222.0: ISO / IEC 13818-1 by the 102 packetizer.
[0028]
Here, the packetized information length is packetized for each slice shown in, for example, ITU-T recommendation H.222.0: ISO / IEC 13818-2 in consideration of data errors in the transmission path.
[0029]
The packetizer 102 supplies the packetized elementary stream packet length detector 103 and the multiplexing buffer 104 of variable length packetized for each slice.
[0030]
The packet length detector 103 detects the PES_packet_length in the packetized elementary stream encoded by ITU-T recommendation H.222.0: ISO / IEC 13818-1, and the packetized elementary stream length (PES_packet_length + 6 bytes (PES header) )) Is memorized.
[0031]
The PCR counter 105 is a counter for generating program_clock_reference_base and program_clock_reference_extension for system synchronization shown in ITU-T recommendation H.222.0: ISO / IEC 13818-1. The program_clock_reference_base and program_clock_reference_extension generated by the PCR counter 105 are supplied to the multiplexing buffer 106.
[0032]
The PCR timer 107 is a timer that counts the periods of multiplexed program_clock_reference_base and program_clock_reference_extension.
[0033]
The multiplex determination unit 108 receives information from the packet length detector 103 and the PCR timer 107 and feeds back the multiplex result to the output control of the multiplexing buffers 104 and 106 and the PCR timer 107.
[0034]
In the TS formatter 109, the output data of the multiplexing buffers 104 and 106 are converted into transport stream packets represented by ITU-T recommendation H.222.0: ISO / IEC 13818-1, and output from the output terminal 110.
[0035]
Here, details of the MPEG encoder 101 will be described.
[0036]
FIG. 2 is a block diagram showing the configuration of the MPEG encoder 101.
[0037]
As shown in FIG. 2, the MPEG encoder 101 includes a blocking circuit 201, a DCT circuit 203, a quantization (Q) circuit 204, a variable length coding (VLC) circuit 205, a motion compensation circuit 215, and a motion vector detection circuit. 216, a rate control circuit 207, a local decoding circuit 212, an output buffer 206, and the like.
[0038]
In FIG. 2, input image data is converted into a digital signal by an A / D conversion circuit 200. The image data converted into a digital signal by the A / D conversion circuit 200 is converted into the aforementioned block of 8 pixels × 8 pixels by the blocking circuit 201 and transmitted to the DCT circuit 203 via the switch 202.
[0039]
The switch 202 is switched depending on whether the input image data is an intra frame (I frame) or another frame (P (forward prediction encoding) frame or B (bidirectional prediction encoding) frame). In the case of a frame, it is connected to the a contact, and in other cases, it is connected to the b contact.
[0040]
In the case of an intra frame, DCT is performed by the DCT circuit 203 and converted from the data in the spatial domain to the data in the frequency domain, and the DCT coefficient obtained thereby is quantized by the quantization circuit 204. Then, after the variable length encoding circuit 205 performs variable length encoding, it is temporarily stored in the buffer 206.
[0041]
On the other hand, in the case of other than the intra frame, the switch 202 is connected to the contact b and the motion compensation described above is performed. That is, reference numerals 213 and 214 denote an inverse quantization circuit and an inverse DCT circuit constituting the local decoder 212. The data quantized by the quantization circuit 204 is returned to the original image by the local decoding circuit 212. It is.
[0042]
Reference numeral 209 denotes a subtracter, 210 denotes a switch that is closed only in a case other than an intra frame, and 211 denotes an adder.
[0043]
The image data decoded by the local decoding circuit 212 outputs a corresponding macroblock in a predetermined frame (preceding frame, succeeding frame or interpolation frame thereof) with reference to the motion vector detected by the motion vector detecting circuit 216. To do.
[0044]
The output of the motion compensation circuit 215 is subtracted from the input image data by the subtractor 209 to obtain a difference value. The difference value is obtained by the DCT circuit 203, the quantization circuit 204 and the variable length coding circuit 205 described above. It is encoded and stored in the buffer 206.
[0045]
The motion vector detection circuit 216 compares the frame data to be encoded with predetermined reference frame data to obtain a motion vector, and the detection output of the detection circuit 216 is supplied to the motion compensation circuit 215. The macro block to be output by the motion compensation circuit 215 is designated.
[0046]
Further, the rate control circuit 207 performs code amount control by switching the quantization step in the quantization circuit 204 based on the occupation amount of the encoded data in the buffer 206. The output of the rate control circuit 207 is also supplied to the inverse quantization circuit 213, and the inverse quantization circuit 213 controls the inverse quantization step based on the output data.
[0047]
Finally, various headers (for example, flags for identifying I, P, and B frames) are added to the encoded data by the addition circuit 208, and transmitted as MPEG data corresponding to the MPEG system.
[0048]
Next, the operation of the multiplexing determination unit 108 will be described with reference to FIG.
[0049]
FIG. 3 is a flowchart showing the operation of the multiplexing determination unit 108.
[0050]
First, in step S301, the PCR timer 107 is reset from the multiple determination unit 108. The PCR timer 107 operates in real time after being reset.
[0051]
Next, in step S302, the packet length detector 103 detects the packetized elementary stream length (PES length) (detects the number of bytes used in the PES length), and the process proceeds to step S303.
[0052]
The PES length is obtained by detecting PES_packet_length in the packetized elementary stream and adding 6 bytes used for the PES header to the detection result.
[0053]
In step S303, 184 bytes corresponding to the payload portion of the transport stream packet shown in ITU-T recommendation H.222.0: ISO / IEC 13818-1 are compared with the detected PES length. Otherwise, the process proceeds to step S311.
[0054]
In step S304, the value of the PCR timer 107 is read, and here, from the 100 ms which is the upper limit value of the PCR field transmission cycle defined in ITU-T recommendation H.222.0: ISO / IEC 13818-1, one transport stream packet worth. It is determined whether or not the value obtained by subtracting the time for transmitting 188 bytes is exceeded. That is, in step S304, it is performed to ensure that the PCR must be output as a TS within a period of 100 ms.
[0055]
In step S304, if the value of the timer 107 does not exceed the value obtained by subtracting the time to transmit 188 bytes for one transport stream packet from 100 ms, the process proceeds to step S305, and if it exceeds, the process proceeds to step S307.
[0056]
In step S305, 184 bytes (video PES) corresponding to the payload of the transport stream packet are output from the multiplexing buffer 104.
[0057]
Next, the process proceeds to step S306, the number of bytes output in step S305 (184 bytes) is subtracted from the previous number of bytes of the PES length, the remaining PES length is detected, and the process returns to step S303.
[0058]
In step S307, the PCR value is output from the multiplexing buffer 106. After outputting the PCR value, the PCR timer 107 is reset in step S308, and the process proceeds to step S309.
[0059]
In step S309, the multiplexing buffer 104 outputs the number of bytes obtained by subtracting the number of bytes for the PCR field from the 184 bytes for the payload of the transport stream packet. In step S310, the number of bytes output from the multiplexing buffer 104 is subtracted from the previous number of bytes of the PES length to detect the remaining PES length, and the process returns to step S303.
[0060]
Next, when the PES length is less than 184 bytes in step S303, the process proceeds to step S311.
[0061]
In step S311, it is determined whether the PES length is equal to or shorter than (184-number of bytes for PCR field). If the PES length is equal to or shorter than (184-number of bytes for the PCR field), the process proceeds to step S312. Otherwise, the process proceeds to step S315.
[0062]
In step S312, the PCR value is output from the multiplexing buffer 106, and in step S313, the PCR timer 107 is reset. Next, the process proceeds to step S314, where a stuffing byte of 184− (PES length + PCR) bytes is inserted.
[0063]
In step S315, all the remaining video PESs are output from the multiplexing buffer 104. Then, the process returns to step S302, and the next PES length is detected.
[0064]
In step S316, the value of the PCR timer 107 is read. Here, one transport stream packet worth from 100 ms, which is the upper limit value of the PCR field transmission cycle defined in ITU-T recommendation H.222.0: ISO / IEC 13818-1. It is determined whether or not the value obtained by subtracting the time for transmitting 188 bytes is exceeded. If not, the process proceeds to step S320. If exceeding, the process proceeds to step S317.
[0065]
In step S317, the PCR value is output from the multiplexing buffer 106. After outputting the PCR value, the PCR timer 107 is reset in step S318. In step S319, the multiplexing buffer 104 outputs the number of bytes obtained by removing the number of bytes corresponding to the PCR field from the 184 bytes corresponding to the payload of the transport stream packet. In step S320, the number of bytes output from the multiplexing buffer 104 is subtracted from the previous number of bytes of the PES length to detect the remaining PES length, and the process returns to step S303.
[0066]
In step S321, stuffing bytes corresponding to the number of bytes of the current PES length subtracted from 184 bytes are inserted, and the remaining video PES is output from the multiplexing buffer 104 in step S322. Then, the process returns to step S302, and proceeds to the processing of the next packetized elementary stream.
[0067]
By executing each step described above, when each variable-length video packetized elementary stream is multiplexed into a fixed-length transport stream packet, PCR is inserted into the video transport stream packet at regular intervals. Instead, when a fraction in which PCR can be inserted occurs in the video data, the PCR is inserted even if the prescribed insertion cycle has not been reached, and stuffing that is wasted during multiplexing is deleted.
[0068]
<Other Embodiments of the Present Invention>
The present invention may be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.) or an apparatus composed of a single device (for example, a copying machine, a facsimile machine).
[0069]
In addition, a program code of software for realizing the functions of the embodiment is provided to an apparatus or a computer in the system connected to the various devices so as to operate the various devices so as to realize the functions of the above-described embodiments. What is implemented by operating the various devices in accordance with a program stored in the computer (CPU or MPU) of the system or apparatus supplied is also included in the scope of the present invention.
[0070]
In this case, the software program code itself realizes the functions of the above-described embodiments, and the program code itself and means for supplying the program code to the computer, for example, the program code are stored. This storage medium constitutes the present invention.
[0071]
As a storage medium for storing the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0072]
Further, by executing the program code supplied by the computer, not only the functions of the above-described embodiments are realized, but also the OS (operating system) in which the program code is running on the computer, or other application software, etc. Needless to say, the program code is also included in the embodiment of the present invention even when the functions of the above-described embodiment are realized in cooperation with the embodiment. Further, after the supplied program code is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the CPU provided in the function expansion board or function storage unit based on the instruction of the program code However, it is needless to say that the present invention also includes a case where the function of the above-described embodiment is realized by performing part or all of the actual processing.
[0073]
【The invention's effect】
As described above, according to the present invention, transmission synchronization information is multiplexed in accordance with the amount of variable-length encoded data generated, so that it is possible to minimize sending unnecessary information on the transmission path.
[0074]
In addition, the multiplexing period of the transmission synchronization information is variable, which is effective against transmission errors. Furthermore, the effect increases as the number of multiplexed programs increases.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an image encoding apparatus as an embodiment of the present invention.
2 is a block diagram showing a configuration of an MPEG encoder 101. FIG.
FIG. 3 is a flowchart showing the operation of the multiplexing determination unit 108;
FIG. 4 is a block diagram showing a configuration of a transmission side of a general digital transmission apparatus according to ISO / IEC 13818-1 to 3.
5 is a block diagram showing a detailed configuration of a TS multiplexer 305 in FIG. 1. FIG.
FIG. 6 is a diagram for explaining a PES / TS conversion format;
FIG. 7 is a diagram for explaining a PES / TS conversion format including PCR.
FIG. 8 is a diagram for explaining a PES / TS conversion format including PCR.

Claims (15)

Input means for inputting variable length encoded first information data;
First packetization means for variable-length packetizing the first information data with a plurality of data strings;
Generating means for generating transmission synchronization information related to the first information data;
Second packeting means for multiplexing the first information data variable-length packetized by the first packetizing means and the transmission synchronization information generated by the generating means into a plurality of fixed-length packets;
Counting means for counting an elapsed time in which the transmission synchronization information is multiplexed;
Detecting means for detecting a packet length of the information string that is variable-length packetized by the first packetizing means;
An encoding apparatus comprising: control means for controlling multiplexing processing of the second packetizing means in accordance with outputs from the counting means and the detecting means.   2. An encoding apparatus according to claim 1, wherein said control means controls to preferentially multiplex said transmission synchronization information when said counting means exceeds a predetermined value.   3. The first packet data according to claim 1, wherein when the first packet data variable-length packetized by the first packetization means is multiplexed with the fixed-length packet, the first packet data is more than the first data number. An encoding apparatus, wherein the transmission synchronization information is multiplexed into the fixed-length packet that is the same as the first packet data when the number is less than the second data number.   4. The encoding apparatus according to claim 1, wherein the first information data is image data, and the image data is encoded according to an MPEG system.   5. The encoding apparatus according to claim 4, wherein the input unit includes an imaging unit that captures a subject image.   6. The encoding apparatus according to claim 1, wherein the control unit multiplexes dummy data for stuffing in accordance with an output of the detection unit.   7. An encoding apparatus according to claim 6, wherein said control means multiplexes dummy data for stuffing according to the output of said counting means. Input means for inputting variable length encoded first information data;
First packetization means for variable-length packetizing the first information data with a plurality of data strings;
Generating means for generating transmission synchronization information related to the first information data;
Second packeting means for multiplexing the first information data variable-length packetized by the first packetizing means and the transmission synchronization information generated by the generating means into a plurality of fixed-length packets;
Detecting means for detecting a packet length of the information string that is variable-length packetized by the first packetizing means;
And a control unit that controls a multiplexing process of the second packetization unit in accordance with an output of the detection unit.   9. The encoding apparatus according to claim 8, wherein the first information data is image data, and the image data is encoded according to an MPEG system.   10. The encoding apparatus according to claim 9, wherein the input unit includes an imaging unit that captures a subject image.   11. An encoding apparatus according to claim 10, wherein said control means multiplexes dummy data for stuffing according to the output of said detection means. An input step of inputting variable length encoded first information data;
A first packetizing step of variable-length packetizing the first information data with a plurality of data strings;
Generating a transmission synchronization information related to the first information data;
A second packetization step for multiplexing the first information data variable-length packetized by the first packetization step and the transmission synchronization information generated by the generation step into a plurality of fixed-length packets;
A counting step of counting an elapsed time in which the transmission synchronization information is multiplexed;
A detection step of detecting a packet length of the information sequence variable-length packetized by the first packetization step;
An encoding method comprising: a control step for controlling a multiplexing process of the second packetization step according to a result of the counting step and the detection step. An input step of inputting variable length encoded first information data;
A first packetizing step of variable-length packetizing the first information data with a plurality of data strings;
Generating a transmission synchronization information related to the first information data;
A second packetization step for multiplexing the first information data variable-length packetized by the first packetization step and the transmission synchronization information generated by the generation step into a plurality of fixed-length packets;
A detection step of detecting a packet length of the information sequence variable-length packetized by the first packetization step;
And a control step for controlling a multiplexing process of the second packetization step according to a result of the detection step. A computer-readable recording medium on which an encoding program is recorded,
A code of an input process for inputting the variable length encoded first information data;
A code of a first packetization step for variable-length packetizing the first information data with a plurality of data strings;
A generation process code for generating transmission synchronization information related to the first information data;
A second packetizing step code for multiplexing the first information data variable-length packetized by the first packetizing step and the transmission synchronization information generated by the generating step into a plurality of fixed-length packets; ,
A counting step code for counting the elapsed time of multiplexing the transmission synchronization information;
A detection step code for detecting a packet length of the information string that has been variable-length packetized by the first packetization step;
A computer-readable recording on which an encoding program is recorded, comprising: a control step code for controlling a multiplexing process of the second packetizing step in accordance with the result of the counting step and the detecting step Medium. A computer-readable recording medium on which an encoding program is recorded,
A code of an input process for inputting the variable length encoded first information data;
A code of a first packetization step for variable-length packetizing the first information data with a plurality of data strings;
A generation process code for generating transmission synchronization information related to the first information data;
A second packetizing step code for multiplexing the first information data variable-length packetized by the first packetizing step and the transmission synchronization information generated by the generating step into a plurality of fixed-length packets; ,
A detection step code for detecting a packet length of the information string that has been variable-length packetized by the first packetization step;
A computer-readable recording medium on which an encoding program is recorded, comprising: a control step code for controlling multiplexing processing of the second packetizing step in accordance with a result of the detection step.

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