JP2001298680A - Digital broadcast signal specifications and receiver - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To extract only a specific audio event from an audio signal in a digital broadcast receiving apparatus to which an audio signal including a plurality of audio channels is input, and adjust the volume balance to a desired volume of a viewer. SOLUTION: Different audio events in a program are allocated to a plurality of input audio channels, downmix coefficients of the respective channels are sent as additional information, and a viewer adjusts the downmix coefficients at a receiver to perform downmixing. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention separates audio constituting one program for each event, and synthesizes and outputs signals transmitted through a plurality of audio channels upon reception. The present invention relates to a receiving device for digital broadcasting.

[0002]

2. Description of the Related Art In a conventional audio broadcasting service such as television broadcasting, a program to which a plurality of audio channels are assigned is a limited service of stereo broadcasting, bilingual broadcasting, and auxiliary audio broadcasting. In digital broadcasting, multi-channel audio broadcasting may be performed.
However, it is difficult for all actual listeners to provide a means for outputting an audio signal completely corresponding to multi-channel audio broadcasting, and the sound of a general television receiver is output in two-channel stereo output or one-channel monaural. The output is generic.

For this reason, it is conceivable that some receivers can reproduce and output only a part of the transmitted multi-channel audio signals. Standards for BS digital broadcasting receivers AR compiled by the Association of Radio Industries and Businesses AR
According to IB STD-B21, a rule is described for downmixing multi-channel stereo audio broadcasting to 2-channel stereo in a receiver having 2-channel stereo audio reproduction. The front right channel of the original audio is R, the front left channel is L, the front center channel is C, the rear right channel is Rs, the rear left channel is Ls, the right channel after downmixing into two channels is the Rt channel, and the left channel. Is the Lt channel and the coefficient of the downmix is k, the following equations (1) and (2) are recommended as the downmix. Lt = k (L + 0.707C + 0.707Ls) (1) Rt = k (R + 0.707C + 0.707Rs) (2) Also, ISO / IEC 13818-7 MPEG-2
According to AAC, the downmix specification is
Four types of downmix coefficients and two types of calculation formulas are defined, and such information is written in an audio elementary stream. Lt = (1 / (1 + 1 / √2 + k)) × (L + C / √2 + (k × Ls)) (3) Rt = (1 / (1 + 1 / √2 + k)) × (R + C / √2 + (k) × Rs)) (4) Lt = (1 / (1 + 1 / √2 + (2 × k))) × (L + C / √2-k × (Ls + Rs)) (5) Rt = (1 / (1 + 1 / √2 + (2 × k))) × (R + C / √2-k × (Ls + Rs)) (6) (3) and (4) are equations 1 and (5) and (6) ) Represents calculation formula 2. For the downmix coefficient k, 1
/ √2, 1/2, 1 / (2 × √2), 0. However, these downmix controls are effective only when downmix output from the previously transmitted L channel, R channel, center channel, and surround channel inputs to two channels, L channel and R channel, is performed. Does not support input or output.

[0004] In addition, if a listener finds it difficult to listen to the sound being broadcast while listening to a certain audio broadcast program,
Adjustment methods such as raising the volume and adjusting the sound quality are applied to the audio signals constituting the program. Conventional receivers for TV broadcasts and audio broadcasts can adjust the sound output from the receiver by adjusting frequency characteristics such as volume adjustment and tone adjustment, noise reduction, etc., and are used in various audio equipment. Have been. One of the features of these technologies is that the effect is constant regardless of the type of audio signal to be processed.

[0005] For example, when an announcer is speaking alone, as in a news program, a filter is applied to the high frequency band to adjust the frequency characteristics and enhance the high frequency gain in order to emphasize the high frequency range of the sound of the announcer. When the process of raising the frequency is performed, an audio signal emitted by the announcer whose high frequency is emphasized is output. On the other hand, in the case of a drama program in which a plurality of people are uttering voices, if a similar filtering process is performed to emphasize the high frequency range of the voice uttered by a certain character, only the voice of the target character is output. Rather, the same filtering process is applied to audio signals emitted by other characters, so that high frequencies are emphasized. In general, a filter is characterized in that an audio signal is input and output in a time-series manner, so that the filter is similarly processed regardless of the content of the audio signal.

[0006]

In everyday life, an acoustic signal emitted from a source of an audio signal and propagated in the air reaches the ear and is perceived as a sound. However, the source of the audio signal is not usually alone. Often. Rather, acoustic signals emitted from various sound source sources are mixed and arrive as one signal at the ear. For example, the sounds that are heard simultaneously while walking in the city include the voice of the person who is talking,
It is emitted from various sound sources, such as a sound of playing a musical instrument, a sound of a car passing, music playing on BGM, and a car noise. If various sound sources constituting one acoustic signal are referred to as audio events, it can be generally said that a plurality of audio events exist in one acoustic signal.

[0007] Similar to the audio signal entering the ear, there are various audio events in the audio signal transmitted by television broadcasting or the like. Normal audio is broadcast on one or two channels for one program. There are various audio events in one channel, such as an audio signal emitted by a certain person, a BGM audio signal, and a sound effect audio signal. In the transmitted audio signal, a plurality of audio signals generated from such a plurality of audio events overlap in time and frequency to form one audio signal.

As described above, when listening to an audio signal in which several audio events appear simultaneously, a masking phenomenon occurs. The masking phenomenon means that when a plurality of audio events occur at the same time, if one audio event has a relatively higher level than another audio event in a certain frequency band, a low-level audio event becomes difficult to hear. It is a phenomenon. In an actual audio program, a case where a plurality of people simultaneously emit sounds, a case where it is difficult to hear only a sound generated by a specific person, or a case where BGs simultaneously playing
This masking phenomenon is considered to have occurred when the volume of the M sound is too large to hear the voice of the person who wants to listen.

[0009] When the masking phenomenon occurs, the level of an audio signal generated by an inaudible audio event is increased,
In the frequency domain, by making the level relatively higher than the signal of other events, it is possible to improve the sound so as to be hard to hear. For that purpose, it is necessary to independently process two audio events that overlap in frequency. Not only when it is difficult to hear only a certain sound like masking, but also when you want to listen only to the sound of a certain character while listening to a drama program, or when you want to reduce the sound of BGM only Changing the parameters for each event requires that a plurality of audio events be processed independently, as in the case of the masking phenomenon. In the conventional audio processing method using filter processing, it is difficult to extract an audio event from one audio signal and process only the audio event.

[0010] Consider that channel assignment is performed for each audio event using a multi-channel. The aim of the current operation of multi-channel audio is to provide an environment in which audio can be heard from multiple directions when actually listening to audio. That is, the sound to be heard from the position of the speaker at the time of listening is assigned to the sound of each channel. Therefore, the mechanism of downmixing these multiple sounds into two channels is to try to use sound signals that can be heard from multiple directions as two-channel sounds, and to control the channels independently. Is not provided.

[0011]

SUMMARY OF THE INVENTION In an audio signal having a plurality of audio events, it is possible to control the audio events independently by using a technique of multi-channel transmission by multi-channel broadcasting. IS
MPEG specified in O / IEC 13818-7
In 2-AAC, it is possible to transmit audio signals of up to eight channels. Utilizing this multi-channel audio output, one channel is assigned for each audio event and transmission is performed.

In order to perform such output, it is necessary to have a plurality of audio channels at the stage of creating audio signals for each program. For example, in the case of a drama program, the voice of the character A is on the first channel, the voice of the character B is on the second channel, the voices of the other characters are on the third channel, the voice of the narrator is on the fourth channel, B
A channel is assigned to each audio event, such as the GM audio as a fifth channel. Next, when the output form when the sound is finally output from the receiver is a two-channel configuration of the L channel and the R channel, the sound channel assigned to each sound event is set to 2ch at an appropriate volume level. I need to mix. At that time, the following calculation formula is introduced to perform an appropriate downmix.

When the audio channel is downmixed into two channels, Lt and Rt, the downmix coefficient is k
rn, kln (n = 1, 2,...)
Calculate as in (8). Lt = (kl1x1ch) + (kl2x2ch) + (kl3x3ch) + (kl4x4ch) + (kl4x4ch) + (kl5x5ch) (7) Rt = (kr1x1ch) + (kr2x2ch) + (kr3x3ch) + (kr4x4) (Kr5x5ch) (8) Formulas (3), (4), (5), and (6) have one downmix coefficient for 5-channel audio, but the formulas (7), (7) In 8), a downmix coefficient is assigned to each channel channel.
By changing the value of the downmix coefficient in the receiver using the calculation formulas (7) and (8), the volume can be adjusted for each channel. By using such a down-mix calculation formula and a signal in which a channel is assigned to each audio event, the audio event assigned to the channel can be converted to the same L channel and R channel output audio as before. Can be controlled independently.

[0014]

(Embodiment 1) FIG. 1 is a block diagram showing a receiving apparatus according to a first embodiment of the present invention. In FIG. 1, reference numeral 100 denotes a receiving means for receiving a signal from an antenna. Show. The data input to the receiving means 100 is a signal obtained by multiplexing a plurality of pieces of video information, audio information, and data information and digitally modulating them. In the present invention, an input audio signal is a multi-channel audio, and a channel is assigned to each audio event.

For example, if the input sound is a sound of a television program, the sound of the character A is transmitted to the first channel,
The sound of the person B is assigned to the second channel, the sound of the other person is assigned to the third channel, the BGM is assigned to the fourth channel, and the sound effect is assigned to the fifth channel. This audio is assumed to be downmixed by the receiver. By downmixing each channel at an appropriate volume, an audio signal intended by the program maker can be finally obtained.
When different audio events are sent to the audio from 1ch to 5ch, if M is the downmixed audio and kn is the downmix coefficient for each channel, the downmix calculation formula of Expression (9) is used. M = (k1 × 1ch) + (k2 × 2ch) + (k3 × 3ch) + (k4 × 4ch) + (k5 × 5ch) (9) In order to perform downmixing using equation (9), the receiver grasps the downmix coefficient for each channel. There is a need to. The downmix coefficient for each channel shown in FIG. 5 is multiplexed on the additional information signal as additional information. An example of the method will be described.

[0016] A standard (ARIB STD) for program arrangement information used for digital broadcasting, compiled by the Radio Industries and Business Association.
According to -B10), in digital broadcasting, various information about each program can be sent as a table. Among them, EIT (Event Inf.) Which provides information about a program such as a program name, a broadcast date and time, and a description of the program contents.
Each parameter of the audio elementary stream constituting the program can be indicated in an audio component descriptor inserted in a table called an “operation table” or the like.

The audio component descriptor has a data structure as shown in FIG.
The type of the audio component can be indicated in an 8-bit field called t_type (component type). The components that are currently standardized from 0x01 to 0x09 in FIG. 7 are shown. The stream assumed in the present invention is premised on that each channel is assigned to each audio event and downmixed in the receiver, and such a stream does not apply to the component type that has been already defined. For this reason,
A stream in which a component type is assigned from 0x0A to 0x11 in FIG. 7 for each audio event is newly defined by dividing it into the number of constituent channels.

The extended event descriptor inserted in the same EIT or the like provides a detailed description of the event (program) (FIG. 8). In order for the receiver to appropriately downmix the stream to which the channel is assigned for each audio event, it is necessary to transmit the downmix coefficient in the calculation formula shown in Expression (9), and to transmit the downmix coefficient to this extended event descriptor. Insert inside. In FIG. 8, item_descripton_char indicates a transmission channel number, and item_char indicates a downmix coefficient corresponding to the channel. Hereinafter, it is assumed that a digital broadcast signal obtained by multiplexing such a main signal including an audio signal and an additional information signal including additional information is received.

The operation in the configuration of the first embodiment will be described. The data input to the receiving means 100 is a signal obtained by multiplexing a plurality of pieces of video information, audio information, and data information and digitally modulating them. The receiving unit 100 performs digital demodulation, error correction, and the like, and outputs a signal in which a plurality of video and audio such as an MPEG2 transport stream and other data are multiplexed.

The signal separating means 101 is a packet I of the component of the program which the user has instructed to tune in with the tune instructing means.
Using D, the corresponding video data and audio data are filtered and sent to the video signal reproducing means 103 and the audio signal reproducing means 104, respectively. The video signal input to the video signal reproducing means is a signal encoded by MPEG2 or the like, and the video signal reproducing means comprises an MPEG video decoder, which decodes the video signal and outputs it to a video presenting means such as a monitor. Do.

The audio signal reproducing means 104 receives coded audio such as MPEG2 AAC including a plurality of channels, and performs decoding processing using an AAC decoder or the like. When an audio signal including a plurality of channels is decoded, the audio signal reproducing unit independently outputs the audio signal to the output audio synthesizing unit 106 without synthesizing each channel. For example,
When an audio signal composed of three-channel audio is input, the audio signal reproducing unit outputs the signal to the output audio synthesizing unit as a three-channel signal. The tuning instruction means 102 outputs the packet ID of the component constituting the channel to be tuned to the signal separating means 101.

The additional information processing means 105 can use the SI information and the like to extract stream information such as a packet ID and program information for filtering by the output signal separating means. In the present invention, in order to obtain a downmix coefficient for each channel, the additional information processing means 105 extracts the descriptors shown in FIGS. When the synthesized output instructing unit determines that the component type in the audio component descriptor shown in FIG.
The channel number indicated by em_dscrption_char and the corresponding downmix coefficient value indicated by item_char are acquired, a downmix table shown in FIG. 5 is created, and this table is output to the output speech synthesis means 106.

A signal from the audio signal reproducing means is input to the output audio synthesizing means independently for each channel. The output voice synthesizing means extracts the downmix coefficient of each channel from the obtained downmix table, multiplies each input channel by the coefficient using the calculation formula (Equation 9), performs synthesis, and outputs the result to a speaker or the like.

(Embodiment 2) FIG. 2 is a block diagram showing a digital broadcast receiving apparatus according to a second embodiment of the present invention. When watching a program of a multi-channel audio signal to which a channel is assigned for each audio event, by changing the downmix coefficient when downmixing,
Downmixing can be performed with an arbitrary channel balance. The viewer selects an arbitrary audio event and changes the downmix coefficient of the audio channel corresponding to the event, so that the viewer can adjust the channel balance for each audio event. To enable such an operation, it is necessary to insert specific audio content assigned to each channel into the additional information.

FIG. 9 shows an example of the item description and the extended description contents in the extended event descriptor. When a certain TV program has a 5-channel audio configuration for each audio event, the item description indicates the audio content of the channel, and the extended description indicates the downmix coefficient. Hereinafter, additional information including such information is transmitted from the additional information processing means 205 to the composite output instructing means 2.
Send to 07. The combining output instructing unit creates the video display table shown in FIG. 4 from the additional information, and outputs the table to the video combining unit 209.

The column of the selected sound in the video display table of FIG. 4 contains the name of the sound event in the item description, and the volume level visually represents the downmix coefficient of the extended description. The viewer looks at the displayed video, selects a sound whose volume is to be adjusted, and performs an adjustment operation using a volume adjustment button or the like. A channel number corresponding to an audio event, which is input from a viewer through a remote controller or the like, and a volume adjustment instruction signal are input to the composite output instruction unit 207. The composite output instructing means updates the video display table of FIG. 4 sent to the output video switching means and updates the downmix table sent to the output audio synthesizing means according to the channel number and the volume adjustment instruction signal, thereby finally outputting the data. The voice that is played can be updated. Other operations are the same as those in the first embodiment.

(Embodiment 3) FIG. 3 is a block diagram showing a digital broadcast receiving apparatus according to a third embodiment of the present invention. It is assumed that a multi-channel audio signal to which a channel is assigned for each audio event is downmixed at the receiver, but it is necessary to change the downmix method depending on the form of the audio presenting means output from the receiver. is there. For example, if each audio event receives audio assigned to three channels, and the output of the receiver is an L-channel, R-channel, and center-channel configuration, to perform an optimal downmixing, the following equation is used. Calculation formulas such as 10), (11), and (12) are required. The downmixed audio is Mo (o = L, R,
C), the downmix coefficient is kon (o = L, R, C,
n = 1, 2, 3, 4). ML = (kL1x1ch) + (kL2x2ch) + (kL3x3ch) (10) MR = (kR1x1ch) + (kR2x2ch) + (kR3x3ch) (11) MC = (kC1x1ch) + (kC2x2ch) + (kC3x3ch) In order to perform a proper downmix, it is necessary to create a downmix table for multi-channel output as shown in FIG. In addition, this table requires the number of patterns of the output audio form. As an example, the audio output form
If the L channel, the R channel, the center channel, the surround L channel, and the surround R channel are used, a downmix table including seven output modes is required as shown in FIG.

FIG. 13 shows a description example of an extended event descriptor for transmitting all downmix coefficients. FIG.
The number below Loop of 3 is the loop number of the largest item, and only in the first loop, the specific audio content assigned to the channel is shown in the extended description, and is not described in the second and subsequent loops. The downmix coefficient is inserted into the item description column for each loop in a form corresponding to the input channel. The Loop number corresponds to the Item number in FIG. 12, and the downmix table in FIG. 12 can be created from the extended event descriptor.

The output mode of the receiver is previously selected by the viewer with reference to FIG. 11 in the composite output instruction means 307, and the mode number is stored. The combining output instruction means 307 associates the stored mode with the table number of the downmix table in FIG.
A downmix table 0 is created and output to the output video switching means 309 and the output audio synthesis means 305.
Other operations are the same as those in the second embodiment.

[0030]

As a viewer's need for conventional audio broadcasting, there is a demand to adjust only a specific audio in a program. For example, if you find it difficult to hear the sound of a particular character in a program with multiple characters,
This means that the volume of only the voice of the character is increased, or when the volume of the BGM is felt to be loud, only the volume of the BGM is reduced. However, when there are a plurality of audio events in one audio signal, for example, when there are a plurality of characters, it is very difficult to extract only an audio signal of a specific person.

Digital broadcasting using an MPEG system or the like has enabled multi-channel broadcasting, and it has become possible to broadcast a plurality of audio channels for one program. However, conventional multi-channel audio broadcasting has specifications that depend on the audio output form of the receiver, and audio signals corresponding to the L channel, R channel, center speaker, surround speaker, and the like are assigned to each channel.

In the present invention, the transmission is performed according to a different specification from the conventional one while utilizing the existing multi-channel broadcasting system. Using a signal to which an audio channel is assigned for each audio event, a calculation formula for downmixing them is newly introduced, and a downmix coefficient for each channel is transmitted. The receiver can use these to perform downmixing according to the output format, not only ensuring the same audio output as before, but also controlling each audio event easily by controlling each channel. did it.

As a result, when performing a multi-channel broadcast assigned to each audio event, information as to what kind of audio is assigned to which channel as additional information can be obtained by inserting information into the program arrangement information. Adjustment of audio parameters for each audio event that was not possible,
A receiving device that can be easily changed without being conscious of multi-channel sound can be provided. Further, by defining an output channel pattern and including a downmix coefficient corresponding to the output mode in the additional information, it is possible to create a downmix sound optimized for the output form.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a digital broadcast receiving apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a digital broadcast receiving apparatus according to a second embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of a digital broadcast receiving apparatus according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a video display table output from a composite output instruction unit to an output video switching unit in the second and third embodiments of the present invention.

FIG. 5 is a diagram showing a downmix table output to an output voice synthesizing means assumed in the first and second embodiments of the present invention;

FIG. 6 is a diagram showing an audio component descriptor in which component information of an input audio is described in the first, second, and third aspects of the present invention.

FIG. 7 is a diagram showing contents of a component type in an audio component descriptor in which component information of an input audio is described in the first, second, and third aspects of the present invention.

FIG. 8 is a diagram showing an extended event descriptor for inserting a downmix coefficient in the first, second and third embodiments of the present invention;

FIG. 9 is a diagram showing a description example regarding downmix audio shown in an extension descriptor in the second and third embodiments of the present invention.

FIG. 10 is a diagram showing a downmix table output to an output voice synthesizing unit in the third embodiment of the present invention.

FIG. 11 is a diagram showing a downmix table showing downmix coefficients of all output channel modes in the third embodiment of the present invention.

FIG. 12 is a diagram illustrating a configuration of a third embodiment of the present invention.
Diagram showing description example of extension descriptor

FIG. 13 is a diagram showing a mode of an output channel of the receiver in the third embodiment of the present invention.

[Explanation of symbols]

 100, 200, 300 Receiving means 101, 201, 301 Signal separating means 102, 202, 302 Tuning instruction means 103, 203, 303 Video signal reproducing means 104, 204, 304 Audio signal reproducing means 105, 205, 305 Additional information processing Means 106, 206, 306 Output voice synthesizing means 107, 207, 307 Synthetic output instructing means 108, 208, 308 Voice signal presenting means 109, 209, 309 Video signal presenting means 210, 310 Output video switching means

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Claims (3)

[Claims] 1. A digital broadcast receiving apparatus for digitizing main information and additional information, and receiving a packetized and multiplexed digital broadcast broadcast signal.
When the audio signal of the main information is composed of a plurality of audio channels, synthesis parameters are given to each audio channel so that a plurality of channels can be synthesized and a new audio channel can be synthesized by the receiver. Receiving means for receiving a digital broadcast signal inserted into the receiving means, signal separating means for filtering and separating an audio signal, a video signal, and an additional information signal specified by a tuning instruction means from a signal input from the receiving means, A video signal reproducing unit that decodes and reproduces the video signal separated by the signal separating unit and outputs it to the video signal presenting unit, and decodes and reproduces the audio signal separated by the signal separating unit and outputs it to the output audio synthesizing unit. Audio signal reproducing means, additional information processing means for decoding the additional information separated by the signal separating means, Processing the information related to the combined output of a plurality of voices out of the additional information decoded by the additional information processing means, and synthesizing output instructing means for instructing a combined output processing of a plurality of voices; and a plurality of channels input from the audio signal reproducing means. A digital broadcast receiving apparatus comprising output voice synthesizing means for synthesizing an audio signal into a one-channel audio signal according to a synthesizing instruction signal from the synthesizing output instruction means and outputting the synthesized audio signal to an audio signal presenting means. 2. The digital broadcast receiving apparatus according to claim 1, wherein the audio signal of the main information includes a plurality of audio channels, and receives the digital broadcast signal in which the content of each audio channel is inserted into additional information. Output video switching means for displaying specific audio contents for each audio channel to a viewer when performing synthesis processing of a plurality of audios by means, and synthetic output for selecting audio from the viewer and adjusting the volume for each channel 2. The digital broadcast receiving apparatus according to claim 1, further comprising an instruction unit. 3. The digital broadcast receiving apparatus according to claim 1, wherein the mode of the channel of the audio to be output is input to the synthesis output instructing means, whereby the output synthesizing means converts and outputs the audio to two or more channels. 3. The receiving device for digital broadcasting according to 3.