JPH11168706A - Voice delay control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ovation a voice delay control system in which sending back delay information from a receiver side to a transmitter side is not necessary. SOLUTION: Separated image data (h) are decoded by an image decoding circuit 21 of a reception section 2, given to an image D/A converter circuit 20, where the data are converted into an analog image signal (j) and it is outputted to an external device such as a monitor. Based on decoded data (k), a deciding rate detection circuit 22 detects a decoding rate, a reception delay time control circuit 23 detects a reception delay time set in advance and provides an output of the detected delay time to a reception delay circuit 24. Voice data (i) are given to the reception delay circuit 24, where the data (i) are delayed just by the reception delay time detected by the reception delay time control circuit 23. A digital voice signal (m) converted by a voice decoding circuit 26 is converted into an analog voice signal (n) at a voice D/A converter circuit 25 and outputted to an external device such as a loudspeaker.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an audio delay control system, and more particularly, to an audio delay control system in a video conference system.

[0002]

2. Description of the Related Art Conventionally, an image CODEC (codec; coder / decoder device) used in a video conference system.
Is designed to vary the compression ratio of an image in accordance with the transmission speed of a transmission path to be used, so that the compression processing time of an image varies. Therefore, the transmission of an image signal is generally
This delays the transmission of the audio signal, and the delay time of the image signal varies depending on the transmission path used.

For example, Japanese Standard Television System (NT)
SC) to transmit a moving image signal of 4.2 MHz
Requires the transmission band of the transmission path. On the other hand, the telephone line having the narrowest transmission band has only the transmission band of 3 kHz. Therefore, the image signal in the video conference system minimizes the number of scanning lines, the number of image transmissions per second is extremely small (quasi-moving image), and the image signal is greatly compressed. May be as long as 0.5 seconds, for example.

It is known that a difference in transmission delay time between an image signal and an audio signal causes a sense of incongruity. Generally, a delay circuit is inserted in a transmission path of the audio signal to synchronize the time between the image signal and the audio signal. To reduce discomfort. The time synchronization between the image signal and the audio signal is called lip sync (meaning that the audio is synchronized with the movement of the lips).

[0005] The required delay amount of the delay circuit of the audio signal transmission line for obtaining the lip sync differs depending on the transmission speed (transmission band) of the transmission line. Therefore, the amount of delay of the audio delay circuit needs to be adjusted (switched) as the transmission path changes.

Japanese Patent Application Laid-Open No. 2-82887 discloses a method of detecting a delay time of an audio signal, in which delay information of a transmitting station and delay information of a receiving station are calculated, and the information is transmitted from the receiving side to the transmitting station apparatus. And a method of varying the amount of delay of the audio delay circuit on the transmission side at the transmission side.

[0007]

Problems to be Solved by the Invention Japanese Patent Laid-Open No. 2-82887
In the case of the proposal described in Japanese Unexamined Patent Publication, there is a problem that it is necessary to send back delay information from the receiving side to the transmitting side. In addition, when there are a plurality of receiving sides, there is a problem that cannot be dealt with.

[0008] It is an object of the present invention to provide a voice delay control system in which there is no need to send back delay information from a receiving side to a transmitting side.

[0009]

SUMMARY OF THE INVENTION An audio delay control system according to the present invention is an audio delay control system for a video conference system comprising at least a pair of image codecs for mutually transmitting and receiving an image signal and an audio signal via a transmission line. Wherein the receiving side includes a decoding rate detecting means for detecting a decoding rate of the received image signal, and a receiving voice delay means for delaying the received voice signal by a time corresponding to the detected decoding rate. It is characterized by the following.

[0010] Further, the transmitting side includes coding rate detecting means for detecting a coding rate of a transmission image signal, and transmission voice delay means for delaying a transmission voice signal by a time corresponding to the detected coding rate. It is characterized by including.

Another audio delay control system according to the present invention is an audio delay control system for a video conference system comprising at least a pair of image codecs for mutually transmitting and receiving an image signal and an audio signal via a transmission line, On the transmitting side, in addition to the delay time according to the encoding of the transmission image signal, the total delay time of the video signal is also stored in advance in consideration of the delay time due to the decoding of the reception image signal on the reception side. And delay means for delaying the transmission voice according to the storage delay time of the storage means.

Still another audio delay control system according to the present invention is an audio delay control system for a video conference system comprising at least a pair of image codecs for mutually transmitting and receiving image signals and audio signals via a transmission line. On the receiving side, in addition to the delay time according to the encoding of the received image signal, the delay time of the total video signal in which the delay time due to the decoding of the transmitted image signal at the transmitting side is also stored in advance. It is characterized by including storage means, and delay means for delaying a received voice signal in accordance with the storage delay time of the storage means.

The operation of the present invention is as follows. The video conference system according to the present invention automatically adjusts the audio delay time on the receiving side or the transmitting side according to the transmission speed of the transmission path to be used.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of an image CODEC of an audio delay control system according to the present invention. As shown in FIG. 5, a video conference system related to the present invention includes a plurality of images CODEC, for example, 6 to 9 and a public line (transmission line) 5 connecting the images CODEC.

The image CODEC, which is the main component of the audio control system according to the present invention, is sometimes used as a transmitting side (station) and sometimes as a receiving side (station) in a video conference system, but is basically the same. Therefore, only one is shown in FIG.

FIG. 1 shows an image CODE according to the present invention.
The transmission unit 1 of C receives an image input signal a from an image camera or the like.
A / D conversion circuit 10 for converting a digital image signal c into a digital image signal c, an image encoding circuit 1 for compressing the digital image signal c into a transmission image signal e corresponding to the transmission speed of the transmission path 5
1.

A sound A / D for converting a sound input signal b from a microphone (lophone) or the like into a digital sound signal d.
A conversion circuit 15, a voice coding circuit 16 for converting the digital voice signal d into a transmission voice signal f corresponding to the transmission path 5,
Transmission delay circuit 14 for providing necessary delay to transmission audio signal f
It consists of.

Further, a coding rate detecting circuit 1 for detecting coding rate (compression rate) information g of the image coding circuit 11
2. A transmission delay time control circuit 13 for extracting a necessary delay time of an audio signal from a ROM (Read Only Memory) 17 based on an encoding rate and controlling a transmission delay circuit 14.

The receiving section 2 includes an image decoding circuit 21 for decoding the received image signal h into a digital image signal p, and an image D / A conversion circuit 20 for converting the digital image signal p into an image output signal j for outputting to a monitor or the like. It consists of.

Further, a reception delay circuit 24 for giving a necessary delay to the reception audio signal i, an audio decoding circuit 26 for decoding the output of the reception delay circuit 24 into a digital audio signal m, and outputting the digital audio signal m to a speaker or the like. Audio output signal n
The audio D / A conversion circuit 25 converts the audio data into a digital signal.

Further, a decoding rate detecting circuit 2 for detecting coding rate (compression rate) information k of the image decoding circuit 21
2. A reception delay time control circuit 23 for extracting a necessary delay time of the audio signal from the ROM 27 based on the encoding (decoding) rate and controlling the reception delay circuit 24.

The transmission image signal e and the transmission audio signal b of the transmission section 1 are transmitted via a multiplexing / demultiplexing circuit 3 for multiplexing transmission signals and separating reception signals, a transmission line interface 4 for interfacing with a transmission line 5, and a transmission line 5. Image of the receiving side
Transmitted to C.

The received image signal h and the received audio signal i received from the image CODEC on the transmitting side via the transmission line 5, the transmission line interface 4 and the multiplexing / demultiplexing circuit 3 are:
It is input to the receiving unit 2.

Further, as shown in FIG. 2 and FIG. 3, respectively, the receiving side audio delay control circuit (reception delay circuit 24, reception delay time control circuit 23, decoding rate detection circuit 22),
Alternatively, the transmission-side audio delay control circuit (the transmission delay circuit 14,
Transmission delay time control circuit 13, coding rate detection circuit 1
There may be a circuit configuration in which 2) is omitted.

In general, in an image CODEC used for a video conference system or the like, an image compression processing time varies depending on a transmission speed of a transmission path 5 to be used, and the compression processing time is higher as the degree of compression is higher (lower bit rate). become longer. For this reason, the processing time is different from that of the audio system in which the compression processing time is short, resulting in a time lag between the image and the audio.

The embodiment of the present invention shown in FIG.
In the general video conference system shown in FIG.
Detects the coding rate value and decoding rate value of the image in the DEC, sets the audio transmission delay time and the reception delay time from the detection result, and synchronizes the image and audio (lip sync).
Can be completed automatically.

A system according to another embodiment of the present invention in which a delay time is set only on the transmission side of the image CODEC shown in FIG. 2 is transmitted from one transmission station such as a broadcasting system shown in FIG. This is effective for a system for transmitting to an unspecified number of receiving stations. Similarly, a system according to yet another embodiment of the present invention for setting a delay time only on the receiving side of the image CODEC shown in FIG. 3 includes a large number of transmitting stations like a monitoring system shown in FIG. This is effective for a system that receives a transmission signal from a single receiving station.

The transmission delay time settings 61 and 71 are set to RO
This is performed by reading from M17. The reception delay time settings 62, 72 to 92 are performed by reading from the ROM 27.

The operation of the embodiment of the present invention will be described with reference to FIG. The transmitting side detects the coding rate value coded by the image coding circuit 11 by the coding rate detection circuit 12 (for example, 64k, 128k, 384k, 768).
k, 1536 kbps, etc.), and the transmission delay time control circuit 13 in the next stage gives the transmission delay circuit 14 a voice delay amount corresponding to a predetermined coding rate. The transmission delay circuit 14 delays the audio signal by a predetermined audio delay time and transmits the signal to the transmission line 5. On the receiving side,
It has a similar configuration.

Image CO used for video conference system
The DEC has a transmitting unit 1 and a receiving unit 2. The transmitting unit 1
An analog image signal a and an analog audio signal b are input from outside. The input analog image signal a is the image A /
It is converted into a digital image signal c in the D conversion circuit 10. The converted digital image signal c is encoded in the image encoding circuit 11, and the encoded image data e is input to the multiplexing / demultiplexing circuit 3.

Further, the coding rate detecting circuit 1 uses the coded data g coded by the image coding circuit
In step 2, the coding rate value is detected. Based on the detected coding rate value, the transmission delay time control circuit 13 detects the transmission delay time (see FIG. 4) stored in the ROM 17 and outputs it to the transmission delay circuit 14.

On the other hand, the input analog audio signal b is converted into a digital audio signal d in the audio A / D conversion circuit 15. The converted digital audio signal d is encoded in the audio encoding circuit 16, and the encoded audio data f is input to the transmission delay circuit 14. The transmission delay circuit 14 delays the voice only by the transmission delay time detected by the transmission delay time control circuit 13, and the multiplexed / demultiplexed circuit 3 multiplexes and transmits the multiplexed signal to the transmission line interface 4.

In the receiving section 2, the multiplexing / demultiplexing circuit 3 separates the multiplexed data from the transmission line interface 4 into image data h and audio data i. The separated image data h is decoded by the image decoding circuit 21, and the decoded digital image signal p is input to the image D / A conversion circuit 20. The digital image signal p input to the image D / A conversion circuit 20 is converted into an analog image signal j and output to an external device such as a monitor.

The decoded data k is input to a decoding rate detection circuit 22. The decoding rate detection circuit 22 detects a decoding rate value. Based on the detected decoding rate value, the reception delay time control circuit 23 detects a preset reception delay time (see FIG. 4) stored in the ROM 27 and outputs it to the reception delay circuit 24.

On the other hand, the audio data i separated by the multiplexing / demultiplexing circuit 3 is input to the reception delay circuit 24. The reception delay circuit 24 delays the sound only by the reception delay time detected by the reception delay time control circuit 23. Receiving delay circuit 24
The data delayed by the voice signal is converted by the voice decoding circuit 26 into a digital voice signal m. The converted digital audio signal m is converted into an analog audio signal n by the audio D / A conversion circuit 25 and output to the outside such as a speaker.

FIG. 4 shows an example of the delay time setting value. FIG.
The delay times shown in FIG.
And a value corresponding to the transmission rate is read, and the read delay time is delayed by voice.

Next, another embodiment of the present invention will be described with reference to FIGS. For a standardized image CODEC from different manufacturers, it is necessary for the transmitting side and the receiving side to adjust the audio delay separately, but in the case of the same manufacturer, the delay time of the transmitting / receiving side is estimated based on the coding rate. Therefore, the apparatus configuration can be further simplified by performing the audio delay processing only on the transmission / reception side or only on the reception side.

FIG. 2 is a block diagram of the embodiment of the present invention shown in FIG.
In this configuration, the reception delay circuit 24 and the ROM 27 are deleted.
This is effective for a one-point to multi-point system such as the broadcasting system shown in FIG.

In the example of FIG. 2, the total signal delay time is calculated in advance by taking into account the delay time due to the decoding of the received image at the receiving side, in addition to the delay time due to the encoding of the transmitted image at the transmitting side. It is stored in the ROM 17.

Similarly, FIG. 3 shows a configuration in which the coding rate detection circuit 12, the transmission delay time control circuit 13, the transmission delay circuit 14, and the ROM 17 are deleted from the embodiment of the present invention shown in FIG. This is effective for a multi-point → one-point system such as the monitoring system shown in FIG.

In this example, on the receiving side, the total signal delay time is calculated by taking into account the delay time due to the decoding of the transmission image at the transmission side in addition to the delay time due to the encoding of the reception image at the reception side. It is stored in the ROM 27 in advance.

[0043]

As described above, the present invention has an effect that the audio delay time can be automatically set in accordance with the transmission speed used in operating the video conference system. That is, conventionally, the audio delay time previously determined according to the transmission speed to be used is manually set, but such an operation is not required.

Further, even if the transmission speed is changed depending on the conference mode, the audio time is set at the same time, so that a conference in which the image and the audio are synchronized (lip sync) without any discomfort can be realized at any time. .

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of another embodiment of the present invention.

FIG. 3 is a block diagram of still another embodiment of the present invention.

FIG. 4 is an explanatory diagram of a required audio delay time with respect to a coding (decoding) rate stored in a ROM.

FIG. 5 is an explanatory diagram of a video conference system.

[Description of Code] 1 Transmitter 2 Receiver 3 Multiplexing / Demultiplexing Circuit 4 Transmission Line Interface 5 Transmission Line 10 Image A / D Conversion Circuit 11 Image Encoding Circuit 12 Encoding Rate Detection Circuit 13 Transmission Delay Time Control Circuit 14 Transmission Delay Circuit 15 Audio A / D conversion circuit 16 Audio encoding circuit 17, 27 ROM 20 Image D / A conversion circuit 21 Image decoding circuit 22 Decoding rate detection circuit 23 Reception delay time control circuit 24 Reception delay circuit 25 Audio D / A Conversion circuit 26 Audio decoding circuit

Claims (6)

[Claims] An audio delay control system for a video conference system comprising at least a pair of image codecs for mutually transmitting and receiving image signals and audio signals via a transmission path, wherein a receiving side decodes a received image signal. An audio delay control system comprising: a decoding rate detecting means for detecting a decoding rate; and a receiving audio delaying means for delaying a received audio signal by a time corresponding to the detected decoding rate. 2. A transmission side comprising: a coding rate detecting means for detecting a coding rate of a transmission image signal; and a transmission voice delay means for delaying a transmission voice signal by a time corresponding to the detected coding rate. The audio delay control system according to claim 1, further comprising: 3. The reception audio delay unit includes a memory unit in which a time according to the decoding rate is stored in advance.
3. The audio delay control system according to claim 1, wherein the received audio signal is delayed according to the stored time. 4. The transmission audio delay unit includes a memory unit in which a time corresponding to the encoding rate is stored in advance.
4. The audio delay control system according to claim 2, wherein the transmission audio signal is delayed according to the stored time. 5. An audio delay control system of a video conference system comprising at least one pair of image codecs for mutually transmitting and receiving image signals and audio signals via a transmission path, wherein a code of a transmission image signal is transmitted on a transmission side. Storing means for preliminarily storing a total delay time of a video signal in consideration of a delay time due to decoding of a received image signal on the receiving side, in addition to a delay time corresponding to the decoding, and a storage delay of the storage means. A delay means for delaying a transmission voice signal according to time. 6. An audio delay control system of a video conference system comprising at least a pair of image codecs for mutually transmitting and receiving image signals and audio signals via a transmission path, wherein a code of a received image signal is received on a receiving side. Storing means for preliminarily storing a total delay time of a video signal in consideration of a delay time due to decoding of a transmission image signal on the transmission side, in addition to a delay time corresponding to the conversion, and a storage delay of the storage means. A delay means for delaying a received voice signal in accordance with time.