JPS6166487A - Switching system for video signal - Google Patents

Abstract

PURPOSE:To detect a speech channel whose count result is maximum and constant and send an output through switching by comparing the level of each speech signal at every constant period and counting how many times a maximum level exceeds the constant value for every channel. CONSTITUTION:Speech signals inputted from speech input signal terminals 1a-1d have amplitude variation smoothed by smoothing circuits 2a-2d and sampled values are obtained by sampling circuits 3a-3d at every constant period T1. The sampled values lA-lD of the respective speech signals are applied to a level comparing circuit 4 to make a level comparison among respec tive channels, detecting a sampled value having the maximum level. Then, the maximum level for the maximum-level channel or a level 0 for other channels is inputted to level decision circuits 5a-5d to send '1' to counters 6a-6d when the level exceeds some level. When the value of the maximum level is found smaller than the constant value by the level decision making, it is ignored, so the influence of a low-level noise is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field to which the invention pertains) The present invention relates to a method for selecting one video signal from among a plurality of ground video signals in a system such as a multipoint video conference between a plurality of points. The present invention relates to a video signal switching method that performs switching.

(Prior Art) Conventionally, in this type of switching system, a method has been considered in which the levels of each audio signal are compared and the video signal corresponding to the audio signal with the highest level is selected and switched. This is based on the idea that, for example, in a multi-point video conference, the point transmitting the highest level audio signal is regarded as the point where the speaker is currently speaking, and the video of that point is selected. However, in the conventional method, it is difficult to use the voice during a certain pause period during the speech of the participant or during a period when the voice level is low.

Video switching occurs even when there is a voice or noise for an extremely short period of time from another location, which generally results in frequent switching, which has the disadvantage of being extremely bothersome to the viewer.

(Purpose of the invention) The present invention provides video processing based on conventional audio level comparison.

To overcome the drawbacks of the switching method, the amplitude changes of each audio signal are smoothed prior to level comparison.

Comparing levels at regular intervals T□ and detecting only those whose maximum level as a result of this comparison is equal to or higher than a certain value;
counting the number of times the maximum level is equal to or greater than a predetermined value for each audio signal channel at a predetermined period T2, and detecting an audio signal channel for which the counting result is maximum and equal to or greater than the predetermined value;
The present invention attempts to provide a video signal switching method that selects and switches the corresponding video signal,
The drawings will be explained in detail below.

(Structure and operation of the invention) FIG. 9 is a block diagram of an embodiment showing the structure of a switching control circuit according to the present invention, and shows a case where one of four video signals is selected and switched.

la, lb, lc, and Id are audio input signal terminals, respectively, and 2a.

2b, 2c, 2d are smoothing circuits, 3a*3b
t3c+3d is a sampling circuit, 4 is a level comparison circuit, 5a
, 5b, 5c, and 5d are level determination circuits, 6a, 6b, 6c, and 6d are counter circuits, 7 is a count comparison circuit, 8 is a timer, 9 is a count value determination circuit, IO is a switching determination circuit, lla, llb, llc and 11d respectively indicate switching determination output terminals, and "Ajm, t
r, , ao are the input sample value levels to the nine-level comparator circuit 4, and nA+n1ync+n11 is the counter 6a.

Outputs 6b, 6c, 6d, n is the output of the counting comparison circuit 7 and is the maximum value among the outputs nA+nl+nc+nO,
A, B, C, and D are the outputs of the counting comparison circuit 7, and the output is nA+n.
A signal indicating which one of l*nc+nD is the largest, 2 is the output of the count value determination circuit 9, and A', B'CI', and DI are output signals of the switching determination circuit.

Next, the operation will be explained based on FIG.

The audio signals input from each audio input signal terminal 1a=1d are smoothed for amplitude changes in each smoothing circuit 28-2d. This smoothing circuit is realized by an analog low-pass filter when the input signal is in analog format;
If the input signal is in digital format, a digital low-pass filter (e.g. averaging multiple samples before and after)
realized by This smoothing process suppresses instantaneous peak components of the signal amplitude and impulsive noise components.

Sample values of the smoothed audio signal are taken out at regular intervals T1 in sampling circuits 38 to 3d. If the input signal is in analog format, this circuit is realized by a normal sampling circuit with a period T□, and if it is in digital format, it is realized by a circuit that thins out the input samples and extracts one sample every period T1.

In this way, the sample value QA-6 of each audio signal extracted every fixed period T! The signal is then added to the level comparison circuit 4, where level comparison is performed between each channel and the sample value of the maximum level is detected.

The inputs to the next level determination circuits 5a to 5d are set to the maximum level for the maximum level Chapol, and to the 0 level for the other channels.

For example, when QA is at the maximum level, the level judgment circuit 5
The input to a is O, and the inputs to 5b to 5d are O.

Each level judgment circuit compares the input level to it with a predetermined threshold L (> O), and if the input level is ≧L, "1" is added to the next counter, and the input level is set to 1. If so, send tt O+y. For example, when the current is at the maximum level, the level judgment circuit 5a compares IIA with the threshold value, and if QA≧L, the output of the level judgment circuit 5a is 1'', 11. (If it is L, the output of 5a is The output is “
0''. In this case, the level determination circuits 5b to 5
Since the input to d is 0, O<L, and the outputs of 5b to 5d are all "0'".

With this level judgment, even if the maximum level is reached as a result of level comparison, if the maximum level value is less than a certain value, it will be ignored. The effects of noise, etc. can be removed.

Each of the counter circuits 6a to 6d has a level determination circuit 5.
Input II I I+ sent from 8 to 5d with period T
Count over 2 (>T□). That is, the number of times the level comparison result is maximum and the maximum value is equal to or greater than a certain value is counted for each channel by the period T2, and each count value is set as nAln1lnclnD.

The count value nA''nQ, which is the output of the counters 6a to 6d, is sent to the next count comparison circuit 7, where the count value nA''n.

Comparisons are made between each other, and the maximum value n is calculated every 5 cycles T2.

is detected. Outputs A, B, C, and D of the count comparison circuit 7 are II I II for the channel with the maximum count value as a result of the count comparison described above, and 71047 for the others.
shall be.

Also, the maximum value among the counted values nA=n is calculated by the counting comparison circuit 7.
The output is output as nM. For example, if the count value nA is the maximum as a result of comparison, A=“1″′.

B=C=D=“O” lnM=nA. These outputs A, B, C.

D is sent to the next switching judgment circuit 10, and output n is sent to the count value judgment circuit 9.

The above operations of the counter and the count comparison circuit 7 are repeated at a period T2. This control is performed by a timer 8. That is, the reset and start of the counter and the operation of the count comparison circuit are controlled in the T2 cycle by instructions from the timer.

The count value judgment circuit 9 compares the maximum value n1 with a predetermined threshold value N, and if n≧N, Z=“1”, nM
<N, Z=II OII is output and sent to the switching determination circuit 10.

In addition to this Z, the outputs A, B, C, and D from the count comparison circuit 7 are input to the switching judgment circuit IO, and as already mentioned, only one of A, B, C, and D is "1". , all the rest “
0''.Switching determination control is performed by the following algorithm.

■If Z=II OII, no switching is performed.

■If 2="1", 111 out of A, B, C, D If
Select and switch the channel.

■ means that the maximum count value n during a certain period T2 is a constant value N
This indicates that switching is not performed when the value is less than .

As a result, even if short-term vocalizations or noises occur on other channels during silent or paused states,

Therefore, frequent switching can be prevented.

For example, the specific processing in the switching determination circuit 10 is as follows.
2 and A, B, C, and D may be calculated.

That is, A' = A-Z, B' = B-Z, C' =
Find C-Z, D' = D-Z and connect terminals 11a to lid
Output to.

For example, if nv=nA;ii:t then Z=L
dllll, A = III.

Since B=C=D=“O”, A'=1'1", B'
=C'=D' =“O”. Also - nv=nA
If <L then Z=“0”A=It l II.

A=B=C=“O” so A'=B'=C'=D
'=“0”.

Switching of video signals is performed using these A'' to D'. That is, if any of A' to D' is 1'', the video signal corresponding to that audio signal channel is selected. Switch. Note that if the corresponding video signal has already been selected at the time of switching, that state may be maintained. A'~D'
If any of them is It_O11, switching is not performed and the state already selected at that time is maintained.

(Effects) As explained above, one aspect of the present invention is to smooth signal amplitude changes prior to level comparison, and to smooth out changes in signal amplitude when the maximum level detected as a result of level comparison between each channel is equal to or higher than a certain value. The number of occurrences of the maximum effective level is set every certain period.

Count each channel, compare the counting results among each channel, detect the channel that gives the maximum count value, and only those whose maximum count value is greater than a certain value are considered valid, and the corresponding The current video signal is selected and switched.

Due to the configuration and operation described above, it is possible to prevent undesirable frequent switching due to short-term vocalizations from others, noise, etc. during a pause period during speech or in a silent state, etc.
A stable video switching method can be realized. Therefore 1
The present invention is extremely effective when applied to switching between output images from a plurality of cameras in a multipoint video conference room.

[Brief explanation of drawings]

The figure is a block diagram of an embodiment showing the configuration of a switching control circuit according to the present invention. la, lb, lc, ld - audio input signal terminal, 2a, 2
b, 2c. 2d...Smoothing circuit, 3a, 3b, 3c, 3d...
- Sampling circuit, 4...Level comparison circuit, 5a,
5b, 5c, 5d...level determination circuit, 6a, 6
b, 6c, 6d...counter circuit, 7...
- Count comparison circuit, 8...Timer, 9...Count value judgment circuit, 10...Switching judgment circuit. 11a, llb, Ilc, 1ld-switching determination output terminal,
'A+1'R+Qc, io... Kugata sample value level to the level comparison circuit, nA+n++ync+no "'
Counter circuit output, n, ... Output of count comparison circuit, maximum value among n^, nl, nctnD, Z... Output of count value judgment circuit, A, n, C, D ... Count comparison How the circuit comes out, A', 8"c', o'... How the switching judgment circuit comes out. Patent applicant Nippon Telegraph and Telephone Corporation! 28 Brother!

Claims (1)

[Claims] In communication using a plurality of video signals and a plurality of audio signals corresponding to each video signal, the method selects and switches one video signal from the plurality of audio signals based on the level of each audio signal. Then, the first means for smoothing the amplitude change of each audio signal, the sample values of each smoothed audio signal are taken out at regular intervals T_1, the levels are compared between each sample value, and the level is calculated. a second means for detecting an audio signal channel in which the maximum level is the maximum and the maximum level is equal to or higher than a certain value; comprising means for counting each signal channel, comparing the counted values between each channel, and detecting the audio signal channel whose counted value is the maximum and its maximum counted value,
A video signal switching method characterized in that the video signal channel corresponding to the audio signal channel is switched at each of the predetermined periods T_2 only when the maximum count value is equal to or greater than a predetermined value.