JPH03101490A - Method and apparatus for picture information transmission - Google Patents

Abstract

PURPOSE:To prevent extreme increase in a code quantity with refresh by expressing a refresh line number or a refresh picture element number with less additional information, multiplexing the information onto a picture signal and sending the result. CONSTITUTION:A coder consists of a refresh control circuit 1, a subtractor 2, a quantizer 3, an adder 4, an in-frame prediction device 5, an inter-frame prediction device 6, a switch 7 and a variable length coder 8. In the case of applying periodic refresh, n-line each or n-picture element each of refreshment is implemented and the refresh line number or the picture element number is multiplexed onto a coding signal and the result is sent. Thus, huge increase in the code quantity due to refresh is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image information transmission method and apparatus for rewriting the screen of a moving image signal.

[Conventional technology]

FIG. 6 shows a video conference system using a conventional encoding device for a low bit rate moving picture signal such as 64 kilobits.

In this system, when an error occurs due to a failure in the transmission path, the decoder side requests the encoder to rewrite the screen using another transmission path. For example, suppose that stations A and B are holding a two-way TV conference as shown in FIG. Assume that a transmission path error occurs while transmitting the encoded image signal from station A to station B. In this case, the image signal decoded by the decoder of the B station will be distorted due to the influence of the transmission path error.

At this time, the decoder detects an error and generates a screen rewriting request signal. A description of the error detection method will be omitted here. The screen rewriting request signal is multiplexed with the encoded image signal of the B station by the encoder of the B station and sent to the A station. Then, the decoder of the A station separates the screen rewriting request signal sent from the B station during decoding and supplies it to the encoder of the A station.

When the encoder of station A receives the screen rewriting request signal,
Encoding was performed in screen rewriting mode and a new image signal was transmitted to station B.

[Problem to be solved by the invention]

The above-mentioned conventional low bit rate image information transmission method and device such as 64 kilobits has a very small transmission capacity, so rewriting (refreshing) the screen is done through the transmission path;
Only when an error occurs and the image on the decoder side is distorted, the screen is rewritten using the method described above. However, in the case of one-sided feed for purposes such as monitoring, the screen rewriting request signal cannot be sent from the decoder to the encoder, so the screen rewriting method described above cannot be used. Therefore, when an image information transmission apparatus with a low bit rate such as 64 kilobits is used in one-sided transmission for purposes such as monitoring, it is necessary for the encoder to automatically perform refreshing by some method.

[Means to solve the problem]

The image transmission method of the first invention of the present application is low bit rate video encoding that performs encoding on a screen-by-screen basis using inter- and intra-screen correlation, and refreshes the screen in n-line or 5n-pixel units. A coding method for expressing the refresh line number or refresh pixel number with a small amount of additional information and multiplexing it into an image signal for transmission, and detecting a refresh area from the multiplexed refresh line number or refresh pixel number. and then switches the predictor based on the detected result.

Further, the image information transmission device of the second invention of the present application is a device that encodes a moving image signal using correlation between screens and within a screen, and includes an input moving image signal and a prediction signal supplied from a selection means. means for obtaining a prediction error signal from the local decoded signal; means for quantizing the prediction error signal; means for obtaining a local decoded signal from the output of the quantization means and a prediction signal supplied from the selection means; an intra-frame predictor that generates an intra-predicted signal, an inter-frame predictor that generates a 7-frame inter-predicted signal from the locally decoded signal, and which of the output of the inter-frame predictor and the output of the intra-frame predictor; a selection means for selecting one of them; a refresh control means for giving an instruction to the selection means and the variable length encoder to refresh a predetermined area at a predetermined period; and variable length encoding means for multiplexing refresh line numbers or refresh pixel numbers given from the refresh control means.

Further, the image information transmission device of the third invention of the present application is a decoding device that decodes encoded signals using inter-screen and intra-screen correlation, and the image information transmission device is a decoding device that decodes encoded signals using inter-screen and intra-screen correlation. variable length decoding means which restores the signal to the original signal, separates the multiplexed refresh line number or refresh pixel number and supplies it to the refresh control means; and output of the variable length decoding means and selection means. means for obtaining a decoded signal from an output prediction signal; an intraframe predictor that generates an intraframe prediction signal from the decoded signal; an interframe predictor that generates an interframe prediction signal from the decoded signal; and the interframe prediction. selection means for selecting either the output of the intra-frame predictor or the output of the intra-frame predictor according to instructions from the refresh control means; and refresh control means for giving a selection instruction to the selection means.

[Effect]

In a video encoding device with a low bit rate such as 64 kilobits, since the transmission capacity is very small, it is necessary to reduce side information other than the encoded image signal as much as possible, so encoding is performed in units of screens and synchronization signals etc. is being deleted. FIG. 5A shows an example of the structure of an encoded signal. In normal encoding, the correlation between screens is used to encode only the portion where a change has occurred with respect to the previous screen, thereby increasing the encoding efficiency and reducing the amount of code per screen. The encoded signal is then multiplexed with a frame synchronization signal, encoding parameters, etc., and then transmitted.

When refreshing, the entire screen is encoded using intra-screen correlation, which inevitably lowers the encoding efficiency compared to normal encoding, resulting in a huge amount of code per screen. become. Therefore, if refresh is performed on a screen-by-screen basis at a predetermined cycle, it will take 5 to 10 times more time than normal to transmit the refresh screen, resulting in a delay in the next screen being sent. I end up.

As a result, the screen pauses and becomes a still image, making it very unsightly.

Therefore, the screen rewriting control method of the present invention gradually refreshes the screen while moving by n lines or n pixels at a predetermined period, thereby preventing an extreme increase in the amount of code due to refresh, and thereby temporarily reducing the screen time. Prevent outage. In a screen to be refreshed, intra-frame prediction is performed for the area to be refreshed, and inter-frame prediction is performed for areas other than the refreshed area. Therefore, since two types of prediction methods are used in the screen to be refreshed, information indicating the attributes of the encoded signal is required.

For example, if refreshing is performed while moving n lines at a time for each predetermined screen, if the number of the refreshed line is multiplexed into the encoded signal as shown in FIG. There is no need to add attribute information to each pixel, and side information can be reduced. The same holds true when refreshing n pixels at a time.

In order to decode the signal encoded as described above, the refresh line number or pixel number multiplexed in the encoded signal is extracted. And, excerpt 1-
The region indicated by the attribute information is decoded using normal interframe prediction, and the region indicated by the attribute information is refreshed by intraframe prediction. Furthermore, the remaining areas may be decoded using normal interframe prediction. As described above, when performing periodic refresh in a low bit rate video encoding device that performs encoding on a screen-by-screen basis, refresh is performed for n lines or n pixels at a time, and refresh line numbers or pixel numbers are By multiplexing the code into a coded signal and transmitting the code, it is possible to prevent a huge increase in the code amount due to refreshing and to easily perform decoding.

〔Example〕

Next, the present invention will be explained in more detail by giving examples.

FIG. 1 is a block diagram of a first embodiment of the present invention, and FIG. 2 is a detailed block diagram of a refresh control circuit of this embodiment.

An example will be described in which refresh is performed while moving by n lines at every predetermined frame period. In FIG. 1, an input moving image signal is supplied to a refresh control circuit 1 and a subtracter 2 via a line 100. The refresh control circuit 1 stops execution of refresh and instructs the position where refresh is to be performed.

The refresh control circuit 1 will be explained in detail with reference to FIG. The refresh circuit l is a sync separator 1
0, division period 11, 13, integrator 12゜14, comparator 15
, a latch 16 and a switch 17. Sync separator 10 separates a sync signal from an input moving image signal supplied via line 100. Then, based on the separated synchronization signal, an F pulse indicating a frame break and
Generates an H pulse indicating line separation. The F pulse generated by the synchronous separator lO is supplied to the frequency divider 13. Further, the F pulse is supplied to the frequency divider 11 as a reset pulse. The H pulse is then supplied to the frequency divider 11. The frequency divider 11 is reset at the beginning of the F pulse supplied from the synchronous separator 10, and divides the frequency of the H pulse 7 into 1/n. The 1/n pulse of the output of the frequency divider 11 is supplied to the integrator 2. The integrator 12 integrates a value n every time a 1/n pulse is supplied from the frequency divider 11. For example, if the number of lines per screen is 525, when the integration result reaches 524, the integration result will be reset to 0 when the next 1/n pulse is supplied, and a 1/n pulse will be supplied. The operation of adding up the value n each time is repeated. Totalizer 12
The line number of the output of is supplied to comparator 15 and latch 16.

Next, the branching unit 13 receives the F supplied from the synchronous separator 10.
The pulse is frequency-divided into k-period pulses. In this periodic pulse, the first frame time is 1, and the subsequent pulses are O. The output of the frequency divider 13 is a pulse with a period of 14. Supplied to comparator 15 and switch 17. Integrator I4 is frequency divider 13
Every time a pulse of a certain period is supplied, a value n is accumulated.

Then, when the accumulated value reaches 524, the accumulation result is returned to 0 when a pulse of the next cycle is applied, and the operation of integrating the value n every time a pulse of k cycles is applied is repeated.

The output signal of the integrator 14 is supplied to a comparator 15. Comparator 15 compares the number indicating the line number supplied from integrator 12 with the value of the signal supplied from integrator 14 . Then, the output is set to 1 only when the periodic pulse supplied from the frequency divider 13 indicates 1 and the compared values are equal, and O is output otherwise. The output signal of the comparator 15 is supplied to the latch 16 as a set signal, and is also supplied to the switch 7 via a line 170 as a switching signal for the predictor. latch 1
6 stores the line number given from the integrator 12 when the set signal supplied from the comparator 15 becomes 1, and stores that value until the next set signal is given. A signal indicating the refresh line number of the output of the latch 16 is supplied to one of the switches 17. switch 17
A constant indicating that it is not a refresh line number is fixedly given in advance to the other input. Then, the switch 17 outputs a predetermined constant when the pulse with the period k supplied from the frequency divider 13 indicates O, and when the pulse with the period k supplied from the frequency divider 13 indicates 1, the switch 17 outputs the constant given from the latch 16. Outputs the updated refresh line number. The output of switch 17 is supplied to variable length encoder 8 via line 180.

The subtracter 2 subtracts the input moving image signal supplied via the line 100 and the prediction signal supplied from the switch 7 to obtain a prediction error signal. The prediction error signal output from the subtracter 2 is supplied to a quantizer 3. The quantizer 3 quantizes the prediction error signal supplied from the subtracter 2. The signal quantized by the quantizer 3 is sent to an adder 4 and a variable length encoder 8.
supplied to Adder 4 adds the signal supplied from quantizer 3 and the signal supplied from switch 7 to obtain a locally decoded signal. The locally decoded signal output from the adder 4 is supplied to an intraframe predictor 5 and an interframe predictor 6.

The intra-frame predictor 5 generates an intra-frame predicted signal using intra-screen correlation, based on encoded previous pixels or pixels of the previous line. The intraframe prediction signal output from the intraframe predictor 5 is supplied to the switch 7 . The interframe predictor 6 delays the locally decoded signal supplied from the adder 4 by approximately one frame time, and generates an interframe predicted signal using the correlation between screens. The interframe prediction signal output from the interframe predictor 6 is supplied to a switch 7 . When the predictor switching signal supplied via line 170 is 0, switch 7 selects the output of interframe predictor 6 and performs normal interframe encoding. When the predictor switching signal is 1, the output of the intraframe predictor 5 is selected and refreshed. The predicted signal output from switch 7 is supplied to subtracter 2 and adder 4 .

Next, the variable length encoder 8 performs variable length encoding on the prediction error signal supplied from the quantizer 3 using an efficient code such as a no-fuman code, and further reduces redundancy. . Then, the variable length encoder 8 multiplexes the refresh line number supplied via the line 180, together with a frame synchronization signal, encoding parameters, etc., into a code with reduced redundancy. The multiplexed signal and the redundancy-reduced code are first stored in a buffer memory, and the encoding speed is matched with the transmission path speed. The output signal of the variable length encoder 8 is transmitted to a decoder via a transmission path.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. The variable length coded signal is supplied to the variable length decoder 30 via the transmission path 300 in FIG. The variable length decoder 30 first stores the variable length code supplied via the transmission line 300 in a buffer memory inside the variable length decoder 30, and matches the speed of the transmission line with the speed of decoding. Then, the variable length decoder 30 reads the variable length code in which the synchronization signal and the like are multiplexed from the buffer memory, and detects the frame synchronization signal. When the frame synchronization signal is detected, the reading of the code is stopped once the encoding parameters, refresh line number, etc. following the frame synchronization signal are read out. At this time, the variable length decoder 30 holds the read encoding parameters and refresh line numbers until the encoding parameters and refresh line numbers following the next frame synchronization signal are read out.

The refresh line number line separated by the variable length decoder 30 is supplied to the refresh control circuit 31 via a line 3031. The variable length decoder 3o is connected to F via line 3230.
When the ' pulse is supplied, the waiting state for variable length decoding is released, the redundancy is reduced by performing variable length decoding in synchronization with the F' pulse, and the compressed signal is returned to the original signal.
It is supplied to an adder 33.

Details of the refresh control circuit 31 are shown in FIG. The refresh control circuit 31 includes a frequency divider 31o and an integrator 320.
and a comparator 330. Frequency divider 31
0 indicates frame separation via line 3230.
'Pulse is applied.

Further, an H' pulse indicating line separation is supplied via line 3231. Frequency divider 310 resets the output of frequency divider 310 when the F' pulse is applied. and,
Frequency divider 310 divides the H' pulse by a factor of n and supplies it to integrator 320. The integrator 320 integrates a value n every time a 1/n pulse is supplied from the frequency divider 310.

For example, if the number of lines per screen is 525, the integrator 320 returns the integrated result to 0 when the next 1/n pulse is supplied when the integrated result reaches 524. The operation of integrating the value n is repeated every time one pulse is supplied. The output signal of integrator 320 is provided to comparator 330. Comparator 330 compares the signal supplied from integrator 320 with the refresh line number supplied via line 3031, outputs 1 when the values match, and outputs O when the values differ. Output. The output signal of comparator 330 is provided to switch 34 via line 3134 as the output signal of the refresh control circuit.

The synchronization signal generator 32 generates F' pulses indicating frame divisions and H' pulses indicating line divisions.

The F' pulse generated by the synchronization signal generator 32 is
The signal is supplied to a variable length decoder 30 and a refresh control circuit 31 via 30.

Further, the H' pulse generated by the synchronization signal generator 32 is supplied to the refresh control circuit 31 via a line 3231.

The adder 33 adds the signal supplied from the variable length decoder 33 and the predicted signal supplied from the switch 34 to obtain a decoded signal. The decoded signal output from the adder 33 is supplied to an intraframe predictor 35 and an interframe predictor 36. Further, the decoded signal output from the adder 33 is connected to the line 3300.
is output as the output signal of the decoder. The intra-frame predictor 35 generates an intra-frame predicted signal using intra-screen correlation based on the previous pixel or pixel of the previous line of the decoded signal supplied from the adder 33. The intraframe prediction signal output from the intraframe predictor 35 is
The signal is supplied to switch 34.

The interframe predictor 36 delays the decoded signal supplied from the adder 33 by approximately one frame time, and supplies the delayed signal to the switch 34 as an interframe predicted signal.

Switch 34 selects the output signal of interframe predictor 36 when the predictor switching signal supplied via line 3134 is 0, indicating interframe prediction; If it indicates a refresh,
The output of the intraframe predictor 35 is selected. switch 34
The predicted signal output from is supplied to the adder 33.

Note that when refreshing is performed in units of n pixels, a clock indicating pixel separation is supplied from the synchronous separator 10 to the frequency divider 11 included in the refresh control circuit 1 instead of the H pulse, and the clock is Divide the frequency by n. Then, the integrator 12 integrates the value n every time the 1/n pulse supplied from the frequency divider 11 is supplied, and when the integrated value reaches the final pixel number, the next 1/n pulse 6. Refresh control circuit 31 of decoder
The frequency divider 310 and integrator 320 included in the encoder may also operate in the same way as the encoder.

〔Effect of the invention〕

As explained above, the present invention provides a low bit rate video encoding device that performs encoding on a screen-by-screen basis.
When performing periodic refresh, by refreshing n lines or n pixels at a time and multiplexing the refresh line number or pixel number into the encoded signal and transmitting it, a huge increase in the amount of code due to refresh can be prevented and , can be easily decrypted.

Furthermore, even when a low bit rate moving image encoding device is applied to one-sided moving image communication such as for monitoring purposes, it is possible to quickly eliminate screen disturbances caused by transmission path errors.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the encoder of the present invention, and FIG.
1 is a detailed block diagram of the refresh control circuit 1 in the encoder of FIG. 1, FIG. 3 is a block diagram of an embodiment of the decoder of the present invention, and FIG. 4 is a detailed block diagram of the refresh control circuit 31 in the decoder of FIG. FIG. 5 is a diagram showing an example of the configuration of an encoded signal, and FIG. 6 is a diagram for explaining an example of a conventional image information transmission device. 1.31... Refresh control circuit, 2...
...Subtractor, 3...Quantizer, 4,33...
... Adder, 5゜35 ... Frame inner child 5
1Q instrument, 6. 38... Interframe predictor, 7
, 17, 34... Switch, 8... Variable length encoder, lO... Synchronization separator, 11, 13
゜310... Frequency divider, 12, 14, 320...
...Integrator, 15,330...Comparator, 1
6... Latch, 30... Variable length decoder, 32... Synchronization signal generator.

Claims (3)

[Claims] (1) In a refresh that rewrites the screen in n line or n pixel units in encoding of a low bit rate moving image signal in which encoding is performed in units of screens using inter- and intra-screen correlation, the refresh line number Alternatively, there may be an encoding means that expresses the refresh pixel number with a small amount of additional information, multiplexes it into the video signal, and transmits it, and a predictor based on the result of detecting the refresh area from the multiplexed and transmitted refresh line number or refresh pixel number. and a selection means for switching. (2) means for obtaining a prediction error signal from an input moving image signal and a supplied prediction signal using inter- and intra-screen correlation; a quantization means for quantizing the prediction error signal; and a quantization means for quantizing the prediction error signal. means for obtaining a locally decoded signal from the output of the means and the predicted signal; an intraframe predictor for generating an intraframe predicted signal from the locally decoded signal; and an interframe predictor for generating an interframe predicted signal from the locally decoded signal. a selection means for selecting either the output of the inter-frame predictor or the output of the intra-frame predictor; refresh control means for applying to a long encoder; and variable length encoding means for reducing redundancy with respect to the output of the quantization means and multiplexing refresh line numbers or refresh pixel numbers given from the refresh control means; An image information transmission device comprising: (3) Variable-length decoding means for separating refresh line numbers or refresh pixel numbers multiplexed in encoded signals using inter- and intra-screen correlation, and an output of this variable-length decoding means. means for obtaining a decoded signal from a predicted signal; an intraframe predictor for generating an intraframe predicted signal from the decoded signal; an interframe predictor for generating an interframe predicted signal from the decoded signal; a selection means for selecting either an output or an output of the intra-frame predictor according to an instruction; and an instruction for selecting a predictor according to a refresh line number or a refresh pixel number given from the variable length decoder to the selection means. 1. An image information transmission device comprising: refresh control means for providing refresh control.