JPH0289472A - Picture coding transmitter - Google Patents

Abstract

PURPOSE:To prevent picture quality deterioration from being affected over a wide range even when picture signals over several blocks are missing due to abort of a cell in a transmission line by sending block picture information and a block forming information to each of a high and a low abort rate side channel respectively. CONSTITUTION:Priority is placed over plural channels such as two channels and a picture signal is sent in multi-channel coding through a high-order and a low-order channel with high/low information abort rate respectively. Then one pattern is split into lots of blocks through the low-order channel at the sender side, picture element information sets P1, P2 coded by an in-frame coder 3 are used, and block forming information of a corresponding block such as bit number of information sets P1, P2... by an inter-frame coder 4 at the high-order channel are sent sequentially respectively. Thus, even if the information P of the low-order channel is missing over several blocks due to cell abort of the like in the transmission line, the receiver side can recognizes at which position of the information P on the pattern is missing via the high-order channel, the information P is decoded to attain reproduction of the picture, and the range in the picture quality deterioration is limited only to the block whose information is aborted.

Description

[Detailed Description of the Invention] [Summary] This invention relates to an image encoding and transmitting device that divides a screen into multiple blocks, encodes each block, and transmits the encoded image signals through multiple channels with different discard rates. .

Even if several blocks of image signals are lost due to cell discard on the transmission path, etc., the resulting deterioration of the playback screen is limited to the lost block, so that the deterioration of one image quality can be reduced over a wide range. The purpose is to prevent the spread of

An image encoding and transmitting device that transmits an image signal encoded in blocks through multiple channels provided on the network side with different discard rates, and in which a channel with a high discard rate receives block image information. , and the configuration information of the block of image information of the channel on the high discard rate side is transmitted to the channel on the low discard rate side.

[Industrial application field]

The present invention relates to an image encoding and transmitting apparatus that divides a screen into a plurality of blocks, encodes each block, and transmits the encoded image signals through a plurality of channels having different discard rates.

Such an image encoding and transmitting apparatus is required to be able to prevent the reproduction screen from being distorted as much as possible on the receiving side even if part of the transmitted image information is discarded in the network.

Divide into high-importance components and low-importance components, which are the minimum required for reproduction. 1. Image information with high importance is routed through a channel with a low discard rate, and image information with low importance is routed through a channel with a high discard rate. Each cell is transmitted via a channel, and when discarding a cell, information is discarded first from the less important high discard rate channel side.

A multi-channel coding transmission system has been proposed that can guarantee a minimum quality of reproduced images on the receiving side even if cells are discarded on the transmission path.

[Conventional technology]

In high-efficiency coding methods for image signals, when the encoded image signal is transmitted using a burst multiplex transmission network such as ATV or packet switching, the transmission frame may be distorted due to transmission errors on the transmission path, bumper overflow, etc. It is inevitable that erasures (discarded cells or packets) will occur.

As a way to deal with this, multiple channels with different discard rates are provided on the network side, these channels are prioritized, and the image signals to be transmitted are divided into blocks. In an image encoding device that performs efficiency encoding, as shown in FIG.
The image signal A/D converted by the A/D converter) 21 is encoded in block units by the source encoder 22, and the encoded image signal from the source encoder 22 is further transmitted to the video multiple prefix encoder. At 23, the image signal is variable-length coded together with various block attribute information and multiplexed into a predetermined coded sequence, and this image signal coded sequence is sent to a transmission path via a multi-electrification unit 24 that multiplexes it with audio signals and the like.

As shown in Figure 5, the frame structure of this encoded image signal sequence is such that a unique pattern for synchronization detection (
A unique word UW) is inserted, followed by a block line header, and then block attribute information and pixel information of each block are placed consecutively.

If a cell is discarded for an image signal with such a frame structure, the block information after the discarded part will be out of position on the screen, so even if only a few blocks are discarded, the discarded block It becomes impossible to decode the code of subsequent blocks, and basically it becomes impossible to decode the code until the unique word UW of the next processing unit arrives.

As a result 1, for example, if a unique word is provided in each frame, as shown in FIG.

The screen quality deteriorates over a wide range (hatched area) after the location where the cell was discarded.

Therefore, an object of the present invention is to ensure that even if several blocks of image signals are lost due to cell discard on the transmission path, the resulting deterioration of the playback screen is limited to only the lost block portion. The purpose is to prevent image quality deterioration from spreading over a wide range.

[Means to solve the problem]

The image encoding and transmitting device according to the present invention is an image encoding and transmitting device that transmits an image signal encoded in blocks through a plurality of channels provided on the network side and having different discard rates. The rate side channel transmits the image information of the block.

The channel on the low discard rate side is configured to transmit configuration information of a block of image information of the channel on the high discard rate side.

Furthermore, the image encoding and transmitting device according to the present invention has the following features:
Separating pixel information into a high frequency component and a low frequency component, transmitting the low frequency component Flj pixel information via a low loss rate channel,
The high frequency component pixel information is configured to be transmitted over the high drop rate channel.

[Effect]

On the network side, multiple channels (for example, 2 channels) are prioritized, and channels with a low information loss rate (for example, 2 channels) are prioritized.
An upper channel) and a higher channel (lower channel) are provided, and multi-channel encoded transmission of image signals is performed using these channels.

FIG. 1 shows an example of the signal formant of the transmitted image signal in this case.

On the sending side, one screen is divided into many blocks.

Encoding is performed block by block to generate pixel information P for each block. Then, in the lower channel, only the pixel information P, , P2- of each block is sequentially transmitted. On the other hand, in the upper channel, 1. Block configuration information (for example, the number of bits of pixel information p1.p, -, block attribute information, etc.) of the blocks corresponding to the pixel information p1.p, , P2- transmitted on the lower channel is transmitted.

As a result, even if the block pixel information P of the lower channel is lost for several blocks due to cell discard on the transmission path, in the reception example, it is possible to determine the position on the two screens based on the block configuration information received via the upper channel. It is possible to know whether the pixel information of the block has disappeared.

Therefore, since the correct arrangement position on the screen of the blocks subsequent to the block whose information was discarded is known, the pixel information of these blocks can be decoded to reproduce the image. Therefore, the range of deterioration in image quality can be limited to only blocks where information is discarded.

Blocks after the block whose information was discarded do not suffer from deterioration in image quality.

Further, in another embodiment of the present invention, the pixel information P of a block is changed to a more important component (for example, a low frequency component) P during image reproduction.
' and a less important component (for example, a high frequency component) P'°, and the more important component P' is transmitted via the upper channel. In this way, even if information is discarded for a block consisting of lower channels, only the less important pixel information component P11 will be lost, and therefore, on the receiving side, the pixel information fgP for this block portion will be lost.
' can be received via the upper channel, and based on this pixel information P', it is possible to reproduce the image even if the clarity is somewhat lacking. This makes it possible to suppress image quality deterioration in the block portion where information is discarded.

〔Example〕

The present invention will be described in detail below with reference to one drawing.

An image encoding and transmitting apparatus as an embodiment of the present invention is shown in FIG. In this embodiment, the apparatus of the present invention is used in a multi-channel coded transmission system in which channels with a high discard rate and channels with a low discard rate are provided by prioritizing channels on the network side.

Here, the number of channels is 2 channels.

In Fig. 2, l is a discrete cosine transformer that performs a discrete cosine transform on the image input in units of blocks and converts it into frequency component coefficients, and 2 is a discrete cosine transformer that transforms the output of the discrete cosine transformer l into a low frequency component and a high frequency component. 2 is an intraframe encoder consisting of a quantizer that intraframe encodes the high frequency component u, and 4 is an interframe encoder that interframe encodes the low frequency component u. . The configuration of this interframe encoder 4 is well known, including a subtracter 41, a quantizer 42, and a subtracter 41. Inverse quantizer 43. Adder 44. It is configured to include a frame memory 45 and the like.

5 is a video multiplex encoder that variable-length encodes the output of the intraframe encoder 3;

The output signal is a channel with a high discard rate (lower channel)
is sent out to the network via. 6 is a video multiplex encoder which receives the output of the interframe encoder 4 and the output of the intraframe encoder 3 and encodes these encoded image information together with various block attribute information in variable length; The output signal is sent to the network via a channel with a low drop rate (upper channel).

The operation of this embodiment device will be explained below with reference to FIG. A block image signal obtained by dividing one screen into a large number of blocks is input to a discrete cosine transformer l, where it undergoes a discrete cosine transform and is converted into frequency components. This frequency component is further separated into a low frequency component and a high frequency component H by a coefficient separation block 2, and the low frequency component is interframe encoded by an interframe FF encoder 4, and a high frequency component is n is intra-frame encoded by an intra-frame encoder 3, and each video multiplex encoder 6.5
and multiplexed into a coded stream.

FIG. 3 is a diagram showing an example of a frame structure of a multiplexed coded sequence in an upper channel and a lower channel. In this example, both the upper channel side and the lower channel side perform conditional pixel replenishment on a block-by-block basis, and the invalid information on the lower channel side is run-length encoded.

Conditional pixel replenishment calculates the error between the block to be encoded on the current screen and the block at the same position on the previous screen, and if this error is smaller than a predetermined threshold, the screen movement is Assuming that there is almost no [invalid J information], only the invalid J information is sent, and in the case of this "invalid", the receiving side continues to use the pixel information of the block at the same position on the previous screen to create a playback screen. If the error is greater than the threshold, [-valid] information is sent, and this "valid" information is followed by the pixel information of the block.

First, in the upper channel, information is sent as to whether the block on the low frequency coefficient side (output side of the interframe encoder 4) is "valid" or "invalid". In this case, if it is "valid", low frequency coefficient information ■, ■- is sent together like the first block, third block, etc., and if it is "invalid", it is sent like the second block. Send only "invalid" information to.

Further, in this upper channel, block attribute information of a block of high frequency coefficients (outputs of the three intraframe encoders) on the lower channel side is sent. The block attribute information is "
Information on whether it is “enabled” or “invalid”.

If "valid", the information includes the number of bits of the high frequency coefficient block. However, the invalid information of the lower channel is run-length encoded. That is, when the run length is "0", it indicates that the high frequency coefficient information is "valid", and in this case, the number of bits of the lower channel is also sent. If the run length is a finite number, the high frequency coefficient information will be
In the example in Figure 3, the run length is "98" in the second block, indicating that the run length is "invalid", and blocks from the second block to the 99th block are "invalid". .

Only high frequency coefficient information is sent on the lower channel. However, high frequency coefficient information is not sent for blocks determined to be "invalid". In the example of FIG. 3, the 2nd to 99th blocks are "invalid", so high frequency coefficient information is not sent.

As described above, the low frequency coefficient information, its attribute information, and the high frequency coefficient information are sent via the upper channel,
If high frequency coefficient information is sent via the lower channel, the high frequency coefficient information of the lower channel, which has a high discard rate due to the loss of transmission frames in the network (1)
Even if the high frequency coefficient information is lost, it can be known from the bit number information of the lower channel sent by the upper channel and the run length of the invalid block of the lower channel that the high frequency coefficient information ■ is lost. The playback position on the screen is not disturbed, and therefore lower channel information from the second block onwards can be decoded.

In order to detect the position of a lost block, it is possible to use the disturbance in the coding rule of the block. Namely.

When decoding a block, if the coding rule during encoding is disrupted, it can be estimated that the block has disappeared from that position. In this case, according to the lower channel bit number information from the upper channel.

The encoded sequence can be traced backwards from the position of the unique word of the next frame to determine the position of the end of the block erasure.

On the receiving side, if the loss of a block is detected.

In this way, when cells are discarded, zero information is inserted into the discarded data portion and decoding is performed.

Only the high frequency components of the discarded data portion are decoded in a lost form, and other blocks are not affected by cell discard. Furthermore, since the low frequency coefficient information for the discarded data portion is transmitted via the upper channel, it is possible to reproduce an image of the minimum quality even if it lacks clarity.

Note that decoding can be made easier if the network side inserts dummy data into the discarded data portion and matches the number of bits to maintain a constant amount of data between transmitting and receiving terminals.

Various modifications are possible in carrying out the present invention.For example, in the above-mentioned embodiment, two-channel transmission was used as the number of channels in the multi-channel encoding system, but the present invention is not limited to this, and the number of channels may be three or more. For example, in the case of three channels, the channels are prioritized into upper, middle, and lower channels, and the image information is divided into information of high, middle, and low importance. The lower channel sends lower pixel information, the middle channel sends the lower channel block structure information and middle pixel information, and the upper channel sends the middle channel block structure information and upper pixel information.

Further, the block attribute information is not limited to that of the embodiment, and for example, motion vector information, filter 0N10FF information, intraframe/interframe coding information, etc. can also be sent.

Furthermore, the multi-channel coding transmission method is not limited to the one in the embodiment, and various other methods can be used. Furthermore, the highly efficient encoding method for one pixel information is not limited to the interframe encoding method and intraframe encoding method of the embodiment.

For example, a modification such as using a leaky integral interframe encoding method instead of an intraframe encoding method is also possible.

〔Effect of the invention〕

According to the invention, erasure of transmission frames (cells) is achieved.

Even if several blocks of image signals are lost due to discarding of packets, etc., the resulting deterioration of the playback screen can be prevented.
Only the lost block portion can be minimized, and image quality deterioration can be prevented from spreading over a wide range.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention. FIG. 2 is a block diagram of an image encoding and transmitting apparatus as an embodiment of the present invention. FIG. 3 is a diagram showing an example of a frame structure of an upper channel and a lower channel for explaining the operation of the embodiment device. FIG. 4 is a block diagram showing an example of the configuration of a conventional image encoding and transmitting device. FIG. 5 is a diagram showing a conventional multiplexed encoded sequence, and FIG. 6 is a diagram for explaining the problems of the conventional method. In fig. 1-jlr&D+iy converter 2-coefficient separator 3-intraframe encoder 4-interframe encoder 5.6--video multi-branch encoder 41-subtractor 42--quantizer 43 - Inverse quantizer 44 - Adder frame memory Figure 2 Figure 4 Figure 6

Claims (1)

[Claims] 1. An image encoding and transmitting device that transmits an image signal encoded in units of blocks via a plurality of channels provided on the network side and having different discard rates, the device having a high discard rate. An image encoding and transmitting device configured to transmit image information of a block to a channel on the lower discard rate side, and transmit configuration information of a block of image information of the channel on the high discard rate side to a channel on the low discard rate side. 2. Separating pixel information into a high frequency component and a low frequency component, and transmitting the low frequency component pixel information through a low discard rate channel;
The image encoding and transmitting device according to claim 1, configured to transmit high frequency component pixel information via a high discard rate channel.