Method of re-synchronization for decoding videosignal

FIELD: re-synchronization.

SUBSTANCE: method can be used in decoding channel according to MPEG-4 standard. To provide proper decoding of pressed video data signal, the re-synchronization word RW differs from known words of variable length code VLC as well as from start code of plane of video object and has at least 17 sequent zeros, after which the unit follows, for plane of video object coded to provide two-directional prediction. After error in transmission in pressed video signal is detected, the pressed video data signal can be re-synchronized.

EFFECT: higher efficiency of re-synchronization.

4 cl, 2 dwg

 

The present invention relates to a method of resynchronizing the compressed video signal received by the decoder.

This method Retiming can be used, for example, in the channel decoding according to the MPEG-4 standard for CRT decoding after detection of a transmission error in the received compressed video signal.

PRIOR art

How Retiming known from the MPEG-4 Visual, known as version 1 MPEG-4 Visual, ISO/IEK 14496-2 (ISO - international organization for standardization (ISO); IEC - the international electrotechnical Commission (IEC)).

MPEG-4 video objects are used, which are the objects of a scene that the user can access and which he can manipulate. In order to access the video, you must have an encoded representation of its shape. Copies of the video objects in a given time are referred to as video object planes (hereinafter referred to as AA). The layer object is a group of video object planes, the type of form which is determined by an integer, called formslatest.

The video object plane with the inner coding (hereinafter referred to as I-video object plane (In-AA, I-VOP)) are coded without reference to other images. They provide access points to the coded is the second sequence, where can begin decoding, but they are encoded only with medium compression. Plane video encoded with prediction (hereinafter referred to as P-video object plane (P-AA and P-VOP)), are coded more efficiently using prediction with motion compensation from the previous video object planes with internal encoding or encoded with prediction, and mainly used as a reference for further prediction. Plane video encoded with bi-directional prediction (hereinafter referred to as a video object plane (L-AA, B-VOP)), provide the highest degree of compression, but require previous and subsequent reference video object planes for motion compensation. The motion vectors are determined as appropriate for each area of 16 times 16 lines of video object plane, hereinafter referred to as a macroblock, or area of 8 samples by 8 lines of video object plane, hereinafter referred to as a block. Vop_f_ and vop_f_ are integers that is used when decoding the motion vector.

The way the CRT that are described in the MPEG-4 standard, based on the word resynchronization called as a resynchronization marker (markerless), which is introduced into the compressed video signal. One-bit flag called "Supreme Kerrey", is set to "1" to indicate that the coded video object planes no markermeer, and is set to "0" to indicate that there is such a marker. The word resynchronization defined by the MPEG-4 standard, is a binary sequence of at least 16 zeros, followed by the unit: "0 0000 0000 0000 0001". For the first video object plane or to the plane of the video, where formslatest is set to "dochnyak", markermeer is a 16 zeros, followed by the unit. The length of this markerless depends on vop_f_ for P-video object plane and a larger value of one of the numbers: vop_f_ and vop_f_ for In-plane video. The relationship between the length markermeer and the corresponding f-code is defined as 16+f-code. Markerless equal to (15+f-code) zeros, followed by the unit. It is only when the flag supratemporality set to "0". Markermeer is located just before macroblock aligned on a byte boundary.

The INVENTION

The present invention is to achieve a more reliable re-compressed video signal received by the decoder. The invention taken in consideration the following aspects.

The word resynchronization due is different from all possible bit sequences, that may be contained in a compressed video signal, as there is no a priori knowledge, where it can be a word resynchronization. For example, in the MPEG-4 standard word resynchronization must be different from all the possible code words of variable length (hereinafter referred to as the word efficiency, VLC), as well as the start code of the video object plane, which marks the beginning of the video object plane.

However, the MPEG-4 standard in its present state, allows certain combinations of words efficiency, which can lead to the existence of unexpected words Retiming in a compressed video signal and, as a result, false resynchronization. One combination of bits resulting from decoding of the macroblock belonging to the In-plane of the object and which can lead to such undesirable Retiming is the following:

the mode of the macroblock for In-block (MODB): 00

the macroblock type (MB_TYPE): 0001

the pattern of the coded block

for In-blocks (SWRV): 1 000 00

information quantizer (DBQUANT): 0

the word efficiency (VLC) of the motion vector: 0000 0000 0011. 1.

This example shows a particular combination of words efficiency, which contains a group of 16 consecutive zeros followed by unit: 5 zeros, corresponding to the word efficiency SURV, 1 zero, corresponding to the word efficiency DBQUANT, and 10 zeros, corresponding to the word efficiency of the movement vector is s -15,5. In this case, there is ambiguity between this particular combination of words efficiency and the word resynchronization, which consists of 16 consecutive zeros (15+f-code, and f-code in this case is equal to 1), followed by the unit. A specific combination of words efficiency can emulate the resynchronization, which is not expected. In this case, the video decoder MPEG-4 standard may not correctly decode a compressed video signal.

The way resynchronization in accordance with the present invention differs in that it includes a step of detecting words Retiming, which contains at least 17 consecutive zeros followed by a unit for plane video encoded with bi-directional prediction.

In the result, the above-mentioned method Retiming provides a more reliable resynchronization compressed video signal as it is based on the word resynchronization containing at least 17 consecutive zeros, even if the f-code is equal to the unit, which differs from the previously described specific combination of words efficiency. The above-mentioned method Retiming provides, therefore, the proper decoding of the compressed video signal containing these specific combination of words efficiency.

The present invention also relates to a video decoder, implementing Tsushima this way Retiming, and to the compressed video signal containing the word resynchronization described in method resynchronization.

The present invention finally relates to a method of introducing words Retiming in a compressed video signal to the video encoder implementing this method.

These and other aspects of the invention are evident and explained with reference to the following examples.

BRIEF DESCRIPTION of DRAWINGS

The present invention is described below, as an example, with reference to the accompanying drawings, on which:

figure 1 presents videopoker containing the word resynchronization in accordance with the invention; and

figure 2 presents a block diagram depicting a method of resynchronization in accordance with the invention.

DETAILED description of the INVENTION

The present invention relates to a method of resynchronization, which enables the re-compressed video signal received by the decoder, after detection of a transmission error in said compressed video signal. Typically, the data between the synchronization point before the error and the first point where synchronization is restored, are discarded. If the CRT determines the amount of data discarded by the decoder, it significantly increases the capability of the tools of other types, which in ustanavlivaut data and/or mask the effect of errors.

This method Retiming described in the context of the video signal of the MPEG-4 standard, but it is also applicable to compressed video signals of other types that manipulate video objects.

How Retiming based on the separation plane of the video objects AA at the video packets. This method allows you to provide periodic words Retiming around the compressed video signal. Thus, the length of the video packets based on the number of macroblocks and the number of bits contained in this package, making way Retiming more accurate.

Figure 1 presents a typical videopoker. This videopoker contains:

the word resynchronization (CF, RW), used for marking the beginning of a new videobachata;

- header information such as the address of the macroblock (NUM) of the first macroblock contained in the package, the quantization parameter (Q) and the Code of the Header Extension (HRH, BORE), and the header information necessary to restart the decoding process;

data of the macroblock (MBD).

The word resynchronization must be different from all the possible words efficiency, as well as the start code AA. As indicated in the summary of the invention, a particular sequence of words efficiency creates ambiguity in the case of the word resynchronization of the prior art.

Mentioned th is sequence contains:

the word efficiency mode macroblock for In-block (MODB). This word efficiency MODB is present only in coded macroblocks of the b-video object planes, and is equal to:

- 1, if the macroblock is not present no data SURV, no data MUCURI,

- 01 if the macroblock contains only data MB_TYPE,

- 00, if the macroblock data is present SURV and MUCURI;

the word efficiency of the macroblock type (MB_TYPE). This word efficiency MB_TYPE is present only in coded macroblocks of the b-video object planes, which included a single motion vector. Codes for MUCURI equal to 1, 01, 001 or 0001 depending on the type of the motion vector;

the word efficiency of the coded block pattern for In-blocks (SWRV). This word SURV is a 3-6-bit code, each bit in the code is encoded/dekodiranje the status of the unit. For each opaque block with coefficients corresponding bit in the code is set to "1";

the word efficiency information quantizer (DBQUANT). This word DBQUANT determines the change in the quantizer for b-video object planes. Codes for DBQUANT are 10, 0, or 11;

the word efficiency of the motion vector. The word efficiency is a 1-13-bit code and contains up to 10 consecutive zeros, as described in the following examples:

CodesThe separation of the b vectors
0000 0000 0010 1-16
0000 0000 0011 1-15,5
0000 0000 0011 015,5
0000 0000 0010 016

The definition of the above words efficiency leads to a combination of bits, which contains the maximum of a group of 17 consecutive zeros followed by unit: 6 zeros, corresponding to the word efficiency SURV, 1 zero, corresponding to the word efficiency DBQUANT, and 10 zeros, corresponding to the word efficiency of the motion vector. The mentioned combination of bits may be ambiguous in the case of the word resynchronization with (15+f-code) zeros, if the f-code is equal to 1 or 2. It is possible that as the value of the f-code corresponding to vop_f_ or vop_f_, is a 3-bit integer taking values from 1 to 7, where a value of zero, Smoking, and these values depend on the range of values of the motion vector.

As a result, the length of the word resynchronization must be increased and must contain at least 17 consecutive zeros. The word resynchronization markermeer in accordance with the invention is a binary sequence of at least 16 zeros, followed by the unit: "0 0000 0000 0000 0001". For I-video object plane (I-AA) or a video object plane, where the form of a layer of a video object has a value which their "dochnyak", markermeer is 16 zeros, followed by the unit. The length of this markerless depends on the value vop_f_ for P-video object plane and a larger value of one of the numbers: vop_f_ and vop_f_ for In-plane video. In a preferred embodiment of the dependence between the length markermeer and the corresponding f-code is defined as 16+f-code for P-video object plane and as 16+n+f code for B-VOP. Markerless equal to (15+f-code) zeros, followed by the unit, for a P-VOP, and (15+n+f-code) zeros, followed by the unit for B-VOP, where n is an integer strictly greater than zero. It is only when the flag supratemporality set to "0". Markermeer is located just before the macroblock aligned on a byte boundary.

Figure 2 presents a block diagram depicting a method of resynchronization in accordance with the invention. During decoding (DEC) is a compressed video signal (CS) and a given output signal (OS). The output signal is analyzed during the analysis phase error (ERR). If an error is detected in the compressed video signal, such as, for example, an invalid word efficiency or semantic error in the phase detection (DET) word search Retiming in a compressed video signal. Mentioned the word resynchronization depends on the type of plosko and video and contains:

16 zeros, followed by the unit for the first video object plane;

- (15+(f-code) zeros, followed by the unit for P-video object plane;

- (15+n+f-code) zeros, followed by a unit for In-plane video where

n is an integer. strictly greater than zero.

Finally, when it encounters the word resynchronization, phase synchronization (SYNC) restarts the process of decoding the header information for the next word resynchronization. The macroblock number (NUM) provides spatial resynchronization, while the quantization parameter (Q) allows the resynchronization process differential decoding.

In the first embodiment of the invention, the word efficiency SURV, including 6 consecutive zeros is not a possible combination, since this word efficiency, which would correspond to 6 neodrepanis blocks would include then the word efficiency MODB equal to 1 or 01 (no data SWRV). In this case, the most unfavorable word efficiency SWRV is "100000" and the value of n equal to 1, the corresponding word resynchronization with (16+f-code) zeros, followed by the unit, sufficient to eliminate any ambiguity between these word Retiming and known words of the cap.

In the second embodiment, the invention provides for the word efficiency MODB, Ravne, associated with the word efficiency SURV, including 6 consecutive zeros, as this combination of words efficiency allowed by the MPEG-4 standard. Therefore, the value n is equal to 2, corresponding to the word resynchronization with (17+f-code) zeros, followed by the unit, which prevents any ambiguity in the case of the combination of the words efficiency, including a group of 17 consecutive zeros followed by unit: 6 zeros, corresponding to the word efficiency SURV, 1 zero, corresponding to the word efficiency DBQUANT, and 10 zeros, corresponding to the word efficiency of the motion vector.

How Retiming described in figure 2, is implemented in the integrated circuit, subject to embed, for example, in the video decoder.

The video decoder is designed to receive compressed video signal and includes a detector for detecting the words Retiming in a compressed input video data and the clock for Retiming decoding the compressed input video data, starting with the discovery of the word resynchronization.

The present invention also relates to a method for introducing a compressed video signal words Retiming containing at least 17 consecutive zeros, for example (15+n+f-code) zeros in the preferred embodiment, the followed unit for video data corresponding to In-plane video. This method of introduction is implemented in the integrated circuit, want to embed, for example, the video encoder.

The corresponding video encoder is designed to provide a compressed output video data and provides a means for the introduction of the word resynchronization in the compressed output video data.

In addition, the signal provided by such a video encoder or accept such a decoder may be determined that it contains the word resynchronization, which contains at least 17 consecutive zeros, for example (15+n+f-code) zeros in the preferred embodiment, the followed unit for video data corresponding to In-plane of the video object.

It is obvious that the use of the word "include" and its conjugations do not exclude the presence of any other steps or elements, except those defined in any of the claims. The indefinite article (in English)preceding an element or step does not exclude the presence of many such elements or steps.

1. The way the re-compressed video signal received by the decoder, the compressed video signal contains the word resynchronization, the method includes:

the phase error detection in compressed video signal,

the discovery of the word resynchronization in a compressed video signal, if the error has been detected

this is p detection plane video coded with bi-directional prediction in a compressed video signal,

stage re-decoding the compressed video signal, starting with the discovery of the word resynchronization,

characterized in that the detection step detects words Retiming, which contains at least 17 consecutive zeros followed by a unit for video data corresponding to video object plane, encoded with bi-directional prediction.

2. Video decoder for receiving a compressed video signal containing

a detector for detecting errors in a compressed video signal,

a detector for detecting the words Retiming in a compressed video signal, if the error has been detected

a detector for detecting the plane of the object encoded with bi-directional prediction in a compressed video signal,

synchronizer for re-decoding the compressed video signal, starting with the discovery of the word resynchronization,

characterized in that said detector is adapted to detect words Retiming, which consists of at least 17 consecutive zeros followed by a unit for video data corresponding to video object plane, encoded with bi-directional predskazana the M.

3. The method of introduction of the word resynchronization in a compressed video signal generated by the encoder, in accordance with the recommendations of the standard MPEG-4, characterized in that the method provides the insertion of resynchronization, which contains at least 17 consecutive zeros followed by a unit for video data corresponding to video object plane, encoded with bi-directional prediction.

4. Video encoder for issuing a compressed video signal in accordance with the recommendations of the MPEG-4 standard, containing means for introducing words Retiming in a compressed video signal, characterized in that the means for introducing adapted for insertion of the word resynchronization, which contains at least 17 consecutive zeros followed by a unit for video data corresponding to video object plane, encoded with bi-directional prediction.



 

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