JP2008148004A - Video decoder, digital broadcast receiver, video-decoding method, video-decoding program, and recording medium with video-decoding program stored - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the effect of decode errors on error TS packet, even if there is an error TS packet among TS packets received by a digital broadcasting receiver or a video decoder. <P>SOLUTION: When a decode error is generated due to an error TS packet, in the video decoder 4 of the digital broadcast receiver 1, an error-time start code search portion 10 reads a slice start code decoded, prior to the occurrence of the decode error from an ES buffer 5 and detects the next slice start code from the position of the read-out slice start code by reading the video data by byte units; and then, decoding is resumed from the detected slice start code in a VLC decode processing portion 6, a video data decode processing portion 7, and a syntax analysis portion 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a video decoding device for decoding encoded video data used in digital broadcasting, a video decoding method, a video decoding program, a recording medium storing the video decoding program, and a digital broadcast receiver including the video decoding device. .

  MPEG (Moving Picture Experts Group) -2 is known as an encoding method for encoding audio and moving images when digitized and transmitted. In MPEG-2, in addition to audio and video encoding methods, the MPEG-2 system defines a method for multiplexing encoded video, audio, and additional data, and transmitting and reproducing them in synchronization with each other. Has been.

  In the MPEG-2 system, encoded video data and audio data (ES: Elementary Stream) are stored in a packet called a PES (Packetized Elementary Stream) packet. FIG. 1 shows the structure of the PES packet. The PES packet is a variable-length packet including a PES packet header including time information called PTS (Presentation Time Stamp) and a PES packet payload in which ES is stored.

  Then, the PES packet is divided into packets that are divided into fixed lengths called TS (Transport Stream) packets, and then transmitted after OFDM (Orthogonal Frequency Division Multiplexing) modulation in the case of terrestrial digital broadcasting. On the receiving side, the received signal is OFDM demodulated, the PES packet is restored from the TS packet, and the ES is extracted from the PES packet payload and decoded.

  In the case of terrestrial digital broadcasting, since data is transmitted by radio waves, an error may occur depending on the reception status. Errors that occur during transmission are corrected by error correction of the Reed-Solomon code during OFDM demodulation, but may not be corrected depending on the error. In the OFDM demodulation processing in this case, 1 is set in transport_error_indicator (bit field indicating an error of the TS packet) of the TS header to generate a TS packet.

  In a general digital broadcast receiver, processing for generating an ES from a TS packet generated by OFDM demodulation processing is performed by a TS demultiplexer. When the TS demultiplexer detects a TS packet (error TS packet) with 1 set in the transport_error_indicator of the TS header, the error TS packet is discarded, and a normal TS packet that is not an error is joined together to set the ES. Generate. Accordingly, a decoder (decoder) that decodes (decodes) ES is input except for the ES data included in the discarded error TS packet. For example, referring to FIG. 2, when the error TS packet is TS packet 2, ES of TS packet 3 is input to the decoder after ES of TS packet 1. Since the decoder cannot detect that an error has occurred, it sequentially decodes the input data. However, since the ES of TS packet 1 and the ES of TS packet 3 are not data that should be input continuously, data discontinuity occurs, and a variable length code (VLC) is decoded. Even if the sequence of bits read across the discontinuous points and the sequence of subsequent bits are the sequence of bits corresponding to the VLC specified in MPEG-2 video, it indicates the original encoded data. Since this is not the case, the error in the decoding operation will eventually fail and a decoding error will occur.

  When a decoding error occurs, decoding is stopped until a start code that is information indicating synchronization defined in MPEG-2 video is detected, and decoding is resumed after the start code is detected. Therefore, a normal image was not displayed until the start code was detected.

  Also, if all or part of the start code is included in the ES data of the TS packet after the error TS packet, the bits may be read out of position due to the influence of the discontinuity point. The start code could not be recognized correctly.

  The start code is data (information) for obtaining synchronization when displaying a video added to each sequence, picture, slice, or the like in the MPEG-2 bit stream. For this reason, if the start code cannot be recognized, a normal video image cannot be displayed up to the recognizable start code, and thus an abnormal video image may become wide-ranging. Since MPEG-2 performs inter-frame coding, if an image is not normal in a certain frame, the effect may be spread over a plurality of frames, resulting in a significant decrease in image quality. there were.

For example, a digital broadcast receiver described in Patent Document 1 has been proposed as a countermeasure against errors during reception in such digital terrestrial broadcasting. The digital broadcast receiver described in Patent Document 1 includes a plurality of receivers, and when an error occurs in a TS packet received by one receiver, decoding is performed using the TS packet received by another receiver. .
JP 2006-197167 A

  In the digital broadcast receiver described in Patent Document 1, a plurality of receivers must be prepared, which makes it difficult to reduce the size of the apparatus. In addition, when an error occurs in all receivers, an error TS packet eventually occurs, and a problem that a normal video cannot be displayed until a start code is detected due to a decoding error occurs.

  Accordingly, the present invention provides a video decoding apparatus, a video decoding method, a video decoding program, a recording medium storing a video decoding program, and a video decoding program that reduce the influence of a decoding error caused by an error TS packet even if an error TS packet occurs, for example. It is an object of the present invention to provide a digital broadcast receiver including a video decoding device.

  In order to solve the above-mentioned problem, the video decoding device according to claim 1, wherein the encoded video data is input, and the video decoding device includes decoding means for decoding the video data. Storage means for storing a predetermined amount of video data; synchronization information detection means for detecting information indicating synchronization included in the encoded video data stored in the storage means; and when the decoding means detects a decoding error Error-time synchronization information detecting means for detecting information indicating the next synchronization from the position of the information indicating the synchronization decoded by the decoding means before the decoding error is detected, and the decoding means However, the video data is decoded from the information indicating the synchronization detected by the error-time synchronization information detecting means.

  The video decoding method according to claim 6, wherein encoded video data is input, and the video data is decoded, the video data is stored in a predetermined amount, and the stored encoded video is stored. When data is read and the video data is decoded and a decoding error is detected, the next information indicating the synchronization is detected from the position of the information indicating the synchronization decoded before the decoding error is detected. And decoding from the detected information indicating the next synchronization.

  The video decoding program according to claim 7, wherein encoded video data is input, and a video decoding program for causing a computer to function as decoding means for decoding the video data stores a predetermined amount of the encoded video data. Storage means, synchronization information detection means for detecting information indicating synchronization included in the encoded video data stored in the storage means, and when the decoding means detects a decoding error, the decoding error is detected. Causing the computer to function as error-time synchronization information detecting means for detecting the next information indicating the synchronization from the position of the information indicating the synchronization decoded by the decoding means before being detected, and the decoding means includes the error The video data is decoded from the information indicating the synchronization detected by the time synchronization information detecting means.

  Hereinafter, a video decoding apparatus according to an embodiment of the present invention will be described. When the decoding means detects a decoding error, the video decoding apparatus according to an embodiment of the present invention obtains information indicating the next synchronization from the position of the information indicating the synchronization decoded by the decoding means before the decoding error is detected. The synchronization information detecting means at the time of error detects and the decoding means decodes from the detected information indicating the next synchronization. In this way, when the information indicating the next synchronization cannot be recognized due to the error TS packet, the information indicating the next synchronization can be reliably detected, so that the influence of the display image due to the decoding error is reduced. be able to.

  Further, the error-time synchronization information detection means may read the video data in byte units from the storage means and detect information indicating synchronization. By doing in this way, if the information indicating the synchronization is byte-aligned, the information indicating the synchronization can be detected at an early stage.

  The storage means may store at least information indicating synchronization to information indicating the next detected synchronization. By doing in this way, it is possible to make the capacity minimum necessary for the operation of detecting information indicating synchronization.

  In addition, video storage means for storing video data decoded in the past is provided, and when the decoding means detects a decoding error, it indicates the next synchronization from the information indicating the synchronization decoded immediately before the decoding error is detected. The video up to immediately before the information may be replaced with video data stored in the video storage means. By doing so, since the past video is displayed on the portion where the decoding error is detected and the normal video cannot be output, the influence of the decoding error on the displayed video can be reduced.

  The digital broadcast receiver may include the video decoding device according to any one of claims 1 to 4. In this way, a digital broadcast receiver that is less affected by decoding errors due to error TS packets can be obtained.

  Further, the video decoding method according to an embodiment of the present invention detects information indicating the next synchronization from the position of the information indicating the synchronization decoded before the decoding error is detected when the decoding error is detected, It is made to decode from the information which shows the detected next synchronization. In this way, when the information indicating the next synchronization cannot be recognized due to the error TS packet, the information indicating the next synchronization can be reliably detected, so that the influence of the display image due to the decoding error is reduced. be able to.

  The video decoding program according to an embodiment of the present invention indicates the next synchronization from the position of the information indicating the synchronization decoded by the decoding unit before the decoding error is detected when the decoding unit detects the decoding error. The error synchronization information detecting means detects the information, and the decoding means decodes the detected information indicating the next synchronization. In this way, when the information indicating the next synchronization cannot be recognized due to the error TS packet, the information indicating the next synchronization can be reliably detected, so that the influence of the display image due to the decoding error is reduced. be able to.

  The video decoding program according to claim 7 may be stored in a recording medium. In this way, the video decoding program can be distributed alone as well as incorporated in the device.

  A digital broadcast receiver 1 according to an embodiment of the present invention will be described with reference to FIGS. The digital broadcast receiver 1 is a device that receives a broadcast wave that is encoded by MPEG-2 and OFDM-modulated, and that displays and reproduces video and audio included in the broadcast wave. As shown in FIG. A demodulator 2, a TS demultiplexer 3, a video decoder 4, and a video display device 11 are provided.

  The demodulator 2 demodulates the TS carrier signal to obtain a TS packet, performs error correction by Reed-Solomon error correction at the time of demodulation, and outputs it to the TS demultiplexer 3.

  The TS demultiplexer 3 restores the PES packet from the TS packet input from the demodulator 2 and separates and extracts the video ES as video data encoded from the PES packet and the audio ES as encoded audio data. The video ES is output to the video decoder 4. At this time, the error TS packet is discarded. The audio ES is decoded by an audio decoder (not shown), restored to an audio signal, and reproduced as audio from a speaker or the like. A detailed description of the audio decoding process is omitted. In the following description, the video ES is simply referred to as ES.

  The video decoder 4 as a video decoding device according to an embodiment of the present invention performs decoding processing on the input ES, restores the video signal, and outputs the video signal to the video display device 11. The video decoder 4 includes an ES buffer 5, a VLC (Variable Length Coding) decoding processing unit 6, a video data decoding processing unit 7, a syntax analysis unit 8, a start code searching unit 9, and an error start code searching unit. 10.

  The ES buffer 5 as a storage means is a buffer for storing a predetermined amount of ES input from the TS demultiplexer 3 and is constituted by a semiconductor memory. In this embodiment, the capacity is sufficient to store at least one slice of ES. That is, information from synchronization information to next decoded synchronization information is stored.

  The VLC decoding processing unit 6 as decoding means reads the ES input to the ES buffer 5, performs VLC decoding processing, and outputs the data after VLC decoding processing to the video data decoding processing unit 7.

  The video data decoding processing unit 7 as decoding means and video storage means restores the video signal by performing processing such as inverse quantization, inverse DCT (Discrete Cosine Transform) and motion compensation on the data after the VLC decoding processing.

  The syntax analysis unit 8 serving as a decoding unit detects and detects a start code in order to obtain video format information such as the number of pixels of the video to be decoded, the aspect ratio, or the scanning method stored in the ES buffer 5. The header header such as a sequence header, picture header, or slice header following the start code is analyzed, and information necessary for decoding such as video format information is acquired. The acquired information is output to the VLC decoding processing unit 6 and the video data decoding processing unit 7.

  The start code search unit 9 as the synchronization information detection means decodes video data in a certain processing unit (macro block or the like) video data by the video data decoding processing unit 7, and the next data to be read is a start code (000001 in hexadecimal notation). ) And if it is a start code, the syntax analysis unit 8 is notified. The syntax analysis unit 8 determines the type of start code, that is, the sequence start code, picture start code, or slice start code, and performs syntax analysis.

  The error start code search unit 10 as the error synchronization information detecting means, when a decoding error is detected by the VLC decoding processing unit 6, starts the next start from the position of the start code detected before the decoding error detection. The code is searched and notified to the syntax analysis unit 8.

  The video display device 11 is a device that displays the video signal input from the video decoder 4, and is composed of a CRT, a plasma display, a liquid crystal display, or the like.

  The operation when the ES decoding process is performed in the video decoder 4 of the digital broadcast receiver 1 having the configuration shown in FIG. 3 will be described. First, in order to obtain video format information such as the number of pixels of the video (stream) to be decoded, the aspect ratio, or the scanning method, syntax analysis is performed to obtain the video format information. Next, the decoding processing operation of the ES below the slice layer is started. The operation will be described with reference to the flowchart shown in FIG.

  First, in step S1, the start code search unit 9 determines whether or not the detected start code is a slice start code added to the head of each slice. The process proceeds to S2, and if not (NO), the process proceeds to step S7 because a header other than the slice start code is obtained.

  Next, in step S2, the syntax analysis unit 8 performs a slice layer syntax analysis process and proceeds to step S3.

  Next, in step S3, the VLC decode processing unit 6 performs VLC decode processing for one macroblock and proceeds to step S4.

  Next, in step S4, if a VLC code that does not exist is input in the VLC decode processing unit 6, that is, it is determined whether or not an error has occurred. If a decoding error has occurred (YES), step S8 is performed. If not (NO), the process proceeds to step S5.

  Next, in step S5, the video data decoding processing unit 7 performs macroblock decoding processing (inverse quantization, inverse DCT, motion compensation, etc.) on the macroblock that has been subjected to VLC decoding processing in step S3, and the process proceeds to step S6.

  Next, in step S6, if the VLC decoding processing unit 6 determines whether or not the macroblock subjected to the decoding process in step S5 is the end of the slice, and if it is the end of the slice (in the case of YES), the process proceeds to step S1. If not (NO), the process returns to step S3. The last macroblock is determined by detecting the start code (000001 in hexadecimal notation). For example, FIG. 5 shows the case of terrestrial digital broadcasting. FIG. 5 shows a screen displayed on the video display device 11. In digital terrestrial broadcasting, one slice is almost always set by one line of the screen as shown in FIG.

  In step S7, syntax analysis processing other than the slice layer, such as a picture layer, is performed by the syntax analysis unit 8 and the process returns to step S1.

  In step S8, since a decoding error is detected, the error start code search unit 10 returns to the position of the previously decoded slice start code stored in the ES buffer 5, and starts the next slice from the slice start code. The code is searched and the process returns to step S1. That is, the information indicating the next synchronization is detected from the position of the information indicating the synchronization decoded by the decoding means before the decoding error is detected.

  The search for the slice start code is performed as follows. Normal VLC decoding processing (including start code search and syntax analysis) is performed by decoding with a variable number of bits to process VLC. In step S8, in the MPEG-2 standard, slice processing is performed. The start code is one of 4 bytes from 00000101 to 000001AF in hexadecimal notation, and byte alignment is performed between the start code and the next start code (one bit before the next start code from the start code). The data from the ES buffer 5 can be decoded byte by byte from the slice start code that was previously decoded (recognized) using the fact that the data is evenly divided by bytes (8 bits). Read and detect. That is, the video data is read out from the storage means in units of bytes, and information indicating the next synchronization is detected. In this way, the slice start code can be detected early.

  An example of the operation of the above flowchart will be described with reference to FIG. The macro blocks B to D of the slice n−1 in FIG. 5 are included in the error TS packet, and if a decoding error occurs in the macro block H of the slice n, the macro blocks B to D are not input to the video decoder 4. Therefore, a normal image is not displayed at the positions of the macro blocks B to D. There is a high possibility that the subsequent macroblocks E and F cannot be decoded so that a normal image can be displayed due to the effect of the missing macroblocks B to D. In the first macroblock G of the next slice n, a slice start code is added before the data of the macroblock. Due to the loss of the macroblocks B to D, in one macroblock decoding (step S3), There is a possibility that the slice start code is read by mistake and cannot be recognized.

  Therefore, in step S8 after the occurrence of the VLC decoding error, first, the start code of slice n can be detected by reading in byte units from the position of the start code of slice n-1 that was previously decoded. If the start code of the slice n can be detected, the process returns to step S1 at that time and normal decoding processing is performed. That is, the video data is read from the storage means in byte units, information indicating the next synchronization is detected, and the video data is decoded from the position of the information indicating the detected synchronization. By doing so, conventionally, when a decoding error occurs in the macroblock G, the decoding is stopped until the start code of the slice following the slice n is detected, so that the slice n cannot display a normal image. However, by searching for the start code of slice n, slice n can display a normal image.

  According to the present embodiment, when a decoding error due to an error TS packet occurs in the video decoder 4 of the digital broadcast receiver 1, the error start code search unit 10 performs decoding before the decoding error occurs from the ES buffer 5. The slice start code is read out, and the next slice start code is detected from the slice start code position in bytes, and the syntax analysis unit 8, VLC decode processing unit 6 and video data decoding are detected from the slice start code. Decoding is resumed by the processing unit 7. By doing so, it is possible to minimize the influence of the decoding error due to a part of the ES being lost by the error TS packet in order to recognize the slice start code that could not be recognized conventionally.

  The video decoder 4 is replaced with a CPU and a memory constituting the computer, the ES buffer 5 is replaced with a memory, a VLC decoding processing unit 6, a video data decoding processing unit 7, a syntax analysis unit 8, a start code search unit 9, and an error. The function of the hour start code search unit 10 may be a program executed by the CPU. In this way, even if it is not dedicated hardware, it recognizes the slice start code that could not be recognized in the past due to the decoding error caused by the loss of part of the ES due to the error TS packet in the software on the computer. Therefore, it can function as a video decoder that can be reduced.

  In the above-described embodiment, normal images cannot be displayed in the macro blocks B to F of the slice n-1, but a plurality of past video data decoded due to the inter-frame predictive encoding in MPEG-2. Therefore, the entire slice n-1 may be replaced with a slice at the same position in the past image. For example, when the error start code search unit 10 detects the slice start code of slice n according to the flowchart of FIG. 4, slice n−1 is a past image stored in a memory (not shown) of the video data decoding processing unit 7 ( For example, the error start code search unit 10 instructs the video data decoding processing unit 7 to replace the slice with the position of n-1 in the previous frame). That is, the video from the information indicating the synchronization decoded immediately before the detection of the decoding error to the information immediately before the information indicating the next synchronization is replaced with the video decoded in the past. By doing so, the macroblocks missing from the error TS packet and the macroblocks between the portion missing from the error TS packet and the slice start code can also display a video close to the original video. The influence of the packet can be reduced.

  Further, although the slice start code has been described in the above-described embodiment, a start code that could not be recognized by detecting the picture start code and the sequence start code can be detected in the same manner, and resynchronization can be performed from the detected start code. Video can be displayed.

  In the above-described embodiment, the ES buffer 5 is included in the video decoder 4. However, when the configuration is made of semiconductor components, the video decoder 4 is one component other than the ES buffer 5, and the ES buffer 5 is a separate component. The two parts may be configured separately. Of course, each block may be composed of a single component.

  According to the embodiment described above, the following video decoding device, video decoding method, and video decoding program can be obtained.

(Supplementary Note 1) In the video decoder 4 including the VLC decoding processing unit 6, the video data decoding processing unit 7, and the syntax analysis unit 8 that receive the ES and decodes the ES,
An ES buffer 5 for storing a predetermined amount of ES;
A start code search unit 9 for detecting a slice start code included in the ES stored in the ES buffer 5;
When the VLC decoding processing unit 6 detects a decoding error, an error start code search unit 10 that detects the next slice start code from the position of the slice start code decoded before the decoding error is detected, Prepared,
A video decoder 4 characterized in that a VLC decoding processing unit 6, a video data decoding processing unit 7, and a syntax analysis unit 8 decode an ES from a slice start code detected by an error start code search unit 10.

  According to the video decoder 4, when the information indicating the next synchronization cannot be recognized due to the error TS packet, the slice start code can be reliably detected, so that the influence of the display image due to the decoding error can be reduced. it can.

(Supplementary Note 2) In a video decoding method for inputting an ES and decoding the ES,
When a predetermined amount of ES is stored, the stored ES is read, the ES is decoded, and a decoding error is detected, the next slice start code is read from the position of the decoded slice start code before the decoding error is detected. A video decoding method comprising: detecting and decoding from the detected next slice start code.

  According to this video decoding method, if the information indicating the next synchronization cannot be recognized due to an error TS packet, the slice start code can be reliably detected, so that the influence of the display image due to the decoding error can be reduced. it can.

(Supplementary Note 3) In a video decoding program that causes a computer to function as a VLC decoding processing unit 6, a video data decoding processing unit 7, and a syntax analysis unit 8 that receive an ES and decode the ES,
An ES buffer 5 for storing a predetermined amount of ES;
A start code search unit 9 for detecting a slice start code included in the ES stored in the ES buffer 5;
When the VLC decode processing unit 6 detects a decoding error, the error start code search unit 10 detects the next slice start code from the position of the slice start code decoded before the decoding error is detected. Make it work,
A video decoding program characterized in that a VLC decoding processing unit 6, a video data decoding processing unit 7, and a syntax analysis unit 8 decode an ES from a slice start code detected by an error start code search unit 10.

  According to this video decoding program, if the information indicating the next synchronization cannot be recognized due to an error TS packet, the slice start code can be reliably detected, so that the influence of the display image due to the decoding error can be reduced. it can.

  In addition, the Example mentioned above only showed the typical form of this invention, and this invention is not limited to an Example. That is, various modifications can be made without departing from the scope of the present invention.

It is explanatory drawing of the TS packet in a prior art. It is explanatory drawing of the error TS packet in a prior art. It is a block diagram of the video decoding apparatus concerning one Example of this invention. 4 is a flowchart illustrating a decoding operation of the video decoding apparatus illustrated in FIG. 3. It is explanatory drawing of the slice on a display screen.

Explanation of symbols

1 Digital Broadcasting Receiver 4 Video Decoder (Video Decoding Device)
5 ES buffer (storage means)
6 VLC decoding processor (decoding means)
7 Video data decoding processing unit (decoding means, video storage means)
8 Syntax analyzer (decoding means)
9 Start code search part (synchronous information detection means)
10 Error start code search part (error synchronization information detection means)

Claims (8)

In a video decoding apparatus provided with decoding means for inputting encoded video data and decoding the video data,
Storage means for storing a predetermined amount of the encoded video data;
Synchronization information detection means for detecting information indicating synchronization included in the encoded video data stored in the storage means;
When the decoding means detects a decoding error, synchronization information at the time of detecting information indicating the next synchronization from the position of the information indicating the synchronization decoded by the decoding means before the decoding error is detected Detecting means,
The video decoding apparatus, wherein the decoding means decodes video data from the information indicating the synchronization detected by the error synchronization information detecting means.   2. The video decoding apparatus according to claim 1, wherein the error-time synchronization information detecting unit detects the information indicating the next synchronization by reading the video data in bytes from the storage unit.   The video decoding apparatus according to claim 1, wherein the storage unit stores at least information indicating the synchronization to information indicating the synchronization decoded next. Video storage means for storing video data decoded in the past,
When the decoding means detects a decoding error, the video storage means stores the video from the information indicating the synchronization decoded immediately before the decoding error is detected to immediately before the information indicating the next synchronization. 4. The video decoding device according to claim 1, wherein the video decoding device is replaced with the video data that has been processed.   A digital broadcast receiver comprising the video decoding device according to claim 1. In a video decoding method for inputting encoded video data and decoding the video data,
The video data is stored in a predetermined amount, the stored encoded video data is read out, the video data is decoded, and when a decoding error is detected, the synchronization is decoded before the decoding error is detected. A video decoding method, wherein information indicating the next synchronization is detected from a position of the information indicating, and decoding is performed from the detected information indicating the next synchronization. In a video decoding program for inputting encoded video data and causing a computer to function as decoding means for decoding the video data,
Storage means for storing a predetermined amount of the encoded video data;
Synchronization information detection means for detecting information indicating synchronization included in the encoded video data stored in the storage means;
When the decoding means detects a decoding error, synchronization information at the time of detecting information indicating the next synchronization from the position of the information indicating the synchronization decoded by the decoding means before the decoding error is detected Let the computer function as a detection means,
A video decoding program, wherein the decoding means decodes video data from the information indicating the synchronization detected by the error time synchronization information detecting means.   A computer-readable recording medium storing the video decoding program according to claim 7.

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