JP2007318516A - Program, information processing apparatus, information processing method, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a bit stream whereby decoding is executed by a correct quantization matrix at random decoding. <P>SOLUTION: A bit stream converter 1 reads a quantization matrix Q2 described in a picture header of a B6 picture and overwrites the quantization matrix Q2 to a Q matrix buffer. When receiving a next B7 picture and a P11 picture being a next P picture not describing the quantization matrix, the bit stream converter 1 reads the quantization matrix Q2 overwritten in the Q matrix buffer 14 and describes the quantization matrix Q2 to picture headers of the B7 picture and the P11 picture. Further, as to pictures after the P11 picture, when not receiving a B picture whose picture header describes a quantization matrix, the bit stream converter 1 outputs pictures in a supplied state. The present invention is applicable to bit stream converters or personal computers. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a program, an information processing apparatus, an information processing method, and a recording medium, and particularly to a program, an information processing apparatus, an information processing method, and a recording medium that are suitable for random playback.

In a Long GOP stream of MPEG (Moving Picture Expert Group), a value of a quantization matrix is referred to and decoding is performed (for example, Patent Document 1).
JP 2004-343279 A

  The quantization matrix is an 8 × 8 matrix used for quantization when encoding and decoding MPEG (Moving Picture Experts Group) stream data.

  The quantization matrix described in the bit stream will be described with reference to FIG. The MPEG Long GOP stream usually has quantization matrix information (quantization matrix Q1 in the figure) in the sequence header of the I picture at the head of the GOP. In addition, when there is a change in the quantization matrix in the middle of the GOP, information on the quantization matrix (quantization matrix Q2 and Q2 ′ in the figure) is described in the picture header of the P picture or B picture, In other pictures where the quantization matrix does not change from the previous picture, the quantization matrix data is often not described in the picture header.

  As the quantization matrix, two types of intra and non-intra can be set in the sequence header of the I picture and in the picture header of each of the I picture, P picture, or B picture. Also, in the 4: 2: 2 or 4: 4: 4 stream, as described in the B6 picture in the figure, the luminance (quantization matrix Q2 in the figure) and the color difference (quantization matrix Q2 ′ in the figure) ) Can be defined separately, and in the picture header, a maximum of four types of quantization matrixes can be set by combinations of intra / non-intra and luminance / chrominance.

  As described in Patent Document 1 described above, in a special case, the quantization matrix held by the stream may not be used as it is, but basically, it is described in the stream. A quantization matrix is utilized to perform stream encoding and decoding.

  When decoding an MPEG stream, if there is a change in the quantization matrix in the middle of the stream, after that change, decoding is performed using the changed quantization matrix described in the picture header etc. . However, for example, when there is a change in the quantization matrix in the B picture in the middle of the stream, and the value of the quantization matrix to be used after that is described in the picture header of the B picture, in random playback etc. If decoding of the B picture is not executed, and subsequent decoding is executed from another picture that should be decoded with the same quantization matrix, it will be decoded using an incorrect quantization matrix. , Normal playback is not possible.

  For example, as shown in FIG. 2, when the changed quantization matrix is described in the picture header of the B6 picture in the middle of the GOP, the quantization matrix Q1 set in the first I2 picture is used. Thus, the I2 picture to the P8 picture are encoded, and the B6 picture to the B13 picture are encoded using the quantization matrix Q2 set in the B6 picture. Therefore, in order to normally reproduce this GOP, it is necessary to decode using the quantization matrix Q1 from the I2 picture to the P8 picture and using the quantization matrix Q2 from the B6 picture to the B13 picture.

  However, when random reproduction is started from any of the pictures from B7 picture to B13 picture, the quantization matrix Q2 is not detected in any picture and the picture to be the reference picture, so the quantization matrix Q1 is used. Quantization is performed and image quality deteriorates.

  The present invention has been made in view of such a situation, and makes it possible to prevent deterioration of image quality even in random reproduction by adding simple information as much as possible to stream data and by simple processing. It is.

  A program according to an aspect of the present invention is a program for causing a computer to execute a process of analyzing a bitstream, and sequentially analyzes the bitstream from the front in time to form a B picture included in the bitstream. Determine whether the value of the quantization matrix is described, and if the value of the quantization matrix is described in the B picture, extract the information of the quantization matrix and hold the latest quantization matrix Then, the computer is caused to execute a process including a step of describing the value of the held quantization matrix in a predetermined frame following the B picture in which the information of the quantization matrix is described.

  The predetermined frame is the next P picture in time and the B picture arranged up to the P picture, or the B picture in which the information of the quantization matrix is described, and the quantization matrix. It can be a frame arranged between any frames arranged next in time in which information of quantization matrixes of different values is described.

  Causing the computer to execute a process further including a step of decoding a bitstream in which the value of the held quantization matrix is described in a predetermined frame following the B picture in which the information of the quantization matrix is described Can do.

  The bit stream is an encoded stream encoded by the MPEG encoding method.

  An information processing apparatus according to an aspect of the present invention is an information processing apparatus that analyzes a bitstream, and that sequentially analyzes the bitstream from the front in time and is described in a B picture included in the bitstream Analyzing means for extracting the value of the quantization matrix, holding means for holding the latest quantization matrix extracted by the analyzing means, and a predetermined picture following the B picture in which information on the quantization matrix is described The frame includes a description unit that describes the value of the quantization matrix held by the holding unit.

  The predetermined frame is the next P picture in time and the B picture arranged up to the P picture, or the B picture in which the information of the quantization matrix is described, and the quantization matrix. It can be a frame arranged between any frames arranged next in time in which information of quantization matrixes of different values is described.

  The description means may further comprise decoding means for decoding the bitstream in which the value of the quantization matrix is described.

  The bit stream is an encoded stream encoded by the MPEG encoding method.

  An information processing method according to an aspect of the present invention is an information processing method of an information processing apparatus that analyzes a bitstream, and sequentially analyzes the bitstream from the front in time to form a B picture included in the bitstream. Determine whether the value of the quantization matrix is described, and if the value of the quantization matrix is described in the B picture, extract the information of the quantization matrix and hold the latest quantization matrix And a step of describing the value of the held quantization matrix in a predetermined frame following the B picture in which the information of the quantization matrix is described.

  In one aspect of the present invention, a bit stream is sequentially analyzed from the front in time, it is determined whether a quantization matrix value is described in a B picture included in the bit stream, and the quantization matrix is included in the B picture. When the value of is described, the quantization matrix information is extracted and the latest quantization matrix is held, and the held quantum is stored in a predetermined frame following the B picture in which the quantization matrix information is described. The value of the quantization matrix is described.

  The network is a mechanism in which at least two devices are connected and information can be transmitted from one device to another device. The devices that communicate via the network may be independent devices, or may be internal blocks that constitute one device.

  The communication is not only wireless communication and wired communication, but also communication in which wireless communication and wired communication are mixed, that is, wireless communication is performed in a certain section and wired communication is performed in another section. May be. Further, communication from one device to another device may be performed by wired communication, and communication from another device to one device may be performed by wireless communication.

  The recording device may be an independent device or a block that performs recording processing of the recording / reproducing device.

  As described above, according to one aspect of the present invention, a bit stream can be analyzed, and in particular, a quantization matrix held in a predetermined frame following a B picture in which information on the quantization matrix is described. Since the bitstream in which the value of is written is generated, it is possible to prevent image degradation when the generated bitstream is decoded.

  Embodiments of the present invention will be described below. Correspondences between constituent elements of the present invention and the embodiments described in the specification or the drawings are exemplified as follows. This description is intended to confirm that the embodiments supporting the present invention are described in the specification or the drawings. Therefore, even if there is an embodiment which is described in the specification or the drawings but is not described here as an embodiment corresponding to the constituent elements of the present invention, that is not the case. It does not mean that the form does not correspond to the constituent requirements. Conversely, even if an embodiment is described here as corresponding to a configuration requirement, that means that the embodiment does not correspond to a configuration requirement other than the configuration requirement. It's not something to do.

  A program according to one aspect of the present invention or a program recorded on a recording medium is a program for causing a computer to execute processing for analyzing a bitstream, and sequentially analyzes the bitstream from the front in time ( For example, it is determined whether or not the value of the quantization matrix is described in the B picture included in the bit stream (for example, the process of step S4 of FIG. 15) When the value of the quantization matrix is described in the B picture, the quantization matrix information is extracted and the latest quantization matrix is held (for example, the process of step S5 in FIG. 15), and the quantization The quantization matrix held in a predetermined frame following the B picture in which matrix information is described It describes a value (for example, step S7 in FIG. 15) to execute processing including a step in the computer.

  An information processing apparatus according to one aspect of the present invention is an information processing apparatus (for example, the bit stream conversion apparatus 1 in FIG. 3 or the personal computer 201 in FIG. 13) that analyzes a bit stream, and converts the bit stream into time information. Analysis means (for example, the bit stream analysis unit 12 in FIG. 3 or FIG. 14) for sequentially analyzing from the front and extracting the value of the quantization matrix described in the B picture included in the bit stream, and the analysis Holding means for holding the latest quantization matrix extracted by the means (for example, the Q matrix buffer 14 in FIG. 3 or FIG. 14), and a predetermined number following the B picture in which the information of the quantization matrix is described Description means for writing the value of the quantization matrix held by the holding means in the frame (for example, FIG. 3 or FIG. Comprising a stream combining unit 15) and FIG. 14.

  Decoding means (for example, a decoding processing unit 261 in FIG. 14) for decoding the bitstream in which the value of the quantization matrix is described by the description means can be further provided.

  An information processing method according to one aspect of the present invention is an information processing method of an information processing apparatus (for example, the bit stream conversion apparatus 1 in FIG. 3 or the personal computer 201 in FIG. 13) that analyzes a bit stream, The stream is sequentially analyzed from the front in time (for example, the processing in step S2 and step S3 in FIG. 15), and it is determined whether the value of the quantization matrix is described in the B picture in the bit stream (for example, When the value of the quantization matrix is described in the B picture, the information of the quantization matrix is extracted and the latest quantization matrix is stored (for example, FIG. 15). In step S5), and held in a predetermined frame following the B picture in which the information of the quantization matrix was described The described values of the quantization matrix (for example, step S7 in FIG. 15) includes the step.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 is a block diagram showing a configuration of the bit stream conversion apparatus 1.

  The bit stream conversion apparatus 1 includes an original bit stream acquisition unit 11, a bit stream analysis unit 12, a stream buffer 13, a Q matrix buffer 14, a stream synthesis unit 15, and a bit stream output unit 16.

  The original bitstream acquisition unit 11 receives the supply of the bitstream including the I picture, the P picture, and the B picture, and supplies the bitstream analysis unit 12 with the bitstream.

  The bit stream analysis unit 12 receives a bit stream including an I picture, a P picture, and a B picture, analyzes the bit stream, and, for example, determines the picture type of each picture and the quantum in the picture header. When an analysis result such as whether or not a quantization matrix is described is supplied to the stream synthesis unit 15 and a quantization matrix (also referred to as a Q matrix) is described in a picture header of a B picture, the quantization The matrix value is written into the Q matrix buffer 14. When a new quantization matrix value is written in the Q matrix buffer 14, it is overwritten and saved.

  Two types of quantization matrices, intra and non-intra, must be set in the I-picture sequence header as well as in the I-picture, P-picture, or B-picture header. Can do. Also, in 4: 2: 2 and 4: 4: 4 streams, luminance and color difference can be defined separately, so in the picture header, the combination of intra / non-intra and luminance / color difference can be used. Up to 4 types of quantization matrix can be set.

  In addition, the bit stream analysis unit 12 supplies the supplied bit stream to the stream buffer 13.

  The stream buffer 13 buffers the bit stream supplied from the bit stream analysis unit 12 and supplies the buffer to the stream synthesis unit 15.

  The Q matrix buffer 14 overwrites and stores the quantization matrix supplied by the processing of the bit stream analysis unit 12.

  The stream synthesizing unit 15 is stored in the Q matrix buffer 14 in the picture header of a predetermined frame of the stream supplied from the stream buffer 13 based on the analysis result of the bit stream supplied from the bit stream analyzing unit 12. The latest quantization matrix value is written and supplied to the bitstream output unit 16.

  That is, the stream synthesis unit 15 uses the picture header of each picture from the B picture in which the value of the quantization matrix is described in the picture header to the next P picture in the stream order, or the stream order, The value of the latest quantization matrix stored in the matrix buffer 14 is described in the picture header of each picture up to the B picture before the picture in which the quantization matrix is described, and is supplied to the bitstream output unit 16 To do.

  The bit stream output unit 16 supplies the bit stream, which is supplied from the stream synthesis unit 15 and whose quantization matrix value is described in the picture header of a predetermined frame, to the other via a wired or wireless predetermined communication path. Output to the device.

  The bit stream output by the bit stream output unit 16 may be supplied to a playback device that decodes and outputs the bit stream via a predetermined wired or wireless communication path. Alternatively, the data may be supplied to a recording device that records data on a recording medium such as a semiconductor memory via a predetermined wired or wireless communication path.

  The operation of the bit stream conversion apparatus 1 will be described with reference to FIGS.

  In the bitstream conversion apparatus 1, the bitstream acquired by the original bitstream acquisition unit 11 is supplied to the bitstream analysis unit 12. When the quantization matrix information is described in the picture header of the B picture in the supplied stream, the bit stream analysis unit 12 reads out the information, writes the information in the Q matrix buffer 14, and analyzes the analyzed picture. Is supplied to the stream buffer 13.

  Therefore, as shown in FIG. 4, in the first I2 picture of the GOP, the quantization matrix described in the sequence header is not written in the Q matrix buffer 14 (Q matrix Buffer).

  Then, as shown in FIG. 5, when the B6 picture is supplied from the bitstream acquisition unit 11 to the bitstream analysis unit 12, the bitstream analysis unit 12 displays the quantization matrix described in the picture header of the B6 picture. Q2 is read and overwritten and saved in the Q matrix buffer 14.

  At this time, the quantization matrix Q2 is described in the picture header of the B6 picture output from the bitstream output unit 16.

  Then, as shown in FIG. 6, when the next B7 picture in which the quantization matrix is not described is supplied to the bit stream analysis unit 12 and supplied to the stream synthesis unit 15 via the stream buffer 13, the stream The synthesizing unit 15 reads the quantization matrix Q2 overwritten and stored in the Q matrix buffer 14, writes it in the picture header of the B7 picture, supplies it to the bitstream output unit 16, and outputs it.

  Then, as shown in FIG. 7, the P11 picture, which is the next P picture in which no quantization matrix is described, is supplied to the bit stream analysis unit 12 and supplied to the stream synthesis unit 15 via the stream buffer 13. Even in such a case, the stream synthesizing unit 15 reads the quantization matrix Q2 overwritten and stored in the Q matrix buffer 14, describes it in the picture header of the P11 picture, supplies it to the bitstream output unit 16, and outputs it. Then, in the pictures after the P11 picture, if the B picture in which the quantization matrix is described in the picture header is not supplied, the process of describing the quantization matrix by the stream synthesizing unit 15 is not executed, and the bit stream analyzing unit 12 The picture in the state supplied to is output from the bitstream output unit 16.

  Further, in the 4: 2: 2 or 4: 4: 4 stream, it is possible to separately define a color difference matrix in the extended quantization matrix in the picture header. Therefore, as shown in FIG. 8, the bitstream analysis unit 12 reads the quantization matrix Q2 and the quantization matrix Q2 ′ described in the picture header of the B6 picture, and overwrites and stores them in the Q matrix buffer 14. Similarly, the stream synthesizing unit 15 reads the quantization matrix Q2 and the quantization matrix Q2 ′ that are overwritten and stored in the Q matrix buffer 14, and writes them in the picture headers of the B7 picture and the P11 picture, The data is supplied to the bitstream output unit 16 and output.

  Next, with reference to FIG. 9 to FIG. 12, a case where the bit stream converted in the bit stream conversion apparatus 1 in this way is decoded and reproduced and output will be described.

  As shown in FIG. 9, as is conventionally performed for an MPEG Long GOP in which information of a quantization matrix Q2, which is a quantization matrix having a value different from that of the quantization matrix Q1, is described in the B6 picture. When random decoding is performed, for example, when a P11 picture included in the range indicated by α in the figure encoded by the quantization matrix Q2 is designated as the playback start point, the B6 picture is also used as a reference image Not. For this reason, the P11 picture to be decoded by the quantization matrix Q2 is decoded by the quantization matrix Q1, resulting in a malfunction. That is, in the GOP structure shown in FIG. 9, for any frame from the B7 picture after the B6 picture in which the information of the quantization matrix Q2 is described to the B13 picture before the next I picture, If random decoding is instructed directly without decoding the B6 picture, a malfunction will occur as well.

  Therefore, as described above, in the bitstream conversion apparatus 1, the quantization matrix described in the B picture in the stream is buffered, and from the B picture to the next P picture in the stream order or in the stream order. Next, the value of the buffered quantization matrix is described in the picture header of each picture up to the B picture before the picture in which the quantization matrix is described.

  That is, as shown in FIG. 10, in the bitstream generated in the bitstream conversion apparatus 1 in which the B7 picture and the P11 picture have information on the quantization matrix Q2 in addition to the B6 picture, FIG. As described above, the decoding process is executed with the quantization matrix Q2 regardless of which picture of the section α that has malfunctioned in the original stream is designated as the playback start point, so the wrong quantization matrix is used. Therefore, there is no deterioration of the image.

  Specifically, when random reproduction is performed on the bitstream shown in FIG. 10 generated in the bitstream conversion apparatus 1 and a B7 picture or P11 picture is designated as the reproduction start point, the B7 picture or P11 picture is changed to the B7 picture or P11 picture. Decoding processing is executed using the described quantization matrix Q2. Further, when random playback is performed on the bit stream shown in FIG. 10 generated by the bit stream conversion apparatus 1 and any one of B9 to B13 pictures is designated as the playback start point, the decoding process is performed. By referring to the P11 picture, the decoding process is executed using the quantization matrix Q2 described in the P11 picture.

  As shown in FIG. 11, the most extreme example in which the operation differs in the decoding process between the conventional case and the case using the bitstream conversion apparatus 1 is different from the quantization matrix Q1 in the B0 picture at the beginning of the GOP. This is a case where random decoding is performed on an MPEG Long GOP in which information of a quantization matrix Q2, which is a quantization matrix of values, is described.

  In the case of encoding from a B0 picture immediately after the first I picture using a quantization matrix different from the I picture, in the random reproduction that has been performed in the past, the information of the B0 picture in which the information of the quantization matrix Q2 is described Even if any picture from the subsequent B1 picture to the next I picture is selected as the playback start position for random playback, the picture to be decoded by the quantization matrix Q2 is decoded by the quantization matrix Q1 and malfunctions. It becomes. That is, in a GOP structure (N = 15, M = 3) stream that is usually used in MPEG2, a section of 13 frames malfunctions. If this is generalized, decoding malfunctions when the frame with the number of frames of 2 constituting 1 GOP is designated as the reproduction start position of random decoding.

  However, as shown in FIG. 12, the bit stream generated by the bit stream conversion apparatus 1 is a quantization matrix having a value different from that of the quantization matrix Q1 described in the sequence header of the I picture. From the B0 picture in which the information of the matrix Q2 is described to the next P picture in the stream order, that is, the information of the quantization matrix Q2 is described in the picture header of the B1 picture and the P5 picture. Even if any picture up to the next I picture is selected as a reproduction start position for random reproduction, it is decoded by the quantization matrix Q2, and no malfunction occurs.

  Specifically, when random reproduction is performed on the bitstream generated in the bitstream conversion apparatus 1 shown in FIG. 12 and a B1 picture or P5 picture is designated as the reproduction start point, the B1 picture or P5 picture is changed to the B1 picture or P5 picture. Decoding processing is executed using the described quantization matrix Q2. In addition, when random reproduction is performed on the bitstream generated by the bitstream conversion apparatus 1 shown in FIG. 12 and any one of B3 to B13 pictures is designated as the reproduction start point, the decoding process is performed. By referring to the P5 picture, the decoding process is executed using the quantization matrix Q2 described in the P5 picture.

  The series of processes described above can be executed by hardware or can be executed by software. In this case, for example, the bit stream conversion apparatus 1 includes a personal computer 201 as shown in FIG.

  In FIG. 13, a CPU (Central Processing Unit) 221 executes various processes according to a program stored in a ROM (Read Only Memory) 222 or a program loaded from a HDD 226 to a RAM (Random Access Memory) 223. The RAM 223 also appropriately stores data necessary for the CPU 221 to execute various processes.

  The CPU 221, ROM 222, and RAM 223 are connected to each other via a bus 224. Also connected to the bus 224 are interfaces (I / F) 225-1 to 225-3, an HDD (hard disc drive) 226, a video special effect audio mixing processing unit 227, and a signal processing unit 228.

  Input devices such as a keyboard 202 and a mouse 203 are connected to the interface 225-1. The storage device 204 is connected to the interface 225-2 so that information can be exchanged. The interface 225-3 is connected to external video recording / reproducing apparatuses 205-1 to 205-m so that information can be exchanged. The HDD 226 can drive a hard disk and store various information.

  The video special effect audio mixing processing unit 227 is also connected to the signal processing unit 228, the storage device 204, and the video recording / playback devices 205-1 to 205-m, and the storage device 204 and the video recording / playback devices 205-1 to 205-m. The video signal supplied from any one of m or from the HDD 226 via the bus 224 is subjected to special effects, mixed with audio, etc., and supplied to the signal processing unit 228 for output. Then, the data is supplied to and stored in any of the storage device 204 and the video recording / reproducing devices 205-1 to 205-m.

  The signal processing unit 228 is also connected to the display 229 and the speaker 230. For example, the video signal supplied from the video special effect audio mixing processing unit 227 is supplied to the display 229 for display, or the audio signal is displayed on the speaker 230. To output sound.

  The display 229 includes, for example, a CRT (Cathode Ray Tube), an LCD (Liquid Crystal display), and the like, and displays an image supplied from the signal processing unit 228. The speaker reproduces and outputs the sound supplied from the signal processing unit 228.

  A drive 231 is also connected to the bus 224 as necessary, and a removable medium 206 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory is appropriately installed, and a computer program read from the medium is required. Accordingly, it is installed in the HDD 226.

  In addition, the personal computer 201 may further have a function of decoding the bit stream generated by the conversion.

  In the personal computer 201 described with reference to FIG. 13, a series of processing executed by the above-described bit stream conversion apparatus 1 is executed by software, and functions when the bit stream generated by conversion is decoded are decoded. FIG. 14 shows a functional block diagram for explaining an example.

  Note that portions corresponding to those in FIG. 3 or FIG. 13 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  When the CPU 221 executes a predetermined program, the personal computer 201 has functions equivalent to the original bitstream acquisition unit 11, the bitstream analysis unit 12, the stream synthesis unit 15, and the bitstream output unit 16 of FIG. . Data storage areas corresponding to the stream buffer 13 and the Q matrix buffer 14 are provided in the RAM 223. The data storage area corresponding to the stream buffer 13 and the Q matrix buffer 14 may be provided as a cache memory of the CPU 221 instead of the RAM 223, for example. Further, when the CPU 221 executes a predetermined program, the personal computer 201 further has a function of a decoding processing unit 261 that decodes the compressed encoded data.

  The original bitstream acquisition unit 11 of the CPU 221 acquires the bitstream recorded in the original bitstream storage unit 251 corresponding to any area of the storage device 204, the external video recording / playback device 205, or the HDD 226. To the bitstream analyzing unit 12.

  The bit stream analysis unit 12 of the CPU 221 analyzes the bit stream based on a user operation input by an input device such as the mouse 202 or the keyboard 203, supplies the analyzed picture to the stream buffer 13, and either The latest quantization matrix described in the picture header of the B picture is buffered in the Q matrix buffer 14.

  Then, the stream composition unit 15 of the CPU 221 performs stream ordering from the B picture in which information of the quantization matrix Q2, which is a quantization matrix having a value different from the quantization matrix Q1 described in the sequence header of the I picture, is described. In the picture header of the picture up to the picture up to the next P picture or the B picture immediately before the picture in which a different quantization matrix is described, the latest buffered in the Q matrix buffer 14 Describes the value of the quantization matrix.

  Then, the stream synthesis unit 15 of the CPU 221 converts the generated bit stream into the bit stream output unit 16, specifically, a drive such as an external interface or a memory or a module that controls the drive, the storage device 204, the external The video recording / playback apparatus 205 or the converted bitstream storage unit 271 corresponding to any area of the HDD 226 may be supplied and stored, or may be output to the outside via the I / F 225. Then, it may be recorded on the removable medium 206 via the drive 231 or may be supplied to the decoding processing unit 261 of the CPU 221 for decoding.

  The decoding processing unit 261 uses the quantization matrix described in the sequence header or the picture header to decode the generated bit stream as described with reference to FIG. 10 or FIG. Even when is executed, malfunction caused by referring to an incorrect quantization matrix does not occur, so that deterioration of image quality can be suppressed as compared with the conventional case.

  The decoded frame image data may be output to the outside via the I / F 225, recorded on the removable medium 206 via the drive 231, or supplied to the signal processing unit 228. Then, after predetermined signal processing is performed, the signal may be supplied to the display 229 and reproduced and displayed.

  Next, a stream conversion process executed by the bit stream conversion apparatus 1 of FIG. 3 or the CPU 221 of the personal computer 201 described with reference to FIGS. 13 and 14 will be described with reference to the flowchart of FIG.

  In step S1, the original bitstream acquisition unit 11 (original bitstream acquisition unit 11 of the CPU 221) acquires the original bitstream and supplies it to the bitstream analysis unit 12 (bitstream analysis unit 12 of the CPU 221).

  In step S2, the bit stream analyzing unit 12 (the bit stream analyzing unit 12 of the CPU 221) reads one picture of the supplied original bit stream.

  In step S3, the bit stream analysis unit 12 (the bit stream analysis unit 12 of the CPU 221) analyzes the read picture, and for example, whether the picture matrix of each picture or the quantization matrix is described in the picture header. Get information such as

  In step S4, the bit stream analysis unit 12 (the bit stream analysis unit 12 of the CPU 221) determines whether or not the read picture is a B picture in which a quantization matrix is described in the picture header.

  If it is determined in step S4 that the read picture is a B picture in which the quantization matrix is described in the picture header, in step S5, the bit stream analysis unit 12 (the bit stream analysis unit 12 of the CPU 221) The value of the described quantization matrix is stored in the Q matrix buffer 14 (Q matrix buffer 14 of the RAM 223).

  If it is determined in step S4 that the quantization matrix is not described in the read picture, or after the process of step S5 is completed, in step S6, the bit stream analyzer 12 (the bit stream analyzer 12 of the CPU 221). ) Supplies the analyzed picture to the stream buffer 13 (stream buffer 13 of the RAM 223) and supplies the stream analysis result to the stream synthesis unit 15 (stream synthesis unit 15 of the CPU 221). Then, the stream synthesizing unit 15 determines whether the picture is a P picture next to the B picture in which the quantization matrix stored in the Q matrix buffer 14 is described or a B picture before the P picture. Alternatively, it is determined whether or not it is a B picture up to the previous picture in which the quantization matrix is described.

  In step S6, the picture is the P picture next to the B picture in which the quantization matrix stored in the Q matrix buffer 14 is described, or the B picture before the P picture, or the next If it is determined that none of the B pictures before the picture in which the quantization matrix is described in is included, the process proceeds to step S8 described later.

  In step S6, the picture is the P picture next to the B picture in which the quantization matrix stored in the Q matrix buffer 14 is described, or the B picture before the P picture, or the next In step S7, the stream synthesis unit 15 (the stream synthesis unit 15 of the CPU 221) determines that one of the B pictures up to the previous one of the picture in which the quantization matrix is described is Q. The value of the quantization matrix stored in the matrix buffer 14 is described in the picture header of the corresponding picture data held in the stream buffer 13.

  In step S6, the read picture is the P picture next to the B picture in which the quantization matrix stored in the Q matrix buffer 14 is written, or the B picture before that, or the next quantum. When it is determined that none of the B pictures up to the one before the picture in which the quantization matrix is described, or after the process of step S7 is completed, in step S8, the stream synthesis unit 15 (the stream of the CPU 221) The synthesizing unit 15) supplies the picture data to the bit stream output unit 16 (the bit stream output unit 16 of the CPU 221).

  In step S9, the bit stream output unit 16 (the bit stream output unit 16 of the CPU 221) determines whether or not the processing of all the pictures has been completed. If it is determined in step S9 that all the pictures have not been processed, the process returns to step S2, and the subsequent processing is repeated. If it is determined in step S9 that all the pictures have been processed, the process ends.

  By using the bit stream generated by such processing, it is possible to prevent deterioration in image quality in subsequent decoding processing.

  As described above, the bitstream conversion apparatus 1 or the personal computer 201 to which the present invention is applied receives the compressed bitstream, analyzes it, and describes it in the picture header of the B picture of the original bitstream. The quantized matrix being extracted is extracted and buffered. Then, the buffered quantization matrix is described in the picture header of a predetermined picture.

  By using this bit stream, it is possible to prevent the decoding process from being performed using an erroneous quantization matrix even in random reproduction, and it is possible to prevent image degradation.

  Here, the case where MPEG is used as the codec method has been described as an example, but the present invention can also be applied to the case where codec processing using a quantization matrix and frame correlation is performed. Not too long. For example, AVC (Advanced Video Coding) / H. The present invention is applicable to H.264.

  Note that the AVC / H.264 B picture does not necessarily use the forward and backward bi-directional reference images. Even if prediction is performed using two reference images from the past, Although prediction may be performed using one reference image, it is possible to apply the present invention in consideration of such a case, and by applying the present invention, an erroneous quantization matrix may be used. It is possible to reduce the section where the decoding process is performed, and it is possible to suppress the deterioration of the image.

  As described above, the series of processes described above can be executed by hardware or software. The software is a computer in which a program constituting the software is incorporated in dedicated hardware, or a various personal computer capable of executing various functions by installing various programs. For example, it is installed from a recording medium.

  As shown in FIG. 13, the recording medium is distributed to provide a program to the user separately from the computer, and includes a magnetic disk (including a flexible disk) on which the program is recorded, an optical disk (CD-ROM ( Removable media 206 including a compact disk-read only memory (DVD) (including digital versatile disk), a magneto-optical disk (including MD (mini-disk) (trademark)), or a semiconductor memory.

  Further, in the present specification, the step of describing the program recorded on the recording medium is not limited to the processing performed in chronological order according to the described order, but may be performed in parallel or It also includes processes that are executed individually.

  In the present specification, the term “system” represents the entire apparatus constituted by a plurality of apparatuses.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

It is a figure for demonstrating a quantization matrix. It is a figure for demonstrating a quantization matrix. It is a block diagram which shows the structure of a bit stream conversion apparatus. It is a figure for demonstrating operation | movement of a bit stream converter. It is a figure for demonstrating operation | movement of a bit stream converter. It is a figure for demonstrating operation | movement of a bit stream converter. It is a figure for demonstrating operation | movement of a bit stream converter. It is a figure for demonstrating operation | movement of a bit stream converter. It is a figure for demonstrating the quantization matrix referred in a decoding process. It is a figure for demonstrating the quantization matrix referred in a decoding process. It is a figure for demonstrating the quantization matrix referred in a decoding process. It is a figure for demonstrating the quantization matrix referred in a decoding process. It is a block diagram which shows the structure of a personal computer. It is a functional block diagram for demonstrating the function which a personal computer has. It is a flowchart for demonstrating a stream conversion process.

Explanation of symbols

  1 bit stream converter, 11 original bit stream acquisition unit, 12 bit stream analysis unit, 13 stream buffer, 14 Q matrix buffer, 15 stream synthesis unit, 16 bit stream output unit, 201 personal computer, 221 CPU, 261 decoding processing unit

Claims (10)

A program for causing a computer to execute processing for analyzing a bitstream,
Analyzing the bitstream sequentially from the front in time,
Determining whether a value of a quantization matrix is described in a B picture included in the bitstream;
When the value of the quantization matrix is described in the B picture, information on the quantization matrix is extracted and the latest quantization matrix is held,
A program for causing a computer to execute a process including a step of writing a value of the held quantization matrix in a predetermined frame following the B picture in which information of the quantization matrix is written. The predetermined frame is the next P picture in time and the B picture arranged up to the P picture, or the B picture in which the information of the quantization matrix is described, and the quantization matrix. The program according to claim 1, which is a frame arranged between any of the frames arranged next in time in which information of quantization matrixes of different values is described. A method for causing a computer to execute a process further including a step of decoding a bitstream in which a value of the held quantization matrix is described in a predetermined frame following the B picture in which the information of the quantization matrix is described Item 1. The program according to item 1. The program according to claim 1, wherein the bit stream is an encoded stream encoded by an MPEG encoding method. In an information processing apparatus that analyzes a bitstream,
Analyzing means for sequentially analyzing the bitstream from the front in time and extracting a value of a quantization matrix described in a B picture included in the bitstream;
Holding means for holding the latest quantization matrix extracted by the analyzing means;
An information processing apparatus comprising: a description unit that describes a value of the quantization matrix held by the holding unit in a predetermined frame following the B picture in which information of the quantization matrix is described. The predetermined frame is the next P picture in time and the B picture arranged up to the P picture, or the B picture in which the information of the quantization matrix is described, and the quantization matrix. The information processing apparatus according to claim 5, wherein the information processing apparatus is a frame arranged between any of the frames arranged next in time in which quantization matrix information of different values is described. The information processing apparatus according to claim 5, further comprising decoding means for decoding the bitstream in which the value of the quantization matrix is described by the description means. The information processing apparatus according to claim 5, wherein the bit stream is an encoded stream encoded by an MPEG encoding method. In an information processing method of an information processing apparatus that analyzes a bitstream,
Analyzing the bitstream sequentially from the front in time,
Determining whether a value of a quantization matrix is described in a B picture included in the bitstream;
When the value of the quantization matrix is described in the B picture, information on the quantization matrix is extracted and the latest quantization matrix is held,
An information processing method including a step of describing a value of the held quantization matrix in a predetermined frame following the B picture in which information of the quantization matrix is described.   A recording medium on which the program according to claim 1 is recorded.

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