JP2007221505A - Decoding method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent image data decoded from encoded data from being reproduced by specifying the encoded data that is encoded when a video signal is asynchronously switched without using excess elements. <P>SOLUTION: A decoding part 3 includes a network interface part 21, a stream separating part 23, a video stream analyzing part 25, an internal memory 27, a video decoding part 29, a memory control part 31, a memory 33, a selector 35, and a video signal generating part 37, wherein the video stream analyzing part 25 calculates the period of time data described in the header of a PES packet formed by the stream separating part 23. Consequently, encoded data corresponding to time data whose period is disturbed is specified as data obtained by encoding a part obtained when a video signal is asynchronously switched, and image data is reproduced whose reproduction sequence is ahead of the image data by one instead of the image data decoded from the encoded data. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a decoding method and a decoding device, and more particularly, to a decoding method and a decoding device that receive encoded data and create a video from the encoded data.

  Conventionally, in the device that digitally processes moving images, that is, video signals such as MPEG-2 (Moving Picture Coding Experts Group phase 2) CODEC (Coder / Decoder), video synchronization signals are required in the process. It becomes. Examples of the video synchronization signal include a horizontal synchronization signal and a vertical synchronization signal. For example, an encoding apparatus, that is, an MPEG encoding unit of an encoding apparatus, measures timing using these two synchronization signals, and determines an area to be encoded, an area to be transmitted to a decoding apparatus, and the like. For this reason, when another video signal is input instead of the video signal that has been input to the encoding device until then, the timing of the synchronization signal of the video signal is switched, that is, the encoding device. When the video signal input to is switched asynchronously, the horizontal sync signal and vertical sync signal are disturbed, so that the coding area shifts from the original position. As a result, when the decoded video signal is played back In addition, the video before the switching and the video after the switching are mixedly displayed, or the video is disturbed such that the vertical synchronization or the horizontal synchronization period is displayed.

  Furthermore, in the case of encoding and decoding, for example, in the MPEG system, when the encoded video and sound are decoded and reproduced, the video and sound must be synchronized. The time data indicating the time for performing the process of decoding and reproducing the video and the sound, that is, the time stamp is provided in the packet to be sent to the decoding device side. Since this time data is also provided in the packet based on the synchronization signal, if the synchronization signal is disturbed due to the asynchronous switching of the video signal, the time data is also disturbed. As a result, the decoded video signal When playing the video, the video was disturbed. However, since video signals are frequently switched, such as switching programs in television broadcasting, for example, there has been a demand for a method for eliminating video disturbance at the time of switching.

  Patent Document 1 discloses a decoding device that hides a portion where the video is disturbed with a still image when the video is disturbed in this way. More specifically, in Patent Document 1, a timer is provided in the decoding device, a portion where a video disturbance is detected by the timer is detected, and another still image is reproduced instead of this portion, thereby causing a video disturbance. This is a decoding device that does not reproduce the part.

However, the decoding device disclosed in Patent Document 1 has a problem in that an extra element is required to detect whether or not the video is disturbed by the timer, which increases the manufacturing cost of the decoding device. It was.
JP 2002-152743 A

  The present invention eliminates such disadvantages of the prior art, detects the portion of the image that is disturbed because the image is asynchronously switched without using an extra element, and detects the image disturbance caused by the asynchronous switching. It is an object of the present invention to provide a decoding method and apparatus that do not display.

  In order to solve the above-described problems, the present invention focuses on the fact that when the video is switched asynchronously, the synchronization signal is disturbed, and therefore, the time data created based on this synchronization signal is also disturbed in its cycle. At this time, the period of this time data is calculated, and it is detected whether or not the calculated period is disturbed. As a result, if the period of the time data is disturbed, it is determined that the video has been switched asynchronously, and the image data decoded from the encoded data corresponding to the time data is not reproduced and stored in advance. By reproducing the stored image data, the image data that forms the distorted video is not reproduced. Note that the image data to be reproduced instead of the image data determined to form a distorted video can be the image data of the video immediately before switching.

  According to the present invention, since it is detected that the video is switched asynchronously by using the disturbance of the period of the time data, the video is disturbed due to the video being switched asynchronously without using an extra element. It becomes possible not to display the part which is.

  Next, embodiments of a decoding method and a decoding apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of a decoding unit in the decoding device of the present invention, and FIG. 2 is a diagram showing an example of a use environment of the decoding device including the decoding unit shown in FIG. 2, the same reference numerals as those in FIG. 1 indicate the same configurations. In addition, illustration is abbreviate | omitted and the redundant description is avoided about the part which is not directly related to understanding of this invention. In the following description, each signal is specified by the reference number of the connecting line in which it appears. A decoding device 1 according to the present embodiment is a device that decodes encoded data obtained by encoding a video signal or an audio signal in television broadcasting, and includes a decoding unit 3 and a reproduction unit 5 as shown in FIG. 2 receives the packet 11 sent from the encoding device 7 shown in FIG. 2 via the network 9, decodes the encoded data contained in the packet 11 by the decoding unit 3, and supplies the decoded signal to the reproducing unit 5 To do.

  More specifically, as shown in FIG. 1, the decoding unit 3 includes a network interface unit 21, a stream separation unit 23, a video stream analysis unit 25, an internal memory 27, a video decoding unit 29, a memory control unit 31, a memory 33, the selector 35, and the video signal creation unit 37, and the network interface unit 21 receives the packet 11 sent via the network 9. This packet 11 is a packet conforming to the communication method. The present invention is not limited to packets. For example, in the case of an ATM (Asynchronous Transfer Mode) line, an ATM cell may be used. Further, the packet 11 includes encoded data obtained by encoding the signal 41 such as a video signal and an audio signal, and time data indicating a time when decoding / reproducing processing of the encoded data is performed. These encoded data and time data are created by the encoding device 7 connected to the network 9 as will be described later.

  When the decoding unit 3 of the decoding apparatus 1 receives such a packet 11, the video decoding unit 29 decodes the encoded video signal among the encoded data included in the packet, that is, 1 Image data that is a still image for the screen is created, and the created image data is converted by the video signal creation unit 37 to create the video signal 17. The formed video signal 17 is substantially the same as the video signal input to the encoding device 7. In addition, the encoded audio signal included in the encoded data is decoded by a known method, and sent to the reproduction unit 15 in the same manner. Although not shown, the reproduction unit 15 includes a display device such as a display and a recording device such as an external memory, and displays the created video signal 17 and audio signal on the display or records them on the recording device.

  In this embodiment, the encoding device 7 and the decoding device 1 encode and decode a video signal and an audio signal in television broadcasting, respectively, but the present invention is not limited to this. The encoding device 7 and the decoding device 1 need only be devices that encode and decode at least a video signal. Further, the video signal is not limited to the video signal in the television broadcast, and any video signal can be adopted. The video signal in television broadcasting may be an NTSC (National Television Standard Committee) signal or a PAL (Phase Alternation by Line) signal, and any signal can be adopted.

  As described above, the packet 11 storing the encoded data input to the decoding device 1 shown in FIG. 1 is created by the encoding unit 51 of the encoding device 7 shown in FIGS. FIG. 3 is a block diagram showing an example of the configuration of the encoding unit 51 shown in FIG. In FIG. 3, the same reference numerals as those in FIG.

  The encoding device 7 includes a pre-processing unit 53, a synchronization detection unit 55, a video encoding unit 57, a stream multiplexing unit 59, and a network interface unit 61 as shown in FIG. Is a device that encodes a signal 41 such as the above by a known method. For example, in this embodiment, the encoding device 7 uses the MPEG-2 method to generate encoded data, and multiplexes the generated encoded data such as video and audio, and then conforms to the communication method. Packet 11 is created in the format. A known apparatus can be adopted as such an encoding apparatus 7, and is not limited to the embodiment. In the following description, among the signals 41 input to the encoding device 7, since the audio signal is encoded through substantially the same processing as the video signal, only the video signal will be described.

  When a video signal is input to the encoding device 7, the input video signal is input to the synchronization detection unit 55 and the preprocessing unit 53 of the encoding unit 51 in the encoding device 7, respectively. The synchronization detection unit 55 is a part that detects various synchronization signals such as a vertical synchronization signal, a horizontal synchronization signal, a frame synchronization signal, and the like. The horizontal synchronizing signal is a pulse signal that determines the starting point of the scanning line, and the vertical synchronizing signal is a pulse signal that determines the starting point of the field. The frame synchronization signal is a signal that makes it possible to identify the position of the start point of a frame. When the synchronization detection unit 55 detects these synchronization signals, it sends them to the preprocessing unit 53 and the video encoding unit 57.

  When the video signal is input, the preprocessing unit 53 performs analog / digital conversion based on the synchronization signal from the synchronization detection unit 55, converts the video signal into a digital video signal, and also performs luminance signal and color conversion. This is the part that performs signal separation, that is, Y / C separation. The signal processed by the preprocessing unit in this way is sent to the video encoding unit 57. The video encoding unit 57 encodes the digital video signal sent from the preprocessing unit 53 by the MPEG-2 method to create encoded data. At this time, the area to be encoded and the unit to be sent to the decoding unit are determined using various synchronization signals sent from the synchronization detection unit 55. For example, in the present embodiment, the area to be encoded is determined using the frame synchronization signal and horizontal synchronization signal sent from the synchronization detection unit 55. In this embodiment, since encoding is performed by the MPEG-2 system, time data is generated together with the encoded data in accordance with the frame period signal.

  This time data means that when encoded in MPEG format, the decoding order may be different from the playback order when decoding, so the correct order is necessary, and the decoded video and audio Is generated because it needs to be synchronized with each other, and indicates a time at which decoding / reproduction processing necessary for decoding / reproduction is performed, that is, a time stamp. More specifically, when encoding and decoding in the MPEG format, it is necessary to synchronize the sound and video when decoding and playing the encoded video and sound. Time data indicating the time to perform, that is, a presentation time stamp (PTS) is created. In addition, since the decoding order and the playback order may be different, time data indicating the time for performing the decoding process, that is, a decoding time stamp (DTS) is created.

  FIG. 4 is a diagram conceptually showing time data creation processing in the present embodiment, and conceptually showing the output of the synchronization detector 55 when the video signal A is inputted to the encoder 51. It is. In FIG. 4, the horizontal direction represents time. When the video signal A including the frame synchronization signal 71 having the timing as shown in FIG. 4 is input to the encoding unit 51, the synchronization detection unit 55 synchronizes with the frame synchronization signal 71 of the video signal A having substantially the same timing. The signal 73 is detected, and this frame synchronization signal 73 is supplied to the video encoding unit 57. The video encoder 57 creates time data corresponding to the supplied frame synchronization signal 73 when the video signal A is encoded. For example, in this embodiment, time data is created at substantially the same timing as the head of the rising frame of the frame synchronization signal 73.

  Therefore, the interval between adjacent time data in FIG. 4 is one frame, that is, 1/30 second. For example, the interval between the time data A and the time data B is 1/30 second, and the time data C and D are similarly 1/30 seconds different from the previous time data. In this embodiment, time data is created for each frame at the rising timing of the frame synchronization signal 73. However, the present invention is not limited to this, and time data can be created arbitrarily. It is. For example, the time data can be created at the falling timing of the frame synchronization signal 73, or the time data can be created for each field. Note that the present invention is not limited to this.

  The time data created as described above is packetized together with the encoded data by the video encoding unit 57, multiplexed with an audio packet or the like by the stream multiplexing unit 59, and then sent to the network interface unit 61. The network interface unit 61 converts these multiplexed data into data in a format conforming to the communication method, that is, the packet 11, and transmits the packet 11 to the decoding device 1 via the network 9.

  FIG. 5 is a conceptual diagram of a PES (Packetized Elementary Stream) packet created by the video encoding unit 57 shown in FIG. In FIG. 5, the horizontal direction indicates time. In this embodiment, since encoding is performed using the MPEG-2 system, the encoded data is stored in a PES packet. In the PES packet, encoded data divided into predetermined units determined by the video encoding unit is stored in a predetermined area, that is, in the data area 77 in which data is stored in this embodiment, and the encoded data is also stored. When there is an access unit, that is, the head of a unit to be encoded, time data indicating the time for performing decoding / reproduction processing of the encoded data is provided in the packet header 79, one per PES packet. .

  If the playback time indicated by the PTS and the decoding start time indicated by the DTS are different, both the DTS and the PTS are provided in the packet header 79. Conversely, if both match, only the PTS is included in the packet header 79. Provided. This time data can be created by a known method and provided in the packet header 79 by a known method.

  As described above, the encoding device 7 that performs encoding does not always receive the same video signal. For example, the video signal that has been input so far is switched to another new video signal. The video signal may change. When switching in this way, the video signal before switching and the video signal after switching are synchronized, that is, the timing of the synchronization signal included in the video signal before switching and included in the video signal after switching. When the video signal is switched so that the timing of the synchronization signal substantially coincides, the switching can be performed without causing a problem such as a video disturbance.

  However, for example, as shown in FIG. 6, when the timing of the synchronization signal included in the video signal before switching and the timing of the synchronization signal included in the video signal after switching are switched without substantially matching, That is, when the switching is performed asynchronously, the interval of the synchronization signal is disturbed, and as a result, there is a problem that the video is disturbed when the decoded video signal is reproduced.

  FIG. 6 is a diagram conceptually showing a time data creation process when the video signal is switched, and is asynchronous with the video signal B from the time data B and the time data C shown in FIG. FIG. 6 is a diagram conceptually showing an output of a synchronization detection unit 55 when it is switched at. In FIG. 6, the same reference numerals as those in FIG. In FIG. 6, the portion indicated by the dotted line is displayed for easy understanding of the explanation, but is a signal that does not appear because it is switched.

  As shown in FIG. 6, when the video signal is switched asynchronously, the synchronization detection unit 55 detects the frame synchronization signal from the first vertical synchronization signal after the switching, so that the period of the frame synchronization signal is disturbed when the switching is performed. Will occur. For example, in the example shown in FIG. 6, the interval from the rising timing of the synchronizing signal before switching to the rising timing of the synchronizing signal after switching is longer than the interval in other portions. Thus, the portion where the period of the synchronization signal is disturbed is not encoded well because the video encoding unit 57 determines the area to be encoded based on the synchronization signal. As a result, when the encoded data that could not be encoded successfully is decoded and reproduced, there has been a problem that, for example, a video before switching and a video after switching are mixed.

  Therefore, in order to solve such a problem, the decoding device 1 of this embodiment, when switched asynchronously, as shown in FIG. 6, because the period of the synchronization signal is disturbed, time data created based on the synchronization signal Focusing on the fact that the period of the image is also disturbed, by detecting the disturbance of the period of the time data, the encoded data obtained by encoding the portion where the video is asynchronously switched is specified, and the image data created from the encoded data is obtained. Do not play. For example, in FIG. 6, the time indicated by the time data E is not the time obtained by adding 1 frame time, ie, 1/30 second, to the time data B because the frame synchronization signal is disturbed. Therefore, the encoded data corresponding to the time data E with the irregular interval in this way, that is, the encoded data encoded between the time data B and the time data E, is identified as the portion that could not be encoded successfully. it can. The decoding apparatus 1 according to the present embodiment identifies a portion that has not been successfully encoded from such a disturbance in the time data interval, and does not reproduce a portion that has not been successfully encoded. Details will be described below.

  In FIG. 1, a network interface unit 21 is a part that receives a transmitted packet 11 and outputs a transport stream (TS: Transport Stream) that is a data string from the received packet 11. The output transport stream is input to the stream separation unit 23.

  The stream separation unit 23 separates the input transport stream into individual streams, that is, a video stream, an audio stream, and the like, and creates separated video streams and audio streams. In the following description, the audio stream is decoded by a known method to form an audio signal, and is reproduced by the playback unit 5 in synchronization with the decoded video signal. explain. The separated video stream is input to the internal memory 27 and the video stream analysis unit 25, respectively.

  The video stream analysis unit 25 analyzes time data, M value, and picture type from the input video stream, and controls the memory control signal for controlling the memory control unit 31 in the subsequent stage and selector control for controlling the selector 35 This is the part that creates each signal. In particular, the video stream analysis unit 25 detects the period of time data and creates a selector control signal according to the detection result. More specifically, in this embodiment, the video stream analysis unit 25 temporarily stores time data that is one order before the time data detected this time, and when new time data is detected. Then, the difference between this time data and the stored previous time data is calculated, and it is determined whether or not this difference is a value set in advance, thereby detecting the disturbance of the cycle.

  As a result, if the difference is not a constant value, that is, if the period is disturbed, it is determined that the video signal is a switching part that is switched asynchronously, and this switching part is decoded from the M value and the picture type, and the internal memory Calculate the time output from 27. Further, a selector control signal indicating that the video output from the internal memory is a switching portion, that is, a control signal instructing to select image data from the memory 33 is generated. On the other hand, if there is no disturbance in the cycle, a control signal indicating that the part has not been switched, that is, a control signal instructing to select image data from the internal memory 27 is created.

  On the other hand, the memory control signal is created using a known method. The created memory control signal is input to the memory control unit 31, and the selector control signal is input to the selector 35. Note that any method can be employed for detecting the periodic disturbance, and the present invention is not limited to this embodiment. For example, it is also possible to determine whether or not there is a disturbance in the cycle by calculating the difference from the time data one order after the time data detected this time.

  The internal memory 27 is a memory used for decoding in the video decoding unit 29, and temporarily stores the encoded data included in the video stream and the image data created by decoding the encoded data. The part to save. The video decoding unit 29 is a part that is controlled by a control unit (not shown) and decodes encoded data included in the video stream based on the time data by the MPEG-2 system to create image data. Decoding can be performed using a known method. In the present embodiment, the encoded data is decoded for each frame in accordance with the cycle of the frame supplied to the reproduction unit 5. The decoded image data is sent to the internal memory again. In this embodiment, decoding is performed for each frame. However, the present invention is not limited to this, and decoding can be performed in accordance with encoded data. For example, it can be performed for each field.

  The memory control unit 31 is a part that controls the internal memory 27 and the memory 33 by a memory control signal from the video stream analysis unit 25. For example, the memory control unit 31 controls the internal memory 27 to transfer the image data stored in the internal memory 27 to the selector 35 so that the image data stored in the internal memory 27 is in the correct playback order in the subsequent playback unit 5. send.

  The memory 33 is a part that stores the decoded image data separately from the internal memory 27 under the control of the memory control unit 31. Specifically, this is a part in which image data to be supplied to the reproducing unit 5 is stored instead of the image data sent from the internal memory 27 to the selector 35. In this embodiment, when the image data sent from the internal memory 27 is a switching portion, the image data selected by the selector 35 is stored in place of this image data, and the image data selected from the internal memory 27 is transferred to the selector 35. Image data that is reproduced in time before the image data to be sent, specifically, image data that is one order before the image data sent from the internal memory 27 to the selector 35 is stored. . Note that the image data stored in the memory 33 is not limited to the image data whose playback order is one before that of the image data sent to the selector 35, and the image that is played back instead of the image data that is the switching portion. Any image data can be saved as long as it is data. For example, it may be image data that is one order after the reproduction order.

  Here, in the present embodiment, since the size of the image data is one frame, the memory 33 always stores one frame of image data in the previous playback order. In this embodiment, the memory 33 stores the capacity for one frame in order to reduce the image data capacity in the memory 33, but the present invention is not limited to this, and the memory 33 The amount of image data to be stored can be set to an arbitrary amount. For example, it is possible to store all the decoded image data in the memory 33, and for example, it is possible to store image data for an arbitrary frame decoded so far. Is possible. The present invention is not limited to these.

  The selector 35 is a part for selecting image data to be supplied to the video signal creation unit 37 from the image data stored in the memory 33 or the internal memory 27 under the control of the selector control signal sent from the video stream analysis unit 25 It is. More specifically, the selector 35 selects one of the image data stored in the memory 33 or the image data stored in the internal memory 27 based on the selector control signal. . The selected image data is input to the video signal creation unit 37 for conversion into the video signal 17 to be played back by the playback unit 5.

  The video signal creation unit 37 is a part that converts the image data supplied from the selector 35 into a video signal to be displayed on, for example, a display in the playback unit 5 in the subsequent stage, and creates the original video signal from the image data. Part. In this embodiment, the video signal creation unit 37 multiplexes the luminance signal and the color signal and performs digital / analog conversion to create the video signal 17. The created video signal 17 is sent to the playback unit 5. The reproduction unit 5 reproduces the video signal 17 created by the decoding unit 3 together with the audio signal decoded by a known method, that is, outputs the video signal 17 to the display or recording medium of the display device included in the reproduction unit 5. In the present invention, the configuration of each unit is not limited to the present embodiment, and any configuration can be adopted depending on the decoding device 1.

  FIG. 7 is a flowchart showing an example of the processing procedure of the decoding process when the packet 11 is received in the decoding device 1 shown in FIG. 1 and 7, the packet 11 sent from the encoding device 7 is sequentially received by the network interface unit 21 of the decoding device 1 (step S1). The received packet 11 is converted into a transport stream by the network interface unit 21 and input to the stream separation unit 23. The stream separation unit 23 separates the video stream and the audio stream from the input transport stream (step S2). The separated video stream is converted into a PES packet (step S3). For example, the stream separation unit 23 sequentially converts the video stream into a first PES packet 81, a second PES packet 83, a third PES packet 85,..., An nth PES packet 87 as shown in FIG.

  FIG. 8 is a diagram conceptually showing a PES packet converted by the stream separation unit 23 shown in FIG. 1 and a video signal when the encoded data included in the PES packet is decoded. In FIG. 8, the same reference numerals as those in FIG. In each PES packet 81, 83, 85, 87, encoded data is stored in a predetermined area, and time data is provided in the packet header.

  In FIG. 8, encoded data 89 and 91 and time data 93 and 95 in the first PES packet 81 and the second PES packet 83 are shown, but the first PES packet 85 and the nth PES packet 87 are also shown in FIG. Similar to 81 and the second PES packet 83, encoded data and time data are included. In FIG. 8, n is a positive positive number. For the sake of easy understanding, it is assumed that the decoding order and the reproduction order are the same. That is, for example, the first image data 97 is decoded from the first encoded data 89 included in the first PES packet 81, and the second image data 99 is decoded from the second encoded data 91. The reproduction order is first image data 97, second image data 99,..., Nth image data.

  The PES packet converted by the stream separator 23 is input to the internal memory and the video stream analyzer. When the PES packet is input to the internal memory, the video decoding unit decodes the encoded data based on the time data included in the PES packet (step S4).

  In addition, when the PES packet is input, the video stream analysis unit 25 creates a memory control signal and a selector control signal. Since the memory control signal is created in a known manner, only the creation of the selector control signal will be described. First, when a PES packet is input, the video stream analysis unit 25 detects time data indicating a decoding time, that is, DTS among time data included in the PES packet (step S5).

  For example, when the third PES packet 85 is input to the video stream analyzer 25, the video stream analyzer 25 includes time data indicating a decoding time among the third time data described in the header of the third PES packet, that is, Detect third DTS. When the time data indicating the decoding time and the time data indicating the reproduction time are the same, only the time data indicating the reproduction time, that is, the PTS is included in the packet as the time data. If only the packet is included, the PTS is detected.

  After detection, the difference between the third DTS detected this time and the previously stored DTS in the previous order from the third DTS, that is, in the present embodiment, the difference between the second DTS detected from the second PES packet 83 is calculated. Then, it is determined whether there is any disturbance in the period between the second DTS and the third DTS. Specifically, it is determined whether or not the calculated difference is a certain value (step S6). In the present embodiment, as shown in FIG. 5, since the time data is created for each frame period, the difference between the third DTS and the second DTS is equivalent to one frame when there is no asynchronous switching of the video signal. That is, 1/30 second.

  As a result of calculating the difference, when the difference is a constant value, that is, for one frame, there is no disturbance in the cycle of the second DTS, so the second encoded data 91 corresponding to the second DTS is not asynchronously switched in the video signal. It is determined that Therefore, a selector control signal is generated so as to select image data from the internal memory 27, and the selector control signal is sent to the selector 35.

  Conversely, when the difference is not one frame, that is, when it is longer or shorter than 1/30 seconds, the second encoded data 91 is disturbed in the period of the second DTS. The part switched asynchronously, that is, the switching part is determined. Therefore, the selector control signal is used to calculate a delay time from the M value and the picture type until the switching portion is decoded and output from the internal memory 27, and to select image data from the memory 33 for one frame after the delay time. And a selector control signal is sent to the selector 35. After creating the selector control signal, the video stream analysis unit 25 holds the value of the third DTS in order to calculate the difference from the value of the fourth DTS in the next fourth PES packet, and deletes the value of the second DTS.

  In this embodiment, the difference between a DTS and the DTS one order earlier than this DTS is calculated. If the difference is not a constant value, the encoded data corresponding to the previous DTS is switched. Judging that it is a part. This is because the encoding apparatus 7 starts encoding from the time when the DTS is created. However, the present invention is not limited to this, and the identification of which time data corresponding to the switching portion of the two time data used for calculating the difference is in the encoding device 7. It can be arbitrarily performed according to the timing at which time data is created and the timing of encoding.

  In this embodiment, the DTS, that is, the time data indicating the decoding time is used to detect the disturbance of the period of the time data. However, the present invention is not limited to this. For example, the time data indicating the reproduction time That is, it is also possible to detect the disturbance of the period of time data using PTS. When PTS is used for detection, there is a B picture, so the order of PTS is not always changed even if the PES packet is forward or backward, and the difference may not be one frame. Therefore, when using the PTS, it is necessary to specify the order of the PTS according to, for example, the type of picture, and to calculate the difference using the preceding and succeeding PTS.

  In addition, it is not limited to examining the period of time data every time one packet is received, and an arbitrary method can be adopted to identify a portion where asynchronous switching has occurred. For example, it is possible to consider the period of time data every time a plurality of packets are received. For example, referring to the example of FIG. 8, the difference may be calculated every time two packets are received, that is, every other packet. Specifically, the difference between the first DTS included in the first packet and the third DTS included in the third packet is calculated. If this difference is not two frames, the DTS in the first packet is further calculated. The difference between the DTS in the second packet and the difference between the DTS in the second packet and the DTS in the third packet are calculated, and whether the first encoded data 89 is the switching part or the second encoded data 91 is switched. It is also possible to determine whether it is a part. Note that the present invention is not limited to this.

  As described above, the video stream analysis unit 25 creates a selector control signal. The memory control signal is generated in a known manner. The created selector control signal is sent to the selector 35. The selector 35 selects image data in the internal memory 27 or image data in the memory 33 under the control of the transmitted selector control signal. At the time of selection by the selector 35, the second image data 99 is transmitted from the internal memory 27 to the selector 35, and the image 33 whose reproduction order is one before the second image data, that is, the first image data is transmitted to the memory 33. As one image data 97 is stored, it is necessary to adopt an arbitrary method to synchronize the timings of the video stream analysis unit 25, the video decoding unit 29, the memory control unit 31, the internal memory 27, and the memory 33.

  FIG. 9 is a diagram conceptually showing image data selection processing in the selector 35. 9, the same reference numerals as those in FIG. 8 denote the same components. In FIG. 9, the horizontal direction indicates time. In FIG. 9, for example, it is assumed that the selector 35 has already selected the first image data 97 at time t = 1 and the image data at time t = 2. At this time, when the selector 35 receives a selector control signal indicating that the second image data 99 is not an asynchronously switched portion from the video stream analysis unit 25, at time t = 2, the output from the internal memory 27, that is, the second Image data 99 is selected (step S7). Conversely, when the video stream analyzer 25 receives the selector control signal indicating that the second image data 99 is an asynchronously switched portion, the output from the memory 33, that is, the first image data 97 is selected at time t = 2. (Step S8).

  In this embodiment, since the unit of the image data is one frame, the selector 35 selects the first image data 97 for one frame, that is, the first image data 97 when selecting the first image data 97. The odd field 101 and the even field 103 may be selected, or the first image data 97 is selected for one field, and the selected one field of image data is selected as the odd field at time t = 2. It is also possible to display in both even fields. That is, the selected image data for one field is repeatedly displayed. When the unit of the image data is one field, the image data for one field is stored in the memory 33, so the image data selected by the selector 35 is for one field.

  The image data selected by the selector 35 in this way is sent to the video signal creation unit 37. If the video signal creation unit 37 has not been switched asynchronously, the second image data is switched asynchronously. If so, the first image data is converted to create a video signal 17 (step S9). The created video signal 17 is output to the display of the display device, the recording medium, or the like by the reproducing unit 5.

  As described above, in this embodiment, by comparing the time data, the encoded data obtained by encoding the switched portion is specified, and the reproduction order is changed to the image data decoded from the encoded data. Play back the previous image data. Therefore, it is possible to specify encoded data obtained by encoding the portion that has undergone asynchronous switching without requiring an extra element, and to prevent display of image data decoded from this encoded data. Is possible.

  In addition, this invention is not necessarily limited to a present Example. For example, the decoding in the video decoding unit 29 and the period detection in the video stream analysis unit 25 can be performed at arbitrary timing according to the decoding device 1, and are limited to being performed simultaneously as in the present embodiment. Do not mean. Further, the present invention is not limited to encoding and decoding with the MPEG-2 system, and any system can be adopted as long as it is a system for creating a time stamp.

It is a block diagram which shows the structure of the Example of the decoding part in the decoding apparatus of this invention. It is a figure which shows an example of the usage environment of the decoding apparatus containing the decoding part shown in FIG. FIG. 3 is a block diagram illustrating an example of a configuration of an encoding unit 51 illustrated in FIG. 2. It is a conceptual diagram of the packet produced with the encoding apparatus shown in FIG. It is the figure which showed notionally the creation processing of the time data in a present Example. It is the figure which showed notionally the creation process of the time data at the time of a video signal switching. 3 is a flowchart illustrating an example of a processing procedure of a decoding process in the composite device illustrated in FIG. 1. FIG. 2 is a diagram conceptually showing a PES packet input to the decoding apparatus 1 shown in FIG. 1 and a video signal when decoding encoded data included in the PES packet. It is the figure which showed notionally the selection processing of the image data in a selector.

Explanation of symbols

1 Decryption device
3 Encoder
5 Playback section
7 Encoder
9 network

Claims (8)

A decoding step of decoding encoded data obtained by encoding a video signal using time data indicating a time at which the encoded data is decoded and reproduced, and creating image data;
In a decoding method including a video signal creating step of creating the video signal from the image data, the method includes:
A storage step for storing the image data;
Detection that detects the period of the time data and determines that the image data corresponding to the disturbed time data is an asynchronously switched part of the video signal when the period is disturbed Process,
A selection step of selecting image data to be reproduced from the stored image data based on the determination in the detection step,
When the selection step is determined to be the switching portion in the detection step, the image data that has been reproduced before the image data is selected instead of the image data that is the switching portion,
In the decoding method, the video signal creating step creates the video signal from the selected image data.   The decoding method according to claim 1, wherein the detecting step detects a period of time data indicating a time at which the decoding process is performed.   The decoding method according to claim 1, wherein the detecting step detects a period of time data indicating a time at which the reproduction process is performed.   4. The method according to claim 1, wherein when the selection step is determined to be the switching portion in the detection step, the image data is replaced with the image data that is the switching portion. A decoding method comprising selecting at least one field of image data reproduced immediately before. Decoding means for decoding encoded data obtained by encoding a video signal using time data indicating a time for decoding and reproducing the encoded data, and creating image data;
In a decoding device including a video signal creating means for creating the video signal from the image data, the device comprises:
Storage means for storing the image data;
Detection that detects the period of the time data and determines that the image data corresponding to the disturbed time data is an asynchronously switched part of the video signal when the period is disturbed Means,
Selection means for selecting image data to be reproduced from among the image data stored in the storage means based on the determination in the detection means,
When the selection unit determines that the switching unit is the switching part, the selection unit selects image data reproduced before the image data instead of the image data that is the switching part,
The decoding apparatus according to claim 1, wherein the video signal creating means creates the video signal from the selected image data.   6. The decoding device according to claim 5, wherein the detection unit detects a period of time data indicating a time at which the decoding process is performed.   6. The decoding device according to claim 5, wherein the detection unit detects a period of time data indicating a time at which the reproduction process is performed.   8. The apparatus according to claim 5, wherein when the detection unit determines that the selection unit is the switching part, the selection unit replaces the image data that is the switching part with the image data. A decoding apparatus, wherein at least one field of image data reproduced immediately before is selected.

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