JP2008258665A - Stream reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stream reproducing device capable of seamlessly transitioning to normal playback when an object to be played back catches up with a broadcasting wave during time shift playback. <P>SOLUTION: The stream reproducing device includes a receiving unit 102 which receives a packet with an ES and a PTS containing encoded video or audio data, a buffer 107 which stores packets one after another in a time-shift playback mode and a time-shift storage mode for previously storing packets prior to the time-shift playback mode, correcting units 111 and 116 which replace PTSs contained in the packets stored in the buffer with a correction value corrected based upon magnification at a current playback speed in the time-shift playback mode, and a control unit 104 which stops the operation of the correcting unit when the difference between the PTS and a correction value is equal to or less than a predetermined threshold and changes the current playback mode to the normal playback mode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an apparatus for reproducing video or audio data transmitted by a transport stream.

  In terrestrial digital broadcasting (One Seg) received by a mobile phone based on the third generation, the image data is H.264. H.264 / AVC and audio data are encoded with MPEG-2 AAC. These encoded video data and audio data are referred to as an elementary stream (hereinafter simply referred to as ES), and as a packetized elementary stream (PES) packet (hereinafter simply referred to as a PES packet). It is multiplexed and transported in a transport stream in MPEG-2 SYSTEMS.

  In the transport stream, transport stream packets (hereinafter simply referred to as TS packets) are arranged. In the TS packet, attribute information indicating the type (attribute) of the bit stream constituting video information and audio information, a bit stream, and a program time reference value for synchronization between media (hereinafter simply referred to as PCR). Reference clock information, etc., referred to as “referred to” can be stored. TS packets are transmitted wirelessly or via wire.

  On the receiving side, TS packets are recorded, and when a TS packet having a PCR is received, a system time clock (hereinafter simply referred to as STC) is counted in order to synchronize the clock on the receiving side with respect to the transmitting side. PCR is used to control the STC counter. Specifically, the value obtained by sampling the PCR on the transmission side at 27 MHz is extracted, and the STC is adjusted by comparing with the STC value on the reception side (clock recovery).

  On the receiving side, when the STC value counted by the STC counter becomes equal to or greater than the display time stamp (PTS), the ES is synchronously reproduced. As a stream playback method, in addition to the normal playback mode in which video and audio in TS packets received from broadcast waves are sequentially decoded and played back, the received TS packets are stored in a buffer while the user cannot view (time shift). There is a time-shift playback mode in which the video and audio in the accumulated TS packets are sequentially decoded and reproduced while accumulating the received TS packets one after another when the user can view them.

Patent Document 1 proposes a method for reproducing stored data while synchronizing with the STC on the transmission side. Specifically, when the received TS packet is stored, the reception time of the TS packet is added to the TS packet as time information, and the time information is referred to when the stored data is reproduced to synchronize with the STC on the transmission side. ing.
JP 2002-15527 A

  In time-shift playback, TS packets already stored in the buffer are to be played back, so that the playback is not limited to the normal speed, and higher speed playback may be performed. During high-speed playback, it is necessary to adjust the playback time by correcting the PTS. If the high-speed reproduction is continued, the speed at which the TS packets read from the buffer are reproduced continues to exceed the speed at which the TS packets read from the broadcast wave are accumulated, so that the data in the buffer will eventually run out. Normally, there are two inputs from the buffer and the broadcast wave during time shift reproduction, but when the data in the buffer is exhausted, only TS packets from the broadcast wave are processed. At this point, since the adjustment of the reproduction time has not been completed, it seems to the user that the reproduction is performed at high speed. Therefore, it is necessary to detect that it has caught up with the broadcast wave, end the display time adjustment process, and detect the timing to return to the normal playback mode. If the end timing of this adjustment process cannot be detected properly, the process returns to the normal playback mode. Seamless transition is not possible.

  An object of the present invention is to provide a stream playback device that can seamlessly shift to normal playback when a playback target catches up with a broadcast wave during time-shift playback.

  A stream reproduction apparatus according to an aspect of the present invention includes: a reception unit that receives an elementary stream in which encoded video or audio data is stored; and a packet having a display time stamp; a time-shift reproduction mode; A first buffer for sequentially storing the packets in a time shift accumulation mode for accumulating the packets in advance prior to the time shift reproduction mode; a system time clock value obtained by counting a system time clock; And a correction unit for replacing the display time stamp included in the packet stored in the first buffer with a correction value corrected based on a magnification of the current reproduction speed in the time-shifted reproduction mode. And the difference between the display time stamp and the correction value is A control unit that stops the operation of the correction unit and changes the current playback mode to the normal playback mode; and in the time-shifted playback mode, the packet stored in the first buffer. A second buffer that temporarily stores the elementary stream and the display time time stamp; and a timing determined based on the display time time stamp and the system time clock value stored in the second buffer; And a decoder for decoding the video or audio data from the elementary stream; and a playback unit for reproducing the video or audio data.

  According to the present invention, it is possible to provide a stream playback device that can seamlessly shift to normal playback when a playback target catches up with a broadcast wave during time-shift playback.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a stream playback apparatus according to an embodiment of the present invention includes an antenna 101, a tuner 102, a TS I / F (transport stream interface) 103, a playback mode control unit 104, an input control unit 105, Separator 106, buffer 107, STC (system time clock) controller 108, STC 109, STC counter 110, PTS (display time stamp) corrector 111, PES (packetized elementary stream) extractor 112, buffer 113, a decoder 114, a display 115, a PTS correction unit 116, a PES extraction unit 117, a buffer 118, a decoder 119, a DAC (digital-analog converter) 120, a speaker 121, and a switch 122.

  The antenna 101 receives a broadcast wave transmitted from a broadcast station and transfers it to the tuner 102. The tuner 102 selects a channel to be reproduced from the broadcast wave received by the antenna 101. TS packets in the transport stream transmitted in the channel selected by the tuner 102 are temporarily stored in a buffer (not shown) (hereinafter simply referred to as a broadcast wave buffer).

  When a specified number of TS packets are recorded in the broadcast wave buffer, the TS I / F 103 generates an interrupt signal to the input control unit 105 in order to input the TS packets to the separation unit 106. Here, the specified number is, for example, 1, but may be a different value depending on the implementation of the stream reproducing apparatus. When the input control unit 105 switches the switch 122 to the TS I / F 103 side by the interrupt signal, the TS I / F 103 transfers the designated number of TS packets to the separation unit 106 via the switch 122. The method for transferring the designated number of TS packets is not particularly limited. For example, a buffer for the designated number of TS packets is further prepared, the TS packets are copied to the buffer, and the separating unit 106 copies the TS that has been copied. You may make it refer to a packet. Alternatively, the separation unit 106 may access the broadcast wave buffer and refer to the TS packet directly.

  The reproduction mode control unit 104 notifies the input reproduction unit 105, the separation unit 106, the PTS correction unit 111, and the PTS correction unit 116 of the current reproduction mode. Here, at least three types of playback modes of the stream playback device according to the present embodiment are provided: a normal playback mode, a time shift accumulation mode, and a time shift playback mode.

  In the normal playback mode, the stream playback device sequentially decodes and plays back the video and audio data in the received TS packet. In the time shift accumulation mode, the stream reproduction device continues to accumulate received TS packets in the buffer 107. In the time shift reproduction mode, the stream reproduction apparatus sequentially decodes and reproduces video and audio data in the TS packets accumulated in the buffer 107 while accumulating the received TS packets following the preceding time shift accumulation mode.

  In the time-shift playback mode, it is assumed that the playback speed can be selected, and the playback control unit 104 notifies the PTS correction unit 111 and the PTS correction unit 116 of the current playback speed magnification. The reproduction speed magnification can be selected from a plurality of magnifications including at least equal magnification (1 ×) and high-speed magnification (for example, 4/3 times) used for fast-forward reproduction.

  Switching of the playback mode occurs by an instruction such as a key operation from the user, or by an event such as an incoming voice call if the stream playback device is a portable wireless terminal. Specifically, when the stream playback device is playing back a stream in the normal playback mode, if the user can no longer view the video and audio, the playback mode change instruction is played back by a key operation to change the playback mode to the time shift accumulation mode Input to the mode control unit 104. When the user can start viewing again, a playback mode change instruction is input to the playback mode control unit 104 by a key operation for changing the playback mode from the time shift accumulation mode to the time shift playback mode or the normal playback mode. To do.

  Also, while the stream playback device is playing back the stream in the time-shift playback mode, the user performs a high-speed playback operation such as fast-forward, for example, and the interval between PTSs before and after correction by the PTS correction unit 111 or 116 described later becomes a predetermined threshold value or less. If the PTS correction unit 111 or 116 determines that the processing target has caught up with the broadcast wave. At this time, the PTS correction unit 111 or 116 notifies the playback mode control unit 104 that the processing target has caught up with the broadcast wave, and the playback mode control unit 104 that has received the notification changes the current playback mode to the normal playback mode. change. In addition, if the stream playback device is a portable wireless terminal, the user cannot view video and audio when there is an incoming voice call, and therefore, the apparatus may be configured to automatically shift to the time shift accumulation mode.

  The input control unit 105 switches the switch 122 based on the interruption from the TS I / F 103 and the reproduction mode notification from the reproduction mode control unit 104. That is, the input control unit 105 separates the TS packet transferred from the TS I / F 103 when receiving a notification from the playback mode control unit 104 that the stream playback device is in the normal playback mode or the time shift accumulation mode. The switch 122 is switched so as to be input to the unit 106. When the input control unit 105 receives a notification from the playback mode control unit 104 that the stream playback device is in the time shift playback mode, the TS packet stored in the buffer 107 is input to the separation unit 106. However, when there is an interrupt from the TS I / F 103, the switch 122 is switched once and the TS packet transferred from the TS I / F 103 is input to the separation unit 106, and the switch 122 is again connected to the buffer 107 side. Switch to.

  The separation unit 106 analyzes each syntax from the TS packets transferred via the switch 122 and distributes the TS packets. Here, the syntax refers to a TS header and an adaptation field in the TS packet.

  As shown in FIG. 2, the TS packet is configured as a fixed-length packet of 188 bytes including a 4-byte TS header as a head, an adaptation field that is an arbitrary field, and a payload.

  As shown in FIG. 3A, the TS header stores a 13-bit packet identifier (PID) for indicating whether the TS packet is transmitting video data or audio data. Since the same video data and the same audio data have the same PID, the ES before being packetized can be restored using the PID.

  The TS header also includes a 1-bit transport error indicator (tarportport_error_indicator) indicating the presence or absence of an error mixed in the TS packet, an adaptation field, and a 2-bit length adaptation field control (adaptation_field_control) indicating the presence or absence of a payload. Is also included. Here, as adaptation_field_control, “11” is “adaptation field is present, payload is present”, “10” is “adaptation field is present, no payload”, “01” is “adaptation field is absent, payload is present”, “00” is “reserved” (RFU: Reserved for Future Use).

  The TS header further includes a synchronization byte indicating the head of the TS packet to the decoder and a payload unit start indicator indicating that a new PES packet starts from the payload in the TS packet. ). Further, the TS header further includes a packet priority indicating the importance of the TS packet (transport priority) and a 2-bit length transport scramble control indicating whether the payload in the TS packet is scrambled (transport scramble control). I have. Further, the TS header further includes a 4-bit length continuity counter for detecting whether a TS packet having the same PID as the TS packet has been partially discarded.

  As shown in FIG. 3B, the adaptation field has a variable-length optional field, and a 42-bit long PCR is included in this optional field. The adaptation field further includes an 8-bit adaptation field length (adaptation field length), a 1-bit discontinuity display (discontinuity_indicator) indicating whether or not the time base is switched, a random access indicator (random access indicator), and a stream. It has a priority display (elementary stream priority indicator), 5 flags (5 flags) including a 1-bit PCR flag (PCR_flag) indicating the presence / absence of PCR in the adaptation field, and variable length stuffing bytes (stuffing bytes).

  As shown in FIG. 2, a PES (Packetized Elementary Stream) packet obtained by adding a header called a PES header to the ES and packetizing the ES is divided and stored in the payload.

  As shown in FIG. 3C, the PTS header stores the PTS of the first frame in the PES packet in a 33-bit length field. Here, the PES header is a 24-bit packet start code (packet start prefix), an 8-bit stream ID (stream id), a 16-bit PES packet length (PES packet length), “10”, and 2-bit length. PES scrambling control (PES scrambling control), PES priority (PES priority), data alignment indicator (copy alignment), original / copy (original or copy), 7 flag An 8-bit PES header length (PES header data length) and a variable length optional field (opt) in which PTS is described onal field), and a variable length of stuffing bytes (stuffing bytes).

  The separation unit 106 has a PID filter, and distributes the TS packet according to the PID in the TS header in the transferred TS packet. Specifically, the PID filter sets the value of the PID and the type of the TS packet corresponding to the table information called a program correspondence table (PMT: Program Map Table) possessed by each program.

  In the PMT, a PID value and a TS packet type are recorded in association with each other, and it is possible to determine whether a TS packet having a specific PID value is video, audio, caption, PCR, or the like. . As described above, the PCR is stored in the adaptation field in the TS packet, and may be transmitted together with a payload including video and audio, or may be transmitted alone without the payload. Therefore, a specific PID value may indicate only PCR, or may indicate both PCR and video. In addition, when a program to be viewed is changed by a user operation or the like, the PID filter in the separation unit 106 is reset based on the PMT.

  The separation unit 106 analyzes the PID based on the setting of the PID filter, and distributes the TS packet according to the type of the TS packet. The TS packet sorting process performed by the separation unit 106 differs depending on the playback mode notified by the playback mode control unit 104.

  When the stream playback device is in the normal playback mode, the separation unit 106 inputs the TS packet to the PES extraction unit 112 if the TS packet is video, and inputs the TS packet to the PES extraction unit 117 if the TS packet is audio. . In addition, when the TS packet includes PCR, the separation unit 106 inputs the PCR to the STC control unit 108. In addition, when the PID of the TS packet is not set in the PID filter, the separation unit 106 discards the TS packet.

  When the stream playback device is in the time shift accumulation mode, the separation unit 106 transfers the TS packet to the buffer 107. At this time, when the PID of the TS packet is not set in the PID filter, the separation unit 106 may discard the TS packet in advance. In addition, when the TS packet includes PCR, the separation unit 106 inputs the PCR to the STC control unit 108.

  When the stream playback device is in the time-shift playback mode, the separation unit 106 transfers the TS packet to the buffer 107 if the TS packet is a TS packet transferred from the TS I / F 103. At this time, the separation unit 106 inputs the PCR to the STC control unit 108 when the TS packet includes the PCR. Further, when the TS packet is a TS packet transferred from the buffer 107, the separation unit 106 inputs the TS packet to the PES extraction unit 112 if the TS packet is video, and the PES extraction unit if the TS packet is audio. The TS packet is input to 117. In addition, when the PID of the TS packet is not set in the PID filter, the separation unit 106 discards the TS packet.

  The buffer 107 is a buffer for accumulating TS packets received from broadcast waves when the stream reproduction apparatus is in the time shift accumulation mode or the time shift reproduction mode. The buffer 107 is, for example, a ring buffer, and has a head pointer that indicates the head address of the stored data and a terminal pointer that indicates the end address of the stored data. That is, the buffer 107 accumulates TS packets in order from the beginning, and when the accumulated data exceeds the capacity of the buffer 107, the address pointed to by the end pointer is rewritten to the beginning address of the buffer 107, and overwritten from the data with the oldest accumulation timing. Shall be.

  The STC control unit 108 compares the input PCR with the STC value from the STC counter 110. If the STC value is smaller than the PCR, the STC 109 is controlled to increase the frequency, and if the STC value is larger than the PCR, the STC 109 is controlled to decrease the frequency.

  The STC 109 generates an STC based on the frequency determined by the STC control unit 108 and inputs it to the STC counter 110.

  The STC counter 110 inputs the STC value obtained by counting the STC 109 to the PTS correction unit 111, the decoder 114, the PTS correction unit 116, and the decoder 119. The STC value is also input to the STC control unit 108 for clock recovery.

  The PTS correction unit 111 replaces the PTS transferred from the PES extraction unit 112 with a correction value corrected based on the magnification of the current playback speed. Note that the PTS correction is performed only in the time shift reproduction mode. When the time shift reproduction mode is started, the PTS correction unit 111 detects the STC value increment ΔSTC in the preceding time shift accumulation mode. That is, a value obtained by subtracting the STC value at the start of the time shift accumulation mode from the STC value at the end of the time shift accumulation mode (at the start of the time shift reproduction mode) is ΔSTC. In the case of performing equal magnification reproduction in the time shift reproduction mode, the PTS correction unit 111 sets a value obtained by adding ΔSTC to the input PTS as shown in FIG. 4 as a correction value of the PTS. Hereinafter, an example of PTS correction at the same magnification reproduction will be described in detail with reference to FIG.

  As shown in FIG. 4, it is assumed that the stream reproducing apparatus performs normal reproduction until time T1, accumulates time shift from time T1 to time T2, and performs time shift reproduction from time T2. Note that the STC control unit 108 performs clock recovery using the received PCRs 1 to 4 through all the sections, and synchronizes with the transmission side. The PTS 1 to 3 accumulated in the time shift accumulation mode are corrected by the PTS correction unit 111 as follows. When the time-shift playback mode starts at time T2, the PTS correction unit 111 detects the increment ΔSTC of the count value of the STC counter 110 from time T1 to time T2, and when the TS packet having PTS1 to PTS3 is input, ΔTSC is input. The added PTS ′ 1 to 3 are replaced as correction values, and transferred to the buffer 113.

  Further, the correction of PTS by the PTS correction unit 111 when reproducing at the magnification r in the time shift reproduction mode will be described in detail with reference to FIG. In FIG. 5, the magnification r is 4/3.

  As shown in FIG. 5, the stream playback apparatus performs time-shift playback at the same speed from time T3 to time-shift playback at time of 4/3 speed from time T3 to time T4, and the playback target catches up with the broadcast wave at time T4. Transition to playback. The PTS correction unit 111 corrects by adding ΔSTC to the PTS in the TS packet input as described above until time T3. When the reproduction speed magnification is switched to r (4/3) at time T3, the PTS correction unit 111 causes the corrected PTS interval to be the reciprocal (3/4) times r of the PTS interval before correction. To correct the PTS. Here, the PTS interval is the interval between the PTS currently corrected by the PTS correction unit 111 and the PTS corrected in the past (hereinafter referred to as a reference PTS). As the reference PTS, any PTS may be used as long as the reproduction speed magnification at the time of correction is the same.

  Here, the correction of the PTS 4 will be described. Since the PTS corrected by the PTS correction unit 111 after the reproduction speed magnification becomes r is only PTS3, the PTS interval is obtained using PTS3 as a reference PTS, and PTS4 is corrected. The PTS interval before correction is (PTS4-PTS3). Accordingly, since the corrected PTS interval should be 3 (PTS4-PTS3) / 4, the value obtained by adding the corrected PTS interval to the correction value PTS′3 = PTS3 + ΔSTC of PTS3 is the correction value of PTS4. PTS′4 = ΔSTC + (3PTS4 + PTS3) / 4.

  Next, correction of PTS5 will be described. A reference PTS that can be used to correct PTS5 is PTS3 or PTS4. When the PTS3 is set as the reference PTS, since the interval before correction is (PTS5-PTS3), the correction value PTS′3 of the PTS3 is set so that the PTS interval after correction is 3 (PTS5-PTS3) / 4. When the corrected PTS interval is added to PTS3 + ΔSTC, a correction value PTS′5 = ΔSTC + (3PTS5 + PTS3) / 4 of PTS5 is derived. On the other hand, when the PTS4 is set as the reference PTS, since the interval before correction is (PTS5-PTS4), the correction value PTS4 of the PTS4 is set so that the PTS interval after correction is 3 (PTS5-PTS4) / 4. When the corrected PTS interval is added to '4 = ΔSTC + (3PTS4 + PTS3) / 4, a correction result PTS′5 = ΔSTC + (3PTS5 + PTS3) / 4 of PTS5 is derived. Therefore, if the reproduction speed at the time of correction is the same, the same correction value can be obtained regardless of which PTS is used as the reference PTS.

  Thereafter, the PTS correction value is similarly obtained. The PTS correction unit 111 always inspects the difference between the PTS to be corrected and the correction value, and the difference before and after the PTS correction is a predetermined threshold, for example, one frame. When the interval is less than or equal to the interval, this is notified to the playback mode control unit 104. Based on this notification, the playback mode control unit determines the end timing of the time shift playback mode and seamlessly shifts to the normal playback mode. In the example of FIG. 5, the difference between the PTSi and the correction value PTS′i is equal to or less than one frame interval, and the PTSi correction time T4 is used as the end timing of the time shift playback to seamlessly shift to the normal playback mode. Yes.

  The PES extraction unit 112 extracts ES and PTS from the TS packet having the video ES distributed from the separation unit 106 and transfers the extracted ES and PTS to the PTS correction unit 111. The buffer 113 temporarily stores the ES and the PTS corrected by the PTS correction unit 111.

  The decoder 114 acquires the ES stored in the buffer 113 and decodes it to obtain video data. When the STC value from the STC counter 110 exceeds the PTS stored in the buffer 113, the decoded video data is reproduced from the display 115. The decoder 114 regards the video frame as a fixed frame interval, and this interval is set to be a reciprocal multiple of the reproduction rate magnification r.

  The PTS correction unit 116 performs the same processing as the PTS correction unit 111 on the PTS transferred from the PES extraction unit 117, and transfers the corrected PTS to the buffer 118 together with the ES. The PES extraction unit 117 extracts ES and PTS from the TS packet having the audio ES distributed from the separation unit 106 and transfers the ES and PTS to the PTS correction unit 116. The buffer 118 temporarily stores the PTS and ES corrected by the PTS correction unit 116.

  The decoder 119 acquires ES from the buffer 118 and decodes it to obtain audio data. When the STC value from the STC counter 110 becomes equal to or greater than the PTS stored in the buffer 118, the decoded audio data is digital-analog converted by the DAC 120 and reproduced from the speaker 121.

  Since the number of audio frames that can be reproduced is smaller during high-speed reproduction than in the same-size reproduction, the decoder 119 calculates the frame interval of the audio frames from the sampling frequency acquired in advance from the stream, and the number of samples is the reciprocal of the magnification r. The reproduction time is adjusted by performing a thinning process so as to be doubled.

  The switch 122 switches the input of the separation unit 106 based on a control signal from the input control unit 105. That is, either the TS packet stored in the buffer 107 or the TS packet transferred from the TS I / F 103 is input to the separation unit 106.

Hereinafter, TS packet separation processing in the time shift operation of the stream reproduction device according to the embodiment of the present invention will be described using the flowchart shown in FIG.
When the time shift reproduction starts, the process proceeds to step S201 first. In step S201, the end of time shift reproduction is determined. That is, when the user inputs the switching to the normal playback mode or the time shift accumulation mode to the playback mode control unit 104, the time shift playback mode is terminated, and the playback mode control unit 104 performs input control of the current playback mode. Unit 105, separation unit 106, PTS correction unit 111, and PTS correction unit 116, on the other hand, when the time shift reproduction is continued, separation unit 106 reads the TS packet to be processed from broadcast wave buffer or buffer 107. (Step S202). Next, the separating unit 106 analyzes each syntax of the TS header and the adaptation field in the read TS packet (step S203). Next, the separation unit 106 determines whether or not the TS packet to be processed has been input from the broadcast wave buffer (step S204).

  When the TS packet to be processed is input from the broadcast wave buffer, the separation unit 106 refers to the PID filter and determines whether or not a PID is set (step S205). If the PID is set in the PID filter, the separation unit 106 determines whether the TS packet to be processed has a PCR (step S206). If the TS packet to be processed has a PCR, the separating unit 106 notifies the STC control unit 108 of the PCR, and the STC control unit 108 uses the notified PCR and the STC value from the STC counter 110 to clock the STC 109. Recovery is performed, and the process proceeds to step S208 (step S207). On the other hand, when the TS packet to be processed does not have a PCR (step S206), step S207 is omitted and the process proceeds to step S208. In step S208, the TS packet to be processed is stored in the buffer 107 as the end of the reproduction target data, and the process returns to step S201 to move to the processing of the next TS packet. On the other hand, if the PID is not set in the PID filter (step S205), the separation unit 106 discards the TS packet to be processed, and returns to step S201 to move to processing of the next TS packet.

  On the other hand, when the TS packet to be processed is input from the buffer 107 (step S204), the separation unit 106 determines whether or not PID is set with reference to the PID filter (step S209). When the PID is set in the PID filter, the separation unit 106 determines whether the TS packet to be processed is any one of audio, video, and caption (caption) from the PID search result (step S210). . When the TS packet to be processed is any one of audio, video, and caption, the separation unit 106 distributes the TS packet to the PES extraction unit 112, the PES extraction unit 117, or a caption PES extraction unit (not shown). Next, the PTS correction unit determines whether or not the current reproduction speed is high (step S211). If the current playback speed is high, the PTS correction unit determines whether or not the input process target TS packet includes the head of the frame (step S212). If there is a head of a frame in the TS packet to be processed, the PTS correction unit corrects the PTS in the TS packet to be processed (step S213). Specifically, assuming that reproduction is performed at a magnification r (> 1), by adding 1 / r times the interval between the PTS currently being corrected and the reference PTS described above to the correction value of the reference PTS, A correction value of the PTS currently being corrected is obtained.

  Next, the PTS correction unit determines whether or not the TS packet to be processed is voice (step S214). When the TS packet to be processed is voice, the PTS correction unit 116 determines whether or not the PTS difference before and after the correction in step S213 is equal to or less than one frame interval (step S215). If the PTS difference before and after correction is equal to or less than one frame interval, the PTS correction unit 116 separates the payload from the TS packet to be processed and stores it in the buffer 118 (step S216). Next, the PTS correction unit 116 instructs the playback mode control unit 104 to shift to the normal playback mode, and the time shift playback ends. In this example, the target for determining whether or not to end the time-shift playback mode in step S215 is limited to audio (step S214), but this is because audio has a shorter time interval per frame than video. This is because the deterioration of the quality is conspicuous when the seamless transition to the normal reproduction mode cannot be realized. Therefore, the determination in step S215 is not denied for the video, and the determination in step S214 may be read so as to determine whether the TS packet to be processed is video or audio. In determining whether to end the time-shift playback mode, one frame interval is used as a threshold for the difference between the PTS before and after correction, but this is merely an example of the threshold.

  On the other hand, when the PTS difference before and after the correction is larger than one frame interval (step S215), the PTS correction unit 116 separates the payload from the TS packet to be processed and stores it in the buffer 118 (step S221). The process returns to step S201 to shift to the processing of the TS packet. If the TS packet to be processed is a video or a caption (step S214), the payload is separated from the TS packet to be processed, accumulated in the buffer (step S221), and step S201 is entered to move to the next TS packet processing. Return to. If there is no head of the frame in the TS packet to be processed (step S212), the payload is separated from the TS packet to be processed, stored in the buffer (step S221), and the process proceeds to the next TS packet processing. Return to S201.

  On the other hand, if the PID is not set in the PID filter (step S209), the separation unit 106 discards the TS packet to be processed, and returns to step S201 to move to processing of the next TS packet. Further, when the TS packet to be processed is, for example, a section or PCR other than audio, video, or caption (step S210), a separation process according to the type of the TS packet is performed (step S217), and the next TS packet is processed. The process returns to step S201 to shift to step S201.

  On the other hand, when the current playback speed is equal (step S211), the PTS correction unit determines whether or not the input processing target TS packet includes the head of the PES (step S218). Specifically, referring to the above-described payload unit start indicator in the TS packet, if “1”, it is determined that the TS packet to be processed includes the head of the PES, and “0”. If there is, it is determined that the head of the PES is not included in the TS packet to be processed. If the TS packet to be processed includes the head of the PES, the PTS correction unit determines whether the TS packet has a PTS (step S219). If the TS packet to be processed has a PTS, the PTS correction unit corrects the PTS (step S220). Specifically, as described above, the PTS to be processed is replaced with a correction value obtained by adding ΔSTC to PTS. Next, the PTS correction unit separates the payload from the TS packet to be processed, accumulates it in the buffer (step S221), and returns to step S201 to move to processing of the next TS packet. On the other hand, even if the processing target TS packet does not include the head of the PES (step S218), the PTS correction unit separates the payload from the TS packet and stores it in the buffer (step S221), and the next TS packet The process returns to step S201 to move to the process. Also, when the TS packet to be processed does not have a PTS (step S219), the PTS correction unit separates the payload from the TS packet, stores it in the buffer (step S221), and proceeds to the processing of the next TS packet. The process returns to step S201.

  As described above, in the present embodiment, the PTS is corrected when performing time-shifted reproduction, and the correction is stopped when the difference in PTS before and after the correction becomes one frame interval or less due to high-speed reproduction. Therefore, according to the present embodiment, it is possible to provide a stream playback device that can seamlessly shift to normal playback by detecting the timing when the playback target catches up with the broadcast wave in time-shift playback.

  In this embodiment, the PTS correction is performed by the PTS correction units 111 and 116. However, the playback mode control unit 104 is configured to notify the decoders 114 and 119 of the current playback speed magnification, thereby correcting the PTS. Processing may be performed by the decoders 114 and 119. In addition, the PTS correction may be performed by the PTS correction units 111 and 116 only for the frames having the PTS, and other processes may be performed by the decoders 114 and 119.

  Further, in this embodiment, since the PTS correction units 111 and 116 do not perform video and audio syntax analysis, when the video has a variable frame rate, it is impossible to know the frame interval (for audio, the sampling frequency If it is determined, the frame interval is uniquely determined). Therefore, the PTS interval is corrected assuming that the video has a fixed frame rate. However, since the decoder performs syntax analysis of video and audio, the original PTS interval can be accurately reproduced even when the video has a variable frame rate, and can be reproduced along the original frame interval even during high-speed playback. . However, in reality, even if such an accurate PTS interval is not reproduced and treated as a fixed frame interval, it is considered that the user hardly feels a difference.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. Further, for example, a configuration in which some components are deleted from all the components shown in the embodiment is also conceivable. Furthermore, you may combine suitably the component described in different embodiment.

  For example, in the embodiment described above, both video and audio are described as being subject to reproduction, but only one of them may be subject to reproduction. That is, if only video is to be reproduced, the PTS correction unit 116, PES extraction unit 117, buffer 118, decoder 119, DAC 120, and speaker 121 may be excluded from the stream reproduction device shown in FIG. 1 is to be reproduced, the PTS correction unit 111, the PES extraction unit 112, the buffer 113, the decoder 114, and the display 115 may be excluded from the stream reproduction apparatus shown in FIG.

  In addition, it goes without saying that the present invention can be similarly implemented even if various modifications are made without departing from the gist of the present invention.

1 is a block diagram showing a stream playback device according to an embodiment of the present invention. FIG. 2 is a diagram showing a structure of a TS packet processed by the stream reproduction device shown in FIG. 1, a structure of a transport stream composed of the TS packet, and a structure of a PES packet stored in a payload in the TS packet. (A) The figure which shows the structure of TS header in the TS packet shown in FIG. (B) The figure which shows the structure of Adaptation Field in TS packet shown in FIG. (C) The figure which shows the structure of the PES header shown in FIG. FIG. 3 is a graph for explaining correction of PTS by a PTS correction unit when the stream playback apparatus shown in FIG. 1 performs time-shift playback at the same speed. FIG. 3 is a graph for explaining correction of PTS by a PTS correction unit when the stream playback device shown in FIG. 1 performs time-shift playback at 4/3 times speed. 3 is a flowchart showing a time shift playback operation of the stream playback device shown in FIG. 1.

Explanation of symbols

101 ... antenna 102 ... tuner 103 ... TS I / F
104 ... Reproduction mode control unit 105 ... Input control unit 106 ... Separation unit 107 ... Buffer 108 ... STC control unit 109 ... STC
110: STC counter 111 ... PTS correction unit 112 ... PES extraction unit 113 ... buffer 114 ... decoder 115 ... display 116 ... PTS correction unit 117 ... PES extraction unit 118 ... Buffer 119 ... Decoder 120 ... DAC
121 ... Speaker 122 ... Switch

Claims (6)

A receiver for receiving a packet including an elementary stream in which encoded video or audio data is stored and a display time stamp;
A first buffer for storing the packets one after another in a time-shift reproduction mode and a time-shift accumulation mode for pre-accumulating the packets prior to the time-shift reproduction mode;
A counter that outputs a system time clock value obtained by counting the system time clock; and
In the time-shift playback mode, a correction unit that replaces the display time stamp included in the packet stored in the first buffer with a correction value corrected based on a magnification of the current playback speed;
If the difference between the display time stamp and the correction value is equal to or less than a predetermined threshold, the control unit stops the operation of the correction unit and changes the current playback mode to the normal playback mode;
A second buffer for temporarily storing an elementary stream and a display time stamp in a packet stored in the first buffer in the time-shift playback mode;
A decoder for decoding the video or audio data from the elementary stream at a timing determined based on the display time stamp stored in the second buffer and the system time clock value;
And a playback unit that plays back the video or audio data.   The stream reproducing apparatus according to claim 1, wherein the threshold corresponds to one frame interval.   The correction value is obtained by multiplying the increment from the reference display time time stamp that the correction unit has previously corrected to the display time time stamp that is the current target to the reciprocal of the magnification, and the reference display time time. 2. The stream reproducing apparatus according to claim 1, wherein the stream reproducing apparatus is a value added to the correction value of the stamp.   4. The stream playback device according to claim 3, wherein the reference display time stamp is a display time time stamp that is first corrected by the correction unit at the current playback speed.   4. The stream reproduction according to claim 3, wherein the reference display time stamp is a display time time stamp that is corrected by the correction unit immediately before the display time time stamp that is currently corrected. apparatus.   The stream reproduction apparatus according to claim 1, wherein, in the normal reproduction mode, the second buffer temporarily stores a packet received by the reception unit.

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