JP3921986B2 - Synchronizing apparatus and method, digital broadcast receiving apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital signal synchronization apparatus and method suitable for synchronizing audio and video in a MPEG (Moving Picture Coding Experts Group) 2 stream, and a digital broadcast receiving apparatus.
[0002]
[Prior art]
In digital satellite broadcasting, an MPEG2 transport stream is transmitted. In the MPEG2 stream, a PTS (Presentation Time Stamp) indicating the playback time is sent to the header. This PTS is compared with a reference clock STC (System Time Clock) inside the clock system, and when the PTS and STC match, a process for decoding is performed. As a result, synchronized playback between video and audio is realized.
[0003]
It should be noted that a DTS (Decoding Time Stamp) is provided in the video because there is a special encoded stream transmission order. That is, the I picture and the P picture precede the B picture. Therefore, when the PTS and the DTS are different from each other, both are added to the MPEG2 stream. In the same case, only PTS is added.
[0004]
[Problems to be solved by the invention]
As described above, in the MPEG2 stream, PTS and STC are compared, and if PTS and STC match, decoding is performed to keep video and audio synchronized.
[0005]
However, the PTS sent from the broadcasting station is not always correct. Depending on the signal from the broadcast station, a PTS value with jitter or an illegally delayed PTS value may be sent at an incorrect interval.
[0006]
Conventionally, as described above, the PTS and the STC are compared, and if the PTS and the STC match, the decoding is always performed. When a message is sent, there is a problem that the image is disturbed and the sound is cut off.
[0007]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a synchronization device and method, and a digital broadcast receiving device, which can prevent the screen from being distorted or the occurrence of sound interruption even when there is jitter or delay in the PTS. There is.
[0008]
[Means for Solving the Problems]
First The invention of 1 A reference time generating means for generating reference time information; Playback time information included in the TS (Transport Stream) packet stream and Generated by the reference time generating means Compare with reference time information Comparison Means, Based on the comparison result by the comparison means, Determine whether the time difference between the playback time information and the reference time information is within the threshold Judgment Means, Reproduction control means for controlling the reproduction of the frames included in the stream, the reproduction control means based on the determination result by the determination means The time difference is within the threshold If it is determined, it corresponds to the playback time information. Frame playback starts and the time difference is within the threshold. Is judged Frame to play The Kip or repeat And skip or repeat is performed up to a predetermined number of skips or repeats, At first Time difference Within threshold When it is determined that there is a limit The number of skips or repeats Less often change This The synchronizer characterized by these.
[0009]
Second The invention of A reference time generation step for generating reference time information; Playback time information included in the TS (Transport Stream) packet stream and Generated in the reference time generation step Compare with reference time information Comparison And the steps Based on the comparison result from the comparison step, Determine whether the time difference between the playback time information and the reference time information is within the threshold Judgment And the steps A playback control step for controlling playback of the frames included in the stream, and the playback control step is based on a determination result by the determination step. The time difference is within the threshold If it is determined, it corresponds to the playback time information. Frame playback starts and the time difference is within the threshold. Is judged Frame to play The Kip or repeat And skip or repeat is performed up to a predetermined number of skips or repeats, At first Time difference Within threshold When it is determined that there is a limit The number of skips or repeats Less often change This And a synchronization method characterized by
[0010]
Third The invention includes: means for receiving digital broadcast; means for decoding a stream of TS (Transport Stream) packets from a received signal of digital broadcast; A reference time generating means for generating reference time information; Playback time information included in the TS packet stream and Generated by the reference time generating means Compare with reference time information Comparison Means, Based on the comparison result by the comparison means, Determine whether the time difference between the playback time information and the reference time information is within the threshold Judgment Means, Reproduction control means for controlling the reproduction of the frames included in the stream, the reproduction control means based on the determination result by the determination means The time difference is within the threshold If it is determined, it corresponds to the playback time information. Frame playback starts and the time difference is within the threshold. Is judged Frame to play The Kip or repeat And skip or repeat is performed up to a predetermined number of skips or repeats, At first Time difference Within threshold When it is determined that there is a limit The number of skips or repeats Less often change This And a digital broadcast receiver characterized by the above.
[0011]
It is determined whether or not the absolute value of the difference between the PTS value and the STC value is less than or equal to a predetermined threshold value. If the PTS value is greater than the STC value, it is determined that the playback time is earlier than the real time, and the repeat counter is used. The same frame is repeatedly played back with the indicated value as the limit, and if the PTS value is not greater than the STC value, the playback time is assumed to be slower than the actual time, and the frame decoding is performed with the value indicated by the skip counter as the limit. A process of skipping and reproducing is performed so that the absolute value of the difference between the PTS value and the STC value falls within a predetermined threshold. Then, the threshold value at the time of initial synchronization is set to a value narrower than the threshold value once synchronization is established, and the set value of the repeat counter and the skip counter value at the time of initial synchronization are set after the synchronization is once established. It is larger than the set value of the repeat counter and the set value of the skip counter.
[0012]
Thus, at the time of initial synchronization, synchronization is established until the PTS value and the STC value are surely matched. Once synchronization is established, the PTS value and the STC value are not synchronized. After the reproduction is performed in the asynchronous mode and the initial synchronization is completed, when the jitter is included in the PTS value, the synchronization is not disturbed due to the jitter.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an IRD (Integrated Receiver Decoder) to which the present invention can be applied.
[0014]
In FIG. 1, for example, a digital satellite broadcast radio wave transmitted through a satellite with a 12 GHz band radio wave is received by a parabolic antenna 1 and converted into a 1 GHz band signal by a low noise converter 2 attached to the parabolic antenna 1. Converted. The output of the low noise converter 2 is supplied to the tuner circuit 3. The tuner circuit 3 selects a signal having a predetermined carrier frequency from the received signal, and converts this signal into an intermediate frequency signal. A frequency setting control signal is supplied from the controller 4 to the tuner circuit 3. A reception frequency is set based on this control signal.
[0015]
The output of the tuner circuit 3 is supplied to the demodulation circuit 5. The demodulation circuit 5 performs QPSK (Quadrature Phase Shift Keying) demodulation processing. The output of the demodulation circuit 5 is supplied to the error correction circuit 6. Error correction processing is performed by the error correction circuit 6.
[0016]
The output of the error correction circuit 6 is supplied to the descrambler 7. The descrambler 7 is supplied with the received ECM (Entitlement Control Message) data and EMM (Entitlement Management Message) data, and for descrambling stored in the IC card 8 mounted on the IC card interface 9 Key data is supplied. Further, it is possible to determine whether or not the program can be recorded based on the data of the ECM and EMM.
[0017]
The descrambler 7 descrambles the MPEG transport stream using the received ECM data and EMM data and the key data of the IC card 8. Further, it can be determined whether or not copying is prohibited by ECM data and EMM data. The descrambled MPEG2 transport stream is sent to the demultiplexer 10.
[0018]
The demultiplexer 10 separates a desired packet from the stream from the descrambler 7 based on a command from the controller 4. A packet identifier (PID) is described in the header part of the transmission packet. The demultiplexer 10 extracts video packets and audio packets of a desired program based on this PID. The video packet of the desired program is sent to the video processing circuit 11, and the audio packet is sent to the audio processing circuit 12.
[0019]
The video processing circuit 11 receives a video signal packet from the demultiplexer 10 and performs MPEG2 decoding to form video data. This video data is supplied to the NTSC encoder 13. The NTSC encoder 13 converts the video data decoded by the video processing circuit 11 into an NTSC video signal. The output of the NTSC encoder 13 is supplied to the video output terminal 14. An NTSC composite video signal is output from the video output terminal 14.
[0020]
The audio processing circuit 12 receives the audio packet from the demultiplexer 10 and performs MPEG audio decoding processing to form audio data before data compression. The output of the audio processing circuit 12 is converted into an analog audio signal by the D / A converter 15 and then output from the audio output terminal 16.
[0021]
Input for operating the IRD is performed by the remote controller 18. An infrared command signal from the remote controller 18 is received by the light receiving unit 19 and sent to the controller 4. A modem 17 is provided, and the modem 17 is connected to a telephone line.
[0022]
The present invention is suitable for synchronizing video and audio when reproducing an MPEG stream in the digital satellite broadcasting as described above.
[0023]
FIG. 2 shows the configuration of a video and audio synchronization circuit to which the present invention is applied.
[0024]
2, a demultiplexer 101 (corresponding to the demultiplexer 10 in FIG. 1) separates video packets and audio packets based on the PID. Video packets are sent to the video buffer 102, and audio packets are sent to the audio buffer 109. The output of the video buffer 102 is supplied to the video synchronization processing unit 103 and also supplied to the video decoding unit 104 (corresponding to the video processing circuit 11 in FIG. 1).
[0025]
The output of the audio buffer 109 is supplied to the audio synchronization processing unit 110 and also to the audio decoding unit 111 (corresponding to the audio processing circuit 12 in FIG. 1).
[0026]
Also, in the TS stream, the SCR (System Clock Reference (system time reference value)) and PCR (Program Clock Reference (program time reference value)) are used for setting and calibrating the STC that is the time reference. Will be sent. The SCR and PCR are supplied to the STC counter 108. The STC counter 108 generates an STC serving as a time reference. This STC is supplied to the video synchronization processing unit 103 and also to the audio synchronization processing unit 110.
[0027]
The video synchronization processing unit 103 and the audio synchronization processing unit 110 compare the time indicated by the PTS (or DTS) with the time indicated by the STC serving as a system reference, and when the PTS and the STC match, the video synchronization processing unit 103 and the audio synchronization processing unit 110 By reproducing the signal and the audio signal, the video and the audio are synchronized. The video synchronization processing unit 103 and the audio synchronization processing unit 110 output synchronization instruction signals CMV and CMA when the PTS and STC match.
[0028]
A video packet is supplied from the video buffer 102 to the video decoding unit 104 and a synchronization instruction signal CMV is supplied from the video synchronization processing unit 103. When the synchronization instruction signal CMV is supplied from the video synchronization processing unit 103, the video decoding unit 104 performs video data decoding processing according to the MPEG2 system. The output of the video decoding unit 104 is supplied to the video output processing unit 106 via the frame buffer 105.
[0029]
An audio packet is supplied from the audio buffer 109 to the audio decoding unit 111 and a synchronization instruction signal CMA is supplied from the audio synchronization processing unit 110. When the synchronization instruction signal CMA is supplied from the audio synchronization processing unit 110, the audio decoding unit 111 performs audio data decoding processing. The output of the audio decoding unit 111 is supplied to the audio output processing unit 113 via the PCM buffer 112.
[0030]
FIG. 3 shows the configuration of the video synchronization processing unit 103 and the audio synchronization processing unit 110. Note that the video synchronization processing unit 103 and the audio synchronization processing unit 110 are basically configured in the same manner.
[0031]
In FIG. 3, the PTS acquisition unit 201 extracts the PTS in the PES header information. The output of the PTS acquisition unit 201 is supplied to the (PTS-STC) detection unit 202. The STC from the STC counter 108 is supplied to the (PTS-STC) detection unit 202.
[0032]
The (PTS-STC) detection unit 202 obtains the difference between the STC value and the PTS value. The output of the (PTS-STC) detection unit 202 is supplied to the synchronization instruction unit 203.
[0033]
The synchronization instruction unit 203 is supplied with the output of the (PTS-STC) detection unit 202 and is also supplied with the buffer near full information BUFV or BUFA from the video decoding unit 104 or the audio decoding unit 111. The synchronization instruction unit 203 generates a synchronization instruction signal CMV or CMA from the output of the (PTS-STC) detection unit 202 and the buffer near full information BUFV or BUFA according to the control process described later.
[0034]
Here, the buffer near full information indicates whether the storage state of the video data in the video buffer detected by the video decoding unit 104 is close to overflow in the video processing unit. The audio processing unit indicates whether the storage state of the audio data in the audio buffer detected by the audio decoding unit 111 is close to overflow.
[0035]
FIG. 4 is a flowchart showing the synchronization processing in the video synchronization processing unit 103. In FIG. 4, first, the value of the skip counter is set to Cs1, and the value of the repeat counter is set to Cr1 (step S1). When the PTS value is larger than the STC value, the repeat counter has a playback time that is earlier than the actual time. Therefore, the repeat counter performs playback such that one frame is repeatedly played and the PTS value approaches the STC value. The limit value of the number of repeats is shown. Since the playback time is later than the actual time when the PTS value is not greater than the STC value, the skip counter performs processing such that one frame is skipped for playback and the PTS value approaches the STC value. The limit value of the number of skips is shown.
[0036]
Note that the skip counter value Cs1 and the repeat counter value Cr1 at the time of initial synchronization are larger than the skip counter value Cs2 and the repeat counter value Cr2 (to be described later) once synchronization is established.
Cs1> Cs2
Cr1> Cr2
Set to
[0037]
That is, since it is necessary to establish synchronization once in the initial synchronization, the skip counter value Cs1 and the repeat counter value Cr1 are set to large values.
[0038]
It is determined from the output of the (PTS-STC) detection unit 202 whether or not the absolute value of the difference between the PTS value and the STC value is equal to or less than a predetermined threshold T1 (step S2).
| PTS-STC | ≦ T1
[0039]
Note that the threshold value T1 at the time of initial synchronization is smaller than a threshold value T2 (described later) after synchronization is once established.
T2> T1
Set to
[0040]
That is, at the time of initial synchronization, since it is necessary to establish synchronization completely once, the threshold value T1 is set narrow.
[0041]
If the absolute value of the difference between the PTS value and the STC value is not less than or equal to the predetermined threshold value T1 in step S2, it is determined whether or not the buffer state is near full (step S3). When the buffer state is near full, it is difficult to perform the decoding process synchronously, and therefore it is instructed to perform the image decoding process in the video and audio asynchronous mode (step S4).
[0042]
Here, if the buffer state is not near full, it is determined whether (PTS-STC) is greater than 0 (step S5).
[0043]
If (PTS-STC) is greater than 0, the PTS time is ahead of the time indicated by the STC, so it is necessary to delay playback. In this case, it is determined whether or not the value of the repeat counter is greater than 0 (step S6). If the value of the repeat counter is greater than 0, one-frame repeated display processing is instructed (step S7). The value is decremented by 1 (step S8), and the process returns to step S2.
[0044]
Thus, when the PTS time is ahead of the time indicated by the STC, the reproduction is delayed by repeating the loop of steps S2, S3, S5, S6, S7, and S8, and the value of the PTS is It approaches the value of STC. Each time the loop of S2, S3, S5, S6, S7, and S8 is repeated, the value of the repeat counter is decremented in step S8.
[0045]
In this way, when the PTS value approaches the STC value and it is determined in step S2 that the absolute value of the difference between the PTS value and the STC value is equal to or less than the predetermined threshold value T1, the image decoding process is performed. Is instructed (step S9).
[0046]
Even if the processes of steps S2, S3, S5, S6, S7, and S8 are repeated for the repeat counter set value Cs1, the absolute value of the difference between the PTS value and the STC value is not more than the predetermined threshold value T1 in step S2. If it is not determined that the value of the repeat counter is not satisfied, it is determined in step S6 that the value of the repeat counter is not 0 or more. In this case, it is instructed to perform the image decoding process in the video and audio asynchronous mode (step S4).
[0047]
In step S5, if (PTS-STC) is smaller than 0, the PTS time is delayed from the time indicated by the STC, so it is necessary to proceed with the reproduction. In this case, it is determined whether or not the value of the skip counter is greater than 0 (step S10). If the value of the skip counter is greater than 0, one frame of decoding skip processing is instructed (step S11). The counter value is decremented by 1 (step S12), and the process returns to step S2.
[0048]
As described above, when the PTS time is delayed from the time indicated by the STC, the reproduction is advanced by repeating the loop of steps S2, S3, S5, S10, S11, and S12, and the value of the PTS is changed to the STC value. Approaches the value of. Each time the loop of steps S2, S3, S5, S10, S11, and S12 is repeated, the value of the skip counter is decremented in step S12.
[0049]
In this way, when the PTS value approaches the STC value and it is determined in step S2 that the absolute value of the difference between the PTS value and the STC value is equal to or less than the predetermined threshold value T1, the image decoding process is performed. Is instructed (step S9).
[0050]
Even if the processes of steps S2, S3, S5, S10, S11, and S12 are repeated for the skip counter set value Cs1, the absolute value of the difference between the PTS value and the STC value is less than or equal to the predetermined threshold value T1 in step S2. If it is not determined, the skip counter value is determined not to be greater than or equal to 0 in step S10. In this case, it is instructed to perform the image decoding process in the video and audio asynchronous mode (step S4).
[0051]
Thus, in the initial synchronization, when the time of PTS is ahead of the time indicated by STC, reproduction is delayed by repeating the loop of steps S2, S3, S5, S6, S7, and S8. The value of PTS is brought close to the value of STC. If the PTS time is delayed from the time indicated by the STC, the reproduction proceeds by repeating the loop of steps S2, S3, S5, S6, S10, S11, and S12, and the value of the PTS is changed to the STC value. It can be brought close to the value of. The number of repetitions at this time is indicated by a skip counter value and a repeat counter value, and the skip counter value and the repeat counter values Cs1 and Cr1 are set to large values. Therefore, the synchronization process is performed until the synchronization is ensured.
[0052]
Once the initial synchronization is completed, it is determined in step S2 that the absolute value of the difference between the PTS value and the STC value is equal to or less than a predetermined threshold value T1, and in step S9, an image decoding process is instructed.
[0053]
Then, the skip counter value is set to Cs2, and the repeat counter value is set to Cr2 (step S13). Note that the skip counter value Cs2 and the repeat counter value Cr2 after the initial synchronization are smaller than the skip counter value Cs1 and the repeat counter value Cr1 in the initial synchronization.
[0054]
Then, it is determined from the output of the (PTS-STC) detection unit 202 whether or not the absolute value of the difference between the PTS value and the STC value is equal to or less than a predetermined threshold value T2 (step S14).
| PTS-STC | ≦ T2
[0055]
Note that the threshold T2 after the synchronization is once set is set to a value larger than the threshold T1 at the time of the initial synchronization. That is, after the synchronization is completed once, the threshold value T2 is set wide in consideration of the case where the PTS value includes jitter.
[0056]
If the absolute value of the difference between the PTS value and the STC value is not less than or equal to the predetermined threshold value T2 in step S14, it is determined whether or not the buffer state is near full (step S15). When the buffer state is near full, it is difficult to perform the decoding process synchronously, and therefore it is instructed to perform the image decoding process in the video and audio asynchronous mode (step S4).
[0057]
Here, if the buffer state is not near full, it is determined whether (PTS-STC) is greater than 0 (step S16).
[0058]
If (PTS-STC) is greater than 0, the PTS time is ahead of the time indicated by the STC, so it is necessary to delay playback. In this case, it is determined whether or not the value of the repeat counter is greater than 0 (step S17). If the value of the repeat counter is greater than 0, one-frame repeated display processing is instructed (step S18), and the repeat counter The value is decremented by 1 (step S19), and the process returns to step S14.
[0059]
As described above, when the PTS time is ahead of the time indicated by the STC, the reproduction is delayed by repeating the loop of steps S14, S15, S16, S17, S18, and S19, and the value of the PTS is set. It approaches the value of STC. Each time the loop of steps S14, S15, S16, S17, S18, and S19 is repeated, the value of the repeat counter is decremented in step S19.
[0060]
In this way, when the PTS value approaches the STC value and it is determined in step S14 that the absolute value of the difference between the PTS value and the STC value is less than or equal to the predetermined threshold value T2, the image decoding process is performed. Is instructed (step S9).
[0061]
Even if the loop of steps S14, S15, S16, S17, S18, and S19 is repeated by the repeat counter setting value Cs2, the absolute value of the difference between the PTS value and the STC value is less than or equal to the predetermined threshold T2 in step S14. If it is not determined that the value of the repeat counter is not determined, it is determined in step S17 that the value of the repeat counter is not 0 or more. In this case, it is instructed to perform the image decoding process in the video and audio asynchronous mode (step S4).
[0062]
If (PTS-STC) is smaller than 0 in step S16, the PTS time is delayed from the time indicated by the STC, so that it is necessary to proceed with the reproduction. In this case, it is determined whether or not the value of the skip counter is greater than 0 (step S20). If the value of the skip counter is greater than 0, one frame of decoding skip processing is instructed (step S21). The counter value is decremented by 1 (step S22), and the process returns to step S14.
[0063]
When the PTS time is delayed from the time indicated by the STC, reproduction is advanced by repeating the loop of steps S14, S15, S16, S20, S21, and S22, and the PTS value approaches the STC value. Come. Each time the loop of steps S14, S15, S16, S20, S21, and S22 is repeated, the value of the skip counter is decremented in step S22.
[0064]
In this way, when the PTS value approaches the STC value and it is determined in step S14 that the absolute value of the difference between the PTS value and the STC value is less than or equal to the predetermined threshold value T2, the image decoding process is performed. Is instructed (step S9).
[0065]
Even if the processes of steps S14, S15, S16, S20, S21, and S22 are repeated for the skip counter set value Cs2, the absolute value of the difference between the PTS value and the STC value is less than or equal to the predetermined threshold T2 in step S14. If it is not determined that the value of the skip counter is determined, it is determined in step S20 that the value of the skip counter is not 0 or more. In this case, it is instructed to perform the image decoding process in the video and audio asynchronous mode (step S4).
[0066]
FIG. 5 is a flowchart showing the synchronization processing in the audio synchronization processing unit 110. In FIG. 5, first, the value of the skip counter is set to Cs1, and the value of the repeat counter is set to Cr1 (step 51). Note that the skip counter value Cs1 and the repeat counter value Cr1 at the time of initial synchronization are larger than the skip counter value Cs2 and the repeat counter value Cr2 (to be described later) once synchronization is established.
Cs1> Cs2
Cr1> Cr2
Set to
[0067]
It is determined from the output of the (PTS-STC) detection unit 202 whether or not the absolute value of the difference between the PTS value and the STC value is equal to or less than a predetermined threshold T1 (step S52).
| PTS-STC | ≦ T1
[0068]
Note that the threshold value T1 at the time of initial synchronization is smaller than a threshold value T2 (described later) after synchronization is once established.
T2> T1
Set to
[0069]
If the absolute value of the difference between the PTS value and the STC value is not less than or equal to the predetermined threshold value T1 in step S52, it is determined whether or not the buffer state is near full (step S53). When the buffer state is near full, it is difficult to perform the decoding process synchronously, so that the audio decoding process is instructed in the video and audio asynchronous mode (step S54).
[0070]
Here, if the buffer state is not near full, it is determined whether (PTS-STC) is larger than 0 (step S55).
[0071]
If (PTS-STC) is greater than 0, the PTS time is ahead of the time indicated by the STC, so it is necessary to delay playback. In this case, it is determined whether or not the value of the repeat counter is greater than 0 (step S56). If the value of the repeat counter is greater than 0, one audio frame repeated display processing is instructed (step S57), and the repeat counter is counted. Is subtracted by 1 (step S58), and the process returns to step S52.
[0072]
Thus, when the time of PTS is ahead of the time indicated by STC, reproduction is delayed by repeating the loop of steps S52, S53, S55, S56, S57, and S58, and the value of PTS is It approaches the value of STC. Each time the loop of steps S52, S53, S55, S56, S57, and S58 is repeated, the value of the repeat counter is decremented in step S58.
[0073]
In this way, when the PTS value approaches the STC value and it is determined in step S52 that the absolute value of the difference between the PTS value and the STC value is equal to or less than the predetermined threshold value T1, the audio decoding process is performed. An instruction is given (step S59).
[0074]
Even if the loop of steps S52, S53, S55, S56, S57, and S58 is repeated by the repeat counter setting value Cs1, the absolute value of the difference between the PTS value and the STC value is not more than the predetermined threshold value T1 in step S52. If it is not determined that the value of the repeat counter is not satisfied, it is determined in step S56 that the value of the repeat counter is not 0 or more. In this case, it is instructed to perform the audio decoding process in the video and audio asynchronous mode (step S54).
[0075]
If (PTS-STC) is smaller than 0 in step S55, the PTS time is delayed from the time indicated by the STC, and it is necessary to proceed with the reproduction. In this case, it is determined whether or not the value of the skip counter is greater than 0 (step S60). If the value of the skip counter is greater than 0, one audio frame and decoding skip processing are instructed (step S61). The value of the skip counter is decremented by 1 (step S62), and the process returns to step S52.
[0076]
As described above, when the PTS time is delayed from the time indicated by the STC, the reproduction is advanced by repeating the loop of steps S52, S53, S55, S60, S61, and S62, and the value of the PTS is changed to the STC value. Approaches the value of. Each time the loop of steps S52, S53, S55, S60, S61, and S62 is repeated, the value of the skip counter is decremented.
[0077]
In this way, when the PTS value approaches the STC value and it is determined in step S52 that the absolute value of the difference between the PTS value and the STC value is equal to or less than the predetermined threshold value T1, the audio decoding process is performed. An instruction is given (step S59).
[0078]
Even if the loop of steps S52, S53, S55, S60, S61, and S62 is repeated by the skip counter setting value Cs1, the absolute value of the difference between the PTS value and the STC value is less than or equal to the predetermined threshold value T1 in step S52. If it is not determined that the value of the skip counter is not determined, it is determined in step S60 that the value of the skip counter is not 0 or more. In this case, it is instructed to perform the audio decoding process in the video and audio asynchronous mode (step S54).
[0079]
Thus, in the initial synchronization, when the PTS time is advanced from the time indicated by the STC, the playback is delayed by repeating the loop of steps S52, S53, S55, S56, S57, and S58. The value of PTS is brought close to the value of STC. If the PTS time is delayed from the time indicated by the STC, the reproduction is advanced by repeating the loop of steps S52, S53, S55, S56, S57, and S58, and the value of the PTS is the STC value. To be close to. The number of repetitions at this time is indicated by a skip counter value and a repeat counter value, and the skip counter value and the repeat counter values Cs1 and Cr1 are set to large values. Therefore, the synchronization process is performed until the synchronization is ensured.
[0080]
Once the initial synchronization is completed, it is determined in step S52 that the absolute value of the difference between the PTS value and the STC value is equal to or less than a predetermined threshold T1, and an audio decoding process is instructed in step S59.
[0081]
Then, the skip counter value is set to Cs2, and the repeat counter value is set to Cr2 (step S63). Note that the skip counter value Cs2 and the repeat counter value Cr2 after the initial synchronization are smaller than the skip counter value Cs1 and the repeat counter value Cr1 in the initial synchronization.
[0082]
It is determined from the output of the (PTS-STC) detection unit 202 whether or not the absolute value of the difference between the PTS value and the STC value is equal to or less than a predetermined threshold T2 (step S64).
| PTS-STC | ≦ T2
[0083]
If the absolute value of the difference between the PTS value and the STC value is not less than or equal to the predetermined threshold T2 in step S64, it is determined whether or not the buffer state is near full (step S65). When the buffer state is near full, it is difficult to perform the decoding process synchronously, so that the audio decoding process is instructed in the video and audio asynchronous mode (step S54).
[0084]
Here, if the buffer state is not near full, it is determined whether (PTS-STC) is greater than 0 (step S66).
[0085]
If (PTS-STC) is greater than 0, the PTS time is ahead of the time indicated by the STC, so it is necessary to delay playback. In this case, it is determined whether or not the value of the repeat counter is greater than 0 (step S67). If the value of the repeat counter is greater than 0, one audio frame repeated display processing is instructed (step S68), and the repeat counter is counted. Is subtracted by 1 (step S69), and the process returns to step S64.
[0086]
In this way, when the PTS time is ahead of the time indicated by the STC, the reproduction is delayed by repeating the loop of steps S64, S65, S66, S67, S68, and S69, and the value of the PTS is set. It approaches the value of STC. Each time the loop of steps S64, S65, S66, S67, S68, and S69 is repeated, the value of the repeat counter is decremented in step S69.
[0087]
In this way, if the PTS value approaches the STC value and it is determined in step S64 that the absolute value of the difference between the PTS value and the STC value is less than or equal to the predetermined threshold T2, the audio decoding process is performed. An instruction is given (step S59).
[0088]
Even if the loop of steps S64, S65, S66, S67, S68, and S69 is repeated for the repeat counter set value Cs2, the absolute value of the difference between the PTS value and the STC value is less than or equal to the predetermined threshold T2 in step S64. If it is not determined that the value of the repeat counter is not satisfied, it is determined in step S70 that the value of the repeat counter is not 0 or more. In this case, it is instructed to perform the audio decoding process in the video and audio asynchronous mode (step S54).
[0089]
In step S66, if (PTS-STC) is smaller than 0, the PTS time is delayed from the time indicated by STC, so it is necessary to proceed with the reproduction. In this case, it is determined whether or not the value of the skip counter is larger than 0 (step S70). If the value of the skip counter is larger than 0, one audio frame and decoding skip processing are instructed (step S71). The value of the skip counter is decremented by 1 (step S72), and the process returns to step S64.
[0090]
As described above, when the PTS time is delayed from the time indicated by the STC, the reproduction is advanced by repeating the loop of steps S64, S65, S66, S70, S71, and S72, and the value of the PTS is changed to the STC value. Approaches the value of. Each time the loop of steps S64, S65, S66, S70, S71, S72 is repeated, the value of the skip counter is decremented in step S72.
[0091]
In this way, when the PTS value approaches the STC value and it is determined in step S69 that the absolute value of the difference between the PTS value and the STC value is equal to or less than the predetermined threshold T2, the audio decoding process is performed. An instruction is given (step S59).
[0092]
Even if the loop of steps S64, S65, S66, S70, S71, and S72 is repeated for the skip counter set value Cs2, the absolute value of the difference between the PTS value and the STC value is less than or equal to the predetermined threshold T2 in step S64. If it is not determined, the skip counter value is determined not to be greater than or equal to 0 in step S70. In this case, it is instructed to perform the audio decoding process in the video and audio asynchronous mode (step S54).
[0093]
In the above example, the difference between the PTS value and the STC value is used. Of course, a DTS may be used instead of the PTS.
[0094]
【The invention's effect】
As described above, according to the present invention, it is determined whether or not the absolute value of the difference between the PTS value and the STC value is equal to or smaller than a predetermined threshold value. If the PTS value is larger than the STC value, the playback time is increased. As long as it is earlier than the real time, the same frame is repeatedly reproduced up to the value indicated by the repeat counter, and if the PTS value is not larger than the STC value, the reproduction time is later than the real time and indicated by the skip counter. In this way, processing is performed such that the decoding of one frame is skipped and reproduced so that the absolute value of the difference between the PTS value and the STC value falls within a predetermined threshold. Then, the threshold value T1 at the initial synchronization is set to a value narrower than the threshold value T2 after the synchronization is once established, and the repeat counter set value Cr1 and the skip counter set value Cs1 at the initial synchronization are once synchronized. The set value Cr2 of the repeat counter and the set value Cs2 of the skip counter after the establishment are set.
[0095]
Thus, at the time of initial synchronization, synchronization is established until the PTS value and the STC value are surely matched. Once synchronization is established, the PTS value and the STC value are not synchronized. After the reproduction is performed in the asynchronous mode and the initial synchronization is completed, when the jitter is included in the PTS value, the synchronization is not disturbed due to the jitter.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of an IRD for satellite broadcasting to which the present invention can be applied.
FIG. 2 is a block diagram of an example of a synchronization device to which the present invention is applied.
FIG. 3 is a block diagram of an example of a synchronization processing unit in a synchronization device to which the present invention is applied.
FIG. 4 is a flowchart used to describe an example of a synchronization device to which the present invention is applied.
FIG. 5 is a flowchart used for explaining an example of a synchronization device to which the present invention is applied;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Demultiplexer, 103 ... Video synchronization processing part, 104 ... Video decoding part, 110 ... Audio synchronization processing part, 111 ... Audio decoding part, 202 ... (PTS-STC) Detection unit

Claims (12)

A reference time generating means for generating reference time information;
Comparison means for comparing the reproduction time information included in the stream of TS packets with the reference time information generated by the reference time generation means ;
Based on the comparison result by the comparison means, determination means for determining whether the time difference between the reproduction time information and the reference time information is within the threshold value,
Playback control means for controlling playback of frames included in the stream;
Have
The reproduction control means is
If it is determined that the time difference on the basis of the determination result by the determination means Ru near the above threshold value, to start playing the frame corresponding to the reproduction time information, if the time difference is contemplated determined Do in the threshold , controlled so as to skip or repeat a frame to play,
The skip or repeat is performed as limits predetermined skip count or number of repeats, the first time the time difference is determined to be within the threshold, less the number of skips or the number of repeat times which is the limit Change to times
Synchronization device comprising a call. The reproduction control means is
The time difference on the basis of the determination result by the determination means synchronizer of claim 1 which is adapted to change et it is determined to be within the threshold, the threshold value to a larger value. The reproduction control means is
The predetermined skip count or number of repeats or more, when the skip or repeat is performed, the synchronization device of claim 1 in which the <br/> so to play asynchronously frames to the aforementioned reproduction. The reproduction control means is
Based on the information indicating whether the capacity of the buffer for storing temporarily the data for performing the reproduction is nearly full, the buffer if it is detected that nearly full, playing asynchronously frame the reproduction <br / The synchronization device according to claim 1, which is configured as described above. A reference time generation step for generating reference time information;
A comparison step of comparing the reproduction time information included in the stream of TS packets with the reference time information generated in the reference time generation step;
Based on the comparison result of step of the comparison, a determination step of determining whether the time difference between the reproduction time information and the reference time information is within the threshold value,
A playback control step for controlling playback of a frame included in the stream;
Have
The playback control step is as follows:
If it is determined that the time difference on the basis of the determination result of step of the determination Ru near the above threshold value, to start playing the frame corresponding to the reproduction time information, it intended judged Do in the time difference is above a threshold if, controlled so as to skip or repeat a frame to play,
The skip or repeat is performed as limits predetermined skip count or number of repeats, the first time the time difference is determined to be within the threshold, less the number of skips or the number of repeat times which is the limit Change to times
Synchronization method, wherein a call. The playback control step is as follows:
Et to the time difference on the basis of the determination result of step of the determination is determined to be within the threshold, the synchronization method according to claim 5 which is adapted to change the threshold value to a larger value. The playback control step is as follows:
The predetermined skip count or number of repeats or more, when the skip or repeat is performed, a method of synchronizing according to claim 5 in which the <br/> so to play asynchronously frames to the aforementioned reproduction. The playback control step is as follows:
Based on the information indicating whether the capacity of the buffer for storing temporarily the data for performing the reproduction is nearly full, the buffer if it is detected that nearly full, playing asynchronously frame the reproduction <br / The synchronization method according to claim 5, wherein the synchronization method is performed. Means for receiving digital broadcasts;
Means for decoding a stream of TS packets from the received signal of the digital broadcast;
A reference time generating means for generating reference time information;
Comparison means for comparing the reproduction time information included in the stream of TS packets with the reference time information generated by the reference time generation means ;
Based on the comparison result by the comparison means, determination means for determining whether the time difference between the reproduction time information and the reference time information is within the threshold value,
Playback control means for controlling playback of frames included in the stream;
Have
The reproduction control means is
If it is determined that the time difference on the basis of the determination result by the determination means Ru near the above threshold value, to start playing the frame corresponding to the reproduction time information, if the time difference is contemplated determined Do in the threshold , controlled so as to skip or repeat a frame to play,
The skip or repeat is performed as limits predetermined skip count or number of repeats, the first time the time difference is determined to be within the threshold, less the number of skips or the number of repeat times which is the limit Change to times
Digital broadcasting receiver, wherein the this. The reproduction control means is
The al which the time difference on the basis of the determination result by the determining means is determined to be within the threshold, the digital broadcast receiving device according to claim 9 which is adapted to change the threshold value to a larger value. The reproduction control means is
The predetermined skip count or number of repeats or more, when the skip or repeat is performed, the digital broadcast receiving device according to claim 9 in which the <br/> so to play asynchronously frames to the aforementioned reproduction. The reproduction control means is
Based on the information indicating whether the capacity of the buffer for storing temporarily the data for performing the reproduction is nearly full, the buffer if it is detected that nearly full, playing asynchronously frame the reproduction <br / The digital broadcast receiving apparatus according to claim 9, which is configured as described above.

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