CN101631250B - Synchronizing device and method - Google Patents
Synchronizing device and method Download PDFInfo
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- CN101631250B CN101631250B CN2008101338471A CN200810133847A CN101631250B CN 101631250 B CN101631250 B CN 101631250B CN 2008101338471 A CN2008101338471 A CN 2008101338471A CN 200810133847 A CN200810133847 A CN 200810133847A CN 101631250 B CN101631250 B CN 101631250B
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Abstract
The invention discloses a synchronizing device, which has system time clock (STC), generates output data with a first sampling rate, and comprises a memorizer, a separator, a comparer and a sampling rate converter. The separator receives bit data stream, and captures a packetized elementary stream (PES) from the bit data stream. The separator writes the packetized elementary stream (PES) into the memorizer. The comparer acquires presentation time stamp (PTS) from the packetized elementary stream (PES) and compares the presentation time stamp (PTS) and the system time clock (STC). The sampling rate converter samples the packetized elementary stream (PES) in the memorizer, and generates output data according to the packetized elementary stream (PES). The sampling rate converter changes conversion coefficient thereof according to the comparison result of the comparer.
Description
Technical field
The invention relates to a kind of synchronizer, more especially relevant for a kind of synchronizer of sound/picture signal.
Background technology
In digital broadcasting is used, sound/image be very important synchronously.Transmission end traffic bit data flow is to receiving terminal.This bit data stream comprise the elementary stream package (packetized elementary stream, PES), transmitting data stream (transport stream, TS) and program data stream (program stream).Program frequency reference in the transmission stream TS (program clock reference, PCR) be used for setting up receiving terminal system frequency (system time clock, STC).(presentation time stamp PTS) allows receiving terminal to discern the reproduction time of elementary stream package PES to the presentative time mark that elementary stream package PES is comprised.Yet, have difference slightly between the system frequency STC of transmission end and the system frequency STC of receiving terminal.Especially transmit required time increase along with finishing, system frequency STC difference also can increase.Therefore the output buffer of receiving terminal can operate in overflow (overflow) or not enough (under-run) state of buffering.
In general sound/image synchronization mechanism, system frequency STC that receiving terminal is relatively more own and the presentative time mark PTS that is received.This relatively allows sound/image synchronization mechanism to judge whether reproduction time surmounts with result difference or falls behind the planning time.When reproduction time surmounts the planning time, receiving terminal then stops to play sound/image.When reproduction time falls behind the planning time, then be dropped at some packages of output buffer.Yet, since receiving terminal stop to play and the abandoning of data packet, significantly interrupt in picture or the sound or the fracture meeting is discovered by the user.
Therefore, expectation proposes a kind of synchronizer and method of sound/picture signal, and its sound/image broadcast can not interrupt or data packet can not be dropped.
Summary of the invention
The invention provides a kind of synchronizer, it has system frequency, and (system time clock STC), has the dateout of first sampling rate in order to generation.This synchronizer comprises memory, separator, comparator and sampling rate conversion device.Separator receives bit data stream, and from bit data stream acquisition elementary stream package (packetized elementary stream, PES).Separator writes to memory with elementary stream package (PES).Comparator obtains the presentative time mark from elementary stream package (PES), and (presentation time stamp PTS), and compares presentative time mark (PTS) and system frequency (STC).Sampling rate conversion device has conversion coefficient.Sampling rate conversion device is taken a sample to the elementary stream package (PES) at memory, and produces dateout according to elementary stream package (PES).Sampling rate conversion device changes conversion coefficient according to the comparative result of comparator.
The present invention provides a kind of method for synchronous again, be applicable to and have system frequency (system time clock, device STC), and this device produces dateout.This method for synchronous comprises: receive bit data stream; From bit data stream acquisition elementary stream package (packetized elementary stream, PES); (PES) writes to memory with the elementary stream package; With first sampling rate elementary stream package (PES) in the memory is taken a sample; From elementary stream package (PES) obtain the presentative time mark (presentation time stamp, PTS); Compare presentative time mark (PTS) and system frequency (STC); And the value that changes first sampling rate according to comparative result.
For above-mentioned purpose of the present invention, feature and advantage can be become apparent, a preferred embodiment cited below particularly, and cooperate appended graphicly, be described in detail below.
Description of drawings
Fig. 1 represents the synchronizer according to the embodiment of the invention; And
Fig. 2 represents the method for synchronous according to the embodiment of the invention.
[main element label declaration]
1～synchronizer; 10～separator; 11～memory; 12～comparator; 13～sampling rate conversion device (SRC); 130～computing unit.
Embodiment
Fig. 1 is the synchronizer of expression according to the embodiment of the invention.Consult Fig. 1, synchronizer 1 comprises separator (demultiplexer) 10, memory 11, comparator 12 and sample rate converter (sampling rate converter, SRC) 13.Separator 10 receives from transmission end (not showing among Fig. 1) bit data stream S10.Bit data stream S10 comprise the elementary stream package (packetized elementary stream, PES), transmitting data stream (transport stream, TS) and program data stream (program stream).Program frequency reference in the transmission stream TS (program clockreference, PCR) be used for setting up receiving terminal system frequency (system time clock, STC).(presentation times tamp PTS) allows receiving terminal to discern the reproduction time of elementary stream package PES to the presentative time mark that elementary stream package PES is comprised.
Then, will the detail operations of synchronizer 1 be described.Consult Fig. 1, SRC 13 comprises computing unit 130, and it defines a changing value.By comparing presentative time mark PTS and system frequency STC, comparator 12 judges whether this difference between the two surpasses preset range.Difference when between presentative time mark PTS and system frequency STC surpasses this preset range, comparator 12 output index signal S11.If the difference between presentative time mark PTS and system frequency STC surpasses preset range and the leading system frequency STC of presentative time mark PTS, SRC 13 reduces conversion coefficient according to index signal S11 with above-mentioned changing value.In other words, the value of sampling rate R10 reduces with sampling elementary stream package PES.If the difference between presentative time mark PTS and system frequency STC surpasses preset range and presentative time mark PTS falls behind system frequency STC, SRC 13 increases conversion coefficient according to index signal S11 with above-mentioned changing value.In other words, the value of sampling rate R10 increases with sampling elementary stream package PES.
Fig. 2 is the method for synchronous of expression according to the embodiment of the invention.Consult Fig. 1 and Fig. 2, synchronizer 1 has the system frequency STC of itself.Separator 10 receives bit data stream S10 (step S20), and from bit data stream S10 acquisition elementary stream package PES (step S21).Separator 10 writes to memory 11 (step S22) with the elementary stream package PES that obtains.SRC 13 takes a sample (step S23) to the elementary stream package PES in the memory 11 with sampling rate R10, and produces sampled data (step S24).SRC 13 is by taking a sample to sampled signal with sampling rate R11, and produces the dateout Sout (step S25) with sampling rate R11.Comparator 12 obtains presentative time mark PTS (step S26) from elementary stream package PES, and judges whether the difference between this presentative time mark PTS and system frequency STC surpasses preset range (step S27).The difference of judging between presentative time mark PTS and system frequency STC when comparator surpasses preset range (Yes), and whether in advance 12 of comparators judge presentative time mark PTS system frequency STC (step S28).If comparator 12 is judged the leading system frequency STC of presentative time mark PTS, SRC 13 reduces the value (step S29) of sampling rate R10.If judging presentative time mark PTS, comparator 12 falls behind system frequency STC, 13 values that increase sampling rate R10 of SRC.
Synchronizer 1 and method according to the embodiment of the invention, difference when between presentative time mark PTS and system frequency STC surpasses preset range, the sampling rate R10 of elementary stream package PES is changed by SRC 13, makes memory 12 can not operate in overflow (overflow) or not enough (under-run) state of buffering.Therefore, the difference between presentative time mark PTS and system frequency STC can operate in the preset range always, and wherein, this preset range is to set and can not influence synchronously according to system requirements.Synchronizer 1 of the present invention can not stop to play sound/image or abandon data packet, make the continuable broadcast of sound/picture signal in synchronization program.
Though the present invention discloses as above with preferred embodiment; so it is not in order to limit scope of the present invention; any those skilled in the art; without departing from the spirit and scope of the present invention; when can doing a little change and retouching, so protection scope of the present invention is as the criterion when looking appended the claim scope person of defining.
Claims (6)
1. synchronizer, it has system frequency, has the dateout of first sampling rate in order to generation, comprising:
Memory;
Separator, in order to receive bit data stream and this bit data stream acquisition elementary stream package certainly, wherein, this separator writes to this memory with this elementary stream package;
Comparator obtains presentative time mark in order to this elementary stream package certainly, and relatively this presentative time mark and this system frequency; And
Sampling rate conversion device has conversion coefficient, in order to this elementary stream package at this memory is taken a sample, and produces this dateout according to this elementary stream package;
Wherein, when the difference between this presentative time mark and this system frequency surpasses preset range, and when this presentative time mark surmounted this system frequency, this comparator was exported an index signal, and this sampling rate conversion device reduces this conversion coefficient according to this index signal;
When the difference between this presentative time mark and this system frequency surpasses preset range, and when this presentative time mark fell behind this system frequency, this comparator was exported an index signal, and this sampling rate conversion device increases this conversion coefficient according to this index signal.
2. synchronizer according to claim 1, wherein, this sampling rate conversion device is taken a sample to this elementary stream package with second sampling rate, and this conversion coefficient is defined as the ratio of this second sampling rate to this first sampling rate.
3. synchronizer according to claim 2, wherein, this sampling rate conversion device is taken a sample with the generation sampled signal to this elementary stream package with this second sampling rate, and produces dateout by with this first sampling rate this sampled signal being taken a sample.
4. synchronizer according to claim 2, wherein, this sampling rate conversion device comprises computing unit, in order to the definition changing value, and when the difference between this presentative time mark and this system frequency surpassed this preset range, this sampling rate conversion device changed this conversion coefficient with this changing value.
5. a method for synchronous is applicable to the device with a system frequency, and this device generation dateout, and this method for synchronous comprises:
Receive bit data stream;
From this bit data stream acquisition elementary stream package;
This elementary stream package is write to memory;
With first sampling rate this elementary stream package in this memory is taken a sample;
Obtain the presentative time mark from this elementary stream package;
Relatively whether this presentative time mark and this system frequency surpass preset range to judge the difference between this presentative time mark and this system frequency; And
When the difference between this presentative time mark and this system frequency surpasses this preset range, and if judge this presentative time mark and surmount this system frequency, conversion coefficient then reduced;
When the difference between this presentative time mark and this system frequency surpasses this preset range, and if judge backward this system frequency of this presentative time mark, conversion coefficient then increased.
6. method for synchronous according to claim 5 also comprises:
After the step of this elementary stream package in this memory being taken a sample, produce sampled data with this first sampling rate; And
With second sampling rate this sampled data is taken a sample to produce this dateout, wherein, this second sampling rate is different from this first sampling rate.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2008101338471A CN101631250B (en) | 2008-07-17 | 2008-07-17 | Synchronizing device and method |
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| CN2008101338471A CN101631250B (en) | 2008-07-17 | 2008-07-17 | Synchronizing device and method |
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| CN101631250A CN101631250A (en) | 2010-01-20 |
| CN101631250B true CN101631250B (en) | 2011-05-04 |
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| CN106358051B (en) * | 2015-07-14 | 2019-06-11 | 安富科技股份有限公司 | Method applied to Data correction in multimedia synchronous broadcasting |
| CN106878792A (en) * | 2017-03-14 | 2017-06-20 | 上海兆芯集成电路有限公司 | The audio synchronization method of video stream |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6598172B1 (en) * | 1999-10-29 | 2003-07-22 | Intel Corporation | System and method for clock skew compensation between encoder and decoder clocks by calculating drift metric, and using it to modify time-stamps of data packets |
| CN1679343A (en) * | 2002-06-12 | 2005-10-05 | 罗伯特-博希股份公司 | Method for creating a system clock in a receiver device and corresponding receiver device |
| US7130316B2 (en) * | 2001-04-11 | 2006-10-31 | Ati Technologies, Inc. | System for frame based audio synchronization and method thereof |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6598172B1 (en) * | 1999-10-29 | 2003-07-22 | Intel Corporation | System and method for clock skew compensation between encoder and decoder clocks by calculating drift metric, and using it to modify time-stamps of data packets |
| US7130316B2 (en) * | 2001-04-11 | 2006-10-31 | Ati Technologies, Inc. | System for frame based audio synchronization and method thereof |
| CN1679343A (en) * | 2002-06-12 | 2005-10-05 | 罗伯特-博希股份公司 | Method for creating a system clock in a receiver device and corresponding receiver device |
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| CN101631250A (en) | 2010-01-20 |
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