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Hi Ross,<br>
<br>
Thanks to provide a lot of important info to me.<br>
<br>
One more question on sync topic. Thanks.<br>
If the worst case is<br>
RTSP server receive request from client, the time is 1.576000<br>
Server start finding the latest H264/AAC frames.<br>
H264 frame's presentation time start from 1.000000.<br>
AAC frame's presentation time start from 1.640000.<br>
<br>
When client receive the first H264 frame to play, and receive the first AAC frame and play.<br>
You can see video without audio for 640ms.<br>
<br>
What do you think how to fix this issue?<br>
If we want to sync streams in same session, how can we do?<br>
Please advise. Thanks.
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>$B4s7o<T(B:</b> live-devel <live-devel-bounces@us.live555.com> $BBeI=(B Ross Finlayson <finlayson@live555.com><br>
<b>$B4s7oF|4|(B:</b> 2020$BG/(B8$B7n(B17$BF|(B $B>e8a(B 11:01:36<br>
<b>$BZ@7o<T(B:</b> LIVE555 Streaming Media - development & use <live-devel@us.live555.com><br>
<b>$B<g;](B:</b> Re: [Live-devel] Does live555 exist a way to sync video/audio streams?</font>
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<br>
> On Aug 17, 2020, at 12:27 PM, Eric Hsieh <Eric.Hsieh@liteon.com> wrote:<br>
><br>
> And one question for sync video/audio stream.<br>
><br>
> Background:<br>
> Our system will prepare audio/video frames to memory, always capture frames from driver.<br>
> For video, it is H264, FPS is 30 and driver output one I frame per second.<br>
> For audio, it is AAC, 16KHz.<br>
><br>
> Behavior:<br>
> When player ask RTSP streaming from our server.<br>
> For video stream, we go to memory and find latest I frame to send.<br>
> For audio stream, we go to memory and find latest frame to send.<br>
> On worst case, first timestamp of video frame <= first timestamp of audio frame + 1(second).<br>
><br>
> Question:<br>
> We want to sync video/audio streams when player ask a stream.<br>
> Video/audio streams are belonged to same ServerMediaSession.<br>
> Is it possible to pass the first timestamp of video frame to audio stream?<br>
> Is there a way to sync data between FramedSource?<br>
<br>
Yes. As we note here<br>
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the LIVE555 code does this automatically, *provided that*:<br>
1/ Accurate presentation times (i.e., the $B!H(BfPresentationTime$B!I(B variable) are set each time your $B!H(BFramedSource$B!I(B subclass delivers a frame (i.e., when implementing $B!H(BdoGetNextFrame()$B!I(B, and<br>
2/ These presentation times are aligned to $B!F(Bwall clock$B!G(B time - i.e., the time that you$B!G(Bd get by calling $B!H(Bgettimeofday()$B!I(B.<br>
<br>
Note that you should continue to use the term $B!H(Bpresentation time$B!I(B rather than $B!H(Btimestamp$B!I(B. (The term $B!H(Btimestamp$B!I(B can be confusing, because RTP has $B!G(Btimestamps$B!G(B, but they are used only internally by the RTP/RTCP protocol, and are not visible to server (or client)
application code.)<br>
<br>
Ross Finlayson<br>
Live Networks, Inc.<br>
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