[Live-devel] AAC/H264 RTP Multicast timestamps

[Goran Ambardziev]

Ross,
Thanks for all the help so far!

So, I have a working AAC/H264 application and I'm very close to it 
working just OK, except couple of glitches that needs to be settled.
> Be sure to set "fPresentationTime" properly (in your "AACFramedSource" class) for each AAC frame.  To get proper audio/video sync in each media player client, this presentation time must be properly aligned with the H.264 video presentation times, and with 'wall clock' time (i.e., the time that you'd get by calling "gettimeofday()").
I implemented presentation timestamping like this:
1. There's one shared timeval start presentation time variable 
(startPresentationTime ) between AACFramedSource and H264FramedSource. 
Whichever gets its sample first, it will set the startPresentationTime 
to gettimeofday.
2. After that, in each FramedSource (AAC/H264) fPresentationTime is set 
like this:
        unsigned uSeconds  = PlayTimeOfTheSampleInMicroSeconds;
        fPresentationTime.tv_sec = (uSeconds/1000000) + 
m_presentationStartTime.tv_sec;
        fPresentationTime.tv_usec = (uSeconds%1000000) + 
m_presentationStartTime.tv_usec;

PlayTimeOfTheSampleInMicroSeconds I get from the AAC/H264 encoders, 
respectively.

Is this a good setup?

When I run this, and preview it with VLC, it is kind of working, but 
there are lots of frames and audio buffers dropped, and I get a lot of 
warning messages, like this:
     main warning: playback too late (177441): up-sampling
     main warning: playback way too late (181443): flushing buffers
     main warning: picture is too late to be displayed (missing 655 ms)
     main warning: picture is too late to be displayed (missing 616 ms)
     main warning: picture is too late to be displayed (missing 576 ms)
     main warning: picture is too late to be displayed (missing 536 ms)
     ...

Why can this be happening?

I even tried to set the presentationStartTime to be 1 second ahead in 
the future, but to no avail, i.e.:
     gettimeofday(&m_presentationStartTime, NULL);
    // Set it 1 sec into the future
    m_presentationStartTime.tv_sec += 1;

Thanks,
Goran.