[Live-devel] Audio and Video Synchronization Streaming

[Ross Finlayson]

>I developed a testing application using LiveMedia to multicast a 
>live Audio and Video feed. Video is compressed to an Mpeg elementary 
>stream and Audio is PCM 2 channels 16 bits sampled at 48000 Hz. I am 
>using VLC and SMPlayer as a client that receive the streams. When 
>audio or video is streamed alone over IP then VLC and SMPlayer both 
>play fine the stream. However when I stream both audio and video 
>together I ran into synchronization problem and both VLC and 
>SMPlayer drop either the video and or audio stream. And playback 
>become jerky.
>
>I suspect that I might have missing something when initializing 
>LiveMedia in a context of playing a mixed bag of audio and video 
>stream together. Any hints where I should pay attention to keep both 
>stream synchronized.

You need to make sure that your presentation timestamps (i.e., the 
value of the "fPresentationTime" field that you set in each source 
object when implementing "doGetNextFrame()") is accurate, and aligned 
with 'wallclock' time (i.e., the time that you would get if you were 
to call "gettimeofday()").

If the "fPresentationTime" field - for both your audio and video 
sources - is not set correctly (or not set at all), then you will 
never get proper A/V synchronization.
-- 

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/
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