[libavg-devel] On Synching Audio/Video Output

[Nick Hebner]

Hey All,

I am starting to think about how to accomplish audio/video synching, so I
would like to get some input. I have been using the 'How to Write a Video
Player in Less Than 1000 Lines' tutorial (http://www.dranger.com/ffmpeg/) to
learn more about ffmpeg and AV synching (sections 5 and 6 are relevant to
synching). In this tutorial, the author presents techniques for defining
reference 'clocks' to determine how to adjust the streams when they get out
of sync. Currently I am leaning toward an approach based on synching the
video stream to a constant audio stream for two reasons:

1. From my experience with audio/video data manipulation, it is much easier
to create audible artifacts than visual ones.
2. The audio updates happen more quickly than video, meaning that an audio
clock would be updated more frequently, leaving less error when trying to
interpolate what its value means.

Now that we have support for audio with videos, I think that the 'fps'
property should become a more general 'speed' property which would represent
a scalar of both the sample rate and fps. The 'speed' property would scale
both the sample rate of the audio stream used for resampling as well as the
fps property for video.

So, what do you guys think?

Nick
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