[FFmpeg-user] what is av_rescale_q()?

[Huang Soho]

Hi All,

I use ffmpeg + ffserver to support a stream server.
the video and audio source is from usb webcam.

When I test the stream by VLC, it can get video data , and audio data
respectively.
but I try to use ffserver to output a rtp stream for audio and a rtp stream
for video.
there are not sync.
When I study the code of ffmpeg.c and ffserver.c.
I can see there are a lot of code that does av_rescale_q() for pkt.pts,
pkt.dts and pkt.duration
Can somebody explain more detail about that?
When I can find the document that have detail description about that?