[FFmpeg-user] Web camera and microphone capture via dshow

Rhodri James rhodri at kynesim.co.uk
Mon Aug 1 15:21:17 CEST 2011

On Mon, 01 Aug 2011 07:35:05 +0100, Dmitry Gorbunov  
<atskiisotona at gmail.com> wrote:

> I'm trying to capture and encode video/audio from camera and microphone  
> using
> libavcodec, libavformat and libavdevice. It works, video and audio  
> captures,
> but after encoding it all is messed: everything is extremely speed up  
> (like
> you recorded it at 25 fps and then played at 100). I think I don't get
> something about all that pts/dts stuff and synchronization, but I  
> honestly
> don't know where to look. ffmpeg unfortunately is very poorly documented  
> in
> terms of programming (why? it's so mature, why someone won't write at  
> least
> how library works?). I took muxing example from ffmpeg git and modified  
> it
> to feed encoders with data from webcam and microphone using av_read_frame
> and av_decode_video/audio. Any ideas?

Check the clock speed of your web cam.  I've seen some that clock at
30kHz rather than 90KHz, which will mess up your PTS calculations.

Rhodri James
Kynesim Ltd

More information about the ffmpeg-user mailing list