[FFmpeg-user] vary video bitrate on the fly

Stefano Sabatini stefasab at gmail.com
Mon Jun 24 12:47:45 CEST 2013

On date Sunday 2013-06-23 15:49:17 -0700, John Q wrote:
> Hi All,
> I am new to ffmpeg.
> I am making a video call to a custom mobile app from my custom
> desktop SIP client which uses ffmpeg. I want to decrease the send
> video bit rate on the fly when internet link is bad and back to
> original when it is good again. Its OK if the video quality at the
> other end is bad when I decrease the video bit rate.

> How can I change the video bit rate on the fly? I have seen some
> code in libavcodec/ratecontrol.c but being new to ffmpeg I don't
> understand it much. Can I use it somehow to reduce video bitrate on
> the fly? Is there any sample code available or can some one point me
> to some code which can be used for this purpose?
> Appreciate any links or pointers.

By using the API, you could change the parameters in the encoder
context on the fly, and see how it reacts, it might work more or less
since that scenario is not really well tested, also the configuration
parameters to use depend on the codec used (e.g. MPEG4 vs. x264).

Rigth now using the commandline there is no way to set the parameters
on the fly (might be possible in a more or less remote future when we
will support scripting or a sort of FFmpeg shell).

More information about the ffmpeg-user mailing list