[Ffmpeg-devel] h263+: size of encoded frames after opening ffmpeg

Martin marthi
Fri Jan 19 11:23:59 CET 2007


Michael Niedermayer wrote:
> Hi
> On Wed, Jan 17, 2007 at 11:14:40AM +0100, Martin wrote:
> [...]
>>>>Even better, is there a
>>>>possibility to change the bitrate without closing and reopening ffmpeg?
>>>you can set the quality of frames which affects the bitrate,
>>>closing and reopening within the same stream is generally not allowed
>>>doing so means you are on your own
>>Ok, how can I set the quality within the same stream without closing and
>>reopening? I tried to set the AVCodecContext.crf parameter but it
>>doesn't seem to have any effect on quality and size of outputted frames.
>>Is there another parameter which I can use?
> AVFrame.quality 

Thank you very much, that worked. How is the relationship between
quality and bitrate? Is there a formula which expresses it?

What is the default quality used, if no quality is specified and the
flag is not set?


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