[FFmpeg-user] How do I encode in H264 Baseline but change the GOP?

Etienne Buira etienne.buira.lists at free.fr
Fri May 27 17:19:07 CEST 2011

On Fri, May 27, 2011 at 04:02:26PM +0100, Carl Partridge wrote:
> Hi everyone, I've just joined the mailing list, so thank you in advance for
> having me.
> I am trying to encode to H264/MP3, mux'd into Mpeg1-TS.  It's for HTTP Live
> Streaming, but the decoder only supports baseline profile.
> After some time spent looking at the options, I realised that I could just
> do:
>      ffmpeg -profile baseline -i input.avi -y -async 1 -f mpegts -vcodec
> libx264 -b 1200k -bt 100k -r 25 -acodec libmp3lame -ab 64k -ar 48000 -ac 2
> output.ts
> ....to generate my stream.  (then segment with an appropriate app)
> Unfortunately, this is no good for segmenting, since I have no control over
> the GOP length.  Ideally I would like an IDR (index) frame at the beginning
> of each 10-second segment.  I tried:
>      -g 10     (before AND after the -profile parameter)
> ...unfortunately it seems to be ignored, presumably because the default
> settings that "-profile baseline" applies wipe out everything else.
> Is there any way to specify a GOP interval while forcing everything else to
> constrained baseline, or will I have to manually specify all the various
> X264 flags.  I tried doing this, but wasted hours, since I couldn't find out
> the exact ones that corresponded to constrained baseline profile, and
> something kept bumping the decoder.
> Thanks in advance,

Currently broken. You can use -x264opts for most options, for your
option it's keyint=...
With what you said, I think you also need -flags -cgop

> Carl
> PS: This is all for 'SilverLive', an HTTP Live Streaming client I have
> developed for MS Silverlight.
> -- 
> ________________________________
> *Carl Partridge*
> FatAttitude Ltd
> www.fatattitude.com | follow on twitter <http://www.twitter.com/fatattitude>
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