[x264-devel] [PATCH] pic timing, vui timing info, hrd, and buffering periods

[Gabriel Bouvigne]

Alex Izvorski a écrit :

> Which standards require cfr?  Is that cfr with occasional switching
> (when/how), or completely fixed?  This is very interesting, because I am
> seeing a whole lot of vfr in mpeg2 satellite feeds now, not with
> completely arbitrary times but more along the lines of quickly switching
> between 30/29.97/25/24/23.97, sometimes a few times per minute, so at
> least common practicee seems to be to do sort-of-vfr.

I just thought that those are likely the sources you want to transcode, 
targeting IPTV.
There are several solutions (that you probably already figured out):

*do some black magic interpolation/decimation on the source, in order to 
have a cfr stream

*dynamically reconfigure the encoder when the source frame rate is 
updated (eventually by stopping/restarting it)

*update x264 in order to handle vfr

*set up x264 as your highest frame rate, and have it not marking the 
stream as cfr, neither writing timing information (which will be written 
within the mpeg2-ts level). What will happen is that your real bitrate 
will drop when the input frame rate is reduced, but that should not 
matter much. Of course, any HRD information would be wrong.
(my guess is that you decided on this last one)

--
Gabriel