[Ffmpeg-cvslog] [ffmpeg]: r5416 - in /trunk:ffmpeg.c libavcodec/snow.c tests/regression.sh
Mon May 29 19:31:30 CEST 2006
Luca Abeni wrote:
> Hi Corey,
> On Sun, 2006-05-28 at 17:38 -0700, Corey Hickey wrote:
>> lorenm at natsuki.mplayerhq.hu wrote:
>>> Author: lorenm
>>> Date: Sun May 28 14:38:10 2006
>>> New Revision: 5416
>>> Snow 1pass ratecontrol
>> This seems to work pretty nicely.
> Can you provide an ffmpeg command line to test it?
> I tried some encodings using an mpeg4 file encoded at 350kbps (test.avi)
> as an input:
> 1) ffmpeg -t 60 -i test.avi -strict -2 -vcodec snow -b 50 out.avi
> The bitrate of the encoded out.avi file resulted to be 684.8kbits/s
> 2) ffmpeg -t 60 -i test.avi -strict -2 -vcodec snow -b 600 out.avi
> The bitrate of the encoded out.avi file resulted to be 657.3kbits/s
> This looks good, but
> 3) ffmpeg -t 60 -i test.avi -strict -2 -vcodec snow -b 350 out.avi
> The bitrate of the encoded out.avi file resulted to be 683.0kbits/s
> Not good at all... Note that the original video is 350kbps.
> Also note that in all the 3 cases I obtained about the same output
> During the first encoding (the one with target 50bps), ffmpeg shows
> q=31.0 all the time, so I tried
> ffmpeg -t 60 -i test.avi -strict -2 -vcodec snow -qscale 31 out.avi
> amd I got a 122.0kbits/s file. So, it seems that the ratecontrol is
> trying to set the correct q value (ffmpeg shows that q varies - and the
> q values seem correct), but the snow codec does not seem to be able to
> properly respond to such variations...
> What am I doing wrong? Or did I disunderstand the "1pass ratecontrol"
I nearly always use mencoder, and it's working properly there; I can't
say what the problem is with ffmpeg, but I am seeing about the same
thing you are. Probably Loren can help.
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