[FFmpeg-devel] evaluating the experimental status of ffv1 version 3

Peter B. pb at das-werkstatt.com
Fri Sep 7 15:41:21 CEST 2012

On 09/06/2012 08:49 PM, Michael Niedermayer wrote:
> I think if i didnt miss any tests then theres still a significnat lack
> of tests that where run to have sufficient information on what the
> default should be
> I think that at a minimum 10 samples that cover every combination of
> 8bit, >8bit and RGB,4:2:0,4:4:4 should be tested
> all tests should be done in 1pass, 2pass, and 2pass with a 1pass from
> another file of same type.
> all compressed file sizes should be posted here nicely formated in a
> table, with average, best and worst differences highlighted
> What it is to test, is gop=1 vs gop=300 for FFV1.3
The combination of pix_fmts you mention above, is already done in my
tests, if I understood you correctly (Except for RGB).
I'm encoding the source into each available YUV pix_fmt supported by
FFv1. (btw: Is there any way to list which pix_fmts are supported by a
certain codec? I kind of found it out by brute-force encoding - and
reading the sourcecode)

> then the whole thing again for slices like 1 vs 4 vs 16 slices
> here the material has to span a wide range of resolutions as well
I can already shortly say that the filesize differs tremendously with
different numbers of slices. With the right number of slices, there's a
real speed-gain, but if you use too many slices, it slows down again.
Depends on the number of CPU cores one has got in its machine?

Filesize increases with more slices. Noticeably. I'll provide numbers soon.

> Then we can discuss what defaults should be and what range of
> values should be allowed and what recommanditions to write in the
> docs for the users.
> Or we might try to change ffv1.3 to improve its performance and then
> all tests have to be run again.
The good thing is that Dave and I both have the tests run by a script.
So they are easily reproducable - and repeatable if FFv1 code has changed.

>>> and slice count on the
>>> compression rate (especially with 2pass mode)
>> I have not testing 2 pass mode. Can you provide a working command?
> ffmpeg  -i matrixbench_mpeg2.mpg -an -vcodec ffv1 -strict -2 -slices 4 -level 3 -coder 1 -context 1 -pass 1 ffv1.3-p1.avi
> ffmpeg  -i matrixbench_mpeg2.mpg -an -vcodec ffv1 -strict -2 -slices 4 -level 3 -coder 1 -context 1 -pass 2 ffv1.3-p2.avi
Ah ok! Thanks.
Ignore my previous post then ;)


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