Re: [Cellar] FFV1: FFmpeg default version is "0"?

[Jerome Martinez <[e-mail]>]

On 08/11/2022 11:59, Peter B. wrote:
> However, I've just encoded with current ffmpeg-git and MediaInfo says 
> it's FFV1.0.

Actually it depends on the count of pixels (trigger is if > 720x576)

$ ffmpeg -hide_banner -loglevel error -f lavfi -i 
testsrc=duration=0.040:size=720x576 -c:v ffv1 -y test.mkv && mediainfo 
--Output="Video;%Format_Version%" test.mkv
Version 0
$ ffmpeg -hide_banner -loglevel error -f lavfi -i 
testsrc=duration=0.040:size=720x577 -c:v ffv1 -y test.mkv && mediainfo 
--Output="Video;%Format_Version%" test.mkv
Version 3.4

Source code:
     // Unspecified level & slices, we choose version 1.2+ to ensure 
multithreaded decodability
     if (avctx->slices == 0 && avctx->level < 0 && avctx->width * 
avctx->height > 720*576)
         s->version = FFMAX(s->version, 2);
     if (avctx->level <= 0 && s->version == 2) {
         s->version = 3;
     }

> I'm surprised, and wanted to bring up the discussion here again, 
> suggesting to change the default to FFV1.3?

It is a "political" choice from FFmpeg, also for the count of slices by 
default (always 4, either 720x577 or 4096x2160).

I personally don't care much because I have the count of slices in my 
scripts so version is defaulted to 3, but now that HD is common and 
FFV1.3 is supported for a long time, it may be interesting to change the 
default settings, true.

IMO if the default version is changed, the default count of slices 
should be changed too (change in FFV1 version would already have an 
impact with 4 slices if more than 352x288; as the current default 
setting for FFV1.3 is based on check on 352x288, we could do 4 for SD 
including the ones with extra VBI so 720x608, 12 for HDReady, 16 for 
HD/2K, 64 for UHD/4K, 256 for 8K, for having a similar pixel size of 
slices whatever is the image pixel width).

Note that changing default version has also an impact on compression 
ratio (less compression with 4 slices than with the current 1 for SD 
content).

Jérôme