After trying many combinations, I found that for a given CRF value, the 
smallest size is achieved with a preset equal to 3.
To achieve the same result, I found the combination of preset equal to 3 and 
CRF equal to 33. This keeps the VMAF greater than 96, and the file size and 
processing time are slightly lower than the previous version of ffmepg.

This is the command line for this version.

ffmpeg.exe -i "origen.mp4" -c:a copy -c:v libsvtav1 -crf 33 -preset 3 
-svtav1-params tune=1:fast-decode=1 -pix_fmt yuv420p10le -g 240 "destino.mp4"

I'm not sure if fast-decode works with preset equal to 3 but I don't notice any 
changes if I remove it.

Thank you so much

 On Friday, September 5, 2025 at 02:00:44 AM GMT-4, Ferdi Scholten via 
ffmpeg-user <[email protected]> wrote:


On 04-09-2025 20:59, felix.quintgz--- via ffmpeg-user wrote:
> I have updated the version of ffmpeg that I have from 
> 2023-11-15-git-78f55457c9-full_build-www.gyan.dev to ffmpeg version 
> N-120957-g66e40840d1-20250903 and now the same files encoded with the same 
> parameters are larger.
> The conversion speed of my test file has increased significantly, dropping 
> from 7:38 minutes to 1:20 in the latest version for the same parameters, but 
> the final file size has increased.
> I have tried with several files and the same thing happens in all of them.
>
> This is the line I use for the conversion, the parameters are set for a 
> minimum VMAF of 96.
>
> ffmpeg.exe -i "origen.mp4" -c:a copy -c:v libsvtav1 -crf 32 -preset 6 
> -svtav1-params tune=1:fast-decode=1 -pix_fmt yuv420p10le -g 240 "destino.mp4"
>
> I have a small test file encoded with H.264, 35.7 MB in size. When re-encoded 
> with the old version, it's 25.2 MB, and with the new version, it's 28.9 MB.
> It may not seem like much, but with larger files, the difference is 
> noticeable.
>
> What could be happening?
> Have the parameters changed?
There have been significant changes in libsvtav1 since then so yes, you
should reconsider your command.  Both preset and tune settings have been
changed and behave differently. Most likely you will get comparable
results when you set a lower preset, try 4 to start with.

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