[FFmpeg-user] Different FrameMD5 when converting between loss-less encodings

[Paul B Mahol]

On 11/7/22, Tobias Rapp <t.rapp at noa-archive.com> wrote:
> Hi,
>
> recently when testing I stumbled over the situation that a specific
> 10-bit YUV input file was encoded separately using two different
> loss-less encoders V210 and FFV1. When comparing the FrameMD5 checksum
> of both output files most of the checksums did match, but some of them
> where different (approx. 3% of the frames).
>
> When trying to reproduce the scenario with the attached batch script
> using a video source filter the resulting files even differ in every
> frame. My assumption would have been that the FrameMD5 checksums of both
> files would be the same, as they originate from the same input file and
> the intermediate encoding should be loss-less.
>
> Can someone give a hint where the differences come from? Is there some
> command-line option for bit-exactness missing, or is there something
> going wrong in the decoder/encoders?

The v210 encoder or decoder is buggy. Strange that both C and asm is buggy.
The first pixels at start and end of each scanline are wrong.

>
> Regards,
> Tobias