[FFmpeg-user] Verifying lossless rewrapping/transcoding in one step?

[Paul B Mahol]

On Tue, Aug 6, 2019 at 12:14 PM Moritz Barsnick <barsnick at gmx.net> wrote:

> On Tue, Aug 06, 2019 at 10:07:40 +0200, Paul B Mahol wrote:
> > If I understand correctly, basically need hash of each stream separately
> > (for framehash this already works).
> >
> > That is quite possible to be implemented. Feel free to open feature
> request
> > on FFmpeg bug tracker.
>
> Just to show that it works, I have hacked up a quick proof of concept.
> (Hacked up means: Possibly not clean, not enough reuse of code, ...)
>
> From this for a video stream:
> ./ffmpeg_g -f lavfi -i testsrc -map 0 -t 1 -f hash -
> [...]
> SHA256=c747429bf5d240958db9545b184e2b226f826e67495ad5d46245794bc1b84078
>
> and this for an audio stream:
> ./ffmpeg_g -f lavfi -i anoisesrc=seed=0 -map 0 -t 1 -f hash -
> [...]
> SHA256=4a3aa64bd7ef86ff2afb43c9346076792497cdcfcd741f10a1bea2e016294417
>
> I can now produce this (note the new muxer):
> ./ffmpeg_g -f lavfi -i testsrc -f lavfi -i anoisesrc=seed=0 -map 0 -map 1
> -t 1 -f streamhash -
> SHA256=c747429bf5d240958db9545b184e2b226f826e67495ad5d46245794bc1b84078
> SHA256=4a3aa64bd7ef86ff2afb43c9346076792497cdcfcd741f10a1bea2e016294417
>
> I just couldn't quickly figure out how to prefix the stream specifiers
> (e.g. 0:0, 0:1).
>

Look how framehash does it?


>
> I'm not hapy with submitting a hack as a patch to ffmpeg-devel though.
> ;-) But I can provide the patch here or somewhere else.
>