[FFmpeg-user] Is there a way to re-encode an inefficiently encoded file without losing quality and reducing file size?

[Stéphane Archer]

I'm not sure I understand what you mean, do you mean a hash like md5 and
sha1?
Could you please elaborate and simplify a bit?

On Sat, Sep 30, 2023 at 7:51 PM MediaMouth <communque at gmail.com> wrote:

> What about using a hash to check your existing against your possibly new /
> possibly matching file.  If it's a match don't run ffmpeg on it. Assuming
> i'm understanding what you're trying to achieve, it would seem better
> practice not to touch the file with ffmpeg when you can avoid it.
>
> > On Sep 30, 2023, at 16:43, Stéphane Archer <archerstephane at gmail.com>
> wrote:
> >
> > Let's say you have a video file encoded with high bitrate with the
> > ultra-fast preset in H.264 because you couldn't afford CPU at that time.
> > Now you have a huge file mostly because it was encoded quickly.
> >
> > You are now two days later with access to a good CPU and GPU.
> >
> > If you re-encode that file to save space then you are going to lose
> quality
> > because even AV1 with a high bitrate is lossy (and you want to reduce
> that
> > high bitrate)
> >
> > Otherwise, you can try transcoding using lossless compression but during
> my
> > testing, this is making the file way bigger no matter what I tried.
> >
> > So basically, I can lose quality, or keep the big original file...
> > Do you know a better way? Is there a way to re-encode that inefficiently
> > encoded file without losing quality and reducing file size?
> >
> > Best regards
> >
> > Stéphane Archer
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-- 
Best Regards,

Stephane Archer