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

[MediaMouth]

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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