Re: discrepancy between sox and ffmpeg when extracting parts of flac file

On 2023-02-25 13:32, Jürgen Koslowski via Sox-users wrote:
> I have a large flac file (24bits 96kHz) A.flac containing several
> songs. I can extract those
> bei using either sox (B.flac) or ffmpeg (C.flac) with the same 
> splitting points:
> 
> sox T04.flac B.flac trim 22:26.342 =34:41.708
> ffmpeg -i T04.flac -ss 22:26.342 -to 34:41.708 -compression_level 12
> -c copy C.flac
> 
> Unfortunately, the results seem to differ in important aspects:
> 
> - C.flac that is larger (despite using "-compression_level 12")

How much larger?  And do you mean file size, or number of samples (or 
both)?

What happens if you don't use the compression option for C?


What's the full output from both 'stat' & 'stats' for all the files 
concerned?


> - soxi C.flac as well as ffprobe C.flac shows the wrong lengh, namely
> the length of A.flac

You didn't process A.flac though, but instead T04.flac.  Was it actually
identical to A.flac?  Are you certain of that?



> - dr14_tmeter shows different dynamic range values for B.flac
> (smaller) and C.flac (larger):

That's in itself not necessarily unexpected if the two files contained
different amounts of music.

Also, does the compression you used on one of these files just affect
its size in bytes, or does it also (perhaps minutely) change the sound?


> What is going on here? Are there additional parameters in sox that can
> fix this?

Dunno.  Which version of sox, ffmpeg etc, and on what platform?



-- 
Jeremy Nicoll - my opinions are my own


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