[FFmpeg-user] Compare quality of 2 audio files (was: Conversion wav -> mp3 -> wav)

[Rodolfo Medina]

Maik Waschfeld <Maik.Waschfeld at Maik-Waschfeld.de> writes:

> Hi Rodolfo,
>
>> but all happens is that they play together now…  
>
> Perfect!
> For now.
>
>> On the first of the two, I applied the `invert’ effect.
>
> Are you sure?
>
>> Where’s the comparison…?
>
> That’s what you hear!  If you play two exact files „in sync“, and one of them
> is inverted, you should hear … nothing.
>
> Try with two instances of the same file, not one wav-mp3-wav and the other
> one wav.
>
> The process in detail:
> - select one file in the Finder
> - right click and „Open with“ Audacity
> - select the imported file in Audacity; be sure, that the hole file is
> selected 
> and stays selected for the next step!
> - >Effects>Inverted (my version is german, so it could be named otherwise in
> english)
> - >Import>Sound and select the exact same file, you used on „Open with“
> - Play.
> - If you hear nothing, then the process is correct. If you hear anything but
> silence, then one of your steps was not correct.
> - If you select „Solo“ on one of the tracks, the other track gets muted and
> you 
> can toggle between „the difference“ and the „Solo-ed track.


Thanks...  Yes, now it works also for me exactly as you described.

But my impression is that the whole thing only works when file1.wav and
file2.wav are the same file (silence) or file2.wav is the result of a
conversion of file1.wav.  Instead, I want to compare the quality of file1.wav
and file2.wav fetched, over the net, or copied from CD, from sources completely
different and independent one another.  For example (I suppose and I see that
it works also with mp3 format), now file1.mp3 is fetched from Youtube:

 https://www.youtube.com/watch?v=SgKHI4jEFEo

, and it's Brahms 4th symphony directed by Kurt Sanderling (great!), first
movement; and file2.mp3 is the same piece but copied and converted from audio
CD: same piece, director, execution: all.  In this case, I import file1.mp3, I
invert it, then I import file2.mp3: the game does not succeed: what I hear is
not the difference between them - as it is when file2.mp3 = file1.mp3 -; what I
hear seems rather to be the sum of the two...  Am I wrong?  I hope to be well
explaining myself...  In other words, I wish a tool that detect the differences
from files with different origines, sources and respective histories...  Is
that possibile?

Thanks,

Rodolfo