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Delossifier: Best on original file, or upsampled file?
https://forums.stereotool.com/viewtopic.php?f=3&t=18735		 Page 1 of 1
Author:  All Night [ Tue May 16, 2017 3:41 pm ]
Post subject:  Delossifier: Best on original file, or upsampled file?
If I have somemusic.mp3, if I decompress that I will usually get a 16 bit 44100 kHz sample rate audio.

Is it best to run the Delossifier directly on this file? Would it work better, or worse, if I increased the file to 32 bit first?

How about a 16 bit 22050 kHz file? Would it work better if I resampled to 44100 kHz before running the Delossifier? How about resampling to 44100 kHz AND increasing to 32 bits first?

Just trying to determine the best way to run Delossifier...
Author:  hvz [ Tue May 16, 2017 9:26 pm ]
Post subject:  Re: Delossifier: Best on original file, or upsampled file?
32 bit makes no difference (it won't hurt, I don't think it will make things better - you might want to use the Dequantizer on it though!).

44 kHz makes no difference for the Delossifier, but you could use Absolute Highs for it. And for that to be usable you need to have a 44.1 file, not 22.05.
Author:  All Night [ Tue May 23, 2017 3:47 pm ]
Post subject:  Re: Delossifier: Best on original file, or upsampled file?
I did a test! :P

Original MP3 is MPEG-2 compressed @ 64kbps and 22050 khz.


First here is "Difference" of just Delossifier in Stereo Tool (zoomed in in Audacity), run on direct Lame.exe decode of original file (16 bit 22050 khz WAV):

Image


Next is "Difference" of just Delossifier in Stereo Tool (zoomed in to same magnification), run on Lame.exe decode of original file + resampling to 44100 khz using Sox:

Image


Finally, here is "Difference" of just Delossifier in Stereo Tool (zoomed in to same magnification), run on Lame.exe decode of original file + resampling to 44100 khz and increase to 32 bit using Sox:

Image


It appears there is not much (if any) difference between bit depths, but there is between sample rates. The question is... is the Delossifier more accurate at the increased sample rate, or at the original 22050 sample rate? (I.e., is it removing too much from the 22050 audio?)

(I used a free mp3, it's "Sixteen" by Spheric Lounge, available on their Google Drive here: https://goo.gl/MZvpE6)
Author:  hvz [ Mon Jun 26, 2017 1:24 am ]
Post subject:  Re: Delossifier: Best on original file, or upsampled file?
The Delossifier needs to make certain assumptions about what the encoder did; resampling won't help. I assumed you were talking about 44.1 vs 48 in which case the difference should be small. Now, at 22.05 kHz it could be that the pre-ringing killer is doing too much, but I'm not sure - I never analysed low sample rate audio.
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