Re: The problem about itunes from wav 48 to plus aac 44.1
Reply #2 – 2018-07-09 23:21:33
Probably I-Tunes chops off everything above 19kHz by default for lossy conversion, because it may improve the overall-quality of lossy conversion.
That isn't really an issue. If you don't want it, try to disable that or just use different way to convert. But I would recommend the way through I-Tunes because there is almost nothing useful between 19-22kHz. There are a few very subtile overtones drown in noise and resampling artifacts. But if you disable that, precious bit-rate is wasted for that frequency range. And remember: You have a heavily overcompressed record (the green waveform is a solid brick with no dynamics). If you resample that, the peak level is likely to be raised much so heavy clipping might occur. Lowering the gain by -3dB should be the easiest way to prevent that. It is always better to lower the gain of such recordings by a few dB before lossy conversion because the conversion raises the peak level a bit once more. This could be the reason, why you get different results. Clipping means distortion and distortion means overtones.. and the clipping appearing after conversion is happening during decoding - after the lossy "bottleneck" ;-). Probably, I-Tunes is doing that gain reducing or some limiting for you. On the command-line way you have to do it manually.
Last Edit: 2018-07-09 23:29:32 by Franky666