Re: [SoX-users] Differences recording to OGG and WAV and how to fix this

[fmiser <fm...@gm...>]

> Pander wrote:
> 
> I use the same microphone (USB 24 bit 48kHz) to do the
> following recordings:
> 
> rec -q -r 48000 -c 1 -b 24 -e gsm-full-rate --buffer 16384
> -C 10 test.wav trim 0 360

It seems odd that you are specifying a compression quality
for a .wav file.

> rec -q -r 48000 -c 1 -b 24 -e gsm-full-rate --buffer 16384
> -C 10 test.ogg trim 0 360
> 
> But the result in spectrograms is are very different, see:
> https://i.imgur.com/fTMvDuK.png WAV
> https://i.imgur.com/z6YUcxF.png OGG

A spectrogram is a "picture" of the sound.  If the two
recordings sound different, the spectrograms will also be
different - by as much as the sound is different.

From what I can see of the spectrograms, they don't look to
me like they are the same audio.  The .wav file has a higher
level, and has broadband pulses.  Maybe something like a hand
clap, or wind noise at the mic.

The .ogg file is quieter, and there is a steady tone from 80
to 180 seconds - but at a different frequency than the one
visible in the .wav.

I'm not sure what your goal is for the spectrograms, but if
you are wanting to see the difference between encodings, or
other processing, it usually works better to start with an
audio file rather than a microphone recording so there won't
be a difference in the source - only in the process.

> How do I get rid of the veritcal lines when recoding WAV?

By getting rid of the sound that created them?
 
> How can I get the OGG recording improve use of range?

Maybe by normalizing?

Another oddity I see is you are recording with a sampling
rate of 48 kHz - but the spectrograms display 0 Hz to 180
Hz.  So apparently there is some other processing beyond what
you have listed.  Could the difference in signal level be a
consequence of this other processing?  Or could this
processing have an artifact that is creating broadband pulses?

I'm doing a lot of guessing and speculating!  *smiles*

-- f