Re: Prevent SoX from doing the clipping?

[Jan Stary <hans@stare.cz>]

On Jun 05 08:54:48, p-danijel.domazet@devialet.com wrote:
> Hi list,
> 
> I have a heavily "overflowed" WAV file (samples written in float 32-bit
> format): instead of [-1.0,+1.0], the samples range goes as far as
> [-5.0,+5.0].

How did you obtain this audio file?
Can you put it somewhere for download?

> Using SoX to get raw PCM audio samples from WAV file:

(meaning floating-point PCM?)

> `sox --bits 32 --channels 1 --encoding floating-point --rate 48000
> input.wav output.raw`

This seems pointless: with the format settings before the wav input,
you are overriding what the wav header says.
What does "soxi input.wav" say?

If the input is indeed 32 bit floats @ 48kHz mono,
and the wav header correctly says so,
you don't need to specify that.

You don't need to specify that for the output either,
as SoX will use the same format for the output,
unless told otherwise. So just do

	$ sox input.wav output.raw
	$ play -b 32 -e float -r 48000 output.raw

That does not solve your problem of course.

> I get warnings:
> 
>     sox WARN sox: `input.wav' input clipped 1163400 samples
>     sox WARN sox: `output.raw' output clipped 605664 samples; decrease
> volume?
> 
> When I look into the output, I see the samples were clipped, and the range
> is [-1.0,+1.0] now. However, that is not what I want.

How exactly do you "look" at the raw output float samples?

> I would like to have exactly the same output as input, just in different
> format (RAW instead of WAV). Is there a way to prevent SoX from doing the
> clipping?

You could just strip the WAV header.

	$ sox -n -b 32 -e float file.wav synth 1
	$ sox file.wav file.raw
	$ hexdump -C file.raw

00000000  00 00 00 00 40 c8 6b 3d  28 64 eb 3d 30 0e 30 3e  |....@.k=(d.=0.0>|
          ^^^^^^^^^^^^^^^^^^^^
	  actual audio samples

	$ hexdump -C file.wav

00000000  52 49 46 46 32 ee 02 00  57 41 56 45 66 6d 74 20  |RIFF2...WAVEfmt |
00000010  12 00 00 00 03 00 01 00  80 bb 00 00 00 ee 02 00  |................|
00000020  04 00 20 00 00 00 66 61  63 74 04 00 00 00 80 bb  |.. ...fact......|
00000030  00 00 64 61 74 61 00 ee  02 00 00 00 00 00 40 c8  |..data........@.|
                                         ^^^^^^^^^^^^^^^^^
					 here it starts ...

00000040  6b 3d 28 64 eb 3d 30 0e  30 3e d0 d4 69 3e 76 6a  |k=(d.=0.0>..i>vj|

Putting SoX out of the picture, there will be no clipping;
just strip the wav header (the first 58 bytes in this case).

Jan



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