Re: [SoX-users] Changing precision, not just encoding?

[Cory N. <ph...@gm...>]

On Fri, Dec 16, 2011 at 6:33 AM, Ulrich Klauer <ul...@ch...> wrote:
> Cory Nelson <ph...@gm...>:
>
>>> sox -S -V4 -G in-44k.flac -b 24 out-192k.wav rate -v 192k
>>
>> And I get this debug output, showing 16-bit precision but 24-bit encoding:
>> sox INFO sox: effects chain: input      44100Hz 2 channels 16 bits (multi)
>> ...
>>
>> sox INFO sox: effects chain: dither     192000Hz 2 channels 32 bits
>> sox INFO sox: effects chain: output     192000Hz 2 channels 16 bits
>> (multi)
>>
>> I thought this odd so I went and checked the file -- indeed it is
>> 24-bit with every 3rd byte set to 0, consistent with this debug
>> output.
>>
>> Is it possible to get true untruncated 24-bit output with a single
>> command line? No matter what I try, the output precision gets set to
>> the input's.  I've worked around it for now by making a temporary
>> 32-bit file first, but it's a bit of a hassle.
>
>
> First, in your specific case, the simplest solution is to use --no-dither
> (-D).
>

-D stopped the dither, but unfortunately the output filter is still 16-bit.

>
> This won't solve it in the general case, however; 8-bit source material that
> is to be processed in some way, and the result to be written to CD (16 bit,
> dithered), would be an example. I don't see a way to do this without a
> temporary file at the moment.
>
> I wrote some changes to how this output/dither precision works a while ago,
> but I am not really sure about their impact, so I haven't submitted them yet
> (and perhaps won't do it at all, if they introduce other problems). Any
> comments/tests are welcome, so I am attaching the patches against current
> git master to this message. With these applied, your command line above
> would do what you expected it to do; additionally, there is a new -p option
> to dither for explicitly setting the target precision. (Can also be used to
> compare noise shaping filters: play ex.wav dither -p 6; play ex.wav dither
> -f shibata -p 6; play ex.wav dither -f lipshitz -p 6; etc.)
>
> Ulrich

This seems like a wonderful patch, I'd love to test it out if someone
could supply win32 binaries.

-- 
Cory Nelson