Re: 64bit audio read and write

[Matt Flax <flatmax@flatmax.org>]

On 06/07/16 17:29, Eric Wong wrote:
> Matt Flax <flatmax@flatmax.org> wrote:
>> Hi there,
>>
>> I currently use libsox to load and save audio data. I was wanting to
>> write and read 64bit data, however the generic sox sample type is 32 bit
> Correct, sox does some calculations internally in 64-bit double,
> but data which flows in between the effects is all 32-bit int.
>
>> (from sox.h) :
>> typedef sox_int32_t sox_sample_t;
>>
>> The basic format of the read (and write) functions are :
>> size_t sox_read(
>>       sox_format_t * ft,
>>       sox_sample_t *buf,
>>       size_t len
>>       );
>>
>> Can anyone tell me the basic methodology for reading/writing 64bit audio ?
> It would probably reworking a lot of sox internals and would
> require increased memory bandwidth, hurting performance for
> common <= 32-bit processing.
>
> But, where and how are you working with 64-bit audio
> and what 64-bit audio formats are there?
I think there are 64 bit file formats, aiff-c perhaps ? Also matlab file 
formats should be supporting 64 bits.
Personally, working with filters and various signal processing 
algorithms like that. It is handy being able to save double length 
words, possibly which are generated and synthesised in one way or other ...

>
> I'm not up-to-date with the latest technology, but even 32-bit
> is far beyond the range of human hearing; and last I checked;
> available ADC/DACs can't even make full use of 24-bit (nor
> our ears).
120 dB SPL (threshold of discomfort) is around 20 billion times louder 
then 20 dB SPL (a whisper). That is approximately 24 bits.
However, we can hear down to 10 dB SPL, or lower for young people ... 
that is approximately 40 bits of dynamic range.

Actually, I am not proposing we change the bit depth of sox in its 
signal processing system, however perhaps we can introduce functions to 
read and write 64 bit audio ?
Something like functions to read64 and write64 perhaps ?

>
> On the other hand, moving to 32-bit float would make sense for
> compatibility with 3rd-party plugins (LADSPA for sure, maybe
> LV2?).  Right now, we're constantly converting between
> float/integer in effects chains which hurts performance.
>
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