[PD] audio bit resolution in Pd

[Charles Z Henry]

It's already started.... 32bit DACs are available from AKM and XMOS,
for example.  Although I don't know what software/hardware platform
you'd use to actually make use of this precision, you can build your
own 32-bit sound playback interface with a few boards from HK:
http://www.yuan-jing.com/dacs-decoder/32bit-192khz-usb-dac-decoder-ak4399-wm8805-pcm2706-opa627au-optical-coaxial
http://www.yuan-jing.com/dacs-decoder/xmos-usb-audio-32bit-384khz-dac-decoder-board-pcm5102-tda1308-headphone-amp


On Thu, Apr 23, 2015 at 9:41 AM, Alexandre Torres Porres
<porres at gmail.com> wrote:
> Yep, nice indeed, I guess I learned - in short and in layman's undetailed
> terms - that audio output is ~24bits (a bit higher, but much higher for
> smaller numbers).
>
> Moreover, digital audio cards won't likely have more than 24 bit precision
> for many years to come, so it's just way more than enough.
>
> thanks
>
>
> 2015-04-23 6:43 GMT-03:00 Julian Brooks <jbeezez at gmail.com>:
>
>> Nice. Thanks Chuck, I learnt something.
>>
>> On 22 April 2015 at 23:45, Charles Z Henry <czhenry at gmail.com> wrote:
>>>
>>> On Wed, Apr 22, 2015 at 5:11 PM, Alexandre Torres Porres
>>> <porres at gmail.com> wrote:
>>>
>>> > So I start with this idea that the audio (values from -1 to 1) can't be
>>> > in
>>> > full 32 bit float resolution, it's less. I don't see why that is
>>> > "wrong".
>>> > And then, from it, my first question here was: "what is the audio
>>> > resolution
>>> > then?". I'm still clueless here about this answer.
>>> >
>>> > Moreover, is it more or less than what 24 bit audio cards handle?
>>>
>>> Let me try:
>>>
>>> 32-bit floating point numbers have 24 bits of precision.  Always.  The
>>> remaining 8 bits are just for the sign and exponent.  When the
>>> amplitude of the signals decrease, you don't lose any precision in
>>> floating-point.  The value of the least significant bit (LSB) gets
>>> proportionally smaller.
>>>
>>> However, the output of a 24-bit soundcard always has a fixed
>>> quantization.  The LSB is always the same size.  Smaller numbers have
>>> less precision.
>>>
>>> The mismatch occurs when converting from the 32-bit floats to the
>>> 24-bit fixed point numbers.  Now, the smaller numbers aren't as
>>> precise anymore.  They get rounded to the nearest number in the 24-bit
>>> fixed point system.
>>>
>>> So, yes, the resolution (of small numbers) in floating point (internal
>>> to Pd) is finer than the resolution of those numbers when output
>>> (driver/DAC).
>>>
>>> Also, the 24-bit fixed point format is for values between -1 and 1.
>>> That means that numbers between 0 and 1 have just 23 bits.  In 32-bit
>>> math, the numbers between 0.5 and 1 still have 24 bits of precision
>>> (the sign is held elsewhere).  That means that Pd's internal
>>> resolution is finer than the soundcard resolution for all numbers
>>> between -1 and 1.
>>>
>>> Chuck
>>>
>>> _______________________________________________
>>> Pd-list at lists.iem.at mailing list
>>> UNSUBSCRIBE and account-management ->
>>> http://lists.puredata.info/listinfo/pd-list
>>
>>
>