[PD] audio bit resolution in Pd

Alexandre Torres Porres porres at gmail.com
Thu Apr 23 17:52:12 CEST 2015


What? 32Bit 384KHz dac? And for 50 bucks? what the $*#%@?

2015-04-23 12:43 GMT-03:00 Charles Z Henry <czhenry at gmail.com>:

> 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
> >>
> >>
> >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.puredata.info/pipermail/pd-list/attachments/20150423/7a2109b4/attachment.html>


More information about the Pd-list mailing list