I can see how a filter circuit following a DAC can swing more than the DAC for example if two successive samples are full-scale, but there's no way a DAC can output beyond its own full scale except momentarily while it's settling to a value inside its range. The scaling has to be done before the DAC.
You just can't reconstruct a clipped signal unless the clipping is very mild or the signal is very simple, like a sine wave. What if the signal is +12dBFS white noise?
I meant that if you take 16 bits to be full-scale but you have a 24-bit DAC you _could_ use the 16 LSBs of the DAC as full scale, then you have a lot of headroom but your signal to noise ratio is not as good, and maybe something like this is happening in the default MacOS headphone driver.
Martin
On 2014-01-01 13:50, Chris Clepper wrote:
Nope, the DAC can freely construct intersample peaks as it sees fit and those can easily exceed 0 dBFS. It has been common practice in the industry for more than a decade to reconstruct clipped samples well above 0 dBFS - partially to make up for shitty mixing and mastering prevalent in music, and also because it's the right way to do it.
16 bits full scale and 24 bits full scale are the same 0dBFS signal. The bits are added at the bottom not the top.
On Wed, Jan 1, 2014 at 1:34 PM, Martin Peach <martin.peach@sympatico.ca mailto:martin.peach@sympatico.ca> wrote:
On 2013-12-31 19:32, Chris Clepper wrote: It's very, very easy to avoid any sort of clipping processing by using hardware with drivers that don't have any! Avid, Apogee, MOTU, RME, and many others have bit transparent OSX CoreAudio drivers. Also, any DAC worth it's using can reconstruct far beyond 0dBFS without distortion, so hearing volume increase past -1..1 in software is not surprising. I recall the ADI 1955 and equivalent TI part putting out +12dBFS or something ridiculous, but those ain't Wolfson low power headphone codecs neither! A DAC can only go to 0dBFS by definition. If it appears to go beyond that then something is scaling the input to be less than full scale at "full scale". For instance a 24-bit DAC could be sent 16 16-bit full-scale streams and not clip. Only if 16-bits is considered "full scale" does that make it +12dBFS. Martin _________________________________________________ Pd-list@iem.at <mailto:Pd-list@iem.at> mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/__listinfo/pd-list <http://lists.puredata.info/listinfo/pd-list>
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