[pulseaudio-discuss] [PATCH 2/2] pulse: Bump PA_RATE_MAX to 384 kHz

[Tanu Kaskinen]

On Thu, 2015-12-31 at 11:32 +0530, Arun Raghavan wrote:
> On 31 December 2015 at 11:15, Tanu Kaskinen <tanuk at iki.fi> wrote:
> > On Thu, 2015-12-31 at 09:42 +0530, arun at accosted.net wrote:
> > > From: Arun Raghavan <git at arunraghavan.net>
> > > 
> > > This will likely be needed in the future when we start supporting high
> > > bitrate passthrough, and there actually seem to be people 352/384 kHz
> > > out there (potentially as an intermediate production step).
> > 
> > What's your source for claiming that there seems to be people with such
> > PCM files (I'm assuming you implied PCM files)? If it's only used as an
> > intermediate production step, is there any evidence that people would
> > want to play that intermediate stuff via pulseaudio?
> > 
> > The mpv bug was about a dsf file (which means a dsd stream from sacd?).
> 
> My source is the Internet. :)
> 
> https://en.wikipedia.org/wiki/Digital_eXtreme_Definition

Thanks! It seems that DXD is used at least in one store for
downloadable music[1], and it's delivered as FLAC files (so DXD is not
a file format, it's just a specific set of PCM parameters). FLAC
supports sample rates up to 655 kHz...

[1] https://www.promates.com/music-store/hd-audio

> > Supposedly the stream contents were non-PCM data containing more than 2
> > channels, meant to be played in passthrough mode. And I guess alsa has
> > specified that such content should be wrapped in a 2-channel 384 kHz
> > float fake-PCM stream? I don't like extending the rate range for PCM
> > streams just because alsa's passthrough implementation happens to
> > specify such parameters for fake-PCM streams, but maybe there aren't
> > any better options...
> 
> I certainly don't know of better options. FWIW, some HDA codecs do
> report support for this rate as well. Presumably either the DAC
> supports it (I'd be curious to find out why), or it's supported for
> HBR passthrough. Either way, we'll probably need to end up supporting
> this.

Yes, there seem to be good reasons to bump the max rate.

-- 
Tanu