[alsa-devel] [PATCH 0/3] ALSA: snd-usb: Some small fixes to make Playback Design products work

Takashi Iwai tiwai at suse.de
Tue Mar 19 07:48:07 CET 2013

At Mon, 18 Mar 2013 19:51:09 -0700,
Gabriel M. Beddingfield wrote:
> On 03/18/2013 06:49 AM, Daniel Mack wrote:
> >>> Yes, I  thought about that for a while as well. In fact, the data format
> >>> the device supports on these altsettings is "DSD", but that doesn't have
> >>> a defined value in the UAC2 spec (and strictly speaking, DSD is not even
> >>> PCM).
> >>>
> >>> So when a device is as unspecific as 'raw data', there's not much we can
> >>> do about that except for exposing the same level of uncertainty down to
> >>> the apps, right?
> >>
> >> Yes.  We can add a new format SND_PCM_FORMAT_RAW, but it's not much
> >> better than SND_PCM_FORMAT_SPECIAL after all :)
> >
> > Yes. If at all, we should add a SND_PCM_FORMAT_DSD, and a quirk for that
> > device. But given that there is no application for DSD in userspace
> > either, we probably don't need to care.
> +1
> However, more and more applications are wanting to send non-linear PCM 
> data through ALSA.  So, we probably /do/ need to care.

It depends.  DSD would be still likely feasible to be sent over a PCM
device, as it's an audio stream after all, but most of other non-audio
data wouldn't fit with the "PCM" device.


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