[alsa-devel] Channel map API patches: to be 3.7 or not to be?

Takashi Iwai tiwai at suse.de
Tue Sep 11 10:22:23 CEST 2012

At Tue, 11 Sep 2012 16:10:43 +0800,
Raymond Yau wrote:
> 2012-9-11 上午1:43 於 "Takashi Iwai" <tiwai at suse.de> 寫道:
> >
> > Hi,
> >
> > does anyone have concern if I push the current channel map API patches
> > (in sound-unstable git tree topic/tlv-chmap branch) for linux-next,
> > i.e. for inclusion to 3.7 kernel?
> >
> > I don't worry too much about the kernel API.  This can be refactored
> > later.  But the kernel ABI must retain, so we won't change in an
> > incompatible way any longer once after it's merged to the upstream.
> >
> > So, if anyone sees a flaw in the kernel ABI definition using control
> > elements, let me know.
> >
> > (But note that the API can't be perfect for all generic purposes.
> >  It's designed to be "good enough" for a big lack for multi-channel
> >  streaming.  Of course, this doesn't discourage to use the API for any
> >  other purposes.)
> >
> How about the channel map of the usb mono playback device and those sound
> card which can pan mono to stereo speakers and headphone?

If the device specifies which speaker position the mono channel is
for, then you can map it properly.  Unless it's really specified by
the device, the mono stream is UNKNOWN position in general.

> Pulseaudio developer has just changed the downmixing method
> The mono playback is not left anymore
> https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/416190


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