At Tue, 11 Sep 2012 10:22:23 +0200, Takashi Iwai wrote:
At Tue, 11 Sep 2012 16:10:43 +0800, Raymond Yau wrote:
2012-9-11 上午1:43 於 "Takashi Iwai" tiwai@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.
BTW, this reminds me of an open question: is it useful to add SND_CHMAP_MONO, or is it just redundant?
It's nothing but indicating a mono channel without any channel position, so I supposed SND_CHMAP_UNKNOWN being sufficient. OTOH, SND_CHMAP_MONO would give a clear sign of mono streams while SND_CHMAP_UNKNOWN could be used for any other exceptional purposes.
Takashi