2011/10/14 David Henningsson david.henningsson@canonical.com:
On 10/14/2011 04:47 AM, Feng Wei wrote:
Hi Liam, Mark, Colin, and all, I study the codes in pulseaudio and alsa ucm patch recently, and create a page of my study result. I appreciate your feedback. The page is at https://wiki.linaro.org/WorkingGroups/Middleware/Multimedia/Specs/1111/Audio.... Also if needed, I'm glad to contribute to the integration of alsa ucm in pulseaudio. Thank you.
Oh, nice diagrams :-) Some of them might be useful additions to the PulseAudio wiki.
Thanks :-)
I think the modelling of UCM concepts onto PulseAudio concepts is an important discussion. In PulseAudio, profiles are mainly connected to device strings, how to open the devices, channels supported, whereas ports are just alsa mixer kcontrol changes. UCM verbs, as I understand it, contain both.
My understanding is profile:port and verb:device/modifier are both hierarchical. e.g. we have an alsa device string hw:0,0, and some mixer controls for route speaker or headset. In pa profile, we describe a profile output:analog-stereo with two ports, one for speaker, and the other for headset. In ucm, we define verb "hifi" and two excluded devices speaker and headset, both of the devices have PlaybackPCM hw:0,0. And we can also define two modifiers to switch between speaker and headset. So we can create profile by verb and create profile input/output mappings by devices(merge the same hw device) and create ports by modifier. I'm not sure if it break the original ucm concepts, but I think it can work.
In this context, I have a question: Can more than verb be active at a time for a specific card (e g can both "hifi" and "record" be active for the panda), and if so, how is it described in UCM what verbs that can coexist and which ones are mutually exclusive? I believe PulseAudio is going to need that information in order to be able to know how to create its profiles.
In current alsa ucm implementation, only an active verb is permitted, but it can have more than one devices enabled. In my mind, in "hifi" mode, we can still record something because we have some devices (playback or capture) available.
-- David Henningsson, Canonical Ltd. http://launchpad.net/~diwic