On 10/14/2011 09:39 AM, Feng Wei wrote:
2011/10/14 David Henningsson<david.hennings...@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/AudioIntegration/UCMPulseAudio/Analyzation.
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.
There is also the "Use Case" concept in UCM, Is there always exactly one
verb for every use case? If not, one might wonder if "Use Case" or
"Verb" is what should correspond to the "Profile" concept.
Card, Sink/Source, Profile and Port are the core concepts in PulseAudio.
I think UCM should use alsa-sink, alsa-card and alsa-source, but the
rest of the stuff: pa_alsa_profile_*, pa_alsa_path_*, pa_alsa_mapping -
in short, everything in alsa-mixer.h, I don't think the UCM
implementation should touch them. They are too tightly coupled with the
existing ideas of how to map ALSA kcontrols to Profiles and Ports,
something that UCM does in its own way. So in my opinion, you should
forget about mappings - it's Profile and Port (and Sink/Source) we need
to match against.
As for ports, this again depends on what is mutually exclusive and what
could be used in parallel, I vaguely remember "Modifiers" as something
that could be used in parallel with existing streams, if so, they need
to be separate sinks/sources.
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.
Hmm, for every sink/source, there can only be one active port at a time.
Also, ports on the same sink/source can be changed on the fly without
restarting the stream. Does this fit with the description of a UCM "Device"?
--
David Henningsson, Canonical Ltd.
http://launchpad.net/~diwic
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