[alsa-devel] Logical device name for 4-channel microphones?
Hi,
What is the best source of information about device names ("front", "surround40" etc)? Is it the DeviceNames wiki page[1]? That page was slightly out of date, so I updated and expanded it (review would be welcome).
I'm looking for information specifically about capture device names. The wiki page didn't help me there, as it only listed playback device names. My problem is that I'd like to make Pulseaudio handle 4-channel webcam microphones[2], but I'm not aware of any input device names for 4-channel devices. Are there such device names? If not, what should be done?
Pulseaudio could just use "hw", but I'd prefer there to be a standard device name for 4-channel mics. AFAIK, at playback side, some surround implementations are using multiple devices on one card, and using "hw" wouldn't work in those cases, while e.g. "surround40" can use the multiple devices behind the scenes. I would guess that the same could be the case with some multichannel microphones, and therefore a logical name like "fourchannelmic" would be better than using "hw".
[1] http://www.alsa-project.org/main/index.php/DeviceNames [2] https://bugs.freedesktop.org/show_bug.cgi?id=45813
Tanu Kaskinen wrote:
My problem is that I'd like to make Pulseaudio handle 4-channel webcam microphones[2], but I'm not aware of any input device names for 4-channel devices. Are there such device names?
These device name are useful only for device types that are generic enough. Four-channel microphones aren't.
Regards, Clemens
At Tue, 24 Apr 2012 16:08:45 +0200, Clemens Ladisch wrote:
Tanu Kaskinen wrote:
My problem is that I'd like to make Pulseaudio handle 4-channel webcam microphones[2], but I'm not aware of any input device names for 4-channel devices. Are there such device names?
These device name are useful only for device types that are generic enough. Four-channel microphones aren't.
Hm, we have already surround51 or such specific one, so it's not too bad to have a definition for multi-channel mics. OTOH, surround51 & co were the possible cause of confusions, as there are way too many surround types. A generic type with the channels argument might be more generic?
In anyway, I think it's fine to define some new generic name.
Takashi
On Tue, 2012-04-24 at 16:09 +0200, Takashi Iwai wrote:
At Tue, 24 Apr 2012 16:08:45 +0200, Clemens Ladisch wrote:
Tanu Kaskinen wrote:
My problem is that I'd like to make Pulseaudio handle 4-channel webcam microphones[2], but I'm not aware of any input device names for 4-channel devices. Are there such device names?
These device name are useful only for device types that are generic enough. Four-channel microphones aren't.
Hm, we have already surround51 or such specific one, so it's not too bad to have a definition for multi-channel mics. OTOH, surround51 & co were the possible cause of confusions, as there are way too many surround types. A generic type with the channels argument might be more generic?
In anyway, I think it's fine to define some new generic name.
_From Pulseaudio point of view using "hw" should be fine if you can guarantee that any current or future 4-channel mics can be opened in the 4-channel mode using the "hw:CARD" device name. I'm just worried that there might be cards that split the four channels to e.g. two stereo devices, "hw:CARD,0" and "hw:CARD,1", and then "hw:CARD" won't work. I might be mistaken, but aren't there some such cases with playback, which have to be opened with the "surround" device names to get all the channels?
The "surround" devices also guarantee some specific channel mapping, which may not match what "hw" uses, which is another reason to prefer "surround" over "hw", but I don't think this applies to input side. Therefore, the only possible problem that I can see with "hw" is that it might not provide all channels.
At Tue, 24 Apr 2012 18:28:14 +0300, Tanu Kaskinen wrote:
On Tue, 2012-04-24 at 16:09 +0200, Takashi Iwai wrote:
At Tue, 24 Apr 2012 16:08:45 +0200, Clemens Ladisch wrote:
Tanu Kaskinen wrote:
My problem is that I'd like to make Pulseaudio handle 4-channel webcam microphones[2], but I'm not aware of any input device names for 4-channel devices. Are there such device names?
These device name are useful only for device types that are generic enough. Four-channel microphones aren't.
Hm, we have already surround51 or such specific one, so it's not too bad to have a definition for multi-channel mics. OTOH, surround51 & co were the possible cause of confusions, as there are way too many surround types. A generic type with the channels argument might be more generic?
In anyway, I think it's fine to define some new generic name.
From Pulseaudio point of view using "hw" should be fine if you can guarantee that any current or future 4-channel mics can be opened in the 4-channel mode using the "hw:CARD" device name.
Such a thing can be never guaranteed with "hw" :) The hw provides nothing but what kernel driver provides. And the hardware might be a link of two stereo streams.
Takashi
I'm just worried that there might be cards that split the four channels to e.g. two stereo devices, "hw:CARD,0" and "hw:CARD,1", and then "hw:CARD" won't work. I might be mistaken, but aren't there some such cases with playback, which have to be opened with the "surround" device names to get all the channels?
The "surround" devices also guarantee some specific channel mapping, which may not match what "hw" uses, which is another reason to prefer "surround" over "hw", but I don't think this applies to input side. Therefore, the only possible problem that I can see with "hw" is that it might not provide all channels.
-- Tanu
On Tue, 2012-04-24 at 16:09 +0200, Takashi Iwai wrote:
At Tue, 24 Apr 2012 16:08:45 +0200, Clemens Ladisch wrote:
Tanu Kaskinen wrote:
My problem is that I'd like to make Pulseaudio handle 4-channel webcam microphones[2], but I'm not aware of any input device names for 4-channel devices. Are there such device names?
These device name are useful only for device types that are generic enough. Four-channel microphones aren't.
Hm, we have already surround51 or such specific one, so it's not too bad to have a definition for multi-channel mics. OTOH, surround51 & co were the possible cause of confusions, as there are way too many surround types. A generic type with the channels argument might be more generic?
In anyway, I think it's fine to define some new generic name.
Alright then, what should be the name? Here's one proposal: "4channelinput".
participants (3)
-
Clemens Ladisch -
Takashi Iwai -
Tanu Kaskinen