DeviceNames - Revision history

Tanuk: Fix list syntax

2012-04-21T10:54:40Z

Fix list syntax

Tanuk: Big update

2012-04-21T10:51:19Z

Big update

Perex: /* Some device names should not be used by applications */

2007-08-13T08:24:11Z

‎Some device names should not be used by applications

Perex at 12:05, 12 August 2007

2007-08-12T12:05:30Z

EliotBlennerhassett: migrate from dev

2007-08-06T23:14:47Z

migrate from dev

New page

===Recommended play device names===
default (this one will automatically use dmix for sound cards that do not support hardware mixing of multiple channels)
plug:front
plug:rear
plug:center_lfe
plug:side
plug:surround40
plug:surround51
plug:surround71
spdif or iec958 (This is a special one that routes sound to the digital output of the card, for AC3 and DTS etc.)

The "plug" part implements sample rate conversion and sample format conversion.
If one does not wish either of these conversions, one can use the device name without the prefix "plug:"
If one wishes to only have sample format conversion, there is an alsa api call to disable the resampling feature in the "plug" plugin.
#if SND_LIB_VERSION >= 0x010009
/* Restrict a configuration space to contain only real hardware rates */
err = snd_pcm_hw_params_set_rate_resample(this->audio_fd, params, 0);
#endif

If the user has more than one sound card, e.g:
0 [ICH5 ]: ICH4 - Intel ICH5
Intel ICH5 with ALC650F at irq 201
1 [Audigy2 ]: Audigy2 - Audigy 4 [SB0610]
Audigy 4 [SB0610] (rev.0, serial:0x10211102) at 0x8400, irq 209
2 [Audigy2_1 ]: Audigy2 - Audigy 4 PRO [SB0380]
Audigy 4 PRO [SB0380] (rev.4, serial:0x20071102) at 0x8800, irq 217

The application can select which sound card to use. e.g. to use card 2, one would use:
plug:default:Audigy2_1
plug:front:Audigy2_1
one could also use:
plug:front:2
but using the name is better, as it tracks the card name even if on the next reboot the card number changes, for example, due to USB audio devices.

===Some device names should not be used by applications===
hw
plughw

because ???
----
[https://bugtrack.alsa-project.org/wiki/wikka.php?wakka=DeviceNames Original] created on [[2007-01-14]] by unknown.
[[Category:Development]] [[Category:MigratedFromDev]]

@@ Line 9: / Line 9: @@
 === front ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Analog output.
+* Analog output.
- * Two channels.
+* Two channels.
- * Channel map: front-left, front-right.
+* Channel map: front-left, front-right.
 === rear ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Analog output.
+* Analog output.
- * Two channels.
+* Two channels.
- * Channel map: rear-left, rear-right.
+* Channel map: rear-left, rear-right.
 === center_lfe ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Analog output.
+* Analog output.
- * Two channels.
+* Two channels.
- * Channel map: front-center, lfe.
+* Channel map: front-center, lfe.
 === side ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Analog output.
+* Analog output.
- * Two channels.
+* Two channels.
- * Channel map: side-left, side-right.
+* Channel map: side-left, side-right.
 === surround40 ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Analog output.
+* Analog output.
- * Four channels.
+* Four channels.
- * Channel map: front-left, front-right, rear-left, rear-right.
+* Channel map: front-left, front-right, rear-left, rear-right.
 === surround41 ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Analog output.
+* Analog output.
- * Five channels.
+* Five channels.
- * Channel map: front-left, front-right, rear-left, rear-right, lfe.
+* Channel map: front-left, front-right, rear-left, rear-right, lfe.
 === surround50 ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Analog output.
+* Analog output.
- * Five channels.
+* Five channels.
- * Channel map: front-left, front-right, rear-left, rear-right, front-center.
+* Channel map: front-left, front-right, rear-left, rear-right, front-center.
 === surround51 ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Analog output.
+* Analog output.
- * Six channels.
+* Six channels.
- * Channel map: front-left, front-right, rear-left, rear-right, front-center, lfe.
+* Channel map: front-left, front-right, rear-left, rear-right, front-center, lfe.
 === surround71 ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Analog output.
+* Analog output.
- * Eight channels.
+* Eight channels.
- * Channel map: front-left, front-right, rear-left, rear-right, front-center, lfe, side-left, side-right.
+* Channel map: front-left, front-right, rear-left, rear-right, front-center, lfe, side-left, side-right.
 === spdif or iec958 ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * Digital output.
+* Digital output.
- * Two channels.
+* Two channels.
- * Channel map: front-left, front-right.
+* Channel map: front-left, front-right.
- * With appropriately formatted data, this device can also be used to transmit compressed surround audio. TODO: Point to some documentation.
+* With appropriately formatted data, this device can also be used to transmit compressed surround audio. TODO: Point to some documentation.
 === hdmi ===
- * Direct access to the hardware.
+* Direct access to the hardware.
- * HDMI output.
+* HDMI output.
- * Two channels.
+* Two channels.
- * Channel map: front-left, front-right.
+* Channel map: front-left, front-right.
- * TODO: HDMI supports also more than stereo audio. However, I think I've heard that there are some complications with that. More details needed.
+* TODO: HDMI supports also more than stereo audio. However, I think I've heard that there are some complications with that. More details needed.
 === hw ===

@@ Line 1: / Line 1: @@
-===Recommended play device names===
+The available device names depends on the available hardware and the system configuration. This page describes the "well-known" device names, which should be available whenever the hardware supports them. The system may contain also other device names, but their semantics are not standardized. (TODO: Should a52 and/or dca be added to the playback device names?)
- default (this one will automatically use dmix for sound cards that do not support hardware mixing of multiple channels)
-  plug:front
+== Playback device names ==
- plug:rear
-  plug:center_lfe
+=== default ===
-  plug:side
-  plug:surround40
+'''This is the recommended device name for most applications.''' The default device will usually use Pulseaudio or dmix, i.e. software mixing, which ensures that your application won't prevent other audio applications from working at the same time, in case the hardware doesn't provide mixing support itself.
-  plug:surround51
-  plug:surround71
+=== front ===
-  spdif or iec958 (This is a special one that routes sound to the digital output of the card, for AC3 and DTS etc.)
   #if SND_LIB_VERSION >= 0x010009
   /* Restrict a configuration space to contain only real hardware rates */
   err = snd_pcm_hw_params_set_rate_resample(this->audio_fd, params, 0);
   #endif
 If the user has more than one sound card, e.g:
@@ Line 32: / Line 131: @@
   plug:front:2
 but using the name is better, as it tracks the card name even if on the next reboot the card number changes, for example, due to USB audio devices.
 ----
 [https://bugtrack.alsa-project.org/wiki/wikka.php?wakka=DeviceNames Original] created on 2007-01-14 by unknown.
 [[Category:Development]] [[Category:MigratedFromDev]]

@@ Line 33: / Line 33: @@
 but using the name is better, as it tracks the card name even if on the next reboot the card number changes, for example, due to USB audio devices.
-===Some device names should not be used by applications===
+===Some device names should not be used by ordinary applications===
   hw
   plughw
-because ???
+These devices maps directly to the driver devices and does not handle an abstraction. Of course, a special application might want to do all conversions itself, so using hw: or plughw: device might be appropriate.
 ----
 [https://bugtrack.alsa-project.org/wiki/wikka.php?wakka=DeviceNames Original] created on 2007-01-14 by unknown.
 [[Category:Development]] [[Category:MigratedFromDev]]