Difference between revisions of "Raspberry Pi ALSA"
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== More on the ALSA Sound Drivers and Utilities == | == More on the ALSA Sound Drivers and Utilities == | ||
| − | While ALSA is a powerful tool, it documentation appears is very weak. Also, it appears that the capabilities of ALSA drivers and utilities are very dependent on the hardware used. The best sources of documentation that I found include Advanced Linux Sound Architecture (ALSA) project homepage, | + | While ALSA is a powerful tool, it documentation appears is very weak. Also, it appears that the capabilities of ALSA drivers and utilities are very dependent on the hardware used. The best sources of documentation that I found include [http://www.alsa-project.org/main/index.php/Main_Page Advanced Linux Sound Architecture (ALSA) project homepage], [https://wiki.archlinux.org/index.php/Advanced_Linux_Sound_Architecture archlinux Advanced Linux Sound Architecture], and [http://www.tldp.org/HOWTO/Alsa-sound.html ALSA-sound-mini-HOWTO]. |
| + | [This part is retarded; some useful to pointers to /proc need to be added] | ||
You can find useful information in the directory /proc, which is a “virtual” file system (meaning that it does not exist in real life, but merely is a mapping to various processes and tasks in your computer). | You can find useful information in the directory /proc, which is a “virtual” file system (meaning that it does not exist in real life, but merely is a mapping to various processes and tasks in your computer). | ||
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You can look at the mixer settings by typing amixer without any arguments. This command lists the mixer settings of the various parts of the soundcard. The output from amixer can greatly differ from card to card. Unfortunately you can’t find much documentation on how to interpret the out. | You can look at the mixer settings by typing amixer without any arguments. This command lists the mixer settings of the various parts of the soundcard. The output from amixer can greatly differ from card to card. Unfortunately you can’t find much documentation on how to interpret the out. | ||
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The RPi doesn’t have a “Master” control only “PCM”. So commands like amixer set Master... will not work. You must use amixer set PCM ... | The RPi doesn’t have a “Master” control only “PCM”. So commands like amixer set Master... will not work. You must use amixer set PCM ... | ||
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You can mute /unmute the sound via these commands: amixer set PCM mute and amixer set PCM unmute | You can mute /unmute the sound via these commands: amixer set PCM mute and amixer set PCM unmute | ||
| − | As of August 2012, there appears to be a known bug in RPi ALSA driver that ignores volume settings at the start of playback and always plays at max volume. Therefore, commands like amixer set PCM 50% unmute will not set the volume to 50%, at least until this bug is fixed. Maybe this isn’t really a bug but a limitation of the hardware because there is a workaround for this …. see below. | + | |
| + | As of August 2012, there appears to be a [http://raspberrypi.stackexchange.com/questions/1268/alsa-volume-ignored-when-beginning-playback known bug] in RPi ALSA driver that ignores volume settings at the start of playback and always plays at max volume. Therefore, commands like | ||
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| + | <pre> | ||
| + | amixer set PCM 50% unmute | ||
| + | </pre> | ||
| + | |||
| + | ... will not set the volume to 50%, at least until this bug is fixed. Maybe this isn’t really a bug but a limitation of the hardware because there is a workaround for this …. see below. | ||
== Volume Control == | == Volume Control == | ||
