Saturday, January 31, 2015

[solved] more on Arch sound (fix for chipmunk sound)

No reasonable person likes PulseAudio currently. It's also a mystery why it was ever developed instead of, say, simply enhancing OSS (so we would only have one sound daemon). But, since OSS and ALSA were left behind, it goes without saying that, over time, a Linux distribution is near-certain to become infected with PulseAudio -- it will automatically be installed as a dependency by one application or another. Eventually, PulseAudio is almost certain to interfere with something, for example to make Audacious play MP3's at a chipmunk's pitch. As I write in early 2015, the strategy that works for me is,

crippling Pulse-Audio without removal

You can try a straight-up # pacman -Rs pulseaudio, but dependencies tend not to allow this. So cripple it.
Note: the PulseAudio daemon respawns if not properly neutered.
  • obviously start with $ pulseaudio --kill
  • directory /usr/share/alsa/alsa.conf.d hides a PulseAudio file (50-pulseaudio.conf) which ALSA executes during ALSA startup. This file surreptitiously activates /bin/pulseaudio. Rename it so it's no longer executed, eg "cp 50-pulseaudio.conf 50-pulseaudio_conf.bak", OR change /bin/pulseaudio to /bin/true in the file.
  • stop PulseAudio autospawning by gutting /etc/pulse/client.conf and replacing its lines with
    # custom version
    autospawn = no
    # "/bin/true" doesn't do anything, but no errors
    daemon-binary = /bin/true
  • Check inside /etc/X11/xinit/xinitrc.d to be sure X11 isn't infected. Eliminate any PulseAudio files in that directory.
  • $ systemctl list-units |grep pulse to verify no systemctl pulseaudio targets are present

/usr/share/alsa/alsa.conf vs. /etc/asound.conf

These initializing files use the same commands and formats, as well as one other config file, ~/.asoundrc. Since all 3 files are ALSA initializing files, only one is necessary, delete the other two to avoid interference. I typically keep /usr/share/alsa/alsa.conf because it's the most complete out-of-the-box, and because so many applications (eg. Audacious) load it. Save a copy of the working version for future installs. Not sure how to activate the file under systemd, so I just logout and log-in to be sure the file is read. Next, the alsa.conf configuration.

/usr/share/alsa/alsa.conf ("USAA" here)

USAA has a few problems itself.
  • backup the default USAA, eg # cp /usr/share/alsa/alsa.conf /usr/share/alsa/alsa_conf.bak. Backup any other files that are modified as well.
  • USAA's first subroutine is to load /etc/alsa.conf and /home/foo/.asoundrc. These can have PulseAudio hooks that wrongly set playback frequency. Carefully delete this subroutine, from
    [
    {
    func load
    files [
    {
    @func concat
    strings [
    { @func datadir }
    "/alsa.conf.d/"
    ]
    }
    "/etc/asound.conf"
    "~/.asoundrc"
    ]

    errors false
    }
    ]
    ...to....
    @hooks [
    {
    func load
    files [
    {
    @func concat
    strings [
    { @func datadir }
    "/alsa.conf.d/"
    ]
    }
    ]

    errors false
    }
    ]
    and save.
  • backup and then eliminate any of these which exist
    1. /etc/asound.conf
    2. ~/.asoundrc
    3. ~/.config/asound.conf

verify

Logout, log back in, and then try an Audacious or command line play, etc... $ aplay somefile.mp3

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