Unbreaking Audio for the Unassuming Linux User Daniel T Chen // Ohio LinuxFest 2008

What This Talk Won't Cover “Which sound card should I purchase?” “Which Linux distribution has the best sound support?” “Which application programming interface (API) should I use when writing this whizbang?” “42.”

(Re)Introducing Terminology Open Sound System (OSS) Advanced Linux Sound Architecture (ALSA) Free Firewire Audio Drivers (FFADO) High Definition Audio (HDA) Subsystem identifier (SSID)

Why Sound Doesn't Work out of the Box Audio codec manufacturers enjoy the one-up game, too ALSA/OSS/FFADO simply doesn't support the hardware [yet] Initialising audio devices can be nondeterministic A Linux distribution can't please every potential user, “more than one way to do things”

The User-Developer Paradigm, or We're Wrong As a Community Sheer volume of sound issues noted on issue trackers, blogs, forums, and more, demotivates people “A lot” of publicly available information actually is misinformation “Closed world assumption” exists for Linux sound Developers are users, too

So What's the Problem with Codecs? AC'97 and HDA implementations vary widely Computer manufacturer and model information are insufficient for troubleshooting Even ALSA performs hardware differentiation (by SSID) poorly [for many computers]

“When I was your age...”

“I walked uphill both ways...”

“through snow and broken glass...”

“and I liked it!”

Troubleshooting ALSA Where does my audio issue originate? ALSA alsa-{kernel,driver}/linux Mixer confusion alsa-lib User-supplied configuration files (asoundrc) alsa-plugins PulseAudio/GStreamer/Phonon GNOME session race condition(s) Non-Free software components

Making Your Sound Card Work (The Basics) Submit an issue request to your Linux distribution Include: Output from http://www.alsa-project.org/alsa- info.sh Information about what application you were using when the symptom occurred What you expected the application to do What the application actually did Ask someone, e.g., #alsa/irc.freenode.net, identi.ca, blog, forum

Making Your Sound Card Work (More than the Basics) HDA user with unsupported codec? See also http://helllabs.org/codecgraph/ Attempting to configure multichannel ALSA? See also http://home.cfl.rr.com/infofiles/asoundrc.example s.html

When You Shouldn't Care You use a major desktop environment GNOME 2.24 PulseAudio Qt 4.3 or KDE 4.1 Phonon (Yes, I'm omitting several) You couldn't care less about non-working hardware [and perhaps even buy it to hack on it]

The Bright Future Encouraging vendors to provide unfettered documentation for their hardwares Coalescing Linux distributions' automated hardware reports Improving interoperability between key desktop environments Growing the user-based support community

Demo

Unbreaking Audio for the Unassuming Linux User Daniel T Chen // crimsun/irc.freenode.net/identi.ca http://trilug.org/~crimsun/2008olf.odp Ohio LinuxFest 2008