PulseAudio has been on the receiving end of quite a bit of flaming. Some deserved, a lot not. Most critics have been appeased as PulseAudio has matured and distros make setup smoother, but there are still a number of troll^Wusers who trash it at every opportunity.
Common objections to Pulseaudio includes:
“We don’t need another sound system!”
First of all, that’s what we said when ALSA was introduced. It played out exactly the same way. I have IRC logs from 2004 where the conversation goes “My sound is gone. God damn ALSA!”. “Yeah, I’m starting to think ALSA is like the emperors new clothes. It never works, but people say it’s because you’re a noob.” Then two people immediately chime in saying “works fine here”. Replace ALSA with PulseAudio, and you could have seen it in any forum today.
Second, we definitely do need another sound system. ALSA works ok as an output mechanism, but it’s not a sound layer worthy of a modern operating system. Even when it came out, it was way behind Windows (but far ahead of OSS). In terms of features, ALSA is to PulseAudio what SVGALib is to X11.
“I just want to play sound, I don’t need all these crap features”
Maybe. This is why OSS worked for so long. 90% of use cases are covered by allowing a single app to play audio at any one time. However, there is a lot more to a smooth audio experience. The following things are a non-exhaustive list of convenient features that a layer like PulseAudio can provide:
- On-the-fly output device switching: In “the old days”, you could plug in a headset and the hardware would disconnect the speakers and play through the headset only. Today, the headset might be Bluetooth or USB, so no such hacks are possible. PulseAudio lets you handle this in software!
- Per-application volume control: The ability to turn up the music without also turning up the IM notification sounds. If you use MPlayer with ALSA for example, 9/0 adjusts the system-wide volume, not just MPlayer’s.
- Automatic muting of other audio on incoming phone calls, such as through Skype
- Audio forwarding: Like X11 forwarding? Me too. With PulseAudio, you can also get application audio over the network. pax11publish lets you set PulseAudio settings like network forwarding per-display!
And here are some features that are less day-to-day useful, but very cool:
- Networked audio: You can transmit audio from one (or more) apps to another box. Load Spotify on your laptop and play it via the media center’s speakers!
- Combine two stereo cards into one 4 channel device. The cards don’t even have to be on the same computer!
- Use the monitor device to record application audio, or connect it to a visualizer (demonstrated in a previous post)!
“PulseAudio uses a lot more CPU time than ALSA”
PulseAudio uses a high quality resampling algorithm by default. ALSA supports only one, a simple linear resampler. If, like most people, you can’t hear a difference anyways, you can configure PulseAudio to use a linear algorithm too by adding “resample-method = src-linear” in /etc/pulse/daemon.conf. CPU usage will drop from 10% to 1%!
“Thanks, I love PulseAudio now”