Arch Linux

jon

Member

Registered: 2002-11-28

Posts: 87

High power usage while playing sound

The issue I'm having is that while my sound card is active and playing music I experience a large jump in power usage.

I get similar values for my idle consumption, about 8W in Arch, and 7W in Windows 7, with the same configuration, bluetooth off, Wifi on, backlight 30%. I'm happy with that. In Windows 7 when playing a local MP3 using VLC my power usage goes up to about 9 or 10 watts, which is understandable. However in Arch playing the same MP3 using VLC with everything else idle my usage shoots up to 16 or 17 watts, roughly doubling. Stopping playback brings be back down to normal.

I have all the power-saving settings enabled I can think of, all the kernel options that pertain to Intel integrated graphics, ASPM force, laptop mode enabled and ,snd_hda_intel turning off both the sound card and controller when idle.  Powertop2 lists my top two biggest drains as pulseaudio (using up to 6.5 watts), and hr_timers (about 2.5 watts) while playing audio.

I've been searching around for the past week or so trying to if this is a known bug or just "normal". According to what I've read about PulseAudio and power usage, Pulseaudio is suppose to be a bit more efficient than running with just ALSA. I'm wondering if anyone is having a similar jump is power usage while playing audio.

brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: High power usage while playing sound

I would imagine that pulseaudio is remixing from 44.1 to 48khz, and doing it in the most CPU-intensive way - for which, ALSA's equivalent would be "samplerate_best".

This is a total waste of CPU. My ears cannot tell the slightest difference between that and ALSA's "samplerate_linear", with music.

My first and usual suggestion would be to stop using pulseaudio, if you don't have a specific reason.

Secondly, check whether your soundcard can output at 44.1 - if so, configure the software for that, so it doesn't have to remix.

jon

Member

Registered: 2002-11-28

Posts: 87

Re: High power usage while playing sound

Thanks for the suggestions,

I went poking around in the pulseaudio config files and it looks like pulse uses 44.1 as the default anyway in /etc/pulse/daemon.conf

...
; default-sample-rate = 44100
...

I tried uncommenting it, and restarting pulse but it didn't make any difference. Changing

; enable-remixing = yes

to no didn't make a difference either.

I'd love to get rid of pulse, but it seems to be integrated into Gnome and it does make switching to HDMI audio easy, so I guess I'll keep it around for now.

brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: High power usage while playing sound

That semicolon at the start means it's a *comment* - you did remove the semicolon, didn't you?

jon

Member

Registered: 2002-11-28

Posts: 87

Re: High power usage while playing sound

That semicolon at the start means it's a *comment* - you did remove the semicolon, didn't you?

Yeah, I removed the semicolons for uncommenting the sample-rate, and also when I changed enable-remixing to no. I then killed all pulseaudio processes to make sure the new processes were using the updated configuration. But alas, no difference.