Notices

I'm a bit of a sound-a-holic, being a composer and heavy duty listener, and I've noticed a couple of annoying things about the N900 and it's sound quality.

What I've heard is that the problem has to do with Pulseaudio doing a sample conversion to 48Khz and some software equalizing to make the audio sound better and as worst, automatic limiting to create the so called "wall mix" effect to get higher volume output but killing the dynamics of the track as a side effect (I read that it's a protection so you won't drive too loud volume on the speakers to make them overdrive/break). As much as a normal consumer wouldn't mind these things, they add unnecessary overhead to the N900 cpu and distort the sound in a way that makes me quite annoyed.

As much as I hate to come to the forums asking for someone to make me software that prolly will take days and days to get finished, It's beyond my skillset to code an app that would bypass PA and let me listen to the tracks I've got on the phone as they are (and lets me play tracks managed in a folder/album structure and not just by 1 genre/playlist/etc like the built in one). And I think I can manage to mind the soundvolume without any built in burst protection. Another possibility would be to create a hack on any of the current players to get them bypass PA?

Meanwhile I'll just have to carry another player with me.

Pulse itself is not limiting anything, player could do, here is the test with mplayer (in extras-testing I think):

# mplayer -ao pulse -af volume=20 /path/to/file
or
# mplayer -ao pulse -softvol -softvol-max=1000 /path/to/file
and use 0 and 9 to increase and decrease volume

Setting volume to high values will distort sound.
Looking at the top output "-ao alsa" still played through a pulseaudio

Links:
http://how-to.wikia.com/wiki/How_to_...maximum_volume
http://www.mplayerhq.hu/DOCS/HTML/en/index.html

Hmm. I was just couple of days wondering why cpu utilization was so high when listening simple mp3 files. So is it because of this upmixing?
mafw-dbus-wrapper and couple of pulseaudio processes stedy at 15%-25% i tought that playing mp3 would take max. 4-6% of cpu time.

Yeah there are two factors involved here, the resampleing to 48khz (native sample rate of the audio device) and the eq to prevent speaker damage in pulseaudio.

Pluggin in headphones seems to reduce cpu usage (bypassing the eq)

You can only bypass the resampling by having files that are 48k to begin with.

Hmm, I did use headphones and still had quite high mafw+2*pulseaudio cpu level for mp3 192kbits stereo 44,1khz.

Plugging in the headphones definately does not bypass the limiter -effect. I am unsure what you mean by EQ preventing speaker damage, since as far as I understand, equalizing would not do much to prevent that (unless it's a programmed parametric EQ doing the limiting only at required peaking values and boosting overall volume to compensate, instead of a regular compressor/limiter -effect).

In either case, I'd like the player I use to have a GUI, and correct me if I am wrong, but Mplayer doesn't, so it's not that nice for a Mp3-player. I also read that Mplayer is alot heavier.

Oh and about the CPU consumption, I've read the bug 5974 talk thorougly, and according to it the oversampling does not affect that much, but something else definately is the cuplrit with PA. Hope someone figures a way to around it.

ps. Easiest way to hear the effect is to listen to and old track which is quite far from a steady dynamic maximum, making the limiter work a bit more. I notice it the best (worst ^^) while listening to some Deep Purple/Pink Floyd/Old Metallica etc. Old poorly mastered tracks.

hello, i've just read your topic... and i wanted to see it by myself.
So here we go.
While using the "top" command in x-term, i started listening to music :
- with the speakers, pulse process went around 22% and 30% of the cpu use
- with headphones, cpu utilisation drops between 7% and 12%. I tested with Senheiser HD650 =P

So what do you think ??

I think this should be reported as a bug!

The default music player eats wayy too much CPU without providing a steady playback.
Heavy webpages make the playback stutter and unpleasant.

I solved this problem using MediaBox beta but that doesn't make me very happy either as the volume is stuck at ~65% and the performance is not yet quite as it is desired.

Are U saying that the volume of the N900 isn't at its full capacity ??

Just in MediaBox, audio can be set to full when you send it to background - I use mediabox because it plays smoother when multitasking.

I say audio is not optimized to play smooth enough AND uses too much CPU.