Re: OSS audio results in noise (when playing bass-heavy music)

[coypu%SDF.ORG@localhost]

On Sat, Apr 16, 2016 at 09:30:38AM +0930, Brett Lymn wrote:
> On Fri, Apr 15, 2016 at 09:01:26AM +0000, coypu%SDF.ORG@localhost wrote:
> > 
> > Playing audio from Firefox, it's adding some noise whenever playing bass
> > sounds. It may have to do with me using low-end headphones that are
> > simply not up for it.
> > 
> 
> What sort of noise?  It is consistently there at lower volume levels?
> One possibility is that you are driving the audio too hard and
> introducing clipping - check all the mixer settings, not just the master
> output as you may have something set too high early in the chain which
> is overloading the mixer chain even if the final master output is turned
> down.
> 

Motivated by your response I tried to find more explanations, thank you.

I can't control the mixer levels in NetBSD. I don't even have
'outputs.master' in mixerctl, probably because I use Intel HD audio.

I've tried with an identical setup and mpv rather than firefox, and
mpv plays the audio from the same youtube video fine, without any
added noise.

I've noted that the way mpv plays audio differs from that of firefox,
but because firefox supports many audio drivers, it's hard for me to
find the right code.

Firefox appears to be searching for the offset, whereas mpv asks for
info about a buffer:

 15560      1 mpv      ioctl(0x10, AUDIO_GETBUFINFO, 0x77e391f97480) = 0
 14049     68 firefox  ioctl(0x55, AUDIO_GETOOFFS, 0x78d2af8fe410) = 0

I've noted that the noise can be induced by starting and stopping to
play a bass sound, but playing low frequency sounds continuously will
not (I've tested with a frequency sweep).

Perhaps when playing audio from firefox it is delivering some empty
audio frames which cause a behaviour like starting and stopping the
audio (=> crackling for me).

Thanks for replying.