On Sun, Feb 7, 2010 at 11:07 AM, Jarkko Nikula jhnikula@gmail.com wrote:
On Sat, 6 Feb 2010 19:33:08 +0200 Grazvydas Ignotas notasas@gmail.com wrote:
It's on powerdown, there is a faint pop. It appears its the amp (final part in the path), I tried to toggle it while playing /dev/zero manually and it always pops on powerdown. On powerup there is a small sound cutoff too, probably because of amp capacitors charging, but we decided to leave it instead of halting every sound playing program until the amp gets ready.
My side comment for the /dev/zero test. You may hear pops also if /dev/zero is played as unsigned 8-bit samples on signed DAC since then samples gets converted to maximum negative value.
So there is a difference how the /dev/zero is played. First command below produces a pop because it's playing a pop and second produces a pop only if HW is producing it.
aplay /dev/zero aplay -f S16_LE /dev/zero
I was testing with '-f cd' which should also be signed. Actually doing just 'aplay /dev/zero' makes matters worse, there is some additional 'squeek' noise audible when I turn the volume up.
On Mon, Feb 8, 2010 at 1:39 PM, Mark Brown broonie@opensource.wolfsonmicro.com wrote:
If this goes off too much you might want to tweak the delay ASoC uses to defer power down of DAPM widgets after streams stop. There's a command line option pmdown_time, it really ought to have a sysfs file to tweak but there's not been any demand.
Yes we are already using that (set to 1 minute), and the sysfs file would be useful for us (we have a hack for that in our tree).