[alsa-devel] Audio quality issue - regular clicks are observed

[Pharaoh .]

On 8/23/07, Liam Girdwood <lg at opensource.wolfsonmicro.com> wrote:
>
> On Wed, 2007-08-22 at 22:13 +0530, Pharaoh . wrote:
> > Hi
> > While testing the audio driver using aplay in blocking mode, a periodic
> > murmur is observed, this increases with
> > the audio volume and occurs even when there are no issues like xrun etc.
>
> > Aplay was used in normal read/write mode
> > i.e. no mmap. The song can be heard properly i.e. with no noticable gaps
> aur
> > hisses but the clicks are audible.
>
> Clock domain mismatch issues cause periodic ticks that increase in
> frequency with increasing sample rate. It's possible your clocking the
> codec and controller in two different clock domains. i.e. I2S controller
> (bitclk and frame) clocked from CPU and codec clocked from separate
> crystal.
>
> It's best to make sure that only one clock is clocking both the codec
> and digital audio interface.
>
> Liam
>
>
I tried playing /dev/zero at the same sampling rate as a wav file, but
/dev/zero played without any clicks i.e absolutely no sound heard, but while
playing a wav file using same parameters clicks occur. I am thinking it is
not about clocks mis-match, since I have checked it several times. I was
thinking whether junk data is being processed at end of buffer size, but
since /dev/zero plays well, I am ruling out that possibility also.

What else could explain the latencies at buffer ending as shown in the log
in previous mail.

-Pharaoh.