[linux-audio-user] spdif output clicking noises

[Andrew Lyon]

On 8/29/06, Joshua Boyd <jdboyd at jdboyd.net> wrote:
> On Mon, Aug 28, 2006 at 07:51:14PM +0100, Andrew Lyon wrote:
>
> > When playing media using mplayer or xine,  and outputting using
> > ac3/dts passthru spdif, if I pause and resume playback, or seek, there
> > are brief, horrible clicking noises when playback resumes,  I assume
> > this is because the stream is interrupted and resumes wherever it left
> > off, so it outputs some garbage data that causes the noises.
> >
> > Is there any way to prevent this? Perhaps it is possible to make alsa
> > dump the first 1/2 or even 1/4 second of audio that is played? That
> > would avoid the noises and I  could live with a slight delay when
> > playback  starts.
>
> It is in part a problem with your AC3/DTS decoder.  I have a creative
> labs decoder (surround sound speaker set of some sort of built in
> AC3/DTS decoder), and it has terrible clicking/cracking/popping sounds.
> OTOH, the Dolby Digital decoder (Dolby DP564, a 2U reference decoder),
> generally does not have such trouble.

My decoder is a yamaha dsp home cinema amp, it has generally been fine
with a range of sources, including spdif 5.1 sound from my windows
2003 server using onboard nforce audio, certainly ive not had the
"noise" problem I describe.

> You may be right about it being caused by garbage in the signal upon
> restart.  At least, such garbage would cause such trouble.  If so, just
> dumping the first 1/4 second or whatever won't automatically fix it,
> since that could be throwing away the garbage, then likely the start of
> the next AC3 or DTS packet as well.  A better solution would be to
> intelligently not transmit incomplete AC3 packets, which means it isn't
> quite a true pass through anymore.

I see, and intelligently not transmiting incomplete packets could lead
to delays and would make the passthru much more complicated, it does
seem like a possible solution though.

> I suggest you take this to the mplayer or xine mailing lists.

I will do so, thanks your response.

Andy