[alsa-devel] Problems with the DP MST audio support patchset

[Takashi Iwai]

On Fri, 31 Mar 2017 21:04:37 +0200,
Pascal Wichmann wrote:
> 
> Hi all,
> 
> > I guess the digital-7.1 corresponds to HBR, and it's a special 
> > setup. Meanwhile 5.1 output he has tried is likely the LPCM, so
> > both are in a completely differently manner.
> Thank you, that sounds like a good explanation for my first issue.
> 
> 
> For the other problem, that seems to be some kind of HDMI handshake
> related issue to me.
> I have done some more research and found similar
> problems like [0]. Their solution to enable a pulseaudio loopback seemed
> to improve the situation at first; at least during the last two hours,
> the problem did not occur as often as it did before (without explicitly
> provoking it), but it occurred though.
> 
> In addition, I have disabled the power save options of the snd_hda_intel
> module:
> > options snd_hda_intel power_save=0 power_save_controller=N
> This however does not seem to have any impact on the problem at all.
> 
> I have also found a way to reliably reproduce the problem by muting and
> immediately unmuting the output in alsamixer having some audio running
> - -- this way, the output gets silenced for a few seconds a moment after
> the unmuting almost always.
> 
> Is the above solution using the pulseaudio loopback module not enough to
> prevent handshake issues? Do handshake issues sound suitable at all? Do
> you have any other ideas where the problem may lies?

It's a general problem with many digital receivers.  When the stream
stops, a digital receiver turn itself off until it re-receives a new
stream.  And this on/off takes a few seconds.

Thus, you must not stop the stream, but you'd need to keep sending the
silent stream even if you stop a playback.


Takashi