[mythtv-users] Audio delays on startup of Onkyo amplifier TX-NR646

[Kingsley Turner]

On 12/02/16 13:44, Phill Edwards wrote:
>
>     > I purchased a new receiver in November, an Onkyo TX-NR646.
>     > I send the signal over HDMI from the nVidia card through the amp to
>     > the TV.  So the amp handles all the audio, passes through the video.
>     > So far that's all sweet.
>     >
>     > However...
>     >
>     > Whenever I playback something via mythtv, video appears immediately on
>     > the TV,  and then there's a 3 to 4 second delay before sound starts
>     > up.  So if you're watching a music clip, or a TV show with dialogue at
>     > the start, you have to rewind to hear the whole thing.
>
>
> I have the same receiver and I have the exact same experience. I thought 
> it was just "normal" and the way it is. If you hear back from Onkyo 
> Support I'd live to hear what they say.

Ok, here's what I've found today ...

Configure pulse audio for your HDMI settings.  You might already have it so, 
but mine was still pointing at SPDIF.

And In your /etc/pulse/default.pa comment-out the module that suspends it on 
idle:
e.g.:
# load-module module-suspend-on-idle

Reboot or restart pulse audio.  Whatever ensures the new settings are read.
You can check it with:
# pacmd list-modules | grep -i suspend
There should be no output.

What seems to be happening (for me), is that even though MythTV is 
configured to use alsa:HDMI, it's still doing <something> with Pulse Audio, 
and it looks as if Pulse Audio is the thing sleeping the HDMI connection.  
So we've configured PA *not* to do that.

With this configuration, I now have it down to a ~ 1 second delay on start.
The HDMI light is always on in the receiver, except when a new video starts, 
where it flashes for a second.  This is the ~1 second delay.
I guess that something is quickly dropping the HDMI link on start. Not sure 
yet.  Maybe the interaction between Alsa and PA?

I did set my MythTV audio output to alsa:default - which uses pulse audio.  
This gave me zero delays, but when I tried to play something with DTS-HD 
audio, there was no sound, playback was very jerky, and if I stopped 
playback, mythtv locked at a black-screen.

I might do a bit more research on Pulse Audio and DTS, DTS-HD etc. as this 
gave a better result.

I tried killing Pulse Audio, but mythTV frontend shows an error dialogue and 
restarts it (even if not configured to use it).
I am kind-of tempted to remove pulse audio totally.

So, some progress.

cheers,
-kt

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