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

[Kingsley Turner]

On 16/02/16 10:34, Kingsley Turner wrote:
> 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.
>

After a bit more testing, it seems the start-up delay changes with respect 
to the media as well.
But with the above it's better.  Some of my media start with only a 
split-second delay, but then
stuff like: https://www.youtube.com/watch?v=lkaIoH6Um60 (3 second fried 
prawns) from the local
file-system still has a few seconds delay.

With audio output set to alsa:default, even using the audio test (in setup) 
causes mythfrontend.real to lockup.
Maybe I should start a separate thread on this.

-kt




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