[mythtv-users] HDMI keep alive, maybe via sending silent audio?

[John Veness]

On 16/05/2016 13:43, John Veness wrote:
> I'd still rather find a software fix. A loop like "while [ true ] ; do 
> aplay -q silent.wav ; done" is something I could try. If it works, I 
> would make the wav file a few seconds long, and add a "sleep 120" or 
> similar in there, so that it's not using too much CPU. What I don't 
> know is whether this will nicely mix with Myth's output.

Thanks for everyone's help and advice so far.

Playing with it a bit last night I find that, contrary to what I said 
previously, pausing playback in MythTV does *not* cause the soundbar to 
sleep after three minutes. Only quitting playback and sitting or 
fiddling in the menus will do so.

This makes me confident that there is definitely a software fix for the 
unwanted behaviour I'm seeing. Presumably during paused playback, Myth 
(or Linux, or ALSA or the sound driver) is sending a constant bitstream 
of zeroes or equivalent to the HDMI audio output, which is enough to 
keep the soundbar awake, but when in menus, nothing is sent at all, 
causing it to sleep after three minutes.

The trick is how to send a similar empty bitstream while in menus.

So far I've been trying the aplay command, with no luck. If I do just 
"aplay /usr/share/sounds/alsa/Noise.wav" the command looks like it does 
something for a few seconds, but I hear no sound output.

If instead I do "aplay -L" to list the devices, then "aplay -D 
dmix:CARD=HDMI,DEV=7 /usr/share/sounds/alsa/Noise.wav", which is the 
same audio device I have selected in mythfrontend, the command exits 
straight away, still no sound, and I get the error "aplay: 
set_params:1239: Channels count not available".

All of this testing is while mythfrontend isn't running.

Anyone know how to use aplay, or another similar command, to output 
something to HDMI audio?

John

-- 
John Veness, MythTV user, UK, DVB-T

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mythtv.org/pipermail/mythtv-users/attachments/20160517/0cb7f7f3/attachment.html>