[mythtv-users] rPi3 3.5mm audio out - HDMI

David Engel david at istwok.net
Sat Oct 21 16:36:04 UTC 2017

On Sat, Oct 21, 2017 at 11:46:02AM -0400, Peter Bennett wrote:
> On 10/21/2017 10:46 AM, Barry Martin wrote:
> > And can I tag onto this thread (or should I start a new one?) I am also
> > playing with a RPi3 and have low volume problems but with the HDMI
> > output.  (Haven't tried the 3.5mm output.)  The volume does adjust using
> > the [ and ] keys but maximum is barely audible through my monitor's
> > speakers.  I did not notice a change after adding to .asoundrc and
> > adding the two commands to .profile (and rebooting).  Also tried max_dB
> > 30.0 -- no change. Different commands for the HDMI volume or did I do
> > something wrong?
> This amplification will likely not work with HDMI audio, or you may have to
> change some settings to get it to work.
> In my experience, HDMI audio is digital and volume controls either in mythtv
> or in Linux have no effect on volume. If you are seeing [ and ] having an
> effect you may have something set up wrongly.
> Some suggestions -
> - Run alsamixer before starting mythtv and make sure your volume is set to
> maximum on all devices shown.
> - use raspi-config to force HDMI audio
> - try the digital audio with ALSA instructions, see
> https://www.mythtv.org/wiki/Raspberry_Pi

I can't test it right now to give the exact instructions, but
somewhere in the MythTV audio setup, there is an option for software
volume control.  When that is enabled and the output audio is digital,
MythTV will decode the audio, adjust the volume in software and then
re-encode the audio before sending it out.  Now, this requires some
level of CPU power to do this, but I believe most current CPUs,
including the RPi, should be able to do it.

David Engel
david at istwok.net

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