[mythtv-users] hdmi audio

[Stephen Worthington]

On Wed, 31 Jan 2024 15:05:45 +0800, you wrote:

>The lack of VU control does not happen on other monitors!
>
>I’m using a SAMSUNG LS32A700NWEXXY 32INCH S7 4K monitor. I am trying to not use a USB-audio-line-out (which works fine) but use the monitor headphone output.
>
>All is fine except I have NO VU control. I have tried pulse and alsa controls (where the slider moves) but it has no effect on volume.
>Wunse-upon-a-time I’m sure I recall ‘myth internal volume control’  It seems to be gone. Currently vol [adjusting the mixer] from 0..100% has no effect.
>
>I can turn the speaker volume knob but I’d prefer local control. Any opinions ?
>
>Thanks
>James

So is the audio going to the monitor on the HDMI connection?  If so,
then you need the volume controls for the HDMI audio device, not the
motherboard audio device.  In alsamixer, use F6 and select the HDMI
device.

Then in the mythfrontend audio settings, you normally need to set it
to use one of the ALSA HDMI devices, rather than ALSA:Default or
PulseAudio.  Or you can craft a /etc/asound.conf file to send the
audio to multiple devices at once, so it goes to HDMI and the
motherboard audio at the same time.  I do that for my MythTV box, but
I long ago uninstalled PulseAudio, so it may not work the same for
you.  This is what I have, which sends the sound out the motherboard
IEC958 (S/PDIF) port and the Nvidia HDMI audio port.  Of course, the
names and numbers (CARD and DEV) will differ for your hardware.  I do
not actually understand how ALSA works - I made this file by copying
from various examples and a fair bit of trial and error.

root at mypvr:/etc# cat asound.conf
pcm.!default {
        type hw
        card Generic
}

ctl.!default {
        type hw
        card Generic
}


##############################################################################
# Create an alsa device that sends audio to both the onboard IEC958
(S/PDIF)
# output and the Nvidia graphics card HDMI output.

# First, create a dual device that combines the onboard IEC958 device
and the
# Nvidia HDMI device into one 4 channel device.
pcm.dual {
    type multi
    slaves.a.pcm "plughw:CARD=Generic,DEV=1"    # IEC958 S/PDIF output
    slaves.a.channels 2
    slaves.b.pcm "plughw:CARD=NVidia,DEV=3"
    slaves.b.channels 2

    bindings.0.slave a
    bindings.0.channel 0
    bindings.1.slave a
    bindings.1.channel 1
    bindings.2.slave b
    bindings.2.channel 0
    bindings.3.slave b
    bindings.3.channel 1
}

# Now create a two channel device that routes its source channels to
the
# destination channels on the dual device.
pcm.both {
    type route
    slave.pcm "dual"

    ttable.0.0 1    #Left input to onboard IEC958 left output
    ttable.1.1 1    #Right input to onboard IEC958 right output
    ttable.0.2 1    #Left input to Nvidia HDMI left output
    ttable.1.3 1    #Right input to Nvidia HDMI right output
}
##############################################################################