[mythtv-users] How Myth "sees" an audio device

[Jean-Yves Avenard]

On 17 April 2012 09:21, Pieter De Wit <pieter at insync.za.net> wrote:
> Hi All,
>
> (JYA will most likely answer this one :) )
>
> Is there a command line command that I can run to see what cap. my audio
> device has ? I have a Samsung HD6750w directly connected to my Nvidia GT430
> via HDMI. Yet Myth says it doesn't do TrueHD etc.

What text *exactly* do you see in Setup -> Audio at the bottom of the screen?
like described there:
http://www.mythtv.org/wiki/User_Manual:HDAudioPassthrough

Myth uses the ALSA interfaces to browse all available audio devices,
same as what aplay -L does.

When it comes to reading what's connected to the HDMI interface, this
is done by reading the ELD (EDID like Data) from the device. If it can
be retrieved, you will see the name of the device connected, and what
audio features it reports (AC3, DTS, TrueHD etc...)

you can see that information either in the kernel log (dmesg will show
something like:
[   38.785978] HDMI status: Codec=0 Pin=5 Presence_Detect=1 ELD_Valid=1
[   40.703534] HDMI: detected monitor SP32
[   40.703537]  at connection type HDMI
[   40.703541] HDMI: available speakers: FL/FR LFE FC RL/RR RC FLC/FRC RLC/RRC
[   40.703546] HDMI: supports coding type LPCM: channels = 8, rates =
32000 44100 48000 96000 176400 192000 384000, bits = 16 20 24
[   40.703551] HDMI: supports coding type AC-3: channels = 6, rates =
32000 44100 48000 96000 176400 192000 384000, max bitrate = 1536000
[   40.703556] HDMI: supports coding type DTS: channels = 6, rates =
32000 44100 48000 96000 176400 192000 384000, max bitrate = 1536000
[   40.703560] HDMI: supports coding type DTS-HD: channels = 8, rates
= 32000 44100 48000 96000 176400 192000 384000
[   40.703564] HDMI: supports coding type E-AC-3/DD+ (Dolby Digital
Plus): channels = 8, rates = 32000 44100 48000 96000 176400 192000
384000
[   40.703568] HDMI: supports coding type MLP (Dolby TrueHD): channels
= 8, rates = 32000 44100 48000 96000 176400 192000 384000

you can also see it by doing something like:
cat /proc/asound/card*/eld#*.0

If you run mythfrontend with -v audio ; that information will be shown
in the log.

You must be using ALSA 1.0.25 or later (don't use the 1.0.25 tarball
found on the alsa web site, it's buggy with nvidia cards, get the git
version

> I am running a Ubuntu system updated to 12.04 with the myth repos.

As far as I can tell, 12.04 ships with a kernel containing ALSA 1.0.24
; and as such won't allow to retrieve the ELD value, so myth won't be
able to detect what your amp support.