[mythtv-users] HDMI ac3 passthough audio

[Allen Edwards]

On Mon, Feb 9, 2009 at 5:16 PM, JP Fournier <jape41 at gmail.com> wrote:

> Hi All,
>
> After I got some help from the radeonhd driver list, I am now able to play
> ac3
> audio over HDMI with mplayer via a command line like this:
>
> mplayer -ac hwac3 -ao alsa:device=iec958=1 -vo xv -fs
> 2041_20090208074700.mpg
>
> Can anyone help me figure out what the equivalent settings under mythtv
> would
> be? Obviously I've tried a few variations, but the best I can get is clicky
> static.
>
> regards,
>
> jp


Time to send this out again.  Let me know if you have any additions to this
advice:

Allen



--------------------------------------------------------------------------------------------------------------------------
                     SPDIF over MYTHTV
--------------------------------------------------------------------------------------------------------------------------
For spdif I recommend the following settings:

-----------------------hdmi-----------------------------------
For HDMI cards

Update nvidia drivers.  Mythbuntu users can use "envyng -t" from the command
line after installing it.
Update alsa

run aplay -l and look for an output like this:

  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 3: NVIDIA HDMI [NVIDIA HDMI]

For this case, the key is card o device 3.

Then use this setup:

Audio output device: ALSA:hw:0,3
Passthrough output device: ALSA:hw:0,3
Max Audio Channels: Stereo
Upmix: Passive
Enabale AC3 to SPDIF passthrough checked
Enable DTS to SPDIF passthrough checked
Aggressive sound card buffering off
Use internal volume controls off


For mythmusic: (note, this looks like it is using pulse audio.  There may be
another way)
Utilities/Setup -> Setup -> Media Settings -> Music Settings -> General
Settings
and then set Audio device to ALSA:plughw:0,3


Optional for myth but perhaps a good or bad thing:

asound.conf:

pcm.!default {
        type hw
        card 0
        device 3
}

If you have problems test without myth
mplayer -ao alsa:device=hw=0.3 -afm hwac3 /some/dolbydigital/audio/file.wav
This will verify the hardware


------------------m3n78-em------------------------------------
1st post:
For the m3n78-em with the optical spdif connector on the MB the kernel
module must be loaded with this option:
options snd-hda-intel model=6stack-dig

2nd post:
in MythBuntu i added the same line to /etc/modprobe.d/alsa-base, or, i
should say, the script i ran to update my alsa drivers added it for
me.

----------------------general------------------------------------

Audio output device: ALSA:spdif  <--- this doesn't work for HDMI cards.  See
above
Passthrough output device: ALSA:iec958(AESO 0x02)
max Audio Channels: Stereo  (this feature is broken so this is the required
setting even if you want surround sound)
Upmix: Passive
Enable AC3 to SPDIF passthrough (checked)
Enable ETS to SPDIF passthrough (checked)
Aggressive Sound Card Buffers (unchecked)
Use internal volume controls (unchecked)

Remove or rename asound.conf and .asoundrc if it exists.
If you are running Fedora, remove pulseaudio and all its files.
There was a post that outlined the process but it is gone.  A copy is below.

Run alsamixer and enable iec958.  Use the right arrow key to see it.


-----------------------------Fedora and pulse audio
removal------------------------------------
Copy of someone else's post:

The steps I followed were:
-1- Rename (add "-orig") to cripple:    /etc/pulse
                                       /etc/pulse/default.pa
                                       /root/pulse-cookie
                                       /home/<user name>/.pulse-cookie
-2- Run   rpm -qa | grep "pulse"   and   rpm -qa | grep "pa"    to find
the stuff loaded for pulse audio.  Remove it via yum ("yum remove xxx"),
one item below per run:
                       pulseaudio
                       alsa-plugins-pulseaudio
                       pavucontrol
                       pulseaudio-utils
                       gstreamer-plugins-pulse
                       pulseaudio-core-libs
                       akode-pulseaudio
This leaves:    libflashsupport
               pulseaudio-libs
               akode-pulseaudio
To remove these would take too many other dependencies.

IIRC, there were subsequent notes on several sites that removing only
alsa-plugins-pulseaudio was enough.  I'm not certain that "I recall
correctly" and even if I do, it might not be enough for Fedora 9.  But
I'd probably try that first to see if it (alone) works.  Besides, since
you'll eventually need to do it, there's no harm.



---------------------------------------------------------------------------
Another useful post:

Hi Phil, and others experiencing problems ;-)

(apologies for not responding inline, working with outlook for the moment)

I have different hardware (onboard AMD) yet suffered from similar issues. I
documented the shortest route that worked for me and that I suspect may give
you clues in the right direction on different hardware as well. Here's what
I did:

$ sudo alsactl names

This will output a list of audio/alsa devices into /etc/asound.names

Going through /etc/asound.names, the two relevant entries for me were:

alsactl19 {
       name 'hw:1,3'
       comment 'Physical Device - ATI HDMI (Playback)'
}
alsactl20 {
       name 'plughw:1,3'
       comment 'Physical Device With Conversions - ATI HDMI (Playback)'
}

I found that the first one worked sometimes and the second one always, I
suspect this to depend on the format of the audio.

In mythfrontend -> Utilities/Setup -> Setup -> General -> page 3 I used

ALSA:plughw:1,3

for both "audio output device" and "passthrough audio device".

Unchecked "use internal volume controls"

Lastly, make sure sound over HDMI is not muted:

$ sudo alsamixer -c 1
(-c 1 to select the second device, see device name from asound.names)

Choose the right channel and press 'm' to unmute if needed.

Hope this helps. For me being able to actually go through the list of my
devices in /etc/asound.names was the break-through.

Erik.
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