[mythtv-users] Simultaneous analogue (analog) and S/PDIF output

Jean-Yves Avenard jyavenard at gmail.com
Wed Jan 12 11:39:48 UTC 2011


Hi

On 12 January 2011 21:57, Alex Butcher <mythlist at assursys.co.uk> wrote:

> * Mon Nov 22 2010 Jarod Wilson <jarod at wilsonet.com> 0.24-2
> - Update to release-0-24-fixes, svn revision 27317
> - Add preview image fixup patch from ticket #9256
> - Add alsa passthru device patches from trunk r27306 and r27307
> [...]

I have no idea what those patches are; and to be honest, I have no
intention on investigating what they are... The audio code is in a
current state I specifically intended to be in, if other people
backport stuff, then you're on your own

If I had felt the need the 0.24 branch would required some backports
from trunk, then it would have been done by now.

>
> There's no StereoPCM flag in my GUI. Is the StereoPCM flag you describe the
> MultiChannelPCM row?  If so, that's currently:
>
> | MultiChannelPCM | 0    | xxxxxxxxxxxxxxxxxxxxxxx |

if there's no stereopcm flag , then you are running a too old version of mythtv.

If you're stuck to a SVN revision, then it's no wonder.. Upgrade to
the latest stable branch.

>
> The schema documentation at <http://www.mythtv.org/wiki/Settings_table>
> seems to be out-of-date regarding this.
>
> Presumably the StereoPCM GUI element is the inversion of the MultiChannelPCM
> row value.

it is... Just that multichannelPCM had to be set all the time before,
but I changed it to be only an optional value...

Make sure it's unchecked, it's the same as checking StereoPCM

>
> If I understand you and mythtv-0.24/libs/libmyth/audiooutputsettings.cpp
> correctly, to summarise your settings for non-upmixed stereo over analogue +
> S/PDIF, but passthru for AC3 and DTS (with the caveat that analogue channel
> will need to be muted), I think I need to make these settings:
>
> AudioOutputDevice=ALSA:default

if you're using ALSA:default as your audio output device, how do you
ever expect it to send audio to both analog and digital... Did you
read my previous post ?

> MixerDevice=ALSA:default
> MixerControl=PCM
> MasterMixerVolume=per preferences

I don't know if that would work with the mixer device ; but I would
disable volume control totally for the time being.. volume control can
never work with digital audio

> AudioDefaultUpmix=0
> AudioUpmixType=0
> MusicDefaultUpmix=0
> AC3PassThru=1
> DTSPassThru=1
> AdvancedAudioSettings=1
>
> These I'm less sure about:
> MaxChannels=2 ???

if you have set max channels to 2; then no multichannels output will
ever occur, and obviously you'll never get passthrough working. Stereo
at best.

Sorry, but I thought that it was obvious that to get multichannels
audio working, you would need to configure the speaker set up to at
least 5.1...

if you set it to stereo; the passthrough device will never be used.
Myth will only ever output stereo, and the passthrough device will be
ignored as it's only ever used for multichannels audio

> PassThruDeviceOverride=0 ???
> PassThruDevice='ALSA:iec958:AES0=6' or 'ALSA:iec958:{ AES0 0x06 }' ???
> MultiChannelPCM=0 ???

then re-read again my post just before... because if that's how you
set your device, you obviously didn't read it

Passthrough device override must be set.
ALSA:iec958:AES0=6 or ALSA:iec958:{ AES0 0x06 }

Those are the same. there are a few ways you can define the device in ALSA...

>
> I hope you'll forgive me for being persistent; as well as solving my
> immediate problem I'm trying to make this thread something of a canonical
> explanation of how MythTV handles analogue, S/PDIF, and so on so that people
> with problems can refer to it to debug their problems too (regardless of
> what the GUI reports; we've all seen incidents where the settings GUIs
> report differ from the settings that are actually being /used/).  I'll wiki
> it later, even.

I would forgive you for being persistent, if you at least followed the
instructions I spent time writing for you...

I wrote to use an audio device you created using ALSA configuration,
you are using ALSA:default: wrong.
Some people posted .asoundrc to write to multiple audio device at
once, you should start with those...

I wrote to set the passthru override: you aren't, it's unchecked: wrong


> I'm aware of your status as author of many of these bits (and the original
> VDPAU stuff). My comment was really intended as "Are you sure it /worked/ as
> you describe /as of 21 November 2010/, rather than -trunk or the /current/
> 0.24-fixes'. :-)

I am sure... provided you run the latest version of that particular branch.

We aren't using svn anymore, and haven't been for a few months now...

> But my UI doesn't show some of the settings you describe or at least, not
> with the labels you give them.  I gather others have reported the same
> problem with screenshots (I think you were in the thread).

this is what happens if you aren't running a relatively recent (e.g.
more than 2 months old) version of 0.24..

The issue that the configuration page doesn't show properly on low
resolution screen is something I've fixed in trunk, or in my 0.24 fork
with the new audio code..
I only discovered that Qt completely screwed up the rendering on low
res screen, and to be honest, I have no idea why ..

So to summarise (again :) ):
Output device: ALSA:myfancymixer_i_created_in_asoundrc
Multichannel PCM uncheck
AC3 = DTS = check
Speakers 5.1
upmixer: uncheck
advanced: check
override passthrough: check
passthrough device: ALSA:iec958:AES0=6 (can probably use the default
entry: ALSA:iec958:{ AES0 0x2} ... )

if using updated version of 0.24
Output device: ALSA:myfancymixer_i_created_in_asoundrc
AC3 = DTS = check
Speakers 5.1
upmixer: uncheck
advanced: check
override passthrough: check
passthrough device: ALSA:iec958:AES0=6 (can probably use the default
entry: ALSA:iec958:{ AES0 0x2} ... )
StereoPCM: check


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