[mythtv-users] stereo+AC3/DTS sound to both analog+digital outputs

Allen Edwards allen.p.edwards at gmail.com
Wed Jul 29 23:28:36 UTC 2009

On Mon, Jul 27, 2009 at 11:41 PM, Petr Stehlik<pstehlik at sophics.cz> wrote:
> Hi,
> first the goal I'd like to achieve: to lower the power bill by not
> running my 5.1 receiver when not necessary (an overkill for poor stereo
> sounds of most recordings). Also the receiver eats 40W when idle and
> they often forget to turn it off after watching something.
> My setup: MythTV 0.21 with analog stereo output wired to TV and digital
> output wired to the receiver. The TV has fairly good speakers so it
> would be OK to use just that (and keeping the 5.1 receiver turned off)
> for most recordings, videos and DVDs. But often I'd like to listen to
> the sound in the full 5.1 digital quality so if I turn the receiver on
> I'd like it to play all MythTV sounds.
> MythTV allows to configure AC3/DTS pass-through. With the pass-through
> disabled and no ALSA magic enabled all sound sources (stereo, AC3, DTS)
> play on the analog output only. I miss the sound on the digital output
> here.
> Now if I enable the AC3/DTS pass-through in MythTV then stereo sound
> goes to analog output _only_ (=plays on the TV) while AC3/DTS goes to
> digital output _only_ (plays on the receiver only). This is the worst
> situation for WAF, believe me ;)
> To solve this problem I have added an ALSA magic with a small .asoundrc
> that basically routes everything to the digital output (I guess, I am
> not ALSA expert):
> pcm.!default {
>        type plug
>        slave {
>                pcm "spdif"
>                rate 48000
>                format S16_LE
>        }
> }
> With this .asoundrc in place _everything_ plays on the digital output
> only - I miss the sound on the analog output (= in the TV).
> I am not sure if this is just a configuration issue in MythTV or if it
> can be "fixed" by an advanced ALSA setup or if I'd need some internal
> changes in MythTV. My current setup is the following:
> Sound device: ALSA:default
> Pass-through device: ALSA:iec958:{AES0 0x02}
> Upmix: stereo passive
> I'd like MythTV to work like if the AC3/DTS is _disabled_, i.e. to play
> even the AC3/DTS sounds on the analog output, yet _at the same time_ to
> pass-through all AC3/DTS sounds unmodified to the digital output. Plus
> I'd need to configure ALSA to watch the analog+digital outputs and if
> there is something on the analog but not on the digital one then to
> _copy_ the analog to the digital output so even the poor stereo is
> available on the digital output. All this happening automagically
> without user fiddling with config stuff.
> Sounds complicated? I simply wants MythTV to play all sounds on both
> analog+digital outputs without unnecessary down/upmixing (AC3/DTS passed
> through unmodified).
> Any suggestions, please?
> Thanks
> Petr
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

Let me know if you figure it out.  I have two decoders, one in the
surround system playing 4.1 (no center) and one playing 2.0 that feeds
the TV.  It is a Technics unit and I have to basically leave it on all
the time.  I could not figure out how to get analog and digital sound
out at the same time.


More information about the mythtv-users mailing list