Re: Spdif clock switching?

[Bart de Boer <bart@xxxxxxxxxxxx>]

Matt Garman wrote:

On Fri, May 02, 2008 at 11:20:28AM +0200, Bart de Boer wrote:
  

I got it to work! :D I was telling MythTV to send everything to my
digital output directly. This was wrong. I needed to send
everything to my analog output and let the chip do the work. I'm
now playing music at 44.1 kHz and movies at 48 kHz. :)
    

Would you mind elaborating a bit on what you did exactly in Myth?
  

Hi Matt,

It seems I may have cheered too soon. Yes, I am able to get bitperfect 44.1 kHz sound and bitperfect 48 kHz sound (with and without AC3). Mplayer is somehow able to trigger the system into 48 kHz after listening to 44.1 kHz material. However, after the system is switched to 48 kHz, MythMusic is *not* able to switch the system back to 44.1 kHz resulting in MythMusic not producing any audio anymore. :(

I found a way to trigger the system back into 44.1 kHz mode by going into Ubuntu (8.04) Sound Preferences and play the test sound through "Intel ICH5 - IEC958". I'll hear something click in my receiver. After this MythMusic works fine again producing bitperfect 44.1 kHz audio. :) I don't understand why this happens.

In alsamixer I've also noticed that, when playing AC3 material the "IEC958 Playback AC97-SPSA" slider is automatically switched to 3 (100%). When stopping playback it will automatically switch back to 0 (0%).

I'd be very very grateful if someone has a solution or could shed some light on this weird behaviour!

These are all my current settings:


alsamixer
=========
Unmute "IEC958"
Set "IEC958 Playback AC97-SPSA" to 0 (0%)


MythTV (General)
================
Audio output device: ALSA:default
SPDIF passthrough device: ALSA:iec958:{AES0 0x02}
[x] enable AC3 to SPDIF passthrough
[x] enable DTS to SPDIF passthrough


MythTV (Music)
==============
Audio output device: default


Ubuntu 8.04 - Sound Preferences
===============================
Everything set to: Intel ICH5 - IEC958


.asoundrc
=========
pcm.!default {
   type plug
   slave.pcm "analog-hw"
   # slave.pcm "digital-hw"
   # slave.pcm "dmix-digital"
}

ctl.!default {
   type hw
   card 0
}

pcm.analog {
   type plug
   slave.pcm "analog-hw"
}

ctl.analog {
   type hw
   card 0
}

pcm.analog-hw {
   type hw
   card 0
   ## The default value for device is 0, so no need to specify
   ##  - Uncomment one of the below or create a new "device N" line as appropriate
   ##    for your sound card or
   # device 1
   # device 4
}

ctl.analog-hw {
  type hw
  card 0
}

pcm.digital-hw {
   type hw
   card 0
   ## - Comment out "device 1" above and uncomment one of the below or create a
   ##   new "device N" line as appropriate for your sound card or
   # device 1
   # device 2
   device 4
}

ctl.digital-hw {
   type hw
   card 0
}

pcm.dmix-digital {
   type dmix
   ipc_key 1235
   slave {
      pcm "digital-hw"
      period_time 0
      period_size 1024
      buffer_size 4096
      rate 48000
   }
}

ctl.dmix-digital {
   type hw
   card 0
}


mplayer config
==============
monitoraspect=16:9
fs=yes
vo=xv
# ao=alsa
ao=alsa:device=iec958
# ao=alsa:device=hw=0.4
# ao=alsa:device=spdif
afm=hwac3




-Bart

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