[LAU] doing stereo up mix for 2 channel audio and enabling ac3/dts output through spdif with the xine dvd player in mythtv

Hello,

I have installed mythbuntu 8.04 to replace windows xp media center
2005 and are encountering an issue with it. I've got an a8n-sli
deluxe motherboard with realtek ac'97 compatible alc850 builtin
motherboard audio. I can play back music in mythmusic if my
.asoundrc file is this:

pcm.nforce-hw {
type hw
card 0
}

pcm.!default {
type plug
slave.pcm "nforce"
}

pcm.nforce {
type dmix
ipc_key 1234
slave {
pcm "hw:0,0"
}
}

ctl.nforce-hw {
type hw
card 0
}

Here are the settings that are used in mythtv:

Audio output device: ALSA:default

Passthrough output device: Default

Max Audio Channels: 5.1 Upmix: Passive

x Enable AC3 to SPDIF passthrough
x Enable DTS to SPDIF passthrough

But then sending out the audio through xine doesn't work when playing
back dvd's. Unless of course I use this for an .asoundrc file.

pcm.!default {
type hw
card 0
device 2
## Uncomment the following to use "mixed-analog" by default
# slave.pcm "dmix-analog"
## Uncomment the following to use (unmixed) "digital" by default
slave.pcm "digital-hw"
## Uncomment the following to use "mixed-digital" by default
# slave.pcm "dmix-digital"
}

# Alias for digital (S/PDIF) output on the card
# Do not use this directly--it requires specific rate, channels, and format
pcm.digital-hw {
type hw
card 0
# device 1
# - 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 2
# device 4
}

The sound then is sent out properly with ac3/dts being sent out
compressed and mpeg2 being sent out uncompressed. Here is the
command I use to launch xine:

xine dvd:// -F -V xv -A alsa:device=hw=0,2 --no-splash --no-gui
--no-mouse --borderless

So what I want to do is since the uncompressed audio has to go
through "hw:0,0", can I up convert that using stereo up mix and
encode it to ac3 automatically in real time and then put that
compressed ac3 through the spdif plug which is "hw:0,2". I have
verified that I am sending audio as pass through in xine.

I've been searching for how to do this for the past 2 weeks and are
hoping someone else has already done it so that I can just change the
.asoundrc file settings so that both will work. I'm currently
running a bash script to copy each version of .asoundrc depending on
what I want to do at the time with my mythtv box. I was able to do
it in windows media center 2005 easily enough, can I do it in linux? Thanks.

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Received on Fri May 16 08:15:01 2008