[mythtv-users] Can I get 5.1 audio from MythTV with this setting?

Fri Apr 20 01:54:36 UTC 2012

Ok, here is a question about connecting HD TV, 5.1 surround system and
MythTV. I want to say sorry in front if it sounds little bit dumb or if it
doesn't make sense :-) I was messing up with this last night so thought I
would ask here if it is possible at all since my knowledge of ALSA is
pretty poor.

I have the surround connected to the TV via HDMI (it's an entertainment
unit with DVD player). I have the MythTV box connected to the TV via HDMI
as well. I'm sending the audio from the TV to the surround system via
optical cable (since the TV doesn't have ARC). Can I still get surround
sound from MythTV with this connection? I know I can buy optical cable
switch and have both optical outputs, from the TV and Myth (yes MythTV box
has one too), connected to the surround but I'm just trying to avoid adding
some more cables to the cable forest I have behind the TV stand *sigh*

Some info about MythTV sound card:

igorc at mythtv:~/bluray$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: SB [HDA ATI SB], device 0: ALC889A Analog [ALC889A Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: SB [HDA ATI SB], device 1: ALC889A Digital [ALC889A Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: HDMI [HDA ATI HDMI], device 3: ATI HDMI [ATI HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

igorc at mythtv:~/bluray$ aplay -L
null
    Discard all samples (playback) or generate zero samples (capture)
front:CARD=SB,DEV=0
    HDA ATI SB, ALC889A Analog
    Front speakers
surround40:CARD=SB,DEV=0
    HDA ATI SB, ALC889A Analog
    4.0 Surround output to Front and Rear speakers
surround41:CARD=SB,DEV=0
    HDA ATI SB, ALC889A Analog
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=SB,DEV=0
    HDA ATI SB, ALC889A Analog
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=SB,DEV=0
    HDA ATI SB, ALC889A Analog
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=SB,DEV=0
    HDA ATI SB, ALC889A Analog
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=SB,DEV=0
    HDA ATI SB, ALC889A Digital
    IEC958 (S/PDIF) Digital Audio Output
hdmi:CARD=HDMI
    HDA ATI HDMI, ATI HDMI
    HDMI Audio Output

igorc at mythtv:~/bluray$ cat /proc/asound/card2/codec#0
Codec: ATI RS690/780 HDMI
Address: 0
Function Id: 0x1
Vendor Id: 0x1002791a
Subsystem Id: 0x00791a00
Revision Id: 0x100000
No Modem Function Group found
Default PCM:
    rates [0x40]: 48000
    bits [0x2]: 16
    formats [0x5]: PCM AC3
Default Amp-In caps: N/A
Default Amp-Out caps: N/A
GPIO: io=0, o=0, i=0, unsolicited=0, wake=0
Node 0x02 [Audio Output] wcaps 0x201: Stereo Digital
  Converter: stream=0, channel=0
  Digital: Enabled
  Digital category: 0x0
Node 0x03 [Pin Complex] wcaps 0x400381: Stereo Digital
  Pincap 0x00000094: OUT Detect HDMI
  Pin Default 0x18560010: [Jack] Digital Out at Int HDMI
    Conn = Digital, Color = Unknown
    DefAssociation = 0x1, Sequence = 0x0
  Pin-ctls: 0x40: OUT
  Unsolicited: tag=00, enabled=0
  Connection: 1
     0x02

This file I created when I installed MythTV 0.20 in 2008 to make my sound
work over HDMI output (not sure if I still need it):

igorc at mythtv:~/bluray$ cat /home/igorc/.asoundrc
# ALSA library configuration file

# Include settings that are under the control of asoundconf(1).
# (To disable these settings, comment out this line.)
#</home/igorc/.asoundrc.asoundconf>
pcm.card0 {
  type hw
  card 0
}

pcm.dmixer {
  type dmix
  ipc_key 1025
  slave {
    pcm "hw:2,3"
    period_time 0
    period_size 2048
    buffer_size 32768
    rate 48000
    channels 6   # added this to try mixing 6 channels in the stream
  }
  bindings {
    0 0
    1 1
  }
}

pcm.skype {
  type asym

  playback.pcm "dmixer"
  capture.pcm "card0"
}

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

igorc at mythtv:~/bluray$ dmesg | grep -i alsa
[   17.958820] cx2388x alsa driver version 0.0.7 loaded
[   18.133429] cx88[0]/1: CX88x/0: ALSA support for cx2388x boards

igorc at mythtv:~/bluray$ lsmod | grep ^cx
cx22702                 6140  1
cx88_dvb               22321  1
cx88_vp3054_i2c         2207  1 cx88_dvb
cx88_alsa              10033  1
cx8800                 32442  0
cx8802                 14957  1 cx88_dvb
cx88xx                 80221  4 cx88_dvb,cx88_alsa,cx8800,cx8802

igorc at mythtv:~/bluray$ cat /proc/asound/version
Advanced Linux Sound Architecture Driver Version 1.0.21.

I'm on Mythbuntu 10.04 with MythTV 0.23-fixes and ancient ALSA 1.0.21 looks
like so no ELD. I have selected ALSA:default for device in the MythTV audio
settings, 5.1 for channels and have DTS box ticked. The sound works both
with the recordings and videos playback (both mplayer and internal player)
but I didn't have any AC3 video handy to test last night ...

Thanks in advance for reading this.

Igor
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