[mythtv-users] 32khz AC3 Streams was: Sound problem with AC3 passthrough

[Meatwad]

Rob Baumstark wrote:
> Sorry for generating so much spam - but a little more info that might
> prove to be helpful.  I stumbled into a discussion on the -commit list
> about AC3 passthrough, and decided to try a couple more mplayer
> options...
> 
> '-ao alsa:device=iec958'
>   This plays back the audio perfectly, the receiver indicates PCM
> 48khz.  The video however is sped up to about the speed as the options
> in the previous e-mail.
> 
> '-ao alsa:device=iec958 ac hwac3'
>   This gives the same results as just using '-ac hwac3' - both audio
> and video playback too fast.
> 
> I also captured a little of the mplayer output from that last test
> with '-ac hwac3' on.
> 
> Checking audio filter chain for 32000Hz/2ch/ac3 -> 32000Hz/2ch/ac3...
> AF_pre: 32000Hz/2ch/ac3
> alsa-init: 1 soundcard found, using: iec958
> alsa: 48000 Hz/2 channels/4 bpf/65536 bytes buffer/Signed 16 bit Little Endian
> AO: [alsa] 48000Hz 2ch ac3 (1 bps)
> Building audio filter chain for 32000Hz/2ch/ac3 -> 48000Hz/2ch/ac3...
> [format] Sample format big-endian AC3 not yet supported
> Couldn't find matching filter/ao format!
> Starting playback...

Rob, just started testing your clip only to find that my alsa is having 
issues I haven't even pinned down yet (iec958 and spdif devices not 
recognized ??? yet mplayer and myth pass perfect 48k with ALSA:default 
and my .asoundrc). Rather than hijack your thread, I'll go on about 
fixing my stuff.

However, your clip is playing back fine here with the device=default so 
here is a copy of my .asoundrc

"Couldn't find matching filter/ao format!" looks intereting though. I 
did try removing liba52 from my system to see if that was the culprit 
but myth, mplayer and alsa keep playing the clip (and some of mine) just 
fine.

Following is my .asoundrc (earlier Mike Dean version). HTH

--
mw


=========================================================
# Override the default output used by ALSA.
# If you do not override the default, your default
# device is identical to the (unmixed) analog device
# shown below.  If you prefer mixed and/or digital
# output, uncomment the appropriate four lines below
# (only one slave.pcm line).
#pcm.!default {
#  type plug
## 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 analog output on the nForce2/4 (hw:0,0)
# - This is identical to the device named "default"--which
# always exists and refers to hw:0,0 (unless overridden)
# - Therefore, we can specify "hw:0,0", "default", or "analog"
# to access analog output on the nForce2/4
pcm.analog {
  type plug
  slave.pcm "analog-hw"
}

# Control device (mixer, etc.) for the nForce2 card
ctl.analog {
  type hw
  card 0
}

# Alias for (rate-converted) mixed analog output on the
# nForce2 (hw:0,0)
#  - This will accept audio input--regardless of rate--and
# convert to the rate required for the dmix plugin
# (in this case 48000Hz)
pcm.mixed-analog {
  type plug
  slave.pcm "dmix-analog"
}

# Control device (mixer, etc.) for the nForce2 card
ctl.mixed-analog {
  type hw
  card 0
}

# Alias for (rate-converted) digital (S/PDIF) output on the
# nForce2 (hw:0,2)
#  - This will accept audio input--regardless of rate--and
# convert to the rate required for the S/PDIF hardware
# (in this case 48000Hz)
pcm.digital {
  type plug
  slave.pcm "digital-hw"
}

# Control device (mixer, etc.) for the nForce2 card
ctl.digital {
  type hw
  card 0
}

# Alias for mixed (rate-converted) digital (S/PDIF) output on the
# nForce2/4 (hw:0,2)
#  - This will accept audio input--regardless of rate--and
# convert to the rate required for the S/PDIF hardware
# (in this case 48000Hz)
pcm.mixed-digital {
  type plug
  slave.pcm "dmix-digital"
}

# Control device (mixer, etc.) for the nForce2 card
ctl.mixed-digital {
  type hw
  card 0
}

# The following devices are not useful by themselves.  They
# require specific rates, channels, and formats.  Therefore,
# you probably do not want to use them directly.  Instead use
# one of the devices defined above.

# Alias for analog output on the nForce2 (hw:0,0)
# Do not use this directly--it requires specific rate,
# channels, and format
pcm.analog-hw {
  type hw
  card 0
  # The default value for device is 0, so no need to specify
}

# Control device (mixer, etc.) for the nForce2/4 card
ctl.analog-hw {
  type hw
  card 0
}

# Alias for digital (S/PDIF) output on the nForce2/4 (hw:0,2)
# Do not use this directly--it requires specific rate,
# channels, and format
pcm.digital-hw {
  type hw
  card 0
  device 2
}

# Control device (mixer, etc.) for the nForce2/4 card
ctl.digital-hw {
  type hw
  card 0
}

# Direct software mixing plugin for analog output on
# the nForce2/4 (hw:0,0)
# Do not use this directly--it requires specific rate,
# channels, and format
pcm.dmix-analog {
  type dmix
  ipc_key 1234
  slave {
    pcm "analog-hw"
    period_time 0
    period_size 1024
    buffer_size 4096
    rate 48000
  }
}

# Control device (mixer, etc.) for the nForce2/4 card
ctl.dmix-analog {
  type hw
  card 0
}

# Direct software mixing plugin for digital (S/PDIF) output
# on the nForce2/4 (hw:0,2)
# Do not use this directly--it requires specific rate,
# channels, and format
pcm.dmix-digital {
  type dmix
  ipc_key 1235
  slave {
    pcm "digital-hw"
    period_time 0
    period_size 1024
    buffer_size 4096
    rate 48000
  }
}

# Control device (mixer, etc.) for the nForce2/4 card
ctl.dmix-digital {
  type hw
  card 0
}