[mythtv-users] AC3 Passthrough Problems
Matt Redmon
mythtv-user at comcast.net
Tue Aug 15 05:34:51 UTC 2006
I'm having some problems getting surround sound out of MythTV and into
my receiver.
The following command will put out AC3 surround sound audio:
mplayer -ac hwac3 -ao alsa:device=analog
If I change the device over to "digital" I get static:
mplayer -ac hwac3 -ao alsa:device=digital
Both of the following will put out analog 2-channel audio:
mplayer -ao alsa:device=analog
mplayer -ao alsa:device=digital
But the latter one has static mixed in with the sound
Neither of the following will work in MythTV when "Pass AC3 To SPDIF" is
checked:
ALSA:analog
ALSA:digital
But ALSA:analog will work as long as "Pass AC3 To SPDIF" is not checked.
Xine works just fine for AC3 surround sound. All I had to do was change
the speaker arrangement to Passthrough.
Any idea why both xine and mplayer will work but MythTV won't?
I have an Intel HDA audio device on my D915PBL motherboard. All of my
recordings have AC3 sound.
Thanks!
Matt
My /etc/asound.conf:
# ALSA configuration file
##### USAGE #####
# Save this file as "~/.asoundrc" (for user-specific sound
configuration) or
# "/etc/asound.conf" (for system-wide sound configuration) and specify
ALSA
# device names ad described in the next section.
##### DEVICE NAMES #####
# This configuration file defines four devices for use by the user.
Those
# devices are "analog", "mixed-analog", "digital", and "mixed-digital".
The
# user may also re-define "default" to be identical to one of the
above-named
# devices (i.e. to send all sound output to the digital output unless
otherwise
# specified). Use the device names as described below:
# - "analog" outputs to the analog output directly and (at least on
software
# sound cards) blocks other audio output. After playback completes,
"queued"
# sounds are output in sequence.
# - "mixed-analog" mixes audio output from multiple programs into the
analog
# output (so you can hear beeps, alerts, and other noises while playing
back
# an audio stream).
# - "digital" outputs to the digital output directly. Since most
(all?)
# digital outputs expect 48kHz PCM audio, this may not work for some
playback
# (i.e. CD's--which are 44.1kHz PCM audio--or 32kHz audio streams from
TV
# recordings, etc.).
# - "mixed-digital"
# All other devices created within this file are used only by the
configuration
# file itself and should /not/ be used directly. In other words, do not
use
# the devices "analog-hw", "dmix-analog", "digital-hw", or
"dmix-digital".
##### IMPORTANT #####
# To make this ALSA configuration file work with your sound card, you
will need
# to define the appropriate card and device information for the
"analog-hw" and
# "digital-hw" devices below. You can find the card and device
information
# using "aplay -l".
##### Configuration File #####
# 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).
#
# Note, also, that as of ALSA 1.0.9, "software" sound cards have been
modified
# such that their default "default" device is identical to the
"mixed-analog"
# device. Whether using an ALSA version before or after 1.0.9, it does
no harm
# and has no affect on performance to redefine the device (even if the
# redefinition does not change anything). Also, by using this ALSA
# configuration file, you once again have access to unmixed analog
output using
# the "analog" device.
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"
}
# Control device (mixer, etc.) for the card
ctl.!default {
type hw
card 0
}
# Alias for (converted) analog output on the card
# - 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 card
# - Note that as of ALSA 1.0.9, "software" sound card definitions
redefine
# "default" to do mixing, meaning this device is different from
"default" and
# allows playback while blocking other sound sources (until playback
# completes).
pcm.analog {
type plug
slave.pcm "analog-hw"
}
# Control device (mixer, etc.) for the card
ctl.analog {
type hw
card 0
}
# Alias for (converted) mixed analog output on the card
# - This will accept audio input--regardless of rate--and convert to the
rate
# required for the dmix plugin (in this case 48000Hz)
# - Note that as of ALSA 1.0.9, "software" sound card definitions
redefine
# "default" to do mixing, meaning this device is identical to "default"
for
# "software" sound cards.
pcm.mixed-analog {
type plug
slave.pcm "dmix-analog"
}
# Control device (mixer, etc.) for the card
ctl.mixed-analog {
type hw
card 0
}
# Alias for (converted) digital (S/PDIF) output on the card
# - 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 card
ctl.digital {
type hw
card 0
}
# Alias for mixed (converted) digital (S/PDIF) output on the card
# - 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 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 of of the devices defined above.
# Alias for analog output on the card
# 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
# - Uncomment one of the below or create a new "device N" line as
appropriate
# for your sound card or
# device 1
# device 4
}
# Control device (mixer, etc.) for the card
ctl.analog-hw {
type hw
card 0
}
# 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
}
# Control device (mixer, etc.) for the card
ctl.digital-hw {
type hw
card 0
}
# Direct software mixing plugin for analog output on the card
# 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 card
ctl.dmix-analog {
type hw
card 0
}
# Direct software mixing plugin for digital (S/PDIF) output on the card
# 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 card
ctl.dmix-digital {
type hw
card 0
}
-----------------------------------------------
aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: ALC880 Analog [ALC880 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: Intel [HDA Intel], device 2: ALC880 Digital [ALC880 Digital]
Subdevices: 1/1
Subdevice #0: subdevice #0
-----------------------------------------------
aplay -L
PCM list:
hw {
@args.0 CARD
@args.1 DEV
@args.2 SUBDEV
@args.CARD {
type string
default {
@func getenv
vars {
0 ALSA_PCM_CARD
1 ALSA_CARD
}
default {
@func refer
name 'defaults.pcm.card'
}
}
}
@args.DEV {
type integer
default {
@func igetenv
vars {
0 ALSA_PCM_DEVICE
}
default {
@func refer
name 'defaults.pcm.device'
}
}
}
@args.SUBDEV {
type integer
default {
@func refer
name 'defaults.pcm.subdevice'
}
}
type hw
card $CARD
device $DEV
subdevice $SUBDEV
}
plughw {
@args.0 CARD
@args.1 DEV
@args.2 SUBDEV
@args.CARD {
type string
default {
@func getenv
vars {
0 ALSA_PCM_CARD
1 ALSA_CARD
}
default {
@func refer
name 'defaults.pcm.card'
}
}
}
@args.DEV {
type integer
default {
@func igetenv
vars {
0 ALSA_PCM_DEVICE
}
default {
@func refer
name 'defaults.pcm.device'
}
}
}
@args.SUBDEV {
type integer
default {
@func refer
name 'defaults.pcm.subdevice'
}
}
type plug
slave.pcm {
type hw
card $CARD
device $DEV
subdevice $SUBDEV
}
}
plug {
@args.0 SLAVE
@args.SLAVE {
type string
}
type plug
slave.pcm $SLAVE
}
shm {
@args.0 SOCKET
@args.1 PCM
@args.SOCKET {
type string
}
@args.PCM {
type string
}
type shm
server $SOCKET
pcm $PCM
}
tee {
@args.0 SLAVE
@args.1 FILE
@args.2 FORMAT
@args.SLAVE {
type string
}
@args.FILE {
type string
}
@args.FORMAT {
type string
default raw
}
type file
slave.pcm $SLAVE
file $FILE
format $FORMAT
}
file {
@args.0 FILE
@args.1 FORMAT
@args.FILE {
type string
}
@args.FORMAT {
type string
default raw
}
type file
slave.pcm null
file $FILE
format $FORMAT
}
null {
type null
}
cards 'cards.pcm'
front 'cards.pcm.front'
rear 'cards.pcm.rear'
center_lfe 'cards.pcm.center_lfe'
side 'cards.pcm.side'
surround40 'cards.pcm.surround40'
surround41 'cards.pcm.surround41'
surround50 'cards.pcm.surround50'
surround51 'cards.pcm.surround51'
surround71 'cards.pcm.surround71'
iec958 'cards.pcm.iec958'
spdif 'cards.pcm.iec958'
modem 'cards.pcm.modem'
phoneline 'cards.pcm.phoneline'
dmix 'cards.pcm.dmix'
dsnoop 'cards.pcm.dsnoop'
default {
type plug
slave.pcm dmix-digital
}
analog {
type plug
slave.pcm analog-hw
}
mixed-analog {
type plug
slave.pcm dmix-analog
}
digital {
type plug
slave.pcm digital-hw
}
mixed-digital {
type plug
slave.pcm dmix-digital
}
analog-hw {
type hw
card 0
}
digital-hw {
type hw
card 0
device 2
}
dmix-analog {
type dmix
ipc_key 1234
slave {
pcm analog-hw
period_time 0
period_size 1024
buffer_size 4096
rate 48000
}
}
dmix-digital {
type dmix
ipc_key 1235
slave {
pcm digital-hw
period_time 0
period_size 1024
buffer_size 4096
rate 48000
}
}
-----------------------------------------
Relevant section of modprobe.conf:
# ALSA portion
alias char-major-116 snd
alias snd-card-0 snd-hda-intel
# OSS/Free portion
alias char-major-14 soundcore
# card #1
alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-oss
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