やっとHDMI通じて音声が出た

とりあえず、色々とググっていたら
http://xbmc.org/forum/showthread.php?t=54705&page=15
にて、ASRockの同じ製品を使っている方のフォーラムで設定ファイルを公開してくれている方がいたので、さくっとホームディレクトリの.asoundrcにコピーしたら、ディスプレイ内蔵のスピーカーから音が出ました秊

# ~/.asoundrc or /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 (unmixed) "analog" by default
# slave.pcm "analog-hw"
## 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 3
# - 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 2048
buffer_size 32768
rate 48000
}
}

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

あとは、audaciousで44.1kHzのサンプリングレートのFLACとかを48kHzにコンバートして聴ければ問題無しです。サンプリングレートコンバータをONにするにチェックを入れてファイルを再生しようとするとaudaciousが落ちちゃうんですよね輦
VLCでDVD再生は問題なくできました。
ただ、CPU使用率が45%前後まで行ってしまうので、vdpauをサポートしたプレイヤーに入れ替えたい所です。
ちなみに色々と面倒なんですが、lennyからsidに変更しました。