I have already tried turning IEC958 off while the video was playing, but it did not help. Also, I was reading the MPlayer documentation online and I changed your command line a bit. I used "-afm hwac3" since it works with both DTS and AC3 file formats (the movies I am trying to play have both types of sound tracks). I also added "-channels 6" after "dvd://1" to force 5.1 sound. Here is a sample output when I tried to play "Pirates of the Caribbean" DVD (the results were identical for the "Braveheart" DVD):
cjspinelli@ASUS-A7N8X-Deluxe:~> mplayer -ao alsa:device=hw=0.2 -afm hwac3 dvd://1 -channels 6 -dvd-device /dev/dvd
MPlayer dev-SVN-rUNKNOWN-4.1.0 (C) 2000-2006 MPlayer Team
CPU: AMD Athlon(tm) XP 3200+ (Family: 6, Model: 10, Stepping: 0)
CPUflags: MMX: 1 MMX2: 1 3DNow: 1 3DNow2: 1 SSE: 1 SSE2: 0
Compiled with runtime CPU detection.
Failed to open /dev/rtc: Permission denied (it should be readable by the user.)
Opening joystick device /dev/input/js0
Can't open joystick device /dev/input/js0: No such file or directory
Can't init input joystick
Setting up LIRC support...
mplayer: could not connect to socket
mplayer: Connection refused
Failed to open LIRC support.
You will not be able to use your remote control.
Reading disc structure, please wait...
There are 54 titles on this DVD.
There are 17 chapters in this DVD title.
There are 1 angles in this DVD title.
DVD successfully opened.
MPEG-PS file format detected.
VIDEO: MPEG2 720x480 (aspect 3) 29.970 fps 9800.0 kbps (1225.0 kbyte/s)
Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough
VDec: vo config request - 720 x 480 (preferred colorspace: Mpeg PES)
Could not find matching colorspace - retrying with -vf scale...
Opening video filter: [scale]
The selected video_out device is incompatible with this codec.
Try adding the scale filter, e.g. -vf spp,scale instead of -vf spp.
VDecoder init failed
Opening video decoder: [libmpeg2] MPEG 1/2 Video decoder libmpeg2-v0.4.0b
Selected video codec: [mpeg12] vfm: libmpeg2 (MPEG-1 or 2 (libmpeg2))
Trying to force audio codec driver family hwac3...
Opening audio decoder: [hwac3] AC3/DTS pass-through S/PDIF
No accelerated IMDCT transform found
hwac3: switched to DTS, 768000 bps, 48000 Hz
AUDIO: 48000 Hz, 2 ch, ac3, 768.0 kbit/50.00% (ratio: 96000->192000)
Selected audio codec: [hwdts] afm: hwac3 (DTS through S/PDIF)
alsa-init: using device hw:0,2
alsa: 48000 Hz/2 channels/4 bpf/65536 bytes buffer/Signed 16 bit Little Endian
AO: [alsa] 48000Hz 2ch ac3 (1 bytes per sample)
VDec: vo config request - 720 x 480 (preferred colorspace: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.
VO: [xv] 720x480 => 854x480 Planar YV12
A: 0.6 V: 0.6 A-V: 0.002 ct: 0.017 12/ 10 ??% ??% ??,?% 0 0
demux_mpg: 24000/1001fps progressive NTSC content detected, switching framerate.
The video worked great, but still no audio. It appears as if MPlayer is sending the audio signal, but the signal is not being received by the Cambridge SoundWorks DTT3500 decoder?!? Also, it appears that the alsa driver is using 4 channels, or maybe only 2 channels. What do all of the items on the "alsa:" and "AO:" line mean? Thanks again for the help, I am one step closer. Now I just have to figure out where the audio signal is going. Any thoughts?
PS - I looked at the back of my motherboard and in the manual, and there is not an optical output anywhere. I am not sure what the additional subdevice is in the "aplay -l" output, since there is no optical output (i.e., the motherboard only has only one S/PDIF out, the coaxial).