[mythtv-users] Cracking audio problem over HDMI

[mythtv at blandford.net]

Hello,

I just purchased a new vizio 37 inch TV.

I really want to feed this tv over HDMI, so I also bought a fanless 
9500GT card with 1GB.  I have connected the digital audio header on the 
motherboard to the input on the video card.


In Mythtv, I changed the audio output from alsa:default to alsa:spdif. 
I also enabled passthru thinking the TV would decode ac3, etc.  However, 
I just get a high rate ticking sound with passthru enabled so I am not 
sure what I configured wrong there.

Here are my audio devices:

aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: AD198x Analog [AD198x Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
card 0: Intel [HDA Intel], device 1: AD198x Digital [AD198x Digital]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
# aplay -L
default:CARD=Intel
     HDA Intel, AD198x Analog
     Default Audio Device
front:CARD=Intel,DEV=0
     HDA Intel, AD198x Analog
     Front speakers
surround40:CARD=Intel,DEV=0
     HDA Intel, AD198x Analog
     4.0 Surround output to Front and Rear speakers
surround41:CARD=Intel,DEV=0
     HDA Intel, AD198x Analog
     4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=Intel,DEV=0
     HDA Intel, AD198x Analog
     5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=Intel,DEV=0
     HDA Intel, AD198x Analog
     5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=Intel,DEV=0
     HDA Intel, AD198x Analog
     7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=Intel,DEV=0
     HDA Intel, AD198x Digital
     IEC958 (S/PDIF) Digital Audio Output
null
     Discard all samples (playback) or generate zero samples (capture)


So at present, I have audio configured as ALSA:spdif, Passthru is 
configured to use default, no passthru for ac3, etc is configured.

Audio is working, but it has a crackling sound to it - to the point it 
is unacceptable.

I read the digital wiki page, but I couldn't get the examples to work 
for me.


I tried playing with speaker-test.

Using: speaker-test -Diec958  -c2 twav would play fine on my TV.
But: speaker-test -Diec958  -c6 twav would result in:

Playback device is iec958
Stream parameters are 48000Hz, S16_LE, 6 channels
Using 16 octaves of pink noise
Channels count (6) not available for playbacks: Invalid argument
Setting of hwparams failed: Invalid argument


Does this mean I must feed the TV stereo only?

SO, I am looking for suggestions on how I should best get HDMI audio 
working with this card and configuration.

Michael