[mythtv-users] Cracking audio problem over HDMI

mythtv at blandford.net mythtv at blandford.net
Thu Dec 17 04:48:47 UTC 2009


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
     HDA Intel, AD198x Analog
     Default Audio Device
     HDA Intel, AD198x Analog
     Front speakers
     HDA Intel, AD198x Analog
     4.0 Surround output to Front and Rear speakers
     HDA Intel, AD198x Analog
     4.1 Surround output to Front, Rear and Subwoofer speakers
     HDA Intel, AD198x Analog
     5.0 Surround output to Front, Center and Rear speakers
     HDA Intel, AD198x Analog
     5.1 Surround output to Front, Center, Rear and Subwoofer speakers
     HDA Intel, AD198x Analog
     7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
     HDA Intel, AD198x Digital
     IEC958 (S/PDIF) Digital Audio Output
     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.


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