[mythtv-users] GeForce 9400, AC3/DTS over HDMI?

Troy Goodson TroysLists at Lavabit.com
Tue Jul 7 08:05:11 UTC 2009

I'm having trouble configuring my digital audio over HDMI.  I've  
fiddled with the settings, googled for help, looked at http://www.mythtv.org/wiki?title=AllensDigitalAudioHowto 
, but to no avail :(

While watching live or recorded ATSC TV, I can get stereo-only sound  
over HDMI and I can get digital (AC3 passthrough) over my optical  
connection (Toslink S/PDIF), but I can't seem to figure out the AC3- 
passthrough over HDMI.  If you have this motherboard or this NVIDIA  
chipset, have you got this working? Also, feel free to pass along a  
link to your favorite how-to.  In the meantime, I'm reading the alsa  

Thanks in advance,



I'm using a GIGABYTE GA-E7AUM-DS2H, NVIDIA GeForce 9400. I installed  
MythBuntu from mythbuntu-9.04-desktop-amd64.iso.  I'm using NVIDIA  
driver 180.44, according to "NVIDIA X Server Settings".

I've connected the HDMI from the motherboard to my TV (Panasonic Viera  
TH-42PZ80U) and optical Toslink from the TV to my receiver (Sony STR- 
DE635) (it has only one optical audio input jack).

My Audio settings are:
Audio output device: ALSA:hdmi
Passthrough output device: Default
Max Audio Channels: Stereo
Upmix: Passive
_ Enable AC3 to SPDIF passthrough
_ Enable DTS to SPDIF passthrough
_ Aggressive Sound card buffering
_ User internal volume controls
(none of those are checked)

If I turn on the AC3 and DTS passthrough, I get only noise, a digital,  
choppy, fluttery noise over HDMI. If I use the optical connection (S/ 
PDIF) and change to "Passthrough output device: ALSA:iec958:{ AES0  
0x02 }", the light on my receiver turns on and I get 5.1 audio.

After installing MythBuntu and getting absolutely no audio, I  
discovered that I had to un-mute "IEC958 1" (I think it was that one)  
in alsamixer.

My motherboard's BIOS has settings "Onboard Audio Function" and "HDMI  
Audio", both of which are set to "Auto" (which, according to the  
"Help", means enabled -- the only other setting is "Disabled").

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: NVidia [HDA NVidia], device 0: ALC883 Analog [ALC883 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 1: ALC883 Digital [ALC883 Digital]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 3: NVIDIA HDMI [NVIDIA HDMI]
   Subdevices: 1/1
   Subdevice #0: subdevice #0

$ aplay -L
     HDA NVidia, ALC883 Analog
     Front speakers
     HDA NVidia, ALC883 Analog
     4.0 Surround output to Front and Rear speakers
     HDA NVidia, ALC883 Analog
     4.1 Surround output to Front, Rear and Subwoofer speakers
     HDA NVidia, ALC883 Analog
     5.0 Surround output to Front, Center and Rear speakers
     HDA NVidia, ALC883 Analog
     5.1 Surround output to Front, Center, Rear and Subwoofer speakers
     HDA NVidia, ALC883 Analog
     7.1 Surround output to Front, Center, Side, Rear and Woofer  
     HDA NVidia, ALC883 Digital
     IEC958 (S/PDIF) Digital Audio Output
     HDMI Audio Output
     Discard all samples (playback) or generate zero samples (capture)

FYI, I queried the list about my system in "first build, $695 - extra  
eyes, please" on 4-June-2009
see also http://www.mythtv.org/wiki?title=User:Trogod/System0

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