[LINUX] LPCM over HDMI audio resampling questions?
alanwww1 Wrote:Hi Nmiller !

I have issues with navigation sound. It seems to work with the settings you wrote for .asoundrc, but from time to time i loose navsounds. I realized that i loose it in case i play an ac3, dts passthrough movie and i PAUSE it for 3-4 secs and restart it. After that my navsounds dissapear.

Can you test this with your config ?

I believe what you're seeing or rather hearing is the fact that when no sound is being transmitted the signal is no longer being sent from your HTPC, thus your Receiver changes modes. It is something I see as well. As an example...if I am going through the menu's slowly I won't hear some of the menu sounds and if I watch my Receiver while I'm doing that I can see it losing the signal...but if I'm going through the menu's quickly the signal never drops and the Receiver plays all the sounds. Try moving around the menus quicker and watching the Receiver and tell me what happens.

I don't think this is specific to XBMC but rather hardware related because I see this in Windows as well when XBMC isn't even running. It may even just be specific to HDMI but I haven't tested enough to prove that.

If you're seeing this as just a linux problem I don't know how much help I can be...I'm really a linux noob. I've been a PC guy for ages, am a IT Network/Security Engineer by trade and have had to touch on linux here and there but never anything too advanced. Most of my stuff I've figured out has been due to hours and hours of reading and research in multiple forums and a lucky guess or two...if it wasn't for others posting their success and knowledge I'd probably still be at step 10 out of 50 Smile

Good Luck!

ultrabrutal Wrote:Not a sound is heard via my Onkyo 876 receiver (7.1 setup) nor the Pioneer KRL-37V TV. Tried both hdmi and plughw:0,3.

I'm going crazy here... Any ideas guys?

Take a look to this post:

plue Wrote:With NVIDIA driver if you disable EDID in xorg to use Modlines of standard HD resolutions, you will lost HDMI audio.

You can check by enabling again EDID (the default behavior).

But if you don't want to use the EDID resolutions nor any other options, you should use this options:

Option         "RandRRotation" "False"
    Option         "TwinView" "False"
    Option         "UseEdidFreqs" "False"
    Option         "UseEdid" "True"
    Option         "ExactModeTimingsDVI" "True"
    Option         "UseEdidDpi" "False"
    Option         "DynamicTwinView" "False"
    Option         "ModeValidation" "AllowNon60HzDFPModes,NoEdidMaxPClkCheck,AllowInterlacedModes,NoHorizSyncCheck,NoVertRefreshCheck,NoDFPNativeResolutionCheck,NoVesaModes,NoEdidModes,NoXServerModes,NoPredefinedModes,NoUserModes"
    Option         "UseEvents" "True"

I already had alsa 1.0.20as i'm running kernel 2.6.30.
My alsa-utils from debien testing repo are 1.0.20 too.

I've patched as mentionned in this post the patch_nvhdmi.c, recompiled modules, installed and loaded them.

Unfortunatly i still only have stereo sound with speaker-test or any other test i've made.
No other channels.

Do you think i should recompile asla 1.0.20 from git ? Or did i forget something important to recompile than only the related nv module ?


Need your advice on my issue.

hotlobster Wrote:Hi,
I've patched as mentionned in this post the patch_nvhdmi.c, recompiled modules, installed and loaded them.

Unfortunatly i still only have stereo sound with speaker-test or any other test i've made.
No other channels.

Could be that you have: "MCP67 HDMI" or "MCP73 HDMI".
This models only support stereo.

You can see it if you look to the snd_hda_preset_nvhdmi static structure in the patch file.
I have a MCP79 chipset, so it's supposed to works normally i think.
hotlobster Wrote:Unfortunatly i still only have stereo sound with speaker-test or any other test i've made.
No other channels.

Do you have Xorg up and you are viewing Xorg content on the screen? (you see gnome or kde or whatever that use Xorg.

Ensure that your Xorg with latests nvidia drivers and the config to use EDID (the default behavior).

Ensure that when Xorg is started when your HDMI cable is connected to an amplifier that had previously turned on.

Try 8channels 16bits.
What's the status on this one?

Is it possible to get correct mapping, unaltered bit depth and sample rate when using LPCM output over HDMI?

What is the current status of 8 channel LPCM over HDMI for the modern NVidia chipsets with Alsa 1.0.21(a)? I noticed that in the changelog for the 1.0.21 version it states:

- ALSA: hda - Support NVIDIA 8 channel HDMI audio

does this mean that the patch is no longer needed?

I would test this myself, but atm my receiver doesn't support LPCM over HDMI and would like to buy a new receiver if all the major problems have been sorted out. Has alanwww1 or anyone else tested the latest Alsa version and if you have do we still need to manually edit something to get all bit depths and sample rates working?

Edit: I just downloaded the Alsa source and took a look at the patch file that is now part of the source. It seems to be only enabling 48kHz and 16bits. So it seems that first downloading the Alsa source with the latest Alsa update script and modifying the patch:
    .rates = SNDRV_PCM_RATE_44100 | SNDRV_PCM_RATE_48000 | SNDRV_PCM_RATE_96000 | SNDRV_PCM_RATE_192000,
    .maxbps = 24,
at appropriate lines and then proceeding with the installation would do the trick.
Following this thread it would seem that people have had success in getting multi-channel audio working out of their Nvidia integrated motherboards over HDMI. Unfortunately I was not able to get the same result on my setup.

I have a Zotac ION based MiniITX running Ubuntu 9.04 with the 2.6.28-14-generic #47-Ubuntu SMP kernel. I have used the Alsa upgrade script to bring my Alsa drivers/libs etc up to v1.0.21 and I am running a recent trunk build of XBMC (needed to playback local freeview recordings).

I can only get stereo out of XBMC and speaker-test does not produce any output (which seems strange). This setup is designed to replace my existing original XBOX running XBMC but so far it can't compete when it comes to surround audio.

To be sure that the recently patched 8ch Alsa code was being loaded I updated the info string in the nvcodec module to include "8ch" which I can see when I do an aplay -l :

aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: NVidia [HDA NVidia], device 3: NVIDIA HDMI 8ch [NVIDIA HDMI 8ch]
Subdevices: 1/1
Subdevice #0: subdevice #0

All of my testing is done with X running using the latest NVidia graphics drivers. I would love to get this working, any help much appreciated.
I have updated my 9.04.1 LIVE install to 9.04.2 (on a usb stick) using Putty from a Windows PC using this guide:


Before i upgraded, my Zotac ION330 board would only send 6 channel AAC encoded audio via 'hdmi' or 'iec958' as Stereo PCM. I was informed that this was a limitation of the current drivers for the ION330 board. I was directed to this thread but did not want to apply a patch i didnt really understand (im new to linux), so decided to live without Multichannel PCM from AAC audio for now.

Following my upgrade, 6 channel AAC encoded audio is being seen by the amp as 'multichannel pcm' and no longer as stereo.

Doing the speaker test 'speaker-test -Dhdmi -c6' sound comes through each channel seperately. Unfortunately, the channels are not set correctly as described in this thread.

I seem to have applied this patch by upgrading XBMC. How is this possible?
Has the patch been added to the current build?

My channels are set correctly when i read from AC3 (dolby) encoded audio.

Can i apply a change to fix the channel placements for AAC and not change them when i listen to AC3? (I Dont want to fix one thing by breaking another.)
@chris2922: Can't help with the channel problem as I still don't get more than Stereo PCM but I assume that it will take some Alsa config trickery to get the channels sorted.

Great to hear you made some progress, can you please describe the current state of your setup, kernel version, alsa version, NVidia driver version, any alsa config files in use (/etc/asound.conf or .asoundrc), XBMC audio settings etc.
I will post a detailed guide how to set up alsa for multichannel hd audio with RIGHT speaker matching.

I just need a little time, but i think somewhere this week you will get it.

I will open up a new thread about it.

I am in contact with an Alsa developer who again promised to add the patch for enabling hd rates to the kernel tree, so soon there will be an easier setup. But for the mixed channels there is only the custom .asoundrc file solution so far. I will post that too.

Stay tuned !
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.
Please help out a confused guy a bit... Do I understand correctly that this patch solves getting 44.1 kHz audio pass through with nVidia cards (i.e. with my Asrock ION box)? I really don't want my audio to be altered in any way before reaching the receiver...
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