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Discussion Starter · #1 ·
I am running a Asus P5N7A-VM and with the integrated NVIDIA 9300 I have been able to get HDMI audio working (NVIDIA 180.11 drivers and ALSA 1.0.18a). However I can not get my setup to pass LPCM, 6-Channel, to my reciever. When playing a video with a 6 channel FLAC file in XBMC I am only getting 2 channels on my receiver. I have spent the last few days poking around the internet to see if anyone has successfully been able to pass LPCM in Linux with the new NVIDIA integrated mobos like mine but I haven't been able to find any useful information. Any suggestions on how to solve this problem?
 

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Discussion Starter · #4 ·
Yeah I have converted some Blu-Ray rips in which I have multichannel FLAC files. So I pose the question again, does anybody know if these new iGPU cards can pass LPCM in Linux like they do in Windows? I can't find information anywhere on the web if about multichannel LPCM on Linux.
 

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Last I checked (couple months ago), this wasn't implemented in alsa yet, but they've probably got it going by now. Check the alsa site for your specific audio chip to see. If it is supported, you'll most likely have to dl and compile a newer version of alsa than you're using.
 

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Welcome to the club, neither do the rest of us.


But one of the privileges of running Linux is the need to research and study, because usually you must learn everything about everything, before you can do anything. Only those with good study habits and an IQ north of 130, end up staying with Linux.


So go forth, learn all about Pulse, and come back and share with the rest of us like we do you.
 

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Discussion Starter · #11 ·
Well it is a good thing that I am stubborn because Linux is not going to get rid of me that easily. Thanks for your input. I also found that the new Linux Kernel, 2.6.28, may have what I am looking for. Found this in the changelog:
Quote:
commit 862f76f86d64c2cf34a7ff5ddf0a175073b76534

Author: Takashi Iwai

Date: Wed Jul 30 15:13:29 2008 +0200


ALSA: hda - set up HDMI channels


Set up channel information for HDMI widgets. This will allow LPCM

with multiple channels supported on some HDMI devices.


TODO: It still doesn't check ELD and doesn't change PCM parameters

dynamically.


Signed-off-by: Takashi Iwai

Signed-off-by: Jaroslav Kysela

I will experiment and let you all know what I find out.


-Will
 

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Discussion Starter · #12 ·

Quote:
Originally Posted by mythmaster /forum/post/15425924


That's right, there's a misprint in the wiki that shows "Stable Release (2008-02-06) 1.0.18a". Looking around a bit, it appears this still isn't supported. Sorry.

mythmaster,

What did you read that makes you say LPCM isn't supported. On the AlsaWiki it says that 1.0.18 that:

- ALSA: hda - set up HDMI channels

Set up channel information for HDMI widgets. This will allow LPCM

with multiple channels supported on some HDMI devices.

TODO: It still doesn't check ELD and doesn't change PCM parameters

dynamically.

(This is the same thing that i posted earlier about the new kernel)


Were you able to find something that says that the NVIDIA Linux drivers don't support LPCM multichannel or was it ALSA specific?


-Will
 

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Quote:
Originally Posted by bahndit /forum/post/15426195


This will allow LPCM with multiple channels supported on some HDMI devices.

On the hda-intel part of that page --> http://www.alsa-project.org/main/ind...Intel_driver_2 I didn't see anything about adding multi-channel LPCM support for nvidia, so I'm assuming it still isn't ready. I could easily be wrong about this, though. If noone here can confirm that it's working, and if you can't find any info anywhere else, then a good idea would be to ask about it on the alsa mailing list.
 

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Quote:
Originally Posted by quantumstate /forum/post/15422590


LPCM is almost always stereo only, at least on DVD.

The source audio doesn't have to be LPCM.


Someone may want the software media player (mplayer, VLC, XBMC, etc) to decode good old fashioned Dolby Digital 5.1, DTS 5.1, DTS 24/96 or the new DD+/DTS-HD codecs in the PC to LPCM, then send it out via HDMI, rather than have the receiver decode these codecs. One reason may be bass management, or the desire to use better quality external processing or better external DACs, etc.


So, the source could be a 10 year old DVD with Dolby Digital 5.1, etc, not just new BluRays with multi channel PCM.


For me, I would just need to use the HDMI out as an SPDIF, i.e. send Dolby/DTS bitstreams (undecoded) and stereo PCM (16/44 and 24/96), but I don't need to yet- no receiver with HDMI inputs. I just use a coax SPDIF out from the motherboard.
 

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Quote:
Originally Posted by quantumstate /forum/post/15425903


Only those with good study habits and an IQ north of 130, end up staying with Linux.


.

...opposed to Windows users of the past 7 years or so, whose IQ's have been steadily decreasing to something south of 80
.


I am actually being serious- MS has very successfully engineered XP/VIsta for the masses, dumbing them down further and taking control away with every service pack and OS release since XP.


There are still many tech-oriented users in the Win forum hacking away at registry's, driver revs, etc, though I think there were more low level tinkerers on the Win forums prior to around 2003 or so.
 

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Quote:
Originally Posted by Rgb /forum/post/15610809


The source audio doesn't have to be LPCM.


Someone may want the software media player (mplayer, VLC, XBMC, etc) to decode good old fashioned Dolby Digital 5.1, DTS 5.1, DTS 24/96 or the new DD+/DTS-HD codecs in the PC to LPCM, then send it out via HDMI, rather than have the receiver decode these codecs. One reason may be bass management, or the desire to use better quality external processing or better external DACs, etc.


So, the source could be a 10 year old DVD with Dolby Digital 5.1, etc, not just new BluRays with multi channel PCM.


For me, I would just need to use the HDMI out as an SPDIF, i.e. send Dolby/DTS bitstreams (undecoded) and stereo PCM (16/44 and 24/96), but I don't need to yet- no receiver with HDMI inputs. I just use a coax SPDIF out from the motherboard.

I think you're stretching a bit with the DD/DTS. There's no good reason to decode regular old DD/DTS and output PCM over HDMI unless you were going to downmix to 2-ch, if connecting directly to a TV or similar. DD/DTS decoded on the PC is going to be exactly the same as DD/DTS decoded by the receiver, assuming both are Dolby/DTS certified decoders. And where the decoding is done doesn't affect the ability to use outboard DACs etc


I do agree that decoding THD/DTS-MA to 6-ch PCM is useful, particularly for those with HDMI receivers that do not decode those codecs..
 

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There are some advantages decoding at the PC Software level.


By decoding it allows the PC to process the channels. This would mean...

Normalization could be accomplished across ALL formats (not just 2 channel stereo as it is now)

Volume control could be an option at the PC level (not just at your amp)

EQ adjustment could be possible at the PC level (your amp doesnt support a 'Dynamic Volume' feature? code it on your pc!)


be decoding at the PC we can add audio features in software instead of buying a new amp
 

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Except a PC is nowhere near as good as a decent amp at these things. Ideally, you'd want the PC to touch the audio as little as possible. I want the decoding and outputting, and nothing else. Any extra features introduce more noise.
 
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