SPDIF / Analog Audio

[FuZoRBlade]

I have connected my computer to my amplifier through the SPDIF Optical out port on my motherboard. In the AVWizard, I select the SPDIF Optical option for audio and I get no sound. When I select Analog, the sound comes clearly, but then obviously I cannot play DTS or Dolby sound, it only outputs as PCM.

Why is the SPDIF connection only outputting analog audio???

[colinjones]

FuZoRBlade - SPDIF cannot output analogue of any kind, it is a digital only connection. Do you have any other audio connectors to your amp (eg line/RCA/phono cables)? If not, then it must be outputing digitally through the SPDIF connector - I have no idea why it only does this when you choose analogue, but it isn't possible for it to transmit analogue over that connector...

[teedge77]

Pulse-code modulation (PCM) is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals, then quantized to a series of symbols in a digital (usually binary) code. PCM has been used in digital telephone systems and is also the standard form for digital audio in computers and the compact disc red book format.


still digital. you may be selecting analog but it isnt. have you tested to see if theres any surround capabilities to it after you select analog?

[FuZoRBlade]

I o not have any other audio connetors to my amp at all.. All i have is the optical out... I checked on the amplifier and it doesnt have surround sound at all, just left and right channels. the PCM light is also on. In the AVWizard if i select SPDIF Optical, it wont play any sound at all, even after i close the wizard and pop in a DVD. When I select analog it plays all my sound in analog, but its ONLY connected to my amp through SPDIF Optical..

[teedge77]

i dont understand what the problem is then. what does the setting matter if you are getting the sound still? its digital sound...you dont even have surround sound.

[FuZoRBlade]

I want to be able to play dolby digital and DTS audio.. Im only getting two channels of audio through SPDIF, when i should be getting full 5.1

Thats my problem. I'm getting audio.. but its not surround sound, and it should be. I inserted DTS dvds and dolby digital DVDs, both played in two channels.

[teedge77]

I o not have any other audio connetors to my amp at all.. All i have is the optical out... I checked on the amplifier and it doesnt have surround sound at all, just left and right channels.

can you describe your setup more? what amp? you keep saying you want 5.1 but you just said you only have two channels.

[FuZoRBlade]

Ive got a full 5.1 setup connected to my amplifier. my amplifier is a yamaha RX-v3200. I have connected my computer using optical out to the yamaha receiver. When audio plays on the media center, i look on the reciever and it says that it is only receiving information for the LEFT and RIGHT channels. Whenever I insert a DVD in an external standalone DVD player and play a DVD, It shows that it is receiving information for all of the 6 channels. This is NOT the DVD player in my computer, this is a standalone DVD player.

does this shed more light on my situation?

[teedge77]

ummmm....a little....except you never told us what kind of motherboard you have.

[FuZoRBlade]

Motherboard in this computer is an Asus A8N5X

[colinjones]

FuZoRBlade

I think both teedge77 and I were confused by the same message - you seemed to be saying that you only had the optical out from your amp connected, but I now assume you were talking about the optical out from your motherboard; and then you said your amp doesn't have surround sound at all - again, I am assuming from your later post that your amp is capable of surround sound but isn't receiving a surround signal from your motherboard. With these assumptions in place, I think I know understand - but unfortunately it doesn't really help me help you fix the problem!

Either way, the SPDIF out is only capable of digital transmission of the audio signal, any analogue signal would be rejected and "gated"  by the circuitry. So for whatever reason, your motherboard/LMCE is only directing your (digital) audio signal to the SPDIF connector when you choose the Analogue setting (bizarre!) and no signal at all when you choose the the SPDIF signal - this is the only set of circumstances I can think of that would explain the behaviour you are seeing.

The only thing I can think of that would allow for this combination of weirdness would be a driver problem, or very remotely a hardware problem on the board. Either way I don't know enough about the drivers to help any further here - over to you teedge77!

[teedge77]

well i dont know much about ALSA but i checked around a little. maybe this link will help. if not, your best bet is to search around for "alsa nvidia ck804"


http://ubuntuforums.org/showpost.php?p=553082&postcount=5"


let me know if those instructions work for you.

[12345p]

When you play a movie, the sound card actually doesn't do the 5+1 channel encoding, the 5+1 channel information comes direct from the DVD through the spdif cable.

It is quite likely that the audio source (such as a recorded TV show via tvtuner card or mp3/cd audio) was originally only 2 channels. Your receiver is only getting 2 channels because the linux driver cannot convert a 2 channel audio signal into 6/7/8 channels on the fly. In order to do this, a technology similar to this is required:

http://www.dolby.com/consumer/technology/dolby_live.html

There was at one time a sound card that actually did this: nVidia Soundstorm on the nforce2 chipset (MCP-T) and the original X-Box (I think).  Creative labs never did Dolby Digital Live. Some new variations of the cmedia chipset can also do this, but only on XP as far as I'm aware:

http://www.cmedia.com.tw/?q=en/dolby_live

A driver was available for both Windows XP and Linux for the nFoce2 SoundStorm MCP-T (No driver is available for Vista and no driver that I'm aware does it in ALSA - nVidia provided source? binary blobs? for OSS and as far as I'm aware the driver didn't work in OSS v4).

Does anyone know if it's possible to apt-get oss v3.x and the driver anymore?

[macca]

from the wiki : http://wiki.linuxmce.com/index.php/Sound_Cards

CARD               CHIP                          TYPE                             PCI                SUBSYTEM       NOTES
NVidia CK804     Realtek ALC850 rev 0     on-board (ASUS A8N-E)     10de:0059     1043:812a     Analog Stereo works, S/PDIF output doesn't work