Some help with NVIDIA 560GTX audio HDMI to Onkyo receiver: Multichannel PCM

[Elrandir]

Hey guys, not sure I can find an answer here but worth a go!

I'm using a NVIDIA 560 GTX and am using HDMI to put audio through to my new Onkyo HT-S4505.
I can push a button called "home" on the remote and see the Audio menu where I can choose "info" to see what the input/output is.

When I play an mkv file which has DTS 5.1 ch audio, the info from the Onkyo shows sound as
Input: HDMI 2 (the port) - Multich PCM - 5.1 ch 48 kHz
(no matter what file I play wether 2ch or 5.1, or winamp, or youtube it says this)
Output: Multich - 5.1 ch


Am I getting the best surround sound that I can and should be getting now? The surround sound seems to be sounding ok in any case I heard crisp sounds in the rear right speaker during one scene of the movie.
I've set AC3, kmplayer and nvidia's sound as the 3/2 + SW speakers but on the audio info I'm not seeing the options of supported formats like DTS and other dolby options, are they omitted by Onkyo because PCM is the best? I'm a bit new to this so sorry if it's a silly question.

[vesseblah]

It's not really straightforward, but will try to answer as precise as possible.

It seems like in your setup the PC is decompressing the original Dolby Surround and DTS tracks and is sending unpacked raw bitstream (PCM) over the HDMI cable to your reciever. If you want the compressed DTS or any other signals to be transmitted to the amplifier you need to tell your video players to pass through the audio untouched. It's also possible that your amplifier tells the PC (over HDMI cable) that it can't accept compressed DTS and it's decompressed into PCM for transporting automagically. At least DVD/BluRay players have this kind of negotiations in place for best possible hardware compatibility.

In theory there's no difference between decoding the compressed multichannel audio on PC and moving it over HDMI uncompressed, or sending compressed audio and decoding it in the reciever, but in practice there could be some slight differences in the way the audio is decompressed and one way or the other might sound better.


Both DTS and AC3 (DD5.1) are compressed lossy, while PCM is lossless coding. PCM is rarely used on movies because it takes significantly more discspace even though it's better quality. New DTS-MA and Dolby TrueHD used on BluRay and HD-DVD discs are lossless compressed audio and equal to PCM in quality.

[Elrandir]

thanks for the explanation, would you know how that's setting called in any program so I can test it? I'm not sure which setting that would be in any, I've been browsing around. Is it disabling audio decoding? or audio processing? - nm doesn't seem to be the cause.

[loki504]

try xbmc. its free and one of the best multy media players i have ever seen.

/edit if you try xbmc make sure you check that your reciver supports dolby truehd and dts-hd.

[Elrandir]

No matter what sound I play, wether youtube, winamp, video files in DTS or 2 channels, the input from Onkyo shows that it is receiving 5.1 multichannel PCM. So I guess that's related to the 5.1 setting in sound options for the nvidia card.

[vesseblah]

So I guess that's related to the 5.1 setting in sound options for the nvidia card.

Yep, probably. I guess the Nvidia card will decode anything you try to give it and feed PCM out. It shouldn't be a problem or affect quality at all, but you might want to check audio latency settings from the amplifier to make sure it's on perfect sync with picture.

[Elrandir]

I just found a setting on my onkyo to set the fixed input from the hdmi to for instance DTS, it will detect it or give an error, no matter what DTS mkv file I play, even a LOTR dvd with dts sound, it doesn't detect it (maybe too old that dvd though). So I'll just have to use multichannel pcm, maybe I'll see DTS work on a blueray in the ps3. Thanks for your help, I'm just happy I'm getting good quality and true surround out of it at least I can hear it! haha.

[TechLife]

I just found a setting on my onkyo to set the fixed input from the hdmi to for instance DTS, it will detect it or give an error, no matter what DTS mkv file I play, even a LOTR dvd with dts sound, it doesn't detect it (maybe too old that dvd though). So I'll just have to use multichannel pcm, maybe I'll see DTS work on a blueray in the ps3. Thanks for your help, I'm just happy I'm getting good quality and true surround out of it at least I can hear it! haha.

I have had 1032 problems using HDMI out from probably 5 different motherboards/video cards what solved any and all isues I had anytime was use the HDMI for the video and run a optical audio(fiber optic) from your motherboard it should have it to the receiver. You onkyo setting under audio will give you the option to choose hdmi or optical for the audio of whatever input you are using. I have had 0 problems with audio doing it this way.

[Elrandir]

I have had 1032 problems using HDMI out from probably 5 different motherboards/video cards what solved any and all isues I had anytime was use the HDMI for the video and run a optical audio(fiber optic) from your motherboard it should have it to the receiver. You onkyo setting under audio will give you the option to choose hdmi or optical for the audio of whatever input you are using. I have had 0 problems with audio doing it this way.

I'm considering getting a longer audio cable to try this just to see how it's transmitted as (if it's also multichannel pcm).

[damitchell]

I am having the exact same issue with 560GTX and a Sony AVR. Using HDMI and getting PCM sound. Will try the optical cable tonight and see if that resolves it.