How to get bit perfect playback, DTS5.1 and Dolby Digital 5.1 in MP

[KevL]

HI


I have finally worked this out.

Hope it helps.


Kev

[jameson_uk]

I believe I am getting bitperfect payback (files play back at 44.1 KHz or 48Khz correctly).

I use a CMedia based card with some alternative drivers from Dogber cmediadrivers - Google Code which seem to do the trick.

I got an Overclockers value card for abut £12 which was based on this chipset but I notice you can't seem to get them anymore. Did a little searching and came across this for £5.99 and looks like the same card as mine.

This combination of card and drivers seems to do the trick and is cheap

[KevL]

£5.99 for bitperfect playback sounds like a bargain. Cheaper than an M-Audio Card.


K

[edterbak]

KevL,

Question. Is the same possible with an ATI 3xxx graphics card which is able to output HDMI video PLUS audio over an DVI>HDMI dongle?
At the moment I sometimes have proper sound (5.1). I use this DVI>HDMI dongle from ATI in combination with my HD3450. Basically it adds a SPDIF stream to the DVI output. There is a little connector between the mainboard and the ATI card. What do you think. Possible?

[jameson_uk]

Originally Posted by edterbak

Question. Is the same possible with an ATI 3xxx graphics card which is able to output HDMI video PLUS audio over an DVI>HDMI dongle?
At the moment I sometimes have proper sound (5.1). I use this DVI>HDMI dongle from ATI in combination with my HD3450. Basically it adds a SPDIF stream to the DVI output. There is a little connector between the mainboard and the ATI card. What do you think. Possible?

As I understand the graphics card sound make no difference. It just takes a SPDIF output from your soundcard (in your case it sounds like onboard sound) and combines this with it's video output. I believe you just need a soundcard (and drivers) which support bitperfect playback.

I see there are lots of threads on various forums about people having problems with this but I think it comes down to settings rather than what it is capable of. Someone with this hardware will have to confirm (I just use SPDIF from soundcard straight to my amp) but I am fairly sure the video card is not touching your audio signal so it should be possible.

You say you sometime have property 5.1, what does this mean.... have you tried the test files linked to in the document ? Does your amp have an OSD to tell you what signal it is receiving ??

[KevL]

Hi Edterbak,

I'm not sure about how how your particular MB/graphics card combo work.

Basically the key is to have sound drivers which can pass unprocessed sound via SPDIF to your receiver. For best convenience the drivers should simply pass through SPDIF at its native sample rate. I dont think the way you take the SPDIF signal to its destination matters. Whether you pass it into your HDMI lead via the dongle or just send it in a seperate lead shouldn't affect this (I would guess).

The only question is, will your drivers which put out the SPDIF stream do so without interfering with the stream?


Can you send DTS5.1 successfully to your amp via SPDIF? If you can then you probably have bit perfect sound working and you can connect via your dongle into your HDMI lead - or otherwise - at your convenience.


K




Kev

[edterbak]

I followed you instructions. Of course I dont have a separate soundcart. I use the ATI sound instead. I have disabled the onboard audio itself in Hardware>Devices. This is how I get good and decent audio out of the pc.
Now, I am able to play MKV files and use 5.1 audio in it. MP uses the standard MPA audio decoder in that situation (set to spdif)
In the music section I hear white noise with the standard bass player the PureAudio plugin. If I use the Mplayer plugin I get a normal sound out of my amp, but its in 2 ch stereo only... weird thing it is.

edit
I just noticed that the MKV file uses 48khz. Maybe because it doesnt need to be touched by windows its OK in this situation. 48khz in and 48khz out I believe. The DTS files are in 41.1khz? This could explain things like you said in your document...

[KevL]

Edterbak,

Does your reciever have a way of telling you what format it thinks it is getting from your HTPC? Is it seeing your DTS5.1 audio as a 44.1k stream?

Maybe your sound card is not autoswitching to 44.1KHz for DTS? I have no problem using the BASS player in MP. Once you have disabled its fade-in and crossfading etc it works fine. Of course you must have your PC volume set to 100%.

On my setup I get perfect dts5.1 playback in BASS via SPDIF - but if I turn the volume down - even to 99% (rather than 100%) then I get hissing and no music. Maybe your gain is being reduced by a well hidden control.


Kev

[edterbak]

ah... yes. Just found something. Receiver says its getting 384kbps, 48khz, 3/2/lfe, Dolby digital. atleast this is what I get with a MKV file. When I play the 44.1khz file the receiver gets 48khz pcm...

So probably the switching

[KevL]

yes, I suspect your sound card is resampling to 48k. This will prevent proper dts5.1 playback.

This is really annoying. Just passing the stuff out without messing with the signal is very much easier than resampling etc - yet many sound cards wont do it.

You could try the cheap card mentioned by jameson. It has got to worth a try for £6.

The other option (not as nice though) is to set your onboard sound card to 44.1Khz (if it is possible) and then use your ati card for 48kHz. Then use two seperate outputs to your amp. One for music and the other for film. Of course you then have to switch inputs on your amp.

Kev