sp/dif, lossless, iTunes and resampling/processing

[atledreier]

I have recently hooked my PC to my HT via digital coax cable. I have ripped my most played CDs to apple lossless, and I'm loving iTunes fullscreen on my LCD.

BUT!

I firmly believe the sound is degraded quite a bit compared to playing directly off a CD player. I noticed iTunes have a volume control, so there is at least some processign there. Might be some resampling going on somehwere. My surround processor have no option to display the current input format, so I have no way of checking what my PC is sending, but it sounds flatter and more 'grainy' to my ears. Is there a way to ensure an unprocessed bitstream from a lossless format? I don't care if i have to use another player, but a full screen slick presentation like iTunes is preferred.

I use Vista ultimate, so I can use Media Center. Also, my ouput is via onboard audio on an Asus P5N32-SLi motherboard.

[nova]

I wonder if there is an ASUS utility that would show you whats going on with the on board sound ???
Or maybe something in the Realtek audio panel?

[Josuah]

For starters you can decouple the electrical of your computer and receiver by sending over optical. That might also let you stop using the computer's volume control completely. Not sure, but that's how it works for me over Airport Express.

Another possibility is the reclocking circuit of your receiver isn't so great, and so the jitter associated with the coax output is causing problems. Although arguing over jitter is whole can of worms.

[yourgrandma]

I agree that optical is a better route to take. I wonder if there is any real gain to be had by using a sound card rather than on board. At least you'd be getting better performance fron your computer. I know I heard a difference, but that was also a jump from a HP out to an optical connection.

As for getting rid of the volume control, I haven't found that ability. I can count at least three times the signal hits a volume control in my computer. I just set them all to full.

I can notice a difference when comparing my CD changer to my PC, as well, and I think it's a software issue with my sound card. It has no direct mode to bypass all the shiny effects kids love to use with their logitech speakers.

[atledreier]

I've read a few guides... apparently there is a wrapper driver that will bypass all the fancy bits and output unaltered 44.1/16 bitstream. It's called AVIO. I haven't tried it yet, I went back to using my DVD drive as a transport. I will try it soon, though. I'll post any experience, good or bad here.

[Josuah]

yourgrandma wrote:

As for getting rid of the volume control, I haven't found that ability. I can count at least three times the signal hits a volume control in my computer. I just set them all to full.

All full might be right, but might not. Especially if it's going through three passes. Basically you want zero attenuation or boost occurring through all three, and it might be hard to figure out what that is. Full might actually be a boost.

[yourgrandma]

Well if I switch between the computer and my changer, the levels are perfectly matched, so I have to imagine its pretty much neutral or close to it.

[bobgpsr]

The old way under Windows XP to have the audio bypass the Windows mixer was to use a ASIO driver. I have used such a driver with Foobar2000 with good results.

Vista completely re-did the audio processing to maintain better quality. IIRC the ASIO drivers do not work with the new Vista audio handling. But the audio quality is greatly improved (I use Vista 64 Home Premium on one of my PC's). Like it very much and now I just use the built-in WMP and the motherboard's Realtek, Vista compatible, drivers.

[nova]

I assume you have checked into your sound properties in control panel and set your SPDIF interface properties. Also make sure you do not have any enhancements turned on (virtual surround, speaker phantom etc.) You may also want to check your other programs and make sure you do not have any of this stuff turned on.

Not really up on Vista, but what about IMMDeviceEnumerator or WASAPI or does that really complicate things?