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In Reply to: A very informative posted by Jon L on March 4, 2007 at 10:23:48:
Like Thomas, I am skeptical of the claims of kmixer being bit perfect - that is not my experience, using exactly the same sort of tests that Thomas describes in his posts.Also the Windows system sounds are 22kHz, not 44.1kHz as claimed. This can be verified very easily by inspecting the properties of the actual wave files on any Windows system.
So something is fishy here, but I'm sure Thomas will get to the bottom of it and we'll find out the answer.
PS - Having said the above, there are also claims on the net about specific motherboards with specific chipsets being bit perfect via SPDIF even through kmixer. Perhaps there is more to this than meets the eye.
Follow Ups:
I can speak to the motherboards since I have one in one of my test machines. Certain older realtek HD-audio drivers for XP hapen to work bit perfect. However, none of the current ones do neither are the Realtek drivers for Vista.The specific machine has an AMD motherboard from Shuttle with an ULI Southbridge that supports HD audio. This was an early HD audio solutuion for AMD CPUs. The codec is a Realtek ALC880 and the S/PDIF worked bit perfect for me when I ran XP on it.
However, I also managed to get the Realtek in my Acer TM 8200 to work bit perfect on the optical output with that old driver version under XP. Demonstrating that little oddity is probably the only reason I can still dual boot that machine.Cheers
> Certain older Realtek HD-audio drivers for XP happen
> to work bit perfect. However, none of the current ones do;
> neither [do] the Realtek drivers for Vista.Would you be willing to reveal where to lay hands on these
earlier Realtek drivers (and/or what versions they are)?I put together a PC with an Asus (P5WD2-E Premium)
motherboard a few months ago (Intel 975X chipset,
Realtek ALC882D HD audio codec), and was disappointed
to discover that the "Realtek HD Audio Manager"
(that came with driver package Release 1.51, for XP)
doesn't even allow you to select 44.1 as the
sample rate.P.S. -- I found your post at
http://www.head-fi.org/forums/showthread.php?p=2592777 .So it appears I need to find driver
5.10.0.5221, eh?P.P.S -- Found a Czech site with earlier Realtek
drivers:
http://www.bgslevi.cz/soubor.php?produkt=ALC8xx&typ=o
driver 5.10.00.5221 seems to be part of Release 1.31
(wdm_r131.exe). Claimed to support ALC882. I
guess I'll find out.
It's a 23MB driver package (Realtek WDM_R131.exe). Search shows a few hits on that.Cheers
Thomas
I couldn't remember the motherboard and/or chip.I'm curious as to how the bits get passed "unmolested". Doesn't kmixer multiply everything by 0.999? Or is that a myth?
Does the bit perfect work ALL the time or "most" of the time? Does it work on both HDCD and DTS or only DTS?
If it's only DTS I'm wondering whether it's due to the same mechanism that enables passing DVD DD/DTS directly to SPDIF unmolested.
It just works for all PCM streams 16/44.1. To be honest I have not investigated why.As a guess I assume the driver registers itself in a way that it performs all mixing itself so kmixer is not in the picture. You can hear multiple streams so some code or firmware is doing mixing.
Cheers
Thomas
Might be worthwhile investigating this, since the Benchmark USB DAC could potentially be doing the same thing?I wonder if it's registering itself as having a hardware accelerated AC97 mixer supporting hardware resampling to 48kHz (but then not actually doing the resampling)?
Hmm,probably worth checking but when the driver/hardware does its own mixing, kmixer is not in the loop.
Cheers
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