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In Reply to: DAC-1 USB Implementation posted by jdubs on March 3, 2007 at 19:26:26:
I thought there was one sure-fire test to test if an audio stream was resampled... the DTS test.You simply play back a dts track through a device that has a SPDIF output. If your receiver is set to "audio" it WILL auto-detect the DTS format. If the stream was resampled, you'll get a nice blast of pink noise.
Anyone care to confirm or deny this *seemingly sensible* test?
I have Holst - The Planets in DTS.
Guess what I am going to try tonight...
I will set my default Windows Audio Device to my soundcard and get SPDIF working using waveout or directsound. Yeah. THAT should get the old kmixer working.
I think you *can* get 44.1 OUT of the kmixer. But *internally* the kmixer does it's MIXING at 48khz. How could you *mix* different sample rates and bitdepths? I thought you needed to have identical sample rate and bitdepth at SOME point to mix digitally...
The article claims no "resampling" is done. I think kmixer might resample BACK to the input sample rate... but only after resampling to the default 48khz at SOME POINT in the stream.
Another question is: are we talking kimxer under AC97? Or the new Intel HD-Audio spec? Not the same thing!
I dunno. Those "answers" by the engineer seem just too good to be true based on a collective "experience" with kmixer.
I don't care if it just *works* - I am not a gamer who want to hear my friends sign in and out of chat over my game sounds! We need to be able to account for each step in the process - and know what each is doing to the stream along the way. If you're doing NO DSP crossover or room correction processing, you should be demanding bit-perfect playback.
Otherwise why use a PC at all?
Follow Ups:
< < you should be demanding bit-perfect playback. Otherwise why use a PC at all? > >If that's why you are using a PC, you are spending a lot of time worrying about nothing. The cheapest stand-alone CD player will deliver "bit perfect" playback.
The only reason programs like EAC need to re-read the data multiple times is because they are trying to read at 52x (or whatever). Then you will get read errors. But a normal CD player will never have read errors unless the disc is physically damaged.
For more info on this, go to the Stereophile website and look at some of the old articles written by Robert Harley in the early '90s.
Hey Presto - I tried the DTS test one time with a Sony Vaio laptop and an M-Audio Transit (hooked up to a Denon receiver). I played a DTS file with WMP 10 and lo & behold it worked. Just for fun I found out what happens when I drop the volume to less than 100% - that blast of pink noise you were talking about. So when you test, make sure all your pc volume controls are set to MAX.So you *can* get 16/44 out of kmixer. I think it is a false rumor that the kmixer always resamples to 16/48. But it probably depends on what device you are using.
BTW, the Sony laptop probably had the Intel HD-Audio spec, but I'm not sure what difference that makes since I was not using onboard audio.
The Transit is not using the system provided USB audio driver and the custom M-audio driver is known to bypass kmixer.Cheers
nt
I've encountered a similar situation. I was able to get HDCD playback with MP10 and also Itunes (6.0 ?) With each player, I lost HDCD lock when lowering the media players volume. This was with my old Terretec 2496. Can't make the same happen anymore with my EMU 0404.Greg
Apparently if your device driver advertises itself as having a "hardware mixer" and promises to be compliant to AC97, Windows will let it do the mixing instead of using kmixer.For example, my Audiotrack Prodigy 7.1 will play back DTS files fine, because it *has* a hardware mixer. I think this is also the case for some of the other soundcards based on the Via Envy chipset.
The reason why this discussion is interesting is because the Benchmark USB DAC claims to use generic XP USB drivers, which (I think) do not register as having a hardware mixer to the OS.
PS - a clever idea would be to claim to have a hardware mixer even if you don't, and implement software mixing in the device driver.
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