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Resampling mixer bad. Digital level control - not necessarily.

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In Reply to: Re: not exactly like thought.. posted by PM on March 6, 2007 at 15:12:58:

PM:
First off, I am not sure why you have a windows volume control working if using ASIO or KS. Just don't select any device that you are using (say, for example, use an onboard codec) as the Windows Default Playback device.
With most ASIO soundcards, you get a DSP mixing suite. This means there IS a level control for the device, but it's NOT the kmixer, it doesn't resample, and if set to "100%" or "0db" it's not altering the data in any way. The only trouble with digital volume controls is that the effective dynamic range decreases as you decrease volume.
PM: "So my theory is that even if you use ASIO or KS, you should always check the "Do not use audio feature of the device".
I'm thinking this won't work in all cases - I just proved it does work when using ASIO and the Creative X-fi.
I will try this with the M-Audio Revo (which also has an ASIO driver) and see if it does the same thing. When you disable "audio features" on the device, you also disable "mixer" and "midi" features of the device which may be required to use ASIO.
The crux of the above is that an ASIO based DSP mixer is not one in the same with the Kmixer.
Cheers,
Presto

Follow Ups:

Re: Can DirectSound play without any device - like KS ? - PM 13:29:24 03/07/07 (2)
Here's one more observation that I am having a tough time understanding -
I have a soundcard installed and working properly, but I do not have any devices listed in the "Sounds and Audio Devices", obviously
because I have selected "Do not use audio features" for that device/soundcard. So there is no Window's or the soundcard's mixer/panel available, and any application like WMP, Messenger, windows sounds etc. cannot see this device and wont play.
All that is fine and as expected.
However, fb2k can play just fine via DirectSound. I was expecting it to play KS but not DS. At this point how is KS different (or better) than DS ? Is the flow of data through the layers (mixers, drivers) any different between KS and DS, in this situation ?
- If the device supports it nativly. - rick_m 23:36:14 03/17/07 (0)
  Hi,
  I see this is a rather old thread, but a while back I tried to sort this stuff out and found, like you guys have, that it's a bloody morass. Gleaning what I could from the stuff on MSDN I think part of the confusion is that each device can set up the virtual signal paths ("exposed pins") differently, and pick and choose what functions it wants to handle and which are left to Windows. So it's likely a whole new game for each device. Bottom line, I finally gave up all hope of really understanding it.
  Like you I found that one of the "devices" I was playing with, I think it was the on-board Realtek chip and driver, seemed to support DX10 as a native format so that it could be accessed directly when not mapped through the Windows audio stack. As far as sound quality, DX seemed fine to me. I also played with ASIO but not KS.
  Good luck. Please pass on what you learn...
  Rick
- Direct Sound versus Kernel Streaming. (Need others input here...) - Presto 16:58:39 03/07/07 (0)
  Dammit PM!
  You're asking REALLY good questions here! lol
  AGAIN I thought I knew this one too. I was under the impression that to get away from the windows audio stack and bypass the kmixer you needed to use either:
  a) ASIO output plugin to ASIO driver (ASIO)
  b) ASIO output plugin to ASIO4ALL (actually kernel streaming)
  c) Kernel streaming output plugin (kernel streaming)
  As for Waveout and DirectSound? I thought BOTH used Kmixer.
  Perhaps others can chime in here. Most folks around here use either kernel streaming, ASIO or a USB output.
  USB outputs vary quite a bit. This depends on whether they use the windows driver (usbaudio.sys) or a custom driver. If it's a custom driver, what exactly it's doing can vary quite a bit.
  Now, if you are using directsound, and you can pass a DTS track through (with volume at 100% - no higher or lower) and your receiver auto-detects the DTS format, then SURE... the file has not been munched by Kmixer. This would be a great test.
  You'd be surprised how much of what is "common knowlege" gets quickly debunked from time to time. The rumor-mill and "forum knowlege" in PC Audio is deadly. Not out of malice or anything... it's just that a lot of this stuff is very poorly documented (if at all) or reads like a NASA white paper, or is simply very counter intuitive.
  That's why your questions are excellent ones.
  Cheers,
  Presto

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