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My tests over kmixer effects, Seem to be none...
KikeG
post Jan 16 2003, 09:40
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WinABX developer


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I've been doing some tests over kmixer effect, both using standard waveout and directsound, connecting my TBSC digital output to my Audiophile digital input, under WinXP (no SP1), and I'm sure that with a single stream at 48 KHz, with the TBSC mixer volume at max, the kmixer doesn't touch a bit of the audio stream, it's sent bit-perfectly to the output of the card. At 44.1 KHz I can't be so conclusive, since the TBSC resamples everything to 48 KHz and I've had some problems to test it the same way, but according to my analog measurements in loopback mode of Audiophile output, there is no trace of signal degradation over the 44.1 KHz played data.

...So it's very possible that this kmixer sounding worse than ASIO or k.streaming is our old friend mr. placebo entering into scene again. wink.gif

Anyway, I'll do some more tests in the future.

This post has been edited by KikeG: Jan 16 2003, 09:42
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KikeG
post Jan 20 2003, 13:00
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WinABX developer


Group: Developer
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Member No.: 137



I have only one computer too, but two soundcards in it. I've doing some more tests this weekend.

I've not been able to loopback the digital in and out of the Audiophile, no matter what I try, using latest drivers for both XP and Win98. Your card uses same drivers, but if you are able to record digitally I guess the hardware must be a little different. If using ASIO/KS you get bit-perfect results, that proves it works in your case. (don't try ks of foobar because this prog. already changes the data due to additional internal processing)

In order to check bit-perfect reproduction, I connected the digital output of my TBSC to the digital in of the Audiophile, but this works well only for 48 KHz data, since the TBSC resamples 44.1 KHz.

After doing more tests using this system, I've concluded that, at 48 KHz, the data played is bit perfect. I've checked this recording 20 sec. of music, manually adjusting the starting offset of it, and then mixing with it an inverted copy of the original data, in CEP. The result is all zeroes, that means that the data was exactly the same. This works no matter you use waveout or directsound.

With 44.1 KHz data I've found some differences. It's impossible to use same method because the TBSC internal resampling changes slightly the data depending on what OS and software are you using. In this case, I've relied on traditional signal quality measurements (SNR, dynamic range, frequency response, low level distortion and graphical analysis of the noise spectrum) both using the digital output and the analog output of the TBSC, obtaining same results in both cases. In case of analog output, analog recording was done with the Audiophile in 24 bit mode to obtain greater precision.

I've found that, in case of the TBSC at 44.1 KHz , waveout output uses kmixer resampling whereas directsound and kernel streaming use internal hardware resampling. Kmixer resampling is easily detectable, and offers slightly better high-frequency response (hardly audible), but a noticeably worse SNR due to increased digital distortion (audible? could be, for good systems/ears/music). Disabling directsound acceleration of the card (also called hardware mixing, etc), kmixer gets in too, getting same as with waveout. So, ks and hardware-compatible directsound output offer indistinguishable quality according to these measurements, but waveout distorts a little bit more the signal.

However, dropping the TBSC and looping back just the Audiophile analog in and out the results are the same no matter what I use:waveout, directsound or kernel streaming, or W98 waveout. No difference according to these analog measurements, so I can guess that kmixer does never kick in, in this case. I didn't try ASIO, but I assume there will be no difference.

So, my conclusion: kmixer changes the data depending on your card, drivers and output method. Directsound is not supposed to change the data, at least if your card offers directsound hardware support (hardware mixing or acceleration), but kernel streming is more secure. With good semi-pro cards I guess kmixer won't change the data in any case, but I've only checked this for my card.

Note: all this holds with the mixer wave slider at max. in the case of the TBSC, and with the Audiophile patchbay/router set to hardware output connected to wave output (no monitor mixer selected at the hardware output, please). Otherwise the output data may change due to re-scaling of the data.

I've seen that kmixer acts when simultaneous different sampling rate signals are sent to a non-resampling card (Audiophile in my case) or when the sampling rate/bitdepth is not supported from the card. I've seen also that the resampling quality slider in the audio devices control panel applet only ahs effect when kmixer resampling happens with directsound signals. With waveout signals, kmixer resampling quality is always the max. possible. All this happens as said by Microsoft.

Another note: SSRC resampling is better that TBSC (and any other AC'97 card) resampling, and "more" better than kmixer resampling, so this is another viable option.

Hope this clears up (if possible (?) ) the issue.

This post has been edited by KikeG: Jan 20 2003, 14:19
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Posts in this topic
- KikeG   My tests over kmixer effects   Jan 16 2003, 09:40
- - thomaspf   Could you describe this setup in a bit more detail...   Jan 16 2003, 20:02
- - KikeG   I used WinXP pre-SP1. As I said, at 48 KHz, I use...   Jan 17 2003, 09:46
- - kaiwei   Did anyone actually claimed that it sounds better?...   Jan 17 2003, 11:52
- - KikeG   I don't think anybody has claimed it sounds be...   Jan 17 2003, 12:06
- - dev0   So basically all of thomaspf claims turn out to be...   Jan 17 2003, 16:17
- - thomaspf   Very interesting. All the experiments I did came a...   Jan 17 2003, 17:17
- - Pio2001   Loopbacking a soundcard into itself can lead to pr...   Jan 17 2003, 18:43
- - thomaspf   Interesting. I thought input and output of this ca...   Jan 17 2003, 19:21
- - KikeG   thomaspf, there's one thing I don't unders...   Jan 18 2003, 17:59
- - thomaspf   Strange. I have an M-audio DIO24/96 and I have no ...   Jan 19 2003, 06:11
- - Pio2001   Actually, long ago, I managed the same loopback wi...   Jan 19 2003, 14:51
- - thomaspf   Windows has supported a various driver models over...   Jan 19 2003, 18:03
- - thomaspf   A few more results. First I recreated this little ...   Jan 20 2003, 08:42
- - KikeG   I have only one computer too, but two soundcards i...   Jan 20 2003, 13:00
- - KikeG   So, all software that uses waveout (WinABX, abc/hr...   Jan 20 2003, 13:03
- - KikeG   thomaspf, make sure that in the settings of the pa...   Jan 20 2003, 14:50
- - thomaspf   Looks like we are getting on the same page here...   Jan 20 2003, 18:32
- - KikeG   In my Winamp 2 directsound plugin, I have no optio...   Jan 21 2003, 10:15
- - thomaspf   My DAC/surround sound proc is on it's way back...   Jan 21 2003, 21:58
- - KikeG   Ok, I've managed to get decent drivers for my ...   Jan 24 2003, 17:14
- - Continuum   QUOTE (KikeG @ Jan 24 2003 - 05:14 PM)Ok, I...   Jan 24 2003, 17:41
- - thomaspf   @kikeG I am expecting to get my DAC back this we...   Jan 25 2003, 00:31
- - KikeG   QUOTE (Continuum @ Jan 24 2003 - 05:41 PM)I h...   Jan 26 2003, 14:38
- - KikeG   Player: Winamp 2.81 Drivers: latest M-Audio Dio24...   Jan 26 2003, 14:41
- - thomaspf   I finally got my DAC back and repeated my tests vi...   Jan 29 2003, 08:46
- - Continuum   Are you sure that all volume levels are set to max...   Jan 29 2003, 11:53
- - KikeG   Yes, that could happen, but depends also on the se...   Jan 29 2003, 14:38
- - thomaspf   I set everything up as it shoud and also consulted...   Jan 29 2003, 19:07
- - thomaspf   Here is another tidbit. I had a conversation with ...   Feb 3 2003, 00:09
- - KikeG   This is strange, I hope I had a DTS decoder to mak...   Feb 3 2003, 09:25
- - Pio2001   I get bit perfect digital playback-record in loopb...   Feb 9 2003, 07:26
- - KikeG   I think the relevant results here would be for 44....   Feb 9 2003, 20:16
- - thomaspf   I just checked the Marian WEB site. It looks like ...   Feb 9 2003, 21:10
- - KikeG   OK, I've performed several RMAA (RightMark Aud...   Mar 6 2003, 16:35
- - KikeG   Well, a couple of months ago I managed to get mi C...   Jun 30 2003, 13:03
- - KikeG   Well, I just did a few more tests. I own now both ...   Aug 1 2003, 17:55
- - balazer   I understand that you need to use something like A...   Aug 19 2003, 10:02
- - KikeG   I already answered at the AVS thread. I did all my...   Aug 19 2003, 18:29
- - Patsoe   QUOTE (KikeG @ Jun 30 2003, 01:03 PM)There...   Aug 22 2003, 00:13
- - Peter   I suppose they just perform mixing/resampling at h...   Aug 22 2003, 01:10
- - AstralStorm   It depends on the card and its drivers. TerraTec A...   Aug 22 2003, 01:15
- - Patsoe   QUOTE (zZzZzZz @ Aug 22 2003, 01:10 AM)(ABX a...   Aug 22 2003, 01:22
- - Peter   No sane engineer seriously takes the possibility o...   Aug 22 2003, 01:37
- - AstralStorm   The test was brain-damaged. Mangled sample and no...   Aug 22 2003, 02:21
- - Patsoe   QUOTE (AstralStorm @ Aug 22 2003, 02:21 AM)Th...   Aug 22 2003, 08:06
- - KikeG   External hardware decoding of 44.1 KHz PCM-encoded...   Aug 23 2003, 18:30
- - KikeG   And, even when hardware directsound acceleration c...   Aug 23 2003, 18:35
- - Peter   That's because kernel mixer was designed to pl...   Aug 23 2003, 18:52
- - KikeG   Yes. But if I play something, I'd better prefe...   Aug 24 2003, 20:58
- - Patsoe   QUOTE (KikeG @ Aug 23 2003, 06:35 PM)So, in p...   Aug 24 2003, 21:52
- - KikeG   QUOTE (Patsoe @ Aug 24 2003, 09:52 PM)Well, i...   Aug 25 2003, 20:16


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