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dm said:


"using the kernel streaming (out_ks.dll) I was successful in getting a valid DTS stream out my SPDIF to my external receiver/decoder.

using waveout/directsound plugins all I got was pink noise."


since i got the revo (and use windvd audio through zp), i disconnected the spdif to the receiver. i suppose i was trying to decode the dts on board and pass through the analog outputs to the receiver.


first, can this be done? my receiver can't auto switch between spdif and analog, and there is no quick (i.e. keyboard shortcut) that can switch the revo control panel from one quicksetting (analog) to another (spdif). also, there is only one coax digital input on my receiver (outlaw 1050) which is currently being used by my cable. i will test the spdif connection tonight, but i dont want to have to get a splitter. windvd can decode dts from dvds onboard (pretty sure), so why is there an issue with dts files?


thanks,

kevin
 

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well, the spdif works with the ks_out file. was not able to play the dts wave through windvd, even though i confirmed that dts sound plays from a dvd (decoded on board and passed through analog outputs). what is it about the dts wave that wont decode on board?


kevin
 

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Quote:
Originally posted by thomaspf
I am interested to get to the bottom of this so it would be great if KikeG could share the source file of whatever it is he can play bit perfect. We can then repeat his experiment and see what we find. I will not dismiss the chance that a very specific input signal might survive the kmixer treatment unharmed but I am doubtful for the general case.
Ok, I repeated the test playing DD encoded files, and it showed same results.


I had to reinstall WinXP due to some issues that caused HD data corruption, and reinstalled DIO 2448 WDM drivers too. I used those two available 384 kbps and 640 kbps DD and DTS 44.1 KHz files. I used both Winamp and Foobar2000 directsound output. CMI8738 TTL digital out was recorded with Audiophile coax digital in. The original and recorded data was substracted from each other, being the result all zeroes, what means that both files were 100% identical.


So, again, bit-perfect playback using those WDM drivers.


Still, one thing to know: DIO 2448 drivers apparently don't allow KS playback. DIO2448 shows in Foobar2000 KS drop-down list, but when playback starts, the player reports an impossibility to open device. In other modes it works fine.
 

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â€Still, one thing to know: DIO 2448 drivers apparently don't allow KS playback. DIO2448 shows in Foobar2000 KS drop-down list, but when playback starts, the player reports an impossibility to open device. In other modes it works fine.â€


That means that the DIO2448 driver is not a true WDM driver just like the RME drivers. It is a VxD driver in a WDM wrapper.
 

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Quote:
Still, one thing to know: DIO 2448 drivers apparently don't allow KS playback. DIO2448 shows in Foobar2000 KS drop-down list, but when playback starts, the player reports an impossibility to open device. In other modes it works fine.
The Foobar kernel plug-in is a little buggy. If you have more than one device and want to use k-streaming, switch on your "other" soundcard in multimedia settings, and then use foobar to pick the card that is not selected as your primary.


A little weird, but it works for me.
 

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Quote:
Originally posted by DaveFi
The Foobar kernel plug-in is a little buggy. If you have more than one device and want to use k-streaming, switch on your "other" soundcard in multimedia settings, and then use foobar to pick the card that is not selected as your primary.


A little weird, but it works for me.
I just tried this, but it still doesn't work. I also tried removing the other soundcard, and it doesn't work either, be it with Foobar or Winamp KS output.


This supports the idea that it is not a true WDM driver, but I guess only M-Audio could tell for sure.


I'm going to try to fix my CMI8738 digital input, so that I can record digitally the output of my M-Audio Audiophile.
 

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Hey guys,


I was directed here from another thread.


Will both the DD and DTS files create the noise when they aren't bit-perfect or just the DTS ones, its a little unclear above.


Will this noise be replicated when using the analog outputs, or just with the digital?


Thanks,

Nathan
 

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Discussion Starter · #30 ·
Both DD and DTS bit streams will produce noise when they are sent out the SPDIF digital interface if they have been resampled by kmixer. This is because they are no longer "bit perfect" after the resample and your external DD/DTS decoder gets a bit stream that is corrupted.


In the analog case, I believe that the bit stream is presented "bit perfect" to your software DVD player on your HTPC, it is then decoded by that software and sent out to kmixer and then analog ports. So it is in fact resampled in the analog domain and the signal is degraded a little but not turned to noise. If we had a DVD software player that was ASIO or Kernel Streaming aware, we could bypass the resampling in the analog domain. But none exists yet.
 

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DD and DTS CD's should be fine with WDM K/S (or ASIO w/Media Jukebox). The answer to software decoding for multichannel DD and DTS on DVD-Video is thru DirectSound. "Kmangled" DirectSound. :(


What about Cakewalk SONAR and Sonic Foundry 6.0 with WDM K/S and DD-DTS CD?


Does the Revo use WDM K/S for SRS Circle Surround and TruSurround?


Do WinDVD and PowerDVD have to use DirectSound for SRS Circle Surround and TruSurround?


And doesn't the Audigy 2 Platinum EX use DirectSound for DD and DTS (direct to multichannel speakers, not digital out) - even though it's THX certified?


And is a new DD EX-DTS ES pre/pro that does bypass DirectSound via digital out upgradable and inexpensive? I know that one - NO!
 

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Update:


Well, a couple of months ago I managed to get mi CMI8738 based card digital input to work.


Using it, and bit-perfect recording the digital output of my Audiophile card at 44.1 KHz mode, I've been able to verify that kmixer indeed does something to the data passed to it. The change is very subtle, so it was not detectable on my analog measurements of the soundcard output. What I've verified that kmixer does to 16-bit audio data, is just mangle the last bit of the data. It does like some kind of re-dithering of the signal, adding a very little amount of spectrally uniform noise to the signal, so that it is no longer bit-perfect. It also adds a very little amount (around -120 dB amplitude) of distortion that can be considered negligible.


I have measured this noise but I don't have the results at hand right now, but with this noise added, the dynamic range of the 16-bit signal is still better than 90 dB.


I haven't been able to do same tests with 24-bit audio, because I can't get a 24-bit recorded data, but I think this is a problem of my testing configuration, because on analog measurements, the analog output of the card with kmixer processing was able to produce an analog signal with better dynamic range than the possible with 16-bit audio. I'm trying to fix this.


When using kernel streaming and ASIO, the output is bit-perfect in 16-bit mode, as it was supposed. There's some evidence that using directsound acceleration (also called hardware mixing) does same thing as using kernel streaming, and enables getting bit-perfect output. However, I haven't been able to verify this, since my Audiophile card doesn't support it.


Note that when kmixer is acting and you play 44.1 KHz data, it can do do two different things depending on the driver implementation. The first is just this relatively bening bit mangling I've talked about in this post. But on some cards and modes (wave output instead of directsound, for example), it will resample the signal to 48 KHz, and this is a greater change to the signal. I haven't done very detailed tests over this resampling, but it worsens a little bit more the SNR of the signal, causes some low-level distortion and causes a very slight HF rollof. At first I don't think this is audible under usual listening conditions, but I haven't done any listening tests.
 

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Hi KikeG,


welcome back! When I did my file comparisons a while back, I found that the changes can extend into the last 2 bits not just the lowest order bit but it depends on the wave form.


If we go with the rule of thumb of 1bit being roughly equivalent to 6db of gain, how would I introduce a -120db distortion. Is that some averaging that happens since you found that only every other sample is being changed? I thought with the last 2 bits under attack that means the signal is distorted at -84db.


What are your thoughts around this?


Cheers


Thomas
 

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Well, with proper dither you can retain signals much below the noise floor. It's possible to have a -120 dB tone standing over a -90 dB noise floor, given that you use enough time averaging. That is because the noise floor measurement is wideband, is the sum of the noise from from 20 Hz to 20 KHz, but the tone is just at one frequency. But this also depends on the time averaging used for the measurement. Using 44.1 KHz sampling, with a single FFT of 65536 points it's possible to "see" this -120 dB tone standing over the noise floor. With a 1024 FFT, which would be similar to the ear time averaging, a -120 dB tone would be buried within the noise floor, but not a -100 dB tone. That is relatively easy to see with CoolEdit and its spectral analysis.


Edit: and yes, I found only a slight increase of the wideband noise floor, which was still better than -90 dB, and that -120 dB negligible distortion products.
 

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Well, I just did a few more tests. I own now both a Revo and an Audiophile, so I can play all types of data on the digital output of the Revo and record them with the digital input of the Audiophile. I just did some RMAA 4.3 measurements, and here are the results:


I will give results without A weighting, I like it better.


1st figure is reference, best possible value. 2nd is kmixer bit-mangled output.


Frequency response is totally flat in all cases, so is omitted.


16 bit, 44.1 KHz:

============

Noise: -96.4 dB, -93.4 dB

Dynamic range: 94 dB, 90.9 dB

THD: 0.000%, 0.001%

THD+N: 0.003%, 0.004%

IMD+Noise: 0.006%, 0.008%

Crosstalk @1KHz: -94 dB, -90 dB


The distortion product that appears at the THD measurement is at -110 dB, not -120 as I said previously. It is still a negligible value in my opinion. The biggest difference is the slight increase of the noise floor. As you see, even here the difference is quite small.


24 bit, 44.1 KHz:

============

Noise: -146.3 dB, -141.5 dB

Dynamic range: 139.5 dB, 137.3 dB

THD: 0.000%, 0.000%

THD+N: 0.000%, 0.000%

IMD+Noise: 0.000%, 0.000%

Crosstalk @1KHz: -141.8dB, -137.2 dB


For 32-bit audio, results are slightly better but very similar.


Taking into account that due to real-world constraints of electronics the best hardware available can't have a dynamic range better than around 120 dB, the effect of kmixer bit-mangling in this case is totally negligible.


And, if you play your 16-bit data as 24 bit or 32 bit, the result is that the full 16-bit resolution is retained. In a RMAA measurement, the results in this case were identical to the 16-bit reference results.
 
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