New info on iTunes bit perfect output in Windows

[glt]

Just read this piece in diy about bit perfect playback: http://code.google.com/p/cmediadrivers/wiki/Bitperfect

According to the article, if a few conditions are met, kmixer will be bit perfect. According to this info page in Apple.com: http://docs.info.apple.com/article.html?artnum=301301 iTunes player for XP is a 32-version only application and thus meeting one of the required conditions.

 

Thus, although iTunes does not support ASIO in windows XP, it can still be bit perfect.

 

[The Computer Audiophile]

Hi glt - I read both documents thoroughly and I don't see any mention of iTunes being bit-perfect. The Apple doc stated which version is required for 64 bit operating systems and the other document discussed bit-perfect options for many things.

 

Am I missing something?

 

[glt]

Well, that was my conclusion. If kmixer can behave bit perfect when the 4 conditions are met (itunes for xp being compiled 32-bit for xp was the condition I was concerned with), and if one turns off all processing (equalizer, etc) in iTunes and one sets up Quicktime for 44.1KHz/16 bit, then it will be bit perfect would it not?

 

[The Computer Audiophile]

I'll read it again to see if I come to that conclusion. Hopefully I do!

 

[Wavelength]

Gang,

 

Anything that goes through the KMIXER will NOT be bit perfect. Allot of hoplla is coming from the Marketing company who said their dac was bit perfect all the time.

 

As Microsoft has stated there is always some change in the data REGARDLESS of the settings and streaming in the KMIXER. Much of this started when people said well if you only have one stream and if the player is bit perfect and you run into the wind and so forth... the kmixer will be bit perfect.

 

Wrong!

 

I am not sure about this but one of the things that was suppose to be fixed in SP1 for vista was that DirectSound would be bit perfect. If this is true then iTunes with any interface will be bit perfect.

 

I find Vista and iTunes, J River and many others using direct sound sounds much better than any interface in XP.

 

I still think many of the ASIO drivers screw with the bits or starve the interface. Well something because each of the generic 3 that are available sound different with each application using them.

 

Thanks

Gordon

 

[markr]

Hey Gordon,

 

I'm not trying to start an argument here at all. Your statements are completely valid, as far as they go. I would just like to clarify some 'particulars.' There is no doubt in my mind that audio playback applications for WinXP and the 'generic' ASIO drivers for them have at best, mixed results to my ear. The same cannot be said for professional DAW software and their drivers IMO. One can create and play back totally satisfying audio on WinXP using proper methods. That can be a pain in the butt for setting up a comprehensive party (or critical listening) playlist that sounds the way you want it to though - DAW software just isn't designed to do what iTunes or WinAmp (other apps too) does.

 

My issue with Vista has to do with the hardware required for acceptable performance, and the seemingly never-ending upward spiral in hardware requirements (I know that this exists in the Mac world too) . When my company introduced us to Vista, the case was convincingly made that to get a level of performance equivalent to XP with applications that require heavy system resource usage (quality audio is a biggie here), you had to double the amount of RAM needed to accomplish 'like' results. NOTICE to CA readers: If you are going to use VISTA, and expect good overall performance, DO NOT use less than 4 GB of memory. More is better. This is why you will see that the next generation of PC's will have enough RAM slots available to handle 8GB of memory. There are other geometrically sized jumps in resource hardware requirements that will be necessary. It was also explained to us that (many of) the software and hardware investments that many had made to try to achieve quality audio and video would be obsoleted. - they wouldn't be compatible with the continuing upward 'path' that MS was taking. (what WAS that first wrong turn......?)

 

Is all this 'consumerism', re: buying more stuff bad? I dunno, but I have to tell you that I come from a day when the argument du jour was: "64K? Why do we need all that RAM? We aren't even using 32 of our 48K..." Things have changed. But what makes SENSE?

 

This is what sent me to the Mac. Everything is already in place at a lower minimum hardware requirement. Windows isn't there yet for the most part, IMO. and....my interfaces in XP apparently AREN'T what yours are, Gordon.

 

markr

Microsux Winbloze, but I still use it....

 

PS: Once again Gordon, I thank you for your contributions here at CA, and I DO NOT discount your opinions (I regard them highly) . Please keep posting here!

 

[Wavelength]

Mark,

 

Hey I understand... my first computer had 128 bytes of memory. My first development platform was Zilog's 50th Z80 dev system with 16k of memory and dual 8" single sided floppies. The damn thing had S100 wire wapped boards and a 1mhz processor. Would take 40 minutes to compile a 32k program.

 

All's I am saying is the USB drivers and all the sound drivers are much better written. Actually really much of what is different from XP is the audio section.

 

For the normal guy XP is too hard to grasp to get the same results that you can on vista in a few minutes.

 

Thanks

Gordon

 

[markr]

... Gordon: You are right, I am not a 'normal' guy. It certainly wasn't easy to get WinXP to do what I got it to do with audio (another reason I finally bought a Mac). I have to admit that I haven't gone into the details of the 'new OS' over in Windows land. I suppose that I will HAVE to at some point though.

 

As Chris has said before: It is GREAT to have you here on CA.com!

 

markr

6502--->68k--->x86 (kicking and screaming) --->64X2--->C2D (at least I'm on Unix now)......

 

[glt]

I did some experiments to see what sample rate would kmixer choose. I have C-Media soundcard with spdif out and used the drivers from here: http://code.google.com/p/cmediadrivers/

 

I also have a MSB II DAC that displays the sample rate.

 

I use JRiver with DirectSound in XP, and have songs with different sample rate. Basically, Kmixer will use the sample rate of the song, so if I switch songs, the sample rate also switches.

 

I also used iTunes in XP. Kmixer will follow the setting in the Quicktime control panel. If I set the sample rate to 44.1, the all the songs regardless of their original sample rate will play at 44.1 Khz

 

I then opened both iTunes and JRiver. After toggling back and forth, Kmixer decided to stay stuck at the highest sample rate, regardless of the original sample rate of the songs.

 

I then closed both applications and repeat the first two experiments and kmixer was then faithful to the original sample rate.

 

From this experiment I can conclude that kmixer will not do sample rate conversion if you only have one source of audio, even if you have songs with multiple sample rate.

 

Note that I used DirectSound and not ASIO, so Kmixer was always used.

 

So at least I figured empirically how kmixer behaves wrt to sample rate.

 

Now, for the mixing part, I suppose that if there is no need to mix, then the source data will be left intact would it not?

 

 

 

[silverarrows]

Page 8 of this paper from DCS gives the impression that iTunes can be bit perfect on a PC. Only thing is it's Vista. Can this be done with Windows 7?

http://www.thewelltemperedcomputer.com/Lib/OperatingSystemsHandlingOfSampleRates.pdf

 

[numberforty1]

Gordon - do you have anything to support this statement, or do you simply want KMixer to sound bad?

 

Benchmark Media has done research to show otherwise.

 

"With sample rates up to 96 kHz, we have tested and proven that Kmixer is bit-transparent under normal operating conditions. That is, it will not affect the audio whatsoever, as long as the volume is set to 100% and only one application is playing audio."

 

http://www.benchmarkmedia.com/wiki/index.php/Kmixer

 

Not trying to discredit you or anything, its just that these discussions can get so muddied that I really think people should back up their hard claims that a given software definitely does this or that.