[vkvedam]

Getting a MBP doesn't necessarily mean that you've got to give up on PC. I still use my PC for gaming and few other tweaks that my new MBP doesn't allow me to do. Having said that, Macbook Pro's optical out is outstanding and I can actually hear a lot of difference in the entire audio spectrum compared to the Creative 5.1 Live Sound-Blaster.

 

[floepie]

I was very excited to give this a try when I came across this thread, but unfortunately, iTunes WASAPI doesn't seem to be working on Windows 7. I have 5 test 5-channel WAVs (2 in AC3 format and 3 in DTS), and none work. All work in Foobar with WASAPI output. In iTunes, however, the output is using 48kHz no matter if I select that as an available sampling rate or not in SPDIF device properties. The reason I know it is using 48kHz is that if I attempt to "test" that sampling rate with the Windows test chime, a prompt will indicate that there is another application in use, and that if I continue, that application may not continue to work. That application is iTunes. The prompt only appears when selecting 48kHz with which to test.

So, it seems to be the exclusive sound app, but is using 48kHz instead of 44kHz, which is what Foobar uses for these 5-channel test WAVs. I find it odd, however, that something changes with regard to audio from Vista to W7 with respect to WASAPI.

 

[Ham Sandwich]

Quote:

Originally Posted by floepie /img/forum/go_quote.gif I was very excited to give this a try when I came across this thread, but unfortunately, iTunes WASAPI doesn't seem to be working on Windows 7. I have 5 test 5-channel WAVs (2 in AC3 format and 3 in DTS), and none work. All work in Foobar with WASAPI output. In iTunes, however, the output is using 48kHz no matter if I select that as an available sampling rate or not in SPDIF device properties. The reason I know it is using 48kHz is that if I attempt to "test" that sampling rate with the Windows test chime, a prompt will indicate that there is another application in use, and that if I continue, that application may not continue to work. That application is iTunes. The prompt only appears when selecting 48kHz with which to test. So, it seems to be the exclusive sound app, but is using 48kHz instead of 44kHz, which is what Foobar uses for these 5-channel test WAVs. I find it odd, however, that something changes with regard to audio from Vista to W7 with respect to WASAPI.

Is it possible that iTunes is using WASAPI shared mode rather than exclusive mode?

If iTunes is using shared mode and is playing a 44.1kHz file then playing the chimes at 44.1kHz would work but 48kHz would not. Which is the situation you observed.

Foobar uses WASAPI exclusive mode.

 

[floepie]

Quote:

Originally Posted by Ham Sandwich /img/forum/go_quote.gif Is it possible that iTunes is using WASAPI shared mode rather than exclusive mode? If iTunes is using shared mode and is playing a 44.1kHz file then playing the chimes at 44.1kHz would work but 48kHz would not. Which is the situation you observed. Foobar uses WASAPI exclusive mode.

Yes, then it sounds as if iTunes on Windows 7 is using WASAPI shared mode. While playing a 44.1 file iTunes, I can generate a 44.1kHz chime, but attempting to generate a 48kHz results in the above prompt ("The device is being used by another application..."). This leads me to intuitively believe iTunes is upsampling everything to 48kHz, including the 5-channel DTS WAVs.

While using Foobar WASAPI output, however, I cannot generate a test chime at any of the sampling rates, indicating the use of WASAPI exclusive mode.

So, then it would appear that iTunes 9 can run in WASAPI exclusive mode in Vista, whereas in Windows 7, it runs in shared mode.

 

[Ra97oR]

My iTunes is now doing bitperfect without being told at all. (It was set to direct sound as WASAPI was greyed out) but it did it without me choosing it. Effects such as EQ and Dolby Headphones won't work and I am really happy. xD

 

[somestranger26]

Quote:

Updated: Zune 4 also has bitperfect out

I'd wondered about this, since I couldn't tell a difference between Foobar WASAPI and Zune 3.

 

[Ham Sandwich]

Quote:

Originally Posted by floepie /img/forum/go_quote.gif Yes, then it sounds as if iTunes on Windows 7 is using WASAPI shared mode. While playing a 44.1 file iTunes, I can generate a 44.1kHz chime, but attempting to generate a 48kHz results in the above prompt ("The device is being used by another application..."). This leads me to intuitively believe iTunes is upsampling everything to 48kHz, including the 5-channel DTS WAVs. While using Foobar WASAPI output, however, I cannot generate a test chime at any of the sampling rates, indicating the use of WASAPI exclusive mode. So, then it would appear that iTunes 9 can run in WASAPI exclusive mode in Vista, whereas in Windows 7, it runs in shared mode.

I don't have iTunes 9 installed so I haven't been able to do any testing with it. But I would be surprised if Apple is actually using exclusive mode rather than shared mode with WASAPI. Exclusive mode is just asking for customer complaints, confusion and support. In exclusive mode no other applications will be able to make sounds. That means no Windows system sounds, no playing YouTube while iTunes is open, and many other conflicting situations. A mainstream media player like iTunes is not going to add a feature that can cause that kind of confusion and support headaches. So I suspect that they are most likely using shared mode. Shared mode still has the potential for bit-perfect playback as long as no other applications are trying to make sound at the same time.

I don't know the exact behavior of shared mode when two or more applications try to play sound at the same time. I suspect that the sound from each app will get converted to some standard sample rate (probably 48kHz) and mixed. At that point it is no longer bit-perfect.

 

[lmf22]

I believe iTunes is running shared mode under Vista 32-bit. While playing music in iTunes I can still play other sounds.

In the tests that I did, the receive detected the DTS signal but as soon as another sound was played the DTS signal was cut off and I can hear the other sound. When other sounds stopped, the DTS signal was back. So, iTunes runs in shared mode, and NOT bitperfect when other sounds are playing. When there are no other sounds, it is bitperfect.

 

[mikaronni]

How exactly are people setting iTunes to WASAPI? Do you just set it in Quicktime?

 

[floepie]

I hope those that only see the DTS light up on their receiver without *hearing* the actual music don't think they have the whole bit-perfect thing nailed down. As stated in a previous post, I have 5 of these 5-channel WAV tests (2 in AC3 and 3 in DTS).

For whatever reason, in iTunes, I can get the DTS to light up at the receiver, but there is no sound. Furthermore, none of the L, R, C, etc. channels light up on the receiver. The 5-channel AC3 WAV files result in just clicking noises.

However, in Foobar with WASAPI, all 5 WAV file tests result in music with either the Dolby or DTS icons appearing with all 5 channels appearing in graphical format on the receiver.

I suspect many in here see the DTS light up on their receiver like I do while using iTunes with these DTS WAVs, but in reality, because no sound is played, the test has failed.

 

[glt]

Confirmed: iTunes 9 in Vista 32 is Shared mode when choosing WASAPI.


Experiment:

You choose WASAPI in Quicktime Control Panel and set sample rate to 44.1
You choose Exclusive mode in Sound Control Panel and set sample rate when using shared mode to 96K

You will get a 96K stream

(I use a Musiland USB interface and the Musiland application tells you the sample rate)

 

[sw98]

Quote:

Originally Posted by Ra97oR /img/forum/go_quote.gif I think there is a problem with 64bit OS, mine is greyed out too.

I'm using XP Pro 32-bit, but WASAPI is greyed out for me also using iTunes 9.

 

[TheKisho]

Quote:

Originally Posted by sw98 /img/forum/go_quote.gif I'm using XP Pro 32-bit, but WASAPI is greyed out for me also using iTunes 9.

WASAPI is only available in Vista and Windows 7.

 

[germanium]

Quote:

Originally Posted by lmf22 /img/forum/go_quote.gif You're right. I didn't test it with other applications. Looks like the "automatic pause" only happen when I play YouTube video with Firefox. You can also hear Windows Sounds. I wonder why it only pauses with YouTube videos. Playing other videos with Firefox does not pause iTunes. I have also tried QuickTime movie trailer from Apple's website and CMT music videos; iTunes does not pause. Nevertheless, the playback is still bitperfect. I did some additional tests: 1. Set QuickTime to 44.1KHz 24 bit; soundcard set to 44.1KHz 24 bit Bitperfect (DTS WAV file played fine). 2. Set Set QuickTime to 44.1KHz 16 bit; soundcard set to 44.1KHz 24 bit Bitperfect (DTS WAV file played fine). 3. Set QuickTime to 44.1KHz 24 bit; soundcard set to 44.1KHz 16 bit NOT bitperfect (DTS WAV did not play). 4. Set QuickTime to 44.1KHz 16 bit; soundcard set to 44.1KHz 16 bit NOT bitperfect (DTS WAV did not play). It looks like for my particular soundcard (Juli@) I can only get bitperfect when it is set to 44.1KHz 24 bit, and does not matter what bitrate QuickTime is set at. For multiple sound streams I did the following test: With the DTS WAV file playing, I played a CMT music video from CMT : Videos : Country Music Videos, CMT TV Shows, Original Episodes : New Video As soon as the video plays, the receiver did not detect the DTS signal (NOT bitperfect). iTunes did not pause. But, as soon as I paused the video or closed the Firefox tab, the receiver detected the DTS signal again (bitperfect). So, it looks like when there are other audio streams, the Windows mixer activates and you don't get bitperfect. But when the other audio streams stop, iTunes is bitperfect again. I hope this is clear enough.

When set to 44.1KHz 16 bit your sound card may be adding dither which even though may not be bit perfect does wonders for correcting the huge distortion present in sound at low volumes. Dither allows you to hear sounds that would be completely lost without it.

Dither expands the potential resolution of 16 bit systems to 18-20 bit range before the signal too far below the dithers noise floor. I have picked out sound that was buried in the dithers noise floor by as much as 24db. That yields a bit depth of 19 bits resolution before the signal is completely buried in the dither noise. This dithered resolution brings 16 bit close to 24 bit W/O dither in actual performance when you take into account that 24 bit undithered is going to have a similar distortion profile as 16 bit dithered sound at -108 db assuming perfectly silent electronics driving the 24 bit ADC.

Noise character of typical opamps feeding these 24 bit ADC's may be enough to dither them though just like the analog tapes did in many of the better sounding early CD recordings.

Check to see if your soundcard driver has an option to turn on or off dither. Most do not but who knows.

 

[kikker]

I finally got this to work and verified by a DTS WAV file. The key for me was changing the default audio output in the advanced properties of my default SPDIF audio device to 41000 Hz, 24 bit (Studio Quality). 41000, 16 bit (CD Quality) allowed the DTS light to appear on the receiver, but no audio could be heard.

Now, here is where things get a little strange. In Foobar with its WASAPI output plugin, I am able to playback all DTS WAV files in addition to all AC3 WAV files. In iTunes, however, I can only playback DTS WAV files, whereas the AC3 WAV files result in pure static. What would explain this??