Vista Playback Default Format and Audacity

[NineEyes]

I’m creating a Vista/Audacity DAW and moving all of my Audacity 1.2.6, 44100Hz projects there. I noticed that on Vista, Audacity playback of these projects doesn’t sound quite right (most notably bass guitar tracks, which include a chirpy sound), unless I set the Vista Default Format of the playback device to 44100Hz. Unfortunately, the sound card I want to use only supports 48000Hz playback.

Can somebody explain the problem? Vista’s Windows Media Player has no problem playing 44100Hz Wave files on a 48000Hz playback device. Is it that WMP is performing it's own sample rate conversion, and in this case, Audicity relies on Windows for the SRC?

Is there a better workaround than having to match the Audacity project rate to the default rate of the playback device?

[kozikowski]

Just for grins, with one of your sample music tracks in 1.2.6, change the sample rate in the lower left corner to 48000 and Export As WAV. That should give you a 48000 sample rate sound file. See if that sound OK and opens everywhere.

Are you really trying to move Audacity Projects? Audacity projects are pretty interesting. You may be moving the special effects management files rather than the actual show which is why it behaves funny and sounds weird.

Oh, and nobody ever accused Audacity of being a Digital Audio Workstation...because it's not.

Koz

[NineEyes]

Just for grins, with one of your sample music tracks in 1.2.6, change the sample rate in the lower left corner to 48000 and Export As WAV. That should give you a 48000 sample rate sound file. See if that sound OK and opens everywhere.

Doing this was what led me to believe that Audacity was not performing a SRC when the track sample rate matches the project sample rate....Yes, when I change the project rate to 48000Hz (again, with my 44100Hz tracks), the problem chirping is reduce by, I'd say, 75% with Audacity's default real-time SRC Fast Sinc Interpolation and Rectangular Dither. It is undetectable when I set the real-time SRC to High-quality/Triangle.

Are you really trying to move Audacity Projects? Audacity projects are pretty interesting. You may be moving the special effects management files rather than the actual show which is why it behaves funny and sounds weird.

I have a lot of experience moving projects between machines (Win2K and WinXP) without problems. I did eliminate this variable early on in my experiments by recording a single bass track on Vista at 44100Hz (real, no SRC).

Oh, and nobody ever accused Audacity of being a Digital Audio Workstation...because it's not.

I've done some great things with this software. It's a great free alternative.

[NineEyes]

Using Vista, Audacity playback is colored when the Audacity "Project Rate" is not equal to the default sample rate of the playback device (called the "Default Format" in Vista).

This coloring can be demonstrated on any Vista system. Here's how:
1. Set the Default Format of the playback device to 44100Hz.
2. Start Audacity 1.2.6 or 1.3.x and set the Project Rate to 44100Hz.
3. Import this 44100Hz wav file: http://webpages.charter.net/friedl/Vista_SB_MP3+.wav
4. Play it from Audacity. This is how it should sound.
5. Set the Default Format of the playback device to 48000Hz.
6. Play it again. Notice the chirpy sound.

Does anybody know why this is happening in Vista and not XP? Is there a solution for those of us who cannot match our Audacity Project Rate and playback device sample rate?

[NineEyes]

Instructions for reproducing this issue on any Vista system were posted
[Edit] in previous post.

[steve]

You should have the real-time SRC Fast Sinc Interpolation and Dither = none.
I would recommend setting High Quality SRC, to High Quality / Shaped.

If you still have the problem, then I think the issue is probably with your sound card or sound card drivers. Have you had a look to see if there any updated drivers for your sound card?

It should not matter what sample rate Audacity is using, it should either be supported or not supported. The data that Audacity sends to the sound card driver will be at the project rate, regardless of the format of individual tracks.

I'm a little confused by your description - you say that a 44100 track with a project rate set to 44100 plays OK, but you also seem to imply that this is not an option for you as your sound card does not support 44100.

[NineEyes]

You should have the real-time SRC Fast Sinc Interpolation and Dither = none.

I'll try this when I get home, but my experience leads to me to believe the real-time SRC is only used if the track sample rate is different than the project rate. Your quote here:

The data that Audacity sends to the sound card driver will be at the project rate, regardless of the format of individual tracks.

seems to support this....Never the less, as I said, I'll try it later this evening and report back.

If you still have the problem, then I think the issue is probably with your sound card or sound card drivers. Have you had a look to see if there any updated drivers for your sound card?

I reproduced this issue on 4 different sound cards and on 2 different Vista PCs, all with the latest drivers. All exhibited the problem from Audacity. None of them have the problem with Windows Media Player playing my 44100Hz example wave file at 48000Hz. This is what made me believe it's likely an Audacity problem.

Have you tried my steps to reproduce the issue?

I'm a little confused by your description - you say that a 44100 track with a project rate set to 44100 plays OK, but you also seem to imply that this is not an option for you as your sound card does not support 44100.

Sorry. The card I want to use only supports 48000Hz playback. The 3 other cards I tried support both 44100Hz and 48000Hz.

Thanks.

[steve]

real-time SRC is only used if the track sample rate is different than the project rate.

Yes that's correct.
If a track is at a different sample rate to the project rate, then Audacity will convert it to the project rate on the fly and send the data at the project rate to the sound card driver, which in turn will send it to the sound card, which will convert it into an analogue signal. This is why you should turn off dithering and use Fast Sinc Interpolation, otherwise there is a great deal of processing that needs to be done in real time for each audio channel, which has a very significant impact on efficiency and can introduce various kinds of distortions as the computer tries to keep up. (On low specification machines, the output gets severely disrupted. On higher specification machines the reduced performance may not be too noticeable as long as there are not too many audio channels, but performance will still go down dramatically).

There is a marginal reduction in sound quality when using Fast Sinc Interpolation, though it is barely noticeable (not enough to be described as "chirpy"), but it does not affect the quality of the final audio as mixing, processing and exporting are all done using the high quality settings.

It is on the other hand possible that the distortion that you are noticing could be caused by your computer trying to do too much in real time (dithering). It will be interesting to see how it behaves when you try the faster settings.

Have you tried my steps to reproduce the issue?

I'm far too old and wise to use Vista

[NineEyes]

Steve,

I tried Real-time Fast/None on 3 different sound cards to no effect. In fact, there is nothing I can do with the real-time settings to change the sound, unless I change the project rate to something different than the rate of my tracks - that's where I start hearing a difference between Real-time settings.

For the record, all of my experiments prior to this were performed using the install-defaults for Real-time SRC, which is Fast/Rectangle. Also, my two Vista PCs are high-end and less than a year old so performing a High-quality SRC is not a problem.

I recorded the problem for reference. Here's the track I'm playing:

http://webpages.charter.net/friedl/Vista_SB_MP3+.wav

and here's what it sounds like on Audacity (1.2.6 or 1.3.6) when the sample rate of the sound card is 48000Hz and the Audacity project rate is 44100Hz:

http://webpages.charter.net/friedl/Vist ... ayback.wav

[steve]

How very strange.

I've isolated the distortion

Vista_SB_MP3_resample_noise.ogg.zip

(65.13 KiB) Downloaded 96 times

and it appears to be two frequencies, one at around 3800 Hz and the other around 4000 Hz "chirping" along with your bass notes. (.Ogg file, but I had to zip it so that I could attach it to this post).

In this screen-shot the upper track is the original bass note and the lower track is the isolated "distortion", which is clearly following the shape of the bass waveform.

Screenshot-Vista_SB_MP3+.png (6.24 KiB) Viewed 3043 times

I've never seen anything like this before - it certainly does not occur on my machines (Linux and XP).

I'll ask a couple of people to take a look and see if they have any ideas.