Spontaneous oversampling with no pitch change??!!?

[ghobish]

How did this happen??

Hoping the great minds here can solve this mystery.

I was at home doing a needle drop of an album to use for reference in the studio. Since it was a non-critical operation, I simply recorded on my MacBook Pro into the line input at 44.1k, knowing I would have to upsample to 192k in order to compare it to a studio master within the same session in DP.

After upsampling upon import, in two of the files (both near the end of LP side-long files) the audio spontaneously doubled in speed through the end of the file. In one case it happened about 40 seconds before the end, in the other about 2 minutes. This was not an issue of strange hardware behavior on playback; this change was in the audio file.

Now, even if one can come up with a scenario that supposed the original recording in the Mac going to half the 44.1k sample rate spontaneously- which I have never ever seen happen- there is a kicker: the audio, while doubling in speed, stayed at the same pitch! A simple (if unlikely) sample rate change not properly compensated for on playback should change pitch AND speed together.

For the life of me, I cannot figure out a scenario where the speed could spontaneously double while keeping the pitch intact without deliberately using a tool designed to do EXACTLY that. An accidental use of DP's time stretching tool would have affected the entire file, not just the last couple of minutes.

This is a completely isolated incident, not a recurring problem.

Are there any theories here at all as to how this can possibly happen due to some kind of one-time glitch? I'm desperate to figure this out.

Thanks-

Gary Hobish
A. Hammer Mastering & Digital Media
San Francisco, CA
<http://ahammer.com/>

[kassonica]

what file format did you use BWAV etc?

There was always a problem with SD11 (from memory) on long file lengths..

Also if you used just the inbuilt mac soundcard that may of been an issue...

[MIDI Life Crisis]

Here's my 2¢ possible theory. Could you have run a program during the recording that changed the sample rate. If DP is running at anything but 44.1 and you run Finale, F grabs the system and brings it to 44.1. DP will send up a message and stop functioning but I've never tried this WHILE RECORDING.

So could a program have launched or been running that might have grabbed the system from DP?

Or it might have been an alien race trying to communicate with you. Have you tried playing it backwards? Ok, j/k about the aliens.

[ghobish]

Here's my 2¢ possible theory. Could you have run a program during the recording that changed the sample rate. If DP is running at anything but 44.1 and you run Finale, F grabs the system and brings it to 44.1. DP will send up a message and stop functioning but I've never tried this WHILE RECORDING.

So could a program have launched or been running that might have grabbed the system from DP?

I can't rule that out , which could conceivably explain a spontaneous sample rate change- but that would not explain how the pitch stayed the same. That's the real puzzler. So much so that I was convinced for a while that it had to be that way on LP (until I went back and re-listened) because that phenomenon could not happen without deliberate intent and use of a time-stretch tool set to leave the pitch intact.

Or it might have been an alien race trying to communicate with you. Have you tried playing it backwards? Ok, j/k about the aliens.

Why are you messin' with my mind, Mike?

[MIDI Life Crisis]

Because I love you, man. And I've known you long enough to know you have a sense of humor.