Playback Faster Than Normal, Can't Make It Stop

[kirt1974]

I am a college professor of audio production.
Since we updated our Pro Tools systems to 18.1.0.241, two of my students have had the same problem:
Their sessions playback at a speed that is slightly faster than normal.
I suspect that they may have accidentally pressed a keystroke that set their session to playback faster than normal, but I cannot figure out how to make it playback at normal speed again.
I have tried using the Shuttle Lock Varispeed Transport keystrokes (Ctrl 1 - 9 to change playback speeds), but this does not fix the problem.
Does anyone have any ideas for solutions that we could try?

[Top Jimmy]

First, did they try a hard shutdown and reboot?

Often this indicates a clock mismatch that occurred during recording. What audio hardware et al is being used?


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[kirt1974]

They have tried rebooting, they've also opened their sessions on several different computers, each with different audio hardware. They are using a Mackie 1604i Onyx Firewire console/interface in the recording studio. They are using a UA Apollo Twin Quad in the mixing studio. They've also tried using the iMacs in our computer lab which use the built-in output. It seems as though it must be a setting in their sessions that they've inadvertently enabled? I just can't seem to figure out what they've done?

[Darryl Ramm]

Well the obvious answer is sample rate mismatch. Or mangling that on an import. Have you checked that? I suspect you have but would be good if you tell us what you have already excluded.

What is the ratio of the playback speeds? That usually is a clue. And grab one of the misbehaving audio files and play that back outside Pro Tools.

[albee1952]

Indeed^^^ If you play a 44.1K session at a 48K clock speed, it will be faster(and higher in pitch). One solution is to create a new blank session at 44.1K. Then Import Session Data, grabbing all tracks from the troubled session and DO NOT use SRC(sample rate conversion). This new session should playback correctly

If any setup includes something connected via a digital connection(SPDIF, AES or Lightpipe), that system may have a sample rate mis-match(IOW, the hardware is set to a different sample rate than the session/Pro Tools)

[kirt1974]

They recorded all of the tracks themselves, so no importing of audio files was done.
When we open the audio files in Quicktime, they play at the normal speed.
It's definitely something in the Pro Tools session that is causing the issue.
They created the session at 44.1kHz/16bit.
All of the audio files are the same sample and bit rate as the session.
Since it has happened twice to two separate groups of students, I highly suspect that they've inadvertently hit a keystroke or something to cause the problem.
Of course, since they needed to finish their projects by the due date, I showed them how to import the audio files into another session, which worked fine, but I would really like to discover the source of the problem for future reference in case it happens again so that I might instruct them as to how to fix the issue.

[Darryl Ramm]

Can you measure the speed and pitch difference? That could give a clue.

Otherwise it’s the varispeed you already looked at

Or maybe the students has been messing with elastic audio?

[JammyDeen]

I remember an engineer having this issue at a studio I was at. It turned out to be that OSX audio setting was set to 44.1kHz, Pro Tools was at 48kHz and for some reason Pro Tools was using the OSX clock? It's a little hazy now.

[mandal]

In my case it was a hardware error - but maybe this thread can give you some tip:

http://duc.avid.com/showthread.php?t=348653

[Darryl Ramm]

Originally Posted by JammyDeen

I remember an engineer having this issue at a studio I was at. It turned out to be that OSX audio setting was set to 44.1kHz, Pro Tools was at 48kHz and for some reason Pro Tools was using the OSX clock? It's a little hazy now.

Mmm... may be worth checking what the Mac says the Mac audio/midi clock rate is for those interfaces especially for Built-In Output or if they are using Aggregate IO.

And this should not be happening but if Aggregate IO has the wrong clock rate that might explain why other apps that use Built-In output directly play back OK. Yes I'm making this up/clutching at straws.