Strange audio pitch speedup/slowdown - MacBook Pro

aj_kandy · Post by **aj_kandy** » Thu Aug 02, 2007 6:06 pm

Greetings all,

I was doing a short multitrack audio piece in Live 6 last night. Something happened during recording or file export that made the resulting AIFFs pitched a good deal lower than they were supposed to be.

One piece was 3 vocal overdubs and a single drone note from a synth in Reason, ReWired into the 4th track. Nothing special about it, ran the 3 vocal tracks through the Female Vocals effects chain and then put the Mastering Chain on the master; we recorded it dry and only added the effects during mixing/mastering. Audio recording was set to 24bit WAV, 44.1, using a Mackie Satellite FW interface.

After recording, we played back the tracks several times in Live and they were fine. When I exported them to AIFF and subsequently imported them to iTunes to burn CDs, the results were pitched almost a tone lower than what we'd done.

I re-opened the Live session and lo and behold...it was playing back pitched lower there too, where it hadn't just prior to file export.

I double-checked all the sample rates and settings for CoreAudio and Live; nothing was out of the ordinary. To double-check if it was a system issue, I went to a MySpace site where I knew the pitch and tempo of the songs and strangely....they were playing back faster / higher pitched than normal...and so were tracks playing back from iTunes!

I put this aside for a few hours, let the computer sleep, woke it and double-checked. System / internet audio seemed normal again, but the recorded Live session and individual WAVs from the project were still pitched lower -- whatever had happened had affected them permanently.

I used Tracktion 3 to import the AIFFs and re-pitch them - one was 1.5x off, the other was 1.125x off.

I'm somewhat at a loss to explain this. Could it have been some sort of temporary CoreAudio sample rate glitch? An issue with the interface? Or something to do with Live? I have to do further testing to see if this bug reproduces regularly. I'd done several multitrack sessions with Live 6 back in May that went flawlessly, so the only real change between now and then has probably been some OS X updates.

Currently on MacBook Pro (1st generation Core Duo), 2GB RAM, OS X 10.4.10, Mackie Onyx Satellite FW interface, Live 6.0.3 (last updated Dec 2006)

Amaury · Post by **Amaury** » Fri Aug 03, 2007 9:46 am

Hi,

Could you check if the rendering is also 44100 Hz? And/or if the internal sound card (if it is what Itunes is using) is set to the same sample rate. That definitely sounds like a sample rate issue.

Regards,
Amaury

aj_kandy · Post by **aj_kandy** » Fri Aug 03, 2007 11:20 pm

Only one sound card (the Satellite) was being used during this process -- and it was set to the default, 44.1KHz, 24-bit audio. iTunes and other system audio would have used the same output. The original WAVs recorded by Live to the project file are 24-bit, 44.1KHz; the AIFF render file exported from Live reads as 16-bit 44.1KHz, which is normal for CD audio.

What's bizarre is the way that the recording was fine initially, then seemed to 'slow down' only after export. It's like the whole computer was in a temporary, sped-up time warp which only left the 'slowed down' audio files as evidence.

I wonder if there's something I can find in the system logs, but I doubt it.

Green Gecko · Post by **Green Gecko** » Tue Aug 07, 2007 2:25 am

This may sound really random but I have experienced a lot of random audio playback problems mainly with pitch being ridiculously slow, and it turned out to be the fault of the Last.FM application (www.last.fm).

aj_kandy · Post by **aj_kandy** » Tue Aug 07, 2007 3:01 am

[quote="Green Gecko"]This may sound really random but I have experienced a lot of random audio playback problems mainly with pitch being ridiculously slow, and it turned out to be the fault of the Last.FM application (www.last.fm).[/quote]

Hm, interesting -- but I don't use Last.FM. All that was open at the time was Live -- on a special Music user login which has no extra applications open at startup, it's optimized mean and lean.

Green Gecko · Post by **Green Gecko** » Tue Aug 07, 2007 3:14 am

Have you tried temporarily rendering 24-bit audio as your output to see if it's a problem with Live's rendering?

aj_kandy · Post by **aj_kandy** » Tue Aug 07, 2007 3:27 am

[quote="Green Gecko"]Have you tried temporarily rendering 24-bit audio as your output to see if it's a problem with Live's rendering?[/quote]

Do you mean setting the output bit rate to 24-bit in the main Sound prefs pane? I'll give it a spin, but I'm wondering why ALL audio on my system was affected (sped up temporarily)...

Green Gecko · Post by **Green Gecko** » Tue Aug 07, 2007 3:36 am

I presume you are using the Satellite as your primary sound device, a la an external sound card? (I'm not familiar with how the Satellite works as an audio interface).

What causes the audio to go back to normal again? On my Delta 1010LT's software control panel there is an option to "Lock" the sample rate of the card.

If there's a similar option for your Satellite try enabling that to prevent Live or other applications from changing it. That should prevent any clashes between the sample rates of different programs/hardware, which is likely to be the problem here (knowing a little bit about the the binary PCM theory).

One way or another if all the audio on your system is being warped then something is messing with the Satellite and its sample rate.

Not to sound like a cliche but it's also worth checking for new driver versions. You never know when they get round to updating them in their lunchbreak.

Especially concerning compatibility with new versions of OSX.

aj_kandy · Post by **aj_kandy** » Thu Aug 16, 2007 6:40 am

[quote="Green Gecko"]I presume you are using the Satellite as your primary sound device, a la an external sound card? (I'm not familiar with how the Satellite works as an audio interface).

What causes the audio to go back to normal again? On my Delta 1010LT's software control panel there is an option to "Lock" the sample rate of the card..[/quote]

I just tested this again and in tha Audio MIDI Setup, setting the Satellite to 48Khz instead of 44.1 solves the speedup / slowdown problem. I don't know if I can lock the sample rate; it does seem that Live recorded at 48KHz but iTunes played back and burned files at 44.1, resulting in slower audio playback. This odd 'sample rate stickiness' would explain how I got 'sped up' iTunes and Internet playback, where Live sounded 'normal,' and then again how regular audio sounded normal but the recorded audio then seemed slowed-down.

I was under the impression the system would convert this on-the-fly or stick to Audio MIDI setup prefs??