Audio warbles like stretched tape

[Jeremy Garchow]

Are they 48k aifs?

If they are mp3, this will happen, you need to convert them to aif.

How are you monitoring your audio?

Jeremy

[Andrea Stewart]

Yes, they’re 48k aifs. And I’m monitoring through my Soundsticks. Its strange, it’s never been an issue before.
Is there such a thing as an “audio card” and the audio card has gone bad? Or is it possible the drive isn’t spinning evenly?

Andrea Stewart
Producer/Editor/Director – Owner
Germane Creative LLC

[Reid Caulfield]

Can you actually hear a speed variation? re drive not spinning evenly, digital audio doesn’t work that way. If there are issues with drive throughput then you’d either hear real nastiness (really bad & pervasive clicks, pops & other crap) or nothing at all. The only thing I can think of is that somehow your card is receiving bad clock or is clocking to an unstable internal crystal.

By “clock” I refer to what digital audio devices use to maintain accurate-speed recording & playback. In professional environments, we’ll have a separate (fairly costly) device oversee & maintain this signal (“wordclock”). Then we’ll feed that signal to all of the digital audio devices in the studio so that every device is seeing the same clock. Like “house sync” for video, only much more accurate. Only very high end computer audio cards have an input for this clock signal. Most simply reference to their own internal crystal, which are accurate enough for general video work.

If your audio card has a dying crystal or is somehow searching for an accurate clock signal – OR, if it HAS an input for clock but isn’t seeing valid input – then I guess your issue could arise. Usually the card will just mute & not output anything. So if you can actually hear a speed variations, you either have a bad audio card or the card is trying to keep time to an inaccurate click signal somewhere in the chain.

Reid C

[Andrea Stewart]

Wow Reid. Thank you for a very informative explanation of audio. Being a video person I had no clue how it works. It definitely sounds like that is the problem. Is there a way for me to test the audio card? I would imagine if there is a problem it will persist when it comes time to output to tape.
And do you have any recommendations for a specific card to replace it? I’m on a first generation Intel Dual Core Mac.
Thanks again.
-Andrea

Andrea Stewart
Producer/Editor/Director – Owner
Germane Creative LLC

[Reid Caulfield]

Anyones who’s ever gone out & bought a PC for any reason, not just media work, in the last 25 years, has usually been faced with a line item called “sound card.” There were usually a few choices. If you go buy a Dell right now online you’ll get to a point in the order where you need to decide what sound card you want. Macs have never been that way. All Macs come with this built in to the computer, not as a separate card that takes up a slot. There are limitations to this. Usually it’s stereo only, not 5.1/7.1, the connectors are fairly flimsy small “jacks” and the internal quality of the components is just ok, which affects sound. Fine for general audio use. It’s entirely possible that the internal sound components are failing so you could always take the system to a Mac authorized repair place & have them look at it.

So to your problem: what else do you have hooked up to the Mac? List everything, please. Drives, mice, trackballs, etc. Does this distortion only happen with certain clips, or within certain applications, or does every sound eventually succumb to it? What happens if you play a song off of iTunes?

You have several options for getting sound out of the Mac. PCI cards or external USB or Firewire boxes. Before going down that road, best to figure out what’s going on.

Reid C