Audio Recorder and Syncing...

[jcskeeter]

So if a person uses their choice of audio recorder (H4N, Tascam, Alesis) to recorder audio along with the T2i and the T2i is set for 1080 24P. What is the audio recorder technically recording, time code-wise? I know there's software to sync the audio and the video. But is it actually adjusting the playback speed on the audio to match the video? If I were to manually line up the audio in FCP, would my playback eventually get out of sync when played back?
I haven't purchased an audio recorder yet so that's why I haven't just tried it myself but I was just curious.

BTW
Anyone using one of these right now: Ikey If so, what do you think?
I want one if these but unfortunately I have a gig before they start selling them.

 

[AD Tom]

Of course the real professional way would be synchronizing your audio and video hardware. But if you`re video files are not to long (2-3 minutes) you won`t see a syncing problem. We use very often several recording tools (2-3 cameras, external sound devices) without syncing. Use a clapper board (or your hands) to a find an easy sync-point while editing and everything will be fine.

Cheers

Thomas.

 

[Alex H.]

Of course the real professional way would be synchronizing your audio and video hardware.

Not necessarily. Non-sync, double-system sound is quite common in high-end production. It's the way film has run for a long, long time.

Let's clarify a few things here:

Audio does not have time code, and it does not run on frames. It runs on a sample rate (such as 44.1kHz or 48kHz), which indicates the number of times per second that a data sample of the audio is recorded. So, at 48kHz, the audio is sampled 48,000 times per second.

What audio does have is a clock. Some clocks are imperfect, meaning that they don't record a perfect 48kHz. One device may record 48,051 samples per second. Another may record 47,983. This is why we experience drift between two devices that aren't clocked together.

In film, running at 24 frames per second, an audio recorder may be connected to a master clock that will keep it running at a perfect 48k. That master clock may be connected to both a video recorder and an audio recorder to make sure that both have the same clock. But audio recorders that have TC in record that time code only as metadata for reference; it has no impact on the actual audio.

Digital video standard for audio is 16-bit, 48kHz. The Ikey recorder only goes up to 16-bit, 44.1kHz. This means that the audio will have to be converted to 48kHz before editing, which may or may not cause some artifacting. Ideally, a recorder should be able to record 24-bit, 48kHz.

 

[jcskeeter]

That's great C2V! That's exactly the explanation I was looking for. It makes sense now. This will be my first experience with external sound so lots of questions are coming up.
I'm having trouble picking a recorder out in that price range though. Looking at these right now:
- Tascam DR-07
- Zoom H2 (Seems like an old product but pretty advanced?)
- or the Ikey Audio (even though it has lower quality recording)
- or somehow get my hands on an Zoom H1 before they come out. Anyone know anybody that could help a guy out?? ha

How good is the AGC on these units? I know that's not the ideal thing to do but with my gig I won't be able to ride the levels and film at the same time and my source isn't going to be constant.

 

[Alex H.]

Have you considered renting for now, just to get you through this event?

It'll be less expensive than buying something quickly that's less than what you need. You might find a production rental house in your town, or you can check with Trew Audio (Nashville, Toronto, Vancouver) to rent a recorder from them. They'll ship rentals anywhere.

After that, you can start looking to purchase. At that point, you should also ask yourself if you will ever need to use high quality, professional, external microphones... that requires the need for XLR input and phantom power.

About AGC: avoid it. Set your levels low enough that you have some safety, but not so low that you're missing information.