DR-100 & Drift

[Evan Donn]

Originally Posted by Tim Polster

I went to the Pural Eyes website and watched a how to video for Dual Eyes and "correct for drift" is a menu choice so it is made to fix drifting audio. Syncing is easy, drift correction is not. BTW, drifitng audio is not so related to framerate but moreso related to recording crystals and two different machines running at slightly different timings.

Interesting to know, I've never seen that option in Pluraleyes, looks like it's only available in DualEyes.

I know when discussing drift the usual culprit is the timing of different hardware, but for a while there was a significant drift problem with 5D footage that was specifically related to frame rates and the way FCP interpreted imported audio files based on the project frame rate. It seemed like a lot of people assumed it was a problem with the audio hardware at the time. Now that it's solved though I've done tests with both the H4n and DR100 where I recorded music to the clip length limit on the camera and then synced the audio and there's not even any sign of phasing by the end of the clip, let alone a frame or more of drift - so I'd say drift isn't a problem within that specific time limit. I'm only shooting on the 5D now though, so I haven't had a chance to do tests beyond the 12 minute limit of the camera.

[Tim Polster]

That is interesting. One would think Dual eyes and Plural Eyes would offer the same features.

It is good to know the DR-100 has be created with a mind towards recording timings of video cameras. I would not be interested in Plural Eyes if it does not drift correction. It is easy to sync audio in an audio program (I use Sonar) which has sample level adjustments.

[Chad Johnson]

When fixing drift you are taking one of the files and stretching/compressing one audio file to match another. The act of doing this alters the sound quality. I would not recommend trying to fix drift for the purpose of matching music recorded to multiple recorders. Really, if one is just exchanging good audio for scratch audio recorded on a camera, drift is rarely enough to see a difference as it relates to hearing the voice and seeing the mouth move. If drift gets too bad you make a cut and nudge the file. But to time stretch an audio file introduces artifacts, and in the case of music will cause phase issues, especially if you are blending files from different recorders.

I'm just saying to be careful with any drift correction process. And if recording music make sure all tracks are recorded on the same machine.

[Tim Polster]

I agree and what you say is true Chad but I thought this was the magic of the Pluraleyes program and why everybody seems to be so excited about it. I thought it did correct for drift without issues.

I need to contact the company to see what the software is designed for because I just don't see $150 to only line clips up.

[Brian Luce]

Originally Posted by Chad Johnson

The new Final Cut Pro will have a plural eyes type thing built in!

If you have an EX1 class camera, and only need 2 channels, then that's all you need. The EX1 has the best audio I've ever heard out of a camera. Drift won't be an issue unless you are trying to record music, and blend recordings from 2 different sources. Visually it won't be an issue, but almost immediately you'll hear phase issues. So always record all the audio used on one recorder (for music). I don't know if Oade would do a DR-100. If he doesn't, try Busman Audio. They do mods too, and better.

Originally Posted by Tim Polster

I agree and what you say is true Chad but I thought this was the magic of the Pluraleyes program and why everybody seems to be so excited about it. I thought it did correct for drift without issues.

I need to contact the company to see what the software is designed for because I just don't see $150 to only line clips up.

This is a big deal to me, I record musicians on occassion and if all PE does is line up clips, that's limiting. My problem is that I cannot tell when instruments, certain instruments, fall slightly out of sync. When I show it to the violinist, SHE can tell, I can't. Singing or dialogue is easy, but instruments are difficult. Please let us know you results Tim.

[Chad Johnson]

The question has been answered Brian. Plural Eyes is for lining up clips, not for fixing drift. Like I said, drift isn't an issue unless you mix audio recorded on more than one recorder. If you record music, do it on one recorder with enough tracks to cover what you need. The drift isn't an issue visually. You can always just cut the audio clip and nudge it a couple frames if need be.

[Chad Johnson]

Here's a guy talking about Dual Eyes and fixing drift: Review: Singular Software DualEyes | AusCam Online - Write | Light | Shoot | Edit | Distribute

[Evan Donn]

Originally Posted by Tim Polster

I need to contact the company to see what the software is designed for because I just don't see $150 to only line clips up.

It's not 'only' lining clips up, but that's the primary thing it is designed for - and I suppose the value depends on what kind of shooting you do. If you're doing something like long take concert shoots where you basically need to line up a single audio track with one or two video clips then it's probably not worth it. But if you end up with 50-100 clips from a day's shoot and they all need to be synced to audio or one another it'll pay for itself on the first job you use it for.

[Tim Polster]

Good point Even. I see the value for that situation.

[Predrag Vasic]

Originally Posted by Steve House

...For broadcast work +/- 0.5 frame (no more than 1/2 frame off for sound to either lead or lag picture) is a common limit. "A few frames", even a single full frame, is completely out-of-spec and unacceptable.

Those are the standards, but if I remember well, at Berklee, in audio postproduction class, they teach kids that, for motion picture dialogue, audio lag of 2-3 frames is still acceptable (but never the other way round). This makes some sense, when one thinks about it. Sound always travels much slower than light. At 14m distance (about 40ft), sound is already delayed by the equivalent of one frame. Our brains are ready to accept sound that arrives a bit later than image because of our lifetime experience with this. Keep in mind, though, this refers fairly specifically to dialogue. Other types of sounds are less forgiving.

[Chad Johnson]

And with drift, it's easy to fix when we are just lining up audio with video. You just cut the audio on the timeline, then slide it 1 or 2 frames in the direction it needs to go, then drag the edge of the audio clip (not the whole clip) to fill those frames. Sometimes I'll put a cross-fade where the edges meet if there is a click sound at the cut point.

But if you have audio of music recorded on 2 different recorders, the drift will be heard as phasing, and simply can't be corrected enough for the audio to sound unaffected. I have made the mistake if recording a stereo mic with the camera, then trying to blend that with a board feed recorded into a DR-680, or Sony D-50, but it just doesn't work for long record times. You must record all the used tracks on one recorder, then use the camera audio only for lining up files. After that you mute the camera audio.