Dual system sound help
 

Hi all,
I've been reading Ken Stone's excellent article on location sound (a subject about which I'm determined to overcome my ignorance) and I was struck by his assertion that audio recorded to a device other than the camera (I've been considering the new Marantz PMD 670) will inevitably lose sync in Post. No matter what. He claims it's because that while both may be digital "they are also both completely independently syncronized to their own internal master timing device." This brings me to my DVX100/external device question...

Is there a way to, in effect, maintain a common timing signal between them? I can't find anything in the manual that leads me to believe that the DVX has a gen lock function. In my Avid editing days we of course had a black burst generator in the bay, but I don't have such a critter at home. Is there another way to accomplish this? Can it even be pulled off without high end equipment that's way out of my league? The PMD 670 records to Compact Flash, with DAT quality, but I can't find any reference on their site or anywhere else that addresses this issue.

As always, thanks in advance guys,
Marcia

first off you will need an NLE which can sync to MTC or MIdi timecode like Vegas.
then you will need to find a device (like DAT) which can be slaved to MTC as well.
From there you will need to configure synchronisation at the time of filming (to make life easy), then during edit, you slave the Dat recording to the timecode of the film.
This isnt as easy as ive laid out, howevr this is jsut the basic concept.

the reason why they dont sync is due to the fact that its a moving machine component motor (DVX or even minidisc) which records all the data.
Problem is being a machine, if there is a voltage spike or drop, it could inadvertantly drop RPMS causing this "desync".
Most of the time thou if there is a spike, you will see artifacts on your tape or you wil notice a drop out of some kind. This can be caused by old batteries all the way thru to environmental temperature...

as for sync, one thing you can do is connect the DVX and run it as a master to another DV device (like deck or smaller second cam) which can be used as not only a backup, but as an extension.
The DVX can be configured to record out to another unit, so in effect you can have 2 copies of your recording as a backup plan, OR you can set it to trigger a start in recording on teh connected unit when your tape is close to the end.

What are you trying to synchronise?

Peter,
What I'm concerned about sychronizing is the audio and video for my doc. With all the feature film sound editors I know, I've heard an earful for years about the superior sound quality to be had from recording my audio separately to DAT, or whatever. (The new, cool drives that are replacing DAT's on features are decidedly out of even my fantasy budget.) I never even considered that I would record audio to mini DV for anything that wouldn't be just be backup/a baseline. I never intended to use it in the final cut. I guess I partly posted this question in the hopes that someone could verify that there was a way to indeed use the hot new Marantz technology (or other such) of recording to Compact Flash instead of tape and get around this sync issue. Or that maybe the DVX had a gen lock type feature I hadn't discovered, or that someone knew a way to get around it. The Marantz is like dream technology come true. No transfer is required. You just pop it out of the PMD, transfer the Compact Flash contents to your own computer, import into FCP (or whatever), and voila. You have awesome sound at a fraction of the price (which is why we're in DV, right, to shoot great looking stuff at a fraction of the cost of 35mm and its relate tools?) except that I can't find any info that confims or denies that this sync drift would be an issue with the Marantz setup. I fear it is. I guess I'm just still hoping that there's some kind of doable work-a-round.

With the time I've spent in professional edit bays, it's just beyond belief to me that there isn't a way to more easily get audio which has been recorded separately and my DV video in perfect sync (that will hold) once you've matched to your slate like I used to do with film. Perhaps the bottom line is that I now have to choose between inferior audio recorded solely to the DV in my DVX100 or the expense of a genuine DAT (rental, transfer, etc. is still pricy even though it is rapidly becoming "old" technology) which will really blow my budget.

Bummer. I had such high hopes.
Ciao,
Marcia

Marcia:

The audio in the DVX100 is superior to other DV Cams. For a detailed review by a long-time audio pro:

http://www.dv.com/reviews/reviews_it...eview/wilt0203

Jay Rose, C.A.S., moderates the audio forum at DV.com and after reading posts there along with parts of his book, Producing Great Sound for Digital Video, I get the impression that synch can be maintained for close to 20 minutes.

So long as takes don't exceed this length and that you start and end major takes with the clapper (a tail-slate) then double-system sound is definitely possible for our production level, provided of course, that you account for the points raised in that Ken Stone article (which was written by Dan Brockett not Ken Stone).

I have yet to try myself but I think Dan is against double-system because not many people realize the hassles of going this route and as a general precaution, he simply warns people from pursuing it. In my opinion, lots of production areas can be construed as too difficult, its all a matter of whether its worth your time/resources before making a decision on where to cut corners. If you really want to do a feature length film for a festival, I think its a good idea to see if you can go double-system if at all possible before throwing the towel in.

Might want to check out Jay Rose's book to learn more and this site for additional info and advice: Equipment Emporium. That site has articles and they're helpful too over the phone.

I'm learning a lot too and the posts here at DVInfo are great help.

Stephen and Christopher, I really appreciate your posts. Will definitely read all that you suggest before making any final decision. (My DSL has been acting up, so my internet time has been cut down considerably, but I will get to them... man, Dial-up is hard to put up with after DSL!)

And Stephen, don't get me wrong. I'm a huge fan of the DVX, and I'm aware that it's audio is supposed to be better than other cameras in its class. It's just that external would be that much cleaner, if I can swing it. The plan (unfinanced at this time, but there are realistic possiblities) is to go out to 16mm for the festival circuit, Academy submission, etc. The more press this story can generate the more good I can do for these people. It may be a small story, but to me this is a very personal and important story to tell, and I want to give it the very best I have to give, to do justice to it, for their sake. And while I realize that on the budget I'm working with, it's going to be tough to bring in a class act/professional project, but I'm going to go for, with that as my aim. (Everything is a compromise... this wireless lav is better, but at $250, when I need two, is it THAT much better than two $99 ones by the same company? And on the decisions go!) We'll see how it all plays out as the months wear on. I know it's "going to be a bumpy ride," but it will also be priviledge. And an adventure.

Christopher, I bought a slate early on. My film background mandated it. :-) Thing is, some of the interviews will easily be several hours. But given what you say regarding twenty min. takes, maybe what I can do is basically "watch the clock" and interupt (not always possible) and reslate at relatively set intervals. Hmmm... you guys have given me lots to think about. Will head over to Amazon and give that book a look as well.

Thanks again. These boards are great.
Marcia

I recorded a classical, choral concert, dual system, with no synch problems.
I was using Schoeps microphones, fed to a Mackie VLZ mixer, and sent one pair of line outputs direct the camera, and another pair to a M-Audio USB duo external sound card, connected to to a laptop 2200 Athlon PC (running off the mains, set up as at http://www.musicxp.net/tuning_tips.htm).
I used Vegas 4.0 to record the sound as a .wav file.
It certainly stayed in synch for the duration of each 5 to 20 minutes of continuous playing. As I was videoing the singers, it had to be lip synch accurate.
It's really easy to synch each take using Vegas 4. You just slide the external recorded .wav file until it lines up with the one attached to the .avi video file. If you have a clapper board as a marker, this should be easy. You can fine tune this by expanding the timeline, so that you can line up identical wave patterns. When it's lined up, lock the new audio track to the video, and delete the old audio track.
The sound of the DVX100 is excellent, by the standards of video cameras, and probably OK for dialogue, but not really adequate for classical music. The USB duo allows you to record in 24 bit 96k sound. The 24 bits gives you much more dynamic range, which is essential for full scale classical music, or there will be hiss in the quiet passages. 96k is better than 48k, but you need good Hi Fi equipment to hear the difference. Even if you end up downconverting the 24/96 wav file to 16/48 for video, it still sounds better than the DVX100.
The USB duo is only about $200. (There's a new firewire version which may be better.) You can use any modern laptop. Why not try it?
Patrick

It sounds like the USB duo is an attractive alternative to what I'm doing. I'm using a similar set up but it’s a lot bigger and requires a rack mounted PC and sound card (motu 896). I'd be better off with a laptop and small sound card to be more portable. I've recorded up to 35 minutes without syncing problems with 24/96 with as many as 6 channels. The other thing that I can say is that two DVX100's sync very well together or at least mine do. I've easily gone 60 minutes without any sync problems between cameras. For 5 to 10 minute interview segments, I would not worry too much about slaving time code or sync. You should be fine. But if you can run a mic or two to your DVX100, that woiuld be even easier and give good vocal sound.

This being said, I really want to slave timecode to my cameras or to the sound card. I want to do longer music projects where high-end audio is a must and lip sync is key. The audio may be good on the DVX100 but its not 24/96 and it does not allow me to record 8 channels as does my sound card. The lack of World or SMPTE sync on the DVX100 was the single limiting factor that almost caused me to purchase something else. But there is nothing else in the price range that does sync. In the DVX200, give me sync and a 16x9 CCD and no more and I'll be happy.

Just an update... spent many hours yesterday at sound houses in LA, and after getting a lot of conflicting advice regarding all the scenarios I'll be shooting, the one constant was the old "keep it simple, stupid" rule. These guys are at the top of the heap here for rentals, and are regularly cited around town as "the" experts, so while I maintain the right to ignore at my peril :-) the general tone was forgo dual system sound and record to the cam.

Given that I'll be a crew of one much of the time over the next nine months (and will have film students for help when others are along), I am resigned to thinking their advice is probably the smart way to go. Since what I will be recording will largely be dialogue, events, and ambience they felt wireless or wired lavs, fed either through a mixer or straight into the DVX100, was going to get me close enough that doing it dual sys wasn't worth the trade off. The only exception to that will probably be when I'm recording a large "room" (really a large second story covered deck where meetings are held) and I'll probably want to have mics in each corner at the back, aimed out at those present to get their questions/comments, that would be best fed into something that remains at the back of the room. I'll be at the front recording from that angle, and for safety reasons, I don't think it's probably a good idea to have cables trailing all over the place. In any event, that leg of this journey isn't till next summer. Plenty of time to change my mind on that part. ;-)

In any event, just wanted to say again thanks for all the great feedback. Look forward to more conversations on the boards down the line.
Marcia