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Author Topic: Live Recording  (Read 5411 times)

John Ivan

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Re: Live Recording
« Reply #15 on: May 30, 2004, 03:55:22 PM »

Hi;

Well, If I were doing the whole thing myself I would bring the camera to the studio and have every thing locked when I mixed. I would want to see the video while mixing. One way to do this is to have someone make you a work tape {video} to use for mixing.This would be a version of the final,edited video. I would use the final video with time code on it as the master and lock the adats to it for mixing.then you can mix to dat and send it out to post. You could also use a video machine that has a time code track and stereo audio as well. This way, you could lay back the audio onto the stereo tracks and have a final product. Another way is to bring the cam to the studio and have everything locked up and print video into the software your going to mix to. This way, you've got the video on the hard drive running next to the audio and you have "perfect" copies of it. There are a number of ways to do this.

Remember that, just having time code on the video camera isn't enough. You need to have code from the cam and from the adats running into a box that can compare the two codes and control the speed of the adats. {I think the BRC dose this} It might be that the BRC converts SMPTE to MIDI time code though, witch is fine. There are a bunch of ways to get all this done depending on how many cams there are and how you plan on mixing,wether it's all going to a computer,3/4" video or what ever. Time code seems like a hard thing but, after a while,it's not to bad.
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"Transformation is no easy trick: It's what art promises and usually doesn't deliver." Garrison Keillor

 

clicktrack

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Re: Live Recording
« Reply #16 on: May 30, 2004, 06:38:17 PM »

Hey, guys...sorry to miss some of the party...I'll play a little catch up now...

ivan40 wrote on Sat, 29 May 2004 21:05


Hey click. Wazz--uupp;



N'much...just chillin...oh...I guess that wasn't the question you were looking to have answered... Wink

Quote:


you have more experience then me with this audio for video stuff so,answer this question for me will ya?
How long will audio against video run together without drifting? { With no sync} I know it depends on the stability of the transports and so on but, it can't be long can it? I guess if you do enough slates [Click sounds} on the audio that are matched to visual cues on the video, you could keep it together.



It won't be long at all...in fact, depending on the frame rate in use, the audio versus the video drift will probably become noticable after a few seconds.  Fully intolerable not to long after that.  The reasoning is in how the frame rates versus audio rates got developed.

I won't go into the details of why audio started with 44.1k and then, as technology allowed, expaneded to 48K and above.  If you're not too sure, do a google search on the Nyquist theorem and the spectrum of hearing for the average human ear.  For film, however, they use a few different rates for different things.  I'll assume 29.97 DF (drop frame) for the next bit, as this seems to be used alot for video work in North America (24 fps is widely used as well, but when and why is beyond me...ask a video guy on that one.) In drop frame counting, you drop the 0th and 1st frame of the first second of every minute except for any minute that is divisible by 10 (and you thought audio was complex! At least we count from 1-10 all the time!).  As a result, there is a perpetual accounting being done in the camera time to fix issues with the line rates of the screen.

If your audio, being as simple as we audio guys like it, doesn't account for this, then each minute (except for those divisible by 10) the audio will slip farther ahead than the video.  Needless to say, it won't be long before it becomes painfully apparent that the audio is out with the video.


Quote:


I guess one thing to do is load the audio AND video into a DAW and just keep movin' hacked up bits of the program until it's all locked up but man, What a pain in the ass!! I don't know if my idea will work or not but it's all I could think of.


Some programs automatically take care of this internally if they are capable of loading video into your audio project.  It asumes that the video is master and slaves the audio now-time to the video now-time.  It will slightly speed up or slow down the audio in order to account for the drop frames.  Again, this is something that I'd prefer to avoid...its better to be in sync as it is happening.  If you have a device to read the video black burst and generates a word clock and LTC for your multitrack, you are 100% done with sync issues.  When you edit in post, you set your multitrack to slave playback to video and voila...the machine will do your work for you.  (I'm basing this, by the way on the DA-x8 series.  I haven't used other variants of multitracks with video sync.)

Quote:


Another question I have for you clicktrack is this. Can the Composite video out put of the camera generate a clock signal? I don't know how this stuff works  as well as I should. I've done some post scoring but, that was easy enough as the video sent over was 3/4" sony with time code on the screen and we just printed everything to dat and the post house did finals {jingle stuff for auto industry} so, dose the video out have to be digital to have clock info in it? Thanks for your reply.


HEY debuys, are you still out there? hope some of this is helping. Don't let it overwhelm you bro. You can do it. We'll hang and answer.


You've got me on this one.  I would assume so, but I'm not sure if a clock can be generated by it.  Again a blackbust signal to a black box (MOTU box, JL Cooper box) that generates clock and LTC will be all you need to get this done easily.

Quote:

Remember that, just having time code on the video camera isn't enough. You need to have code from the cam and from the adats running into a box that can compare the two codes and control the speed of the adats.


Amen.  That's the word.  In my earlier discussion yesterday I inferred the LTC (SMPTE or MIDI Time Code) as well as the word clcok, but you are correct that both are needed.  The word clock is the stable count to lock all digital signals to.  The LTC is the count of clocks that gets applied to tape, and that both devices will refer to.  Hope this wasn't too misleading.

Believe it or not, this stuff isn't too complex.  Let the machines do the work for you.  All you need to care about is that the multitrack is slaved to the incoming video and once that's done, you're good to go.  The machine does the rest of the work for you.

Cheers
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John Ivan

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Re: Live Recording
« Reply #17 on: May 30, 2004, 07:18:59 PM »

Hey;

thanks for the info on this. My rig is 3 DA-88's with the sync card and when the new room is built,I want to pick up an old SP machine and practice more post score stuff. The sync card on the DA's is a killer card. I notice it has sony 9 pin also and I assume they make 9-pin compatible controllers that can run the whole rig at once. {all the video machines ,the computer and the DA's}. On the other hand,Can the flagship DA remote do this? I was also thinking that I could set up a controller in software that would do MMC. Could I start and stop the whole mess from the computer? what's the best way to do this with out having to hit play on more than one machine?

Thanks again for your time man. This place is great.

P.S. I had a great text on frame rates for video and all the wacky stuff about drop frame,pull-up-Down and all,,but I can't find the damn thing. I was hoping to help the original poster with this!
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clicktrack

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Re: Live Recording
« Reply #18 on: May 30, 2004, 09:32:21 PM »

The Sync card in the first DA-88 in the chain is all you'd need for a fully-slaved unit.  (This is, of course, separate from the video issues...this is just a simpler sync scenario).  You can, for example have a computer DAW program that transmits MTC/SMPTE out of a midi port, and have the DA-88s track to that.  As soon as your time code is rolling, the recorders will unpause...thereby allowing you to play or record based on the clock.

Configure units 2 and 3 to slave from unit 1 as normal (via the DA-88 link cables etc).  Unit 1 should be slaved to incoming MTC.

I can't give you a step by step on how to configure the card (I sold my DA-88s in favour of DA-78s and my memory on the minute stuff sucks) but follow the manual for both the DA-88 and the SY-88 and you should be good to go.  The internal DIP switches do need to be set up properly, but once that is done, I don't think you'll have much of a problem.

Cheers!
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John Ivan

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Re: Live Recording
« Reply #19 on: May 30, 2004, 11:45:30 PM »

Yeah; I've locked the DA's to my computer using SMPTE for address, and word clock to keep the clocks {tape and Layla} happy and it worked great using the DA's as the master.I used this for flying stuff into cool edit or wavelab for editing. I guess in the case of using video,I would use 3/4" sp as the master and this would trigger the audio machines to start rolling and the computer would follow. I would like to figure a way to control all this from in front of the computer using Midi-machine-control commands. I'll bet this is doable.I just wonder if I need a sony 9-pin controller to make the video roll because the SP machines don't have Midi in. It will be fun to look further into this.

The main reason to get this all together is two fold. #1, I'm a nut case and like to know how all this shit works and #2. I would love to start taking old video stuff,{old films for instance} and get back to some post scoring. I worked with a guy for a while who was really good at it and learned a great deal from him but it's been a while. It could be that there is a market for doing band demo shoots that are pretty high quality with out spending huge money. I would look at older broadcast cams and an insert/ A-B roll editor and mess around getting multi cam shots. It could be fun to do some "shorts" some friends are story boarding also. What fun.


Thanks again for your input.

P.S. I'd like to know more about your live recording stuff. Feel free to drop me a line. I'm easy to find when I'm not on the road playing.

Peace......................
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debuys

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Re: Live Recording
« Reply #20 on: May 31, 2004, 02:52:05 AM »

As of 6am Sunday the 30th we were done. We still opted out of doing any sync. The reasons are many. I'll list them in order of relevance:

1. The video crew arrived only an hour before showtime.

2. 2 of 5 cameras used were consumer grade with on camera mics as only means of recording audio.

3. None of the music sections exceed 7 minutes and thus any drift can be overcome via editing.

4. We will be mixing song by song and overdubing some and so the entire performance will not be continuous.

5. My lack of experience doing audio for video

We actually ended up doing 6 room mics. We started with a pair and it sounded like a studio recording with poor isolation between the instruments. The PA being mono reinforced this and what we got from the first two mics was nothing more than a reverb effect commonly refered to as "club". Go figure.... We added a second pair and the room opened up a bit more and we had a pair of SM 81's left over and 2 more tracks open on the ADATs so we put those right up front. Funny part is, although they were nearly right in front and above the mains the PA was the quietest in these. Also these were the only ones that we put bass roll off on since there were mechanical lights mounted to the same beam.

Speaking of lights, I might warn you guys if you haven't seen it before. The Phantom power in our snakes and cables freaked out the lighting control. It took the lighting tech 2 hours to figure out why his lights were haveing a spaz attack. After makeing sure his cabeling did not cross ours, all was well.



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Robert de Buys
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John Ivan

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Re: Live Recording
« Reply #21 on: May 31, 2004, 11:54:50 AM »

Well good luck with post man. You can do it but it's going to be tough to get this stuff to line up. For audience mics, I always use Omni's. A pair of PZM's properly placed gets the crowd great. It looks like you covered it with cardioids,which is fine. The closest of these to the stage might be useful during music as well.

Let us know how this comes out. We would love to know.


EDIT:: Regarding the lighting problem. I have never seen this happen before. Is the control cable for the lighting a "midi" type cable? It would be important to have a great shield on this cable but, I dont see how + 48v running in a shielded snake would "leak" into it..  It is DC, and only + not - so,I don't know. One thing that is important. When running big live rigs, We always split a 220 into two 110/30 amps and make damn sure the lighting is on it's own curcuit.
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debuys

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Re: Live Recording
« Reply #22 on: June 07, 2004, 12:49:45 AM »

ivan40 wrote on Mon, 31 May 2004 16:54

EDIT:: Regarding the lighting problem. I have never seen this happen before. Is the control cable for the lighting a "midi" type cable? It would be important to have a great shield on this cable but, I dont see how + 48v running in a shielded snake would "leak" into it..  It is DC, and only + not - so,I don't know. One thing that is important. When running big live rigs, We always split a 220 into two 110/30 amps and make damn sure the lighting is on it's own curcuit.


I know little of lighting, so I can only relay what the lighting guy told me. The issue was not with the AC. I made sure I was on the same leg as the FOH mixer for the recording gear and a totally separate leg for the air and lights in the truck. The issue was with the cableing he used to controll the lights (they moved and shifted gells) apparently the cabeling that looks like an XLR cable also uses DC and the phantom power from our cabeling caused his lights to twitch uncontrollably.
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Robert de Buys
Dreamcatchers
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jgreenlee

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Re: Live Recording
« Reply #23 on: June 07, 2004, 05:29:38 PM »

It's DMX-512 protocol used to control intelligent lighting and dimmer packs (as well as fog machines and anything else with a DMX port on it).  512 8-bit channels resulting in 256 steps per channel.  And yeah...Phantom will really screw with it.  That stuff should never travel down the same snake or cabling as the audio.

Peace,

James
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