Best way to sync audio and video?

[newrob1]

I am currently involved in a weekly "live" DVD project where a 3 camera crew film each of 5 bands playing a selected song 2 times throughout their set. I record this on a HD24 and between the 24 track mixdown and the compilation of the 2 takes of video we get a very nice end product. The video and audio are currently sync'd by "eye" and it looks very good. I am more the technical perfectionist type and would like a more professional method of syncing the 2. I know that both the HD24 and the DVCAM decks read SMPTE so what is the best way for me to do this? How do they do the MTV videos? Let me know!

[moon_unit]

Originally Posted by newrob1

I know that both the HD24 and the DVCAM decks read SMPTE ...

You're getting warm.

[hociman]

Originally Posted by moon_unit

You're getting warm.

Enough with the pretense. Either tell him he's not worth your time or tell him how to do it!

At the shoot, use a master timecode generator to send timecode to both the DVcam camera and the HD24. Use a distribution amp to send the timecode to both devices, do not daisychain the timecode!. When it comes time to synchronize the two again, route the timecode output of the DVcam deck to the timecode input of the HD24 and have the HD24 chase the incoming timecode.

[7161]

easiest would be mix down to stereo and then export the master audio file to an editor like VEGAS and do your video in that

[Albert]

Timecode would work well, if you can technically do that.

Another very simple method is to put a sharp sound at the beginning of each video shot. Like the old style clapboard you sww in movie shoots. That is what they used for all those decades to sync up the sound to the picture. So a clapboard, a person doing a single sharp clap, a drummer hitting his sticks together once, these would all work.

The third way would be to have one of the video guys record a scratch audio track with the sound recorder on their video cam. Then you would simply use that as a guide track when laying in your recorded audio.

[Tim Halligan]

Rightio.
What you need to do is get hold of a portable Master TC generator...Aaton make one called the Origin. Most film rental houses will have one... There are others available. Best if you can find one with multiple outputs, and connector types. Most professional video cameras are looking for TC on a BNC connector.

Set the generator up and start it running...pick a number - any number to start from. Time of Day is adequate.

Get all of the cameras (with the monkeys that operate them) and set all of the cameras to TC free run. Jam sync all of the cameras. Check - by eye - that all of the cameras are behaving as expected.
Fix the camera-morons with a steely glare and say "If you change batteries, you MUST re-jam the code. If you don't, I - and the entire post-production department - will kill you SLOWLY."

This is critical because not all cameras remember to count when you remove the batts for more than a few seconds...

If a camera does drop its code...no sweat. Using a BNC cable, two cameras can jam sync, without having to find the master gen. Just use TC OUT on the "good" cam, to TC IN on the "bad one".

When the monkey hits Record, it will be at the master code. Even if they button off during the performance, then restart, the code - because it is free-running will be right.

Also, because the code is now non-continuous, get them to record a liitle earlier that normal...say 15 secs of pre-roll...this will make the video editor's assitant ( ie: the digitise bitch) much happier.

OK, so that's the vid side.

Audio is just the same...but crewed by better people.
Whack the TC into the appropriate hole, leave it there, and set your system to chase incoming TC. When you drop the multi into record it will be at the correct timecode.

Because you are working for a video production, it might also be advisable to sync your system to Video Black.

Not being a PT driver, I can't help you with the gory details on how to do this...


Hope this helps.
Cheers,
Tim

ps. Newrob, I salute you sir, in your quest for accuracy, and for not dropping your standards.

[Randall]

I have a spare Fostex 4030 and 4035 sittin around here I'll make you a fair deal on... PM me if your interested

[tINY]

Thanks, Tim....

Remember to that different clocks will drift differently (if you just "jam synch"). this usually isn't a problem with video, but if you expect 2 hours or continuous audio/video to stay in synch, you migh be in for a surprise.

The good news is that audio to video synch isn't that crittical and 200ms is probably liveable.



-tINY

[hociman]

Originally Posted by tINY

The good news is that audio to video synch isn't that crittical and 200ms is probably liveable.

~6 frames of latency is livable? Are you nuts?

[Tim Halligan]

Originally Posted by tINY

Remember to that different clocks will drift differently (if you just "jam synch"). this usually isn't a problem with video, but if you expect 2 hours or continuous audio/video to stay in synch, you might be in for a surprise.

Yes, you're right. Assuming you could actually get 2 hour tapes, I would expext a little drift. If you want to get really finicky about it, you could get everyone to re-jam between acts. The bigger culprit in sync drift is actually the video.

As it is, the original poster is only recording 2 songs every 30-40 minutes.

Originally Posted by tINY went on...

The good news is that audio to video synch isn't that crittical and 200ms is probably liveable.

You're kidding, right?
Hahahahahahahahahahahahaha! LMFBO x 1000.

Wrong.

The real news is that audio to video sync IS critical. 200ms = 5 PAL frames, and if I submit material that far out of sync, I'll get a tech rejection. Most tech specs will allow for 1 frame of sync error...usually to account for digitising latency on the video side.

Now, I don't have the exact numbers readily available to me, but Digibeta camcorders' internal clocks are rated to about 15 frames of drift per day, and I would expect professional DV cameras to be in a similar league.
Aaton Origins are rated to low single digit frames per day...which is why you'll find them on film sets where double system recording is the norm.

Accuracy is everything when dealing with video.


Cheers,
Tim

[tINY]

I'm glad that equipment is that good these days.

I did some research (after shooting from my hip) and found out that current ITU recomendations for Video/Audio synch are audio +90 / -185 ms. Other sources say that +20 / -60ms or better is a goal to shoot for.

I was basing the 200ms on experience in larger halls and other situations where 75 yards doesn't seem to annoying with visual and audible queues arriving "out of Synch"



-tINY

[Tim Halligan]

Originally Posted by tINY

I did some research (after shooting from my hip) and found out that current ITU recomendations for Video/Audio synch are audio +90 / -185 ms. Other sources say that +20 / -60ms or better is a goal to shoot for.

I was basing the 200ms on experience in larger halls and other situations where 75 yards doesn't seem to annoying with visual and audible queues arriving "out of Synch"

Wow. I didn't realise that the ITU spec was that loose.
This explains why most delivery specs that I have seen are based on EBU - where they are far less tolerant of sync errors of the magnitude you described above. (As a side note, most people when quoting on post-work for tv series ask a number of questions: how many episodes? Stems/M&E required? Is it being sold to Germany or France? If yes, the price goes up to allow for the inevitable tech rejections - "ve have an anomalous number of footsteps..." Seriously, this happens!)

The audio delay from 75+ yards certainly is noticable, but when in the room, with the noise, the atmosphere, and the adrenalin, our brains "allow" for it - or at least don't get too bothered by it.
On video however, sync is absolutely vital. To me, there is nothing more annoying than seeing the drummer - on video - hitting the snare, and having the audio happen after the event...or worse, before...especially when it is not that difficult to get everything locked tight.
The video gives you a perspective that - as an average punter - you couldn't ever hope for... a "perfect view" if you will, and the audio should match that "hyper-realism"
The technology to achieve this is readily available...why not use it.


Newrob, when you say they shoot the same song twice so they can get coverage, do you select the best audio take so the video butchers fit both performances to only one audio take, or do you cut between performances when they do? If so, how do you deal with tempo/tuning anomalies?

Cheers,
Tim

[Sound Sorcerer]

Hello,
You can find more about multi-camera sync sound for video & film here...

[T.RayBullard]

Originally Posted by Sound Sorcerer

Hello,
You can find more about multi-camera sync sound for video & film here...

Nice wendt and portabrace. I have the x4...

[leeascher]

Tim Halligan probably described the most common way to to supply SMPTE time-code to audio and video.

In L.A., the most common master TC master clocks/sync boxes are made by Ambient. I know on the Sony F900 camera, you can set the TC switch to EXT, and leave a jammed Ambient Lockit box plugged in. This system will hold time-code, even after power downs. If your audio recorder doesn't have SMPTE time-code features, you'll have to record the time-code onto on audio channel (which will require a codec in Post to decode the audio signal back into numbers). Most Posties advise recording time-code at -30dB.

Before embarking on your time-code journey, make sure to do your homework. Make sure everything is OK'ed by your Post Production people in terms of frame rates for both audio and video. For NTSC video, sound's TC is usually rolled with 29.97 fps. The TC for the video camera is usually the same, unless it is high def video... which is usually rolled at 23.98 fps. Make sure your Post people designate whether sound's TC should be Drop Frame or Non-Drop Frame.

For more suggestions, you may want to consult the RAMPS (rec.arts.movies.production.sound) newsgroup. Wolf Seeberg has written a few guides on time-code for audio and video, which can be purchased at Location Sound in L.A. www.locationsound.com

[jwh1192]

well ... my .02

in your original post you say you are using DVcam deacks (what model) and HD24 (i could be mistaken but i thought you had to have a BRC or at least an MTP AV to receive SMPTE TC into an HD24 ...

are there video cables running from the cameras to a directors station (where he / she can talk to the cameras from) . if so, add a TC line to that cable and send continous TC to the cameras from your HD24 (if it spits out TC) , or use a master TC generator as the other lads have said above ...

i still feel that sound should be the TC master on shoots like yours ... unless there is a house Sync / TC generator ...

blackburst will help ... i do not think the HD24 has video sync input ... hence why i say you need an MTP AV type box ...

have fun

john

[Henchman]

Originally Posted by tINY

The good news is that audio to video synch isn't that crittical and 200ms is probably liveable.

-tINY

Well, you've obviously NEVER done audio post. If you did, you would know that after 2 frames it starts to look rubbery.

[0VU]

In the absence of central T/C and video/black and burst ref generators, my preferred method is to take feeds from the vidiots of SMPTE/EBU timecode and video and use these to sync the multitrack.

Afaik, an HD24 won't directly input or output SMPTE timecode - it speaks MTC (at least the HD24XR does) so if I'm using HD24/XR, I use a SMPTE-MTC converter, (usually a MOTU MTP/AV) to convert the code and provide sync for the multitrack. THe MTP is first sync'ed the incoming timecode and video. As long as the SMPTE and video sync are maintained all through the mixing, mastering and editing chain, things should stay tight to picture.

I agree with John that on a shoot like yours it's probably easier to make sound the T/C and sync master and distribute it to the cameras/video recorders. I found that when I started doing any real quantity of sound for picture work, it was so much easier to get my own T/C and sync generators and supply the feeds to the video side that it was worth the money to do it (and having the facility actually got me work as it meant one less thing for the vidiots to worry about).

If the cameras are all recoding iso, with no sync or central control/monitoring, you could try using a timecode slate to get reasonable sync at least at the start of the shoot. Drive the slate from your timecode source and get all the cameras to look at it at the start of the shoot. If they can be persuaded to do this at intervals during the shott it might help with any drift as the shoot progresses. It's far from ideal but I've workd to this system several times and it's ok as long as the post guys keep an eye on things. If you're working to film cameras it's about the only easy way that I know of to do it.