Help to sync audio with video

M

MarcusarilliuS_IRL

Member
Hey guys,

New to film making and cameras in general really and need some advice.

I'm using a canon 60D and recording the audio separately onto the pc using cakewalk.
I'm using a terratec phase88 rackmount firewire soundcard that can take an external word clock for synching purposes.
I am using it for recording music(acoustic guitar + voice) so wanted to know what the best way to do this?

I was wondering if you can get something like a programmable word clock and set it to whatever setting the 60D is using , then plug that into the rackmount sound card and then the audio and video will be using same word clock data so you don't get slip in the audio when you sync it afterwards.

Thanks.
 
Word clock is not the same thing as timecode sync. Word clock is for syncing the bit rate between machines. Timecode is actual metadata for media. A different animal entirely.
 
First off "word clock" isn't positional, it's a timing signal. Second there is no wordclock connection on the D60 so even if it did do what you want you still couldn't do it.
TimeCode would give you a positional reference, but the D60 doesn't do that either.

The relatively good news is that you can set the D60's clock to the same as your laptop and your files should have time stamps that are very close so you can figure out which goes to which. Or you can go old school and clearly slate each take. I would highly recomend slating all the time anyway. When you slate make sure whoever does it also reads whats on the slate out loud so it's on the audio recording.

After that you "phase in" the the second audio with the guide track on the video. You could do that by hand or use Pluraleyes. Your on Windows so Dualeyes is probably an even better choice.

IF you slate you can line up the "Clap" visually and is the only thing that works if you don't have a decent guide track.

For short takes your probably fine but I would do some online checking on how stable that card is. You may want to slap a stable word clock on it just to cut down on drift.
 
Sam Mallery said:
Timecode is actual metadata for media. A different animal entirely.
Click to expand...

It's actually a lot more than metadata. The TC stamped on the file is metadata, but what you would be using to sync devices positional references (what they will use to create that metadata time stamp) is a LTC. It's a stream of tones that travel over audio cables between devices.

Your right in that although he was really asking about LTC, all he will lilikely dealing with is TC time stamps.
 
Thanks for the replies guys.

The drift is the thing I was wondering about.
I'm not actually sure how this happens(sorry for the ignorance here :) ) is it that the cameras idea of what 1 second is , differes slightly from the pc or the sound card?
Not really sure.
It's this that I want to correct/avoid anyway.
The actual synching i am ok doing by hand, as long as there is not some drift between the audio and video, so it's drift I want to understand to be able to avoid.

Sorry if I'm not explaining myself very well here :)

Thanks again.
 
MarcusarilliuS_IRL said:
so it's drift I want to understand to be able to avoid.

Sorry if I'm not explaining myself very well here :)

Thanks again.
Click to expand...

Drift is everywhere. The components that make up the electronic circuits are selected based on price of the components, and the target recommended manufacturer's sales price. Hence one can sort of 'assume' that a higher quality device will have less drift... Drift also occurs due to temperature changes, age, etc.

How time is synchronized in many applications, is by means of a reference signal, that is generated by a reference time piece. In the case of film this may be between the camera and the audio recording device. In a studio there may be a 'master' time piece that is distributed throughout the facility, or in the case of a TV broadcast system, distributed throughout the whole network.

GPS devices can with just one satalite visibile receive a 'master clock' and generate reasonably accurate 'local' time values...

The fundamental circuit used to syncrhonize time between devices electronically, is via a circuit called a phase lock loop, aka PLL.

Without a camera and recorder that has such synchronizing features, you can experiment with your devices under various conditions, record with camera and the camera's audio, simultaneously recording with your external recorder, and determine 'drift' in an approximate way, and then make your shot length relatively short. Depending on the quality of the electronics involved, you may never see sufficient drift to worry about, or may just limit your shots to 1,5,10 minutes... between 'slating' the shots.
 
ok ,thanks for that.
Seeing that it's a canon 60D DSLR camera, the max clip length is around 11 minutes, so hopefully that will be alright.

With drift, is it a progressive thing, as in does the gap progressivly grow, or does it go out of sync and then come back in sync, like a breathing motion?

Thanks.
 
Good to know.
I did a video the other night of me playing and singing a song and recorded the audio separately onto my pc using a studio mic.
Then in premiere I alligned the separate audio with the cam audio, then muted the cam audio and exported the video, and seemed to be fine.
The reason i asked about the going in and out of sync thing though is that I got a sense that was happening slightly.
I don't know if I was just staring at it for so long that my eyes were acting funny though?
 
davefisk said:
I've only ever seen drift get worse over time. The gap grows over time.
Click to expand...

Not to belabor the point to much further, but drift due to environmental situations, such as temperature, could vary such that you may not 'see' drift unless you looked at every second of the media. Drift due to the respective time bases being 'off' from their stated frequency, but within the manufacturer's tolerances, and constant, will result in ever increasing difference. (Well there is the case where the time generators are off in the same way...)...

The best you can do is hope the difference is small relative to the time of the shot.
 
MarcusarilliuS_IRL said:
Thanks for the replies guys.

The drift is the thing I was wondering about.
I'm not actually sure how this happens(sorry for the ignorance here :) ) is it that the cameras idea of what 1 second is , differes slightly from the pc or the sound card?
Click to expand...

Digital stuff is all clocked at a high rate (in the megahertz then divided down to the sample rate). The clock can have a number of problems. One is just not running at the right rate, another is stability- it doesn't stay at a steady rate, and the third is jitter - pretty much the same as being unstable but in a sample to sample "waver" kind of way. Less well designed (generally cheaper) clocks tend to suffer from all three to some extent.

The first two are only a big sync issue if you deal with another digital source that is clocking at a different rate. They can be "fixed" by running a word clock to everything. In that case all the devices clock to the same clock and every one runs at the same speed. Jitter is something that can be solved by using a high precision clock as the clock everyone locks to. Jitter causes a subtle (to not so subtle) "smearing" of the signal and a general lack of clarity. It takes a lot of jitter before most people will notice and it doesn't really affect sync since it averages out.

In general you only have to worry about relative drift. If your clock is off by X, but everything else is off the same amount you still remain in sync.

In practical terms digital is off by so little that on takes of say three minutes or less you don't really need to worry about it 99.99% of the time. With your camera you takes are limited to around 10 min or less so you might do some tests but I doubt there will be audible drift over that time. Where you have to get worried is in long documentary shots like concert footage. If you have an hour long take and you are not all locked together I can almost guarantee you will have a problem.

Drift will drift apart because the two (or more) clocks are not running at the same speed. IF the clocks are very stable and you have drift you can figure the difference and time shift one to match the other. But usually if your drifting your not very stable either. Everything other than design should have only a slight difference in clock speed. So if you do a test and it works once it will probably work in other situations. AN easy test is to film a metronome for the full shot with your set up. If you have a drift issue it will be noticeable as the ticks go out of phase with each other.

But again even IF you notice drift in ten minutes that will not actually be a problem for narrative shooting in most cases. A) you will not normally shoot takes that long and B) even if you shot ten minutes straight it would be a very rare film that used more than a few minutes at a stretch. In that case you can tighten the sync on a clip by clip basis.

In general you see more drift problems that get created IN post than ones that come INTO post.
 
I would recommend doing it by slating. But slating is not easy...

I prefer the "burn your fingers first and then you know you can't touch the boiling water" way... But anyway here's some advice

- be sure the slate is in the image (and the closing piece also), when you're in a hurry and have to go fast fast fast fast fast, you surly will forget to slate, do it fast without adapting the scene/take nr and do it fast without looking if it's in the image. Going slower = going faster....remember that. It only takes a few seconds, but saves hours (yes hours) to sync it afterwards.

- don't believe in magic

- never say "we'll fix it in post"...never....specialy when you're a director and are talking about sound :-p

There's a reason that there's one guy only doing slating...only that.... But it saves a lot of time in post....
 
Cheers for the tips ;)

Also another question I had in another post,
I'm editing in premiere CS5. Should I also convert the h.264 files first? If so, what format and settings would you recommend converting the clips with mpeg stream clip?

Thanks.
 
it depends.... But with mpeg streamclip you can try it out.... But don't take "JPEG"... take someting like mov, mpeg, dvpal/dvntsc, things
 
MOV is not a format. It's anything wrapped in a Quick Time wrapper. mpeg? Maybe you mean MJpeg? DV could be fine but it's only SD so not a great choice if your in HD also it has a less than great color space so not great if your doing green screen or color correction etc.

If your on a Mac then Prores is a good choice. It used to be a generally bad choice to edit in h.264 even if your box could handle it. I'm not sure if this is still a big issue. It might be and maybe asking somebody like Stu Maschwitz would get you a "real" answer. The problem is that questions like that are a moving target. A couple of years ago it would be an absolute no no to edit h.264. Now in CS5 I know you can but is it a good idea? If you post this in the video sections then I'm sure you would get a lot of replies and they would probably be strong in each direction so???? The best thing is to really know what your flow is and bias the answers by those with experience that are trying to do the same thing. You will always get some hobbyist who will be working in some weird way and swear by it. And it can be REALLY hard to tell who knows what they are talking about and who doesn't. So if your doing wedding videos pay more attention to the wedding video folks than to the hobbyists or the low budget feature folks because they both have different agendas. You also don't want to focus too much on what the full priced features are doing because that also is a different agenda.
 
Yea I can play h.264 in CS5, but as you say, is it a good idea?
Also when effects are added to clips in CS5 I'm getting choppy playback , so maybe changing format might work better.
Want to choose a format though that won't loose quality.
I'm using PC btw not mac.
 
Are using drop frame rate? Eitherway..it is best by doing the old slating with a clapper board and you can sync from there..If you dont have one. then get it on camera in some way ,clap your hand and also audio sync it and you should be in sync. Just do it like they do when you shoot on film.
 
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