Frame Rate of 702
 

Does anyone know what frame rate the audio runs at in the 702 not the 702TC

is it 30 nd? will it sync with 23.976?

The 702 does not stamp timecode to the BWF files. The 702T does though.

Adding a bit to Jeffrey's note ... audio doesn't have "frames" as such so there is no such thing as an audio frame rate. It does have a sample rate and the 702 is capable of running at a number of different sample rates, including the 44.1 kHz sample rate used for CDs and so for recording music destined for CD and the 48kHz sample rate used for video. But there is no relationship between the video frame rate, hence the elasped time associated with each frame of video which is what timecode is dealing with, and audio sample rate.

i see, so obviously it would be easier to sync audio from a TC capable recorder and a camera running at the same frame or sampling rate.

Well not entirely true here, you need to do some research on timecode and audio sample rates. Cameras do not run at 'sample rates'.. For instance, if I'm using an external recorder and the production is using a film camera.. The camera isn't going to run at 48kHz, 44.1kHz or the like.

Timecode, timecode, timecode.... it's a topic that often confuses pro mixers. Yes it matters, if everybody is using it. However, that said, people used audio for years without it, and so can you. Be aware however that you should at least use a slate to help sync up audio later.

The biggest issue with timecode is that it is stamped on the header of the BWAV file and it's not something that is stripped during the entire audio. By that I mean the timecode states when you pressed record, but it is up to the playback equipment or software to determine what the timecode is once you move away from the beginning of the file.

Some things to think about.
* Who keeps the master clock?
* Do you own a timecode slate?
* Are you using a camera that supports timecode?
* Are you doing real film? -- there are special considerations here....
If you're working on 35mm there is no audio or timecode that gets jammed to the camera, it's all based on the master clock jamming the slate and using the slate, telecine will sync picture and audio for dailies.

I bring all of these up, because it's not simply a matter of spending the extra money for timecode in your recorder. You have to know what to do with it and how it works for it to be of any real value to you. If you're working on a lot of small productions, most won't even know what to do with the timecode and most won't want to use it. It really isn't as critical as people make it sound, just use a dumb slate with a clapper and you'll be fine. If you don't own a time code slate, devices to jam the timecode to cameras, have a camera that supports timecode, then it's all a moot point.

Now don't get me wrong, I love timecode, but you have to have people who understand it to use it properly.

Wayne

I agree with Wayne. People think that timecode will align both audio and video files to each other and keep them in sync over the duration of the shot. It doesn't. Film going through telecine is another story. But with video TC does exactly what a dumb slate does - sets a single point where the audio and video files line up. But once you move away from that lineup point towards the end of the shot, TC does nothing to prevent them from drifitng apart. The video camera's and the audio recorder's sample clocks have to be slaved to each other or otherwise driven to insure they run at exactly the same rate in order to insure there's no drift in the audio versus the video. Most of the time timecode is generated by a totally separate clock from the sample clock and does not lock the files together over their complete length - it only locks them together at one single point.

I returned the 702 and went with the 702TC for a better future investment.
My HVX does not support timecode, but i do figure for the extra $600, its worth to get the TC version for future camera purposes that may support TC in/out

Dont get me wrong, i owned the 702T with the denecke TC slate but didnt help much as my camera does not support other than time of day code. so i went back to the 702, then realized that in three months, i may purchase a TC capable camera and i can jam sync the recorder/camera

what threw me off is that the 702T has all different frame rates to choose from, i just wondered what the 702 would be as a standard (30 ND etc.)

i was given a brief lesson six years ago in film school, but i will revisit and research more about this. i have been doing the manual line up of slate sound and picture, but Timecode (if done well) well save a few headaches.

thanks everyone

Timecode won't help with your present camera unless you use a smart slate jammed from it. Even then it will only be a convenience, nothing more. That being said, I would have made the same choice as you did in getting the 702T model. When you're spending this much money it only makes sense to buy with an eye to the future. Let's say you make a jump up to a Canon XL-H1 with full timecode I/O and genlock capabilities - it's going to be nice not to have to replace your audio recording tools at the same time in order to be able to take advantage of its full capabilities.

NTSC video is typically 29.97 NDF
PAL video is typically 25 frames
24P video is typically 24 frames
Film is typically 30 NDF


I say typical here because there are cases where your settings may vary depending on what post production wants or what a director, etc. wants.

Wayne

exactly steve

You can send TC to the camera's AUDIO input then use a 3rd party plugin in in FCP to read TC from the audio track as if it was from the normal TC track. Yes you will most likely get bleed in the camera from one channel to the other with the TC rendering the other audio track useless but you can still get TC onto the audio track for sync in post. I do think some flavors of Avid may do the same thing. so if you know you can read the TC from the audio track in post, its possible. I supposed the trick is to record the TC low enough it doesn't bleed to you can still possibly use the other audio track.

all that said, many cameras have gotten decent audio handling, so you could also just feed them from the mixer in the first place and skip the external recorder. you have to know your camera and its performance in audio.

I use premiere and not final cut. i would have to say thats an interesting workaround but i still prefer using an external recorder as its preamps are better than any camera's amps, plus i get those extra bits to work with at 24 bit, more processing power and low noise when blending tracks in post.

i also prefer the seperate recorder for collecting fx, foley, room tones, ambiences, V.O., wild lines.

One more time...
TC won't help you sync a seperate audio recording to your camera.

The 7xx series SD recorders are timed with WORDCLOCK. The fact that the 7xxT has a TC generator is almost an artifact, it still syncs itself to its internal WORDCLOCK. The problem is how to convert the wordclock pulse into something the camera can use and lock its TC generator to. Unlike LTC, Wordclock is simply a pulse with no absolute start or stop value.

Once again, the easiest thing to do is use a clapboard at the start, line up the audio and the video to the clapboard in post, and stretch/shrink the audio in post to account for drift.

Good points, but isnt different when the recorder is acting as the master to feed both the recorder and slate?

taken from sound devices website
"The full-featured time code implementation of the 702T is designed specifically for dual-system film and video productions where audio needs to be master"

the frame rates will come in handy eh, 23.976, 29.97, 24, 25, 30 nd

Its internal generator should do the trick at 23.976 with an HD camera

and i will still use a slate just in case

All very true - in fact I wrote Sound Devices tech support and asked if the audio sample rate clocked itself off of incoming timecode when the recorders were supplied with external code and their response was they do not. But its internal TC clock is derived from its audio clock and is highly accurate. That's one reason they suggest using the recorder as the timecode master.

The only time TC will help with a camera that doesn't have timecode I/O and genlock is if you use the recorder as master and send LTC to a camera audio track, then when you import the video clip you instruct the NLE to align the clip into the timeline using the recorded LTC and ignore the TC recorded with picture. Then when you drop the BWF from the recorder into the timeline it will align itself to the LTC. Unfortunately the only editors I've heard of that can read LTC and align to the timeline based on it are Final Cut Pro and Avid and if we're not using either of them recording the LTC is pointless.

You can also jam a smart slate and when importing the cip into the timeline, align the timeline with the numbers shown on the slate, then when you drop the BWF onto the timeline it will autoalign. But unless you have a h*ll of a lot of clips to sync, that seems like an awfully expensive alternative to just visually finding the frame where the sticks of an old fashioned slate bang together and lining it up to the spike on the audio waveform.

You are also absolutely right that unless you can slave the video sync on the camera to the wordclock on the recorder or vice versa nothing you do with the timecode does anything to preserve sync over long shots. At best all TC can do is help with the initial alignment but when you move away from that alignment point, sound and picture will eventually drift out of sync unless the audio and video clocks are slaved to each other. How fast they'll drift out depends on the quality of the clocks - with some cameras you might get away with an hour before you're a frame off but with others it might only be 5 minutes.

Absolutely, but not many, in fact none that I'm aware of, prosumer cameras allow TC input. That seems to be reserved for hi-end studio cams.

Canon XL-H1 and XH-G1 have TC I/O and genlock but they're the only cameras I know of under 10 grand that do.

Its well worth the extra money to buy the 702T in case one purchases a TC capable camera, hopefully "scarlet". I did two short films using the good old line up the audio/slate and probably will continue to do so. In the future, even when using the smart slate, the clapper of it would still help in case the Timecode does drift. Im looking for new ways to save time, hopefully timecode will help with this, but i still wouldnt fully trust it cause machines aint perfect either :)

BTW, SD says their timecode recorders use the frame rate to calculate subsequent timecode values (pg 30 of the 744T manual). So you're right with trying to get it right.

... And then there is "F Samping Rate Modes" which applies when recording for material that will have a 3:2 pulldown removed. I will have to worry about and understand this setting, but my brain hurts eough as it is.

The F timecode rate modes were included on the Deva to help when telecine had older Fostex DV40 machines. There was an issue in them that prevented them from reading and placing the proper timecode from the audio, so Zaxcom after getting complaints from mixers about it, introduced the F version of timecode specifically for the Fostex machines. SD when they introduced the 744T, included the F format since many post houses tend to be SO slow in updating their equipment and it's still an issue. Unless the people doing telecine for you tell you they are having issue with your audio and timecode, then you shouldn't use the 'F' flag on your timecode.

Wayne

My head hurts now but moving on, if im shooting HD at 23.976 and using this setting on the 702T as the master and sending out 23.976 timecode out to a smart slate and to the TC in on the camera,
where is the bottleneck here, other than maybe code drift after a certain time?

The "F" mode on SD recorders helps facilitate direct importation to an NLE timeline in order to maintain sync with film that has been telecined MOS. The recording is made at 48.048Khz, 30ND frame rate, while at the same time being stamped as 48Khz, 29.97ND. This automatically introduces the 0.1% "pulldown" that will keep sound and picture in sync.

Question for Wayne (or whoever): Do you know of a workaround for the Edirol R4 Pro, which does not have an "F" mode, that would accomplish the same thing? (I mention the R4 Pro, since you recommended it as a viable alternative to the 744T. How does it compare with SD on the basis of sound quality? Thanks.)

See the following Tech Note on the Sound Devices web site ...

http://www.sounddevices.com/notes/re...sr-frame-rate/

In short, you should be recording at 48kHz with 29.97 NDF timecode for HD picture shot at 23.976 and edited in an NTSC environment. I thought you said your camera didn't have a TC input?

no it doesnt steve, but when i'm making my soon camera purpose its gonna be a must, thats why iam getting the 702t. so when editing in a 23.976 timeline, doesnt it make sense to record the audio at that rate? unless of course we wont be removing pulldown upon import

I'll confess that there are moments when I think I understand all this with crystal clarity and then the very next moment it's as clear as a pea-soup fog! But if you're going to edit in an NTSC environment the video will be converted to 30 FPS so for your audio frame count to match the eventual video frame count, it needs to be at the NTSC rate.

alright thanks. When are we talking about the video being converted, when rendering perhaps? when importing into the NLE and removing pulldown from the 29.97, it'll be 23.976. so, if one edits at this rate, how does the audio match?
its only gonna match when reinserting 2:3 pulldown, aint it?

i think my question is good, just maybe you misunderstanding me

No, it's an excellent question. I recall seeing somewhere - I think it was Wolf Seeberg's site - just within the last couple of days that with most, if not all, HD cameras generate timecode at 29.97 non-drop even though they're shooting at a 23.976 frame rate. So while 1 second of video has actually recorded 24 frames, the timecode recorded for that same second counts it as 30 frames. In other words, a frame of video is not equal to a frame of timecode - could it get any weirder!

So, my gathering is, its best to record the audio at the 29.97 non drop on the 702t, to edit on the 23.976 timeline which will later match when rendering as pulldown will be reinserted to 29.97 NTSC. yes?

That's what Sound Devices recommends. The 23.976 timeline is used where the video is slated to ultimately be converted to film for release. If your release format will be video you'll be working on a 29.97 FPS timeline.

understood. What if the film is to be hopefully one day be picked up for film release, is 23.976 best? this way one can edit at that rate for film release and insert pulldown for video release?

I think it's generally done the other way around. Edit at 29.97 and remove pulldown if it's eentually picked up and released on film. Take a look at Wolf Seeberg's site - he 'wrote the book' on timecode for 24p.


http://www.wolfvid.com/html/lit.html

... but it does make "sense."

FWIU, DV/HDV cameras (I don't know about the HVX) always output 60 fields per second no matter what frame rate you record in.

So while one second of 24P has 24 unique frames, those frames are repeated at a 2:3 cadance to fit into a 60 fields per second output structure.

And 60i blends two fields together to make a single frame, so you wind up with a frame rate of 30.

It has to do with the fact that no matter what frame rate you record in, DV/HDV always output to tape at 60i. And timecode for 60i has a rate of 30fps.

P.S. I hope I haven't left anything out or misrepresented something.

Yep, makes sense to me, thought at first glance it is counter-intuitive.

Steve, I really don't think this correct. FWIU, you don't want to edit 29.97 with a pulldown if you think you'll be removing the pulldown down the road. In essence the pulldown is a broadcast/playback format. It's not really an editing one.

You first remove the pulldown from all the source media and then edit. Edits are dependent upon frames. If you remove the pulldown after editing but before rendering you will have deleted frames that some effects may depend upon.

An alternative would be to edit with the pulldown and then replace all the source clips with ones w/o the pulldown and render to get a 24P version. But I have no idea if that would still have glitches. I think you could run into timecode problems for one. And what happens to your audio? I believe you'll have to speed it up.

Lastly, you could render and then remove the pulldown, but now the effects have distorted the repeated frames and they are no longer identical. And if the footage does not have pulldown flags, the smart inverse telecine may not work b/c the process depends upon being able to identify like frames by comparing frames with adjacent frames.

But Roshdi, I am learning this whole process myself. I seriously recommend at some point talking to a post production house and running your workflow past them. You have done all this work and are spending money on timecode, etc, you have to be sure you get a real answer from a bona fide expert, which I am not.

True, but how will you deliver your final film? If it's going to DVD, it's going to be NTSC with pulldown. If going to broadcast, it's NTSC with pulldown. The only time you can actually deliver at a true 24FPS is if your final product is either going to be converted to film for theatrical release or will be distributed via the web. And remember that the camera itself is recording at 60i/30FPS even though it's exposing 24FPS, adding the pulldown as it lays the frames down to tape so the pulldown is already going to be there when you ingest into the editor.

Steve, I believe he hopes for a theatrical release--don't we all, LOL :). But seriously, if that's his expectation, then he should remove the pulldown before editing. You can always add it back once you have a final cut.

BTW, I went to Location Sound in North Hollywod today and picked up Wolf Seeberg's book "24P for Sound and Video Assist." I hate say this, but it was one of my worst of uses of $30 that I can recall.

It's very specific to actual cameras and equipment from five years ago. There are voluminous filler pages Xerox'ed from user manuals, and long lists of equipment--much of which is no longer made.

There is a lot of blowing about getting it right, which makes a lot of sense. But it's very short on explaining how things work in way that makes the info useful today.

JMHO and 3,000 cents.

P.S. Thanks for all your help. BTW, much of it has been more valuable than I can say ;) :).

can you believe that, i'm hoping for a theatrical release by being funded $33,000 next year for a film out with a whole bunch of professional actors looking for a demo reel and then they would be fed by like 5 of the sponsors for the film. Then another 7 businesses will pay for all the EPS.
I LOL'd really loud first time i heard it. what a loser i must have been :)

I'll agree that Wolf's book is almost unreadable. But with some effort, there is some good material and advice in there, particularly his workflow summaries. One of the reasons I posted the link to his site is he has put most of the more useful parts online so you don't have to spend the money for all the rest.

Roshdi,

Can't the HVX shoot 24P w/o a pulldown? That would make your life a lot easier.