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Hello, I have a question concerning frame rates for digital movie files.

I am working on a sound design for a New York based project, ( me being UK ). I know PAL and NTSC have different frame rates, but does that apply to a .mov file as well?

Basically, if I design a sound track to the digital movie file I am sent, and I send it back when done, can I be assured it'll sync up at their end, or will it go through a change when on a US mac compared to my UK mac?

I've always imported videos into Pro Tools without ever considering what would happen with a US based video file!!!

Any help would be great, I really don't understand movie stuff!

thanks,

Fred

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Ok, so this is what i believe to be the case. I've actually been seriously questioning myself about this, but i can't think of anything solid enough to change my mind:

For basic sound post, frame rates don't really matter. If they send you a session with burnt in timecode, you really should match your session's frame rate to that of the video so your session TC matches the burnt-in. Apart from that, the only thing that should make you think about session frame rates is when you're linking up with other machines, especially video decks.

Here's why i believe this: Sound doesn't have frames. It has sample rates, but that can only affect the length of your audio if you transfer it from one SR to another without compensating for speed (pitch and length). In Pro Tools, this compensation is automatic. When you bring in your movie file, Pro Tools will play it at the correct speed, regardless of the session frame rate. To do otherwise would take some hefty processing power, and give you a jerky, stuttered image (i'm pretty sure). Pro Tools uses Quicktime to play video, and Quicktime will know at which speed to play the video. You can set your session to any frame rate and all it will affect is the TC ruler and output TC - never the actual speed of the session.

Of course, it's always a good idea to use 2 pip/end sync pips, to make the audio lay back easy and verifiable. Sorry if i'm not that clear, it's a friday afternoon thing. And like i said, if i'm wrong, i would be grateful to be pointed in the right direction.

  • Thank you so much, like I said earlier, I know there ARE considerations, but I just don't know what! Both answers make sense, and I think sync points are certainly the way to ensure alignment with the video. Working over the internet means I want to be sure that what I send will work, and I am a noob in terms of video. Thank you. – Fred Riding Apr 6 '12 at 22:49
  • No worries @Fred. I'm pretty sure that you don't need to worry too much in your situation (apart from matching burnt-in TC). – Roger Middenway Apr 7 '12 at 3:38
  • we work in both NTSC/PAL frame rates at work all the time, including moving projects back and forth between the two. you mention it's really only important when interfacing with other machines, but i'd argue an editor's computer qualifies under that statement. a better wording for your answer might be, "it may not be important while you're working internal to the Pro Tools session, but it's necessary before you output." Pro Tools uses audio samples as it's primary timebase, but editor workstations, decks, etc. use that frame-rate timestamp. That's where the playback speed problems occur. – Shaun Farley Apr 7 '12 at 11:52
  • @Shaun Thanks for the clarification, i didn't know that session frame rates from Pro Tools were embedded in the metadata. I guess this might be something i'll have to look into - i would have thought that 1 second=1 second, regardless of how many samples or frames it's divided into. The only use for frame rates in audio metadata i can think of would be if FCP isn't sample accurate? Or perhaps to help automate pullup/downs? FWIW, i've never had a frame rate related problem delivering to editors in PAL or NTSC. – Roger Middenway Apr 8 '12 at 0:44
  • yeah. unfortunately, 1 second = 1 second isn't always true in video...mainly with those framerates that aren't a nice whole number. that's why we've got 29.97 and 29.97 "drop frame." it's always the video side that's screwing everything up. ;) – Shaun Farley Apr 8 '12 at 4:38
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Yes, it matters. When you import the quicktime into your session, the video track should indicate what the frame rate is (right underneath the track name). [You could also check the file's info/properties to find out.]

Make sure your Pro Tools session is set to match the mov's frame rate in the Session Setup window (CMD+2 on the numeric keypad), and you should be good. [Note: for HD frame rates (i.e. 59.94 or 50) you'll be using the SD equivalent (29.97 or 25 respectively).]

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    So when I get the movie file, I should change Pro Tools settings to match the file, and then I can be assured once I send it off, and they watch it or bung it on a DVD, nothing will slide out of time? That is brilliant, thank you so much :) – Fred Riding Apr 6 '12 at 17:52
  • @Fred Riding - for your part, yes...but it's not a guarantee. we've been having a lot of problems with Final Cut 7 lately where it rewrites the header data of the audio file on import, and it doesn't match the editor's timeline. this is a Final Cut problem, not Pro Tools. make sure that the editor puts in head and tail sync points for a quick confidence check when you send audio back to her/him. – Shaun Farley Apr 6 '12 at 18:15

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