Music Video Speed Up

mjdorris

mjdorris

Well-known member
Hey All--

I know this question has probably been asked a million times, but i've been unable to come up with the keywords that would let me search for it and find the answers.

I'm shooting a music video in 24pn on an HVX. If i record at 48fps, how much faster do i have to speed up the song? is there a direct formula? i would assume i'd need it twice as fast, but what i don't know is if the HVX really shoots 48fps, or if it shoots something like 47.98, as I guess I would end up losing sync by the end of the song.

Any help would be great--i know Barry wrote up a great response to a thread like this once but I can't find it.

Matt
 
I will be doing something similar next week, though with the EX-1.

I haven't tested what it will look like, I just think that effect will look neat. Are there any examples of music videos that have done this in the past?
 
i don't have any that i can think of.

i just remember people talking about it, and my director is really keen on getting a few shots that are over cranked but still sync. if i can't find anything out i'll just shoot at 48fps and double the playback speed on the song, and let you know the results =D
 
Don't know where the thread is, but here is what I pasted in my own archive of information from Barry's wisdom:

Jason


"The basic formula is that you first want to determine your footage playback speed, and once you know that, it tells you how to modify the song. So (in theory) if you're wanting to shoot 48fps slow motion for a 24fps timeline, you'd be getting 2:1 slow motion, so you'd have to speed up the song so that it plays for exactly half as much time as normal.

So again, in theory, you'd take a four-minute song and speed it up so that it plays for exactly two minutes. Then you'd set the HVX into 24pN mode, set your frame rate to 48, and play the sped-up song and have your actor/singer lip-sync to the super-fast version of the song. Then when you play your footage back it'll be in 2:1 slow motion, and you'd marry that version of the footage to your original song, and they should now be in perfect sync.

But they won't be. Because there's theory, and there's this troubling thing called "reality," and the reality here is that the frame rates are not what they say they are. 24fps is not, for example, 24fps; it's 23.976. And 48fps is not 48, nor is it 47.952 (as you might think, if it's twice as fast as 23.976)! It isn't. It's actually 48.17. And 12fps isn't 11.988, it's 12.26. Except if you're on the PAL HVX, where it actually is 12.500, half of 25.000.

So you need to adapt the formula to comply to the actual frame rates. Fortunately the HVX does part of that work for you, by doing the 24pN (or 25pN) conversion in-camera, so we only have to concern ourselves with how much to speed up the song by.

I haven't tested these, but I'd guess they're accurate; if anyone tests them and finds them inaccurate please let us know.

For an NTSC/US HVX, using a 24p timebase, for the following frame rates, adjust the song speed to:

12 fps: make song last 1.956x longer by stretching it to 51.1% speed
18 fps: make song last 1.333x longer by stretching it to 75.0% speed
20 fps: make song last 1.226x longer by stretching it to 81.6% speed
22 fps: make song last 1.067x longer by stretching it to 93.7% speed
26 fps: make song last 0.907x as long as normal; play it at 110.25% speed
30 fps: make song last 0.800x as long as normal; play it at 125% speed
32 fps: make song last 0.747x as long as normal; play it at 133.87% speed
36 fps: make song last 0.672x as long as normal; play it at 148.81% speed
48 fps: make song last 0.498x as long as normal; play it at 200.80% speed
60 fps: make song last 0.400x as long as normal; play it at 250.00% speed

For an NTSC/US HVX, using a 30p timebase, for the following frame rates, adjust the song speed to:

12 fps: make song last 2.445x longer by stretching it to 40.91% speed
18 fps: make song last 1.667x longer by stretching it to 60.00% speed
20 fps: make song last 1.533x longer by stretching it to 65.23% speed
22 fps: make song last 1.333x longer by stretching it to 75.01% speed
24 fps: make song last 1.250x as long as normal; play it at 80.00% speed
26 fps: make song last 1.134x as long as normal; play it at 88.22% speed
32 fps: make song last 0.933x as long as normal; play it at 107.14% speed
36 fps: make song last 0.840x as long as normal; play it at 119.05% speed
48 fps: make song last 0.622x as long as normal; play it at 160.73% speed
60 fps: make song last 0.500x as long as normal; play it at 200.00% speed

For the Euro/PAL camera it's different; the timebase of PAL footage is 25.000 fps, so that makes it easier. But the other frame rates may vary, so it needs some calculation too.

For the PAL/EU/AUS/NZ cam, set the recording mode to 720/25pN, then set your frame rate to whichever your chosen fps is. Then adjust the speed of the song according to this table:

12 fps: make song last 2.000x as long as normal; play it at 50.00% speed
18 fps: make song last 1.400x as long as normal; play it at 71.44% speed
20 fps: make song last 1.266x as long as normal; play it at 78.96% speed
23 fps: make song last 1.080x as long as normal; play it at 92.60% speed
27 fps: make song last 0.920x as long as normal; play it at 108.68% speed
30 fps: make song last 0.840x as long as normal; play it at 119.04% speed
32 fps: make song last 0.778x as long as normal; play it at 128.56% speed
37 fps: make song last 0.680x as long as normal; play it at 147.04% speed
48 fps: make song last 0.520x as long as normal; play it at 192.32% speed
50 fps: make song last 0.500x as long as normal; play it at 200.00% speed"
 
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