Lip Syncing In Slow-motion - Formula

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Hello All,

Everyone's seen the music videos where they shoot under-cranked and the result is slow motion in perfect sync to the music. I know you must "speed up" the music in order to achieve this effect.

What is the exact formula to this logic? I've already searched the postings and even though I found a previous conversation regarding this subject, it did not answer my question.

Specifically, I am interested in shooting 48fps and 60fps. So how "fast" would the song need to be played back at for those two frame rates? I need precise, exact answers. No guessing please.

I'm terrible at math, so a simple answer would much be appreciated!!! :-)

Has anyone done this w/ the HVX before? If so, posting some examples would be helpful to see.

THANK YOU FOR ALL YOUR HELP! THANK YOU THANK YOU THANK YOU!!!!
 
Lip Syncing In Slow-Motion - Formula

Lip Syncing In Slow-Motion - Formula

My playback will be 30fps (29.97)

Please let me know.

CHEERS!
 
The problem with giving exact answers is that the frame rates aren't exact, so even if someone comes in with the magic formula it'll still have to be tested to be sure.

But, with that said, 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
 
Last edited:
Barry, Your My Hero....just wanted to say that....
Fyi... i was also wondering this exact thing for awhile...

Thanks for you always brilliant and useful answer :)

I know we all appreciate your input....
 
soo many numbers...my brain hurt...but that is the most generous and comprehensive response ever...kudos BG.
 
Lip Syncing In Slow-Motion - Forumula

Lip Syncing In Slow-Motion - Forumula

THANK YOU Barry Green!!!

Very much appreciated and so so helpful!!!

Cheers,
Andrew E.
 
Can you guys point me to a video example (preferrably a link I can view on the net) of such a music video that does this sort of thing?
...I don't watch mtv, so I wasn't sure exactly what the end results would look like.
 
I've just finished the shooting of a music video partly using slow-motion. I was so happy to have a 50Hz HVX200 :D 720p/25pN - 50fps just double the audio speed. But keep in mind - it's a challenge for the singer.
 
Barry... man, you're like that blue cookie monster from that show i once watched.
 
I know this is an old post but I am going to shoot some footage in slow mo this Sat and would be happy to post some results. If anyone else has done this please post some examples!
 
I tested by shooting, at 30P, someone singing along with a song that had been sped up to 125%. I placed the footage on a 24P timeline and slowed the footage to 80% and it matched the song at original speed quite nicely. You rock, Barry!!!
 
ZombieSquid said:
I tested by shooting, at 30P, someone singing along with a song that had been sped up to 125%. I placed the footage on a 24P timeline and slowed the footage to 80% and it matched the song at original speed quite nicely. You rock, Barry!!!
Click to expand...

depending on your nle you my be losing frames by doing it this way. you should conform your 30p 125% clips to 24p using something like cinema tools first. then it will drop onto a 24p timeline at the correct speed with no need to slow down.

in fcp if you drop a 30p clip on a 24p timeline, it throws out frames to conform the clip to 24p. then when you slow down to 80%, rather than retrieving the thrown out frames, it creates new ones based on motion which looks artificial.

i have shot a lot of videos overcranked like this. most of the time i playback the song at 200% and shoot 48fps. sometimes i playback at 250% and shoot 60fps. depends on the song and the degree of slow mo i am after.

here is an example of 200%/48fps note: this web version was encoded at 15fps by someone so it looks a little stuttered.

http://alexferra.com/navidomid.mov

here is an example of 250%/60fps - more extreme slomo. long intro, fast forward halfway to get to vocals.

http://youtube.com/watch?v=LLlAisb37DY
 
I did it recently at 200% for overcranking at 60fps for a 24pn project and it worked but extremely hard not to laugh when trying it. Your drummer won't even be able to hit every note he plays because it's just too fast. But when it's done it looks really cool.
 
pmpworks said:
I did it recently at 200% for overcranking at 60fps for a 24pn project and it worked but extremely hard not to laugh when trying it. Your drummer won't even be able to hit every note he plays because it's just too fast. But when it's done it looks really cool.
Click to expand...
60fps over a 24fps timeline is 250%, not 200%.
 
Barry_Green said:
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
Click to expand...

This Graph is super what i been after thats right super
 
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