TECH TUESDAY: Speeding up a song to shoot a slow motion music video

Good day everybody, welcome to Tech Tuesday with Joel Burke. This is my first post for the New Caribbean Cinema blog, and I will be addressing and posting cool tech tips, features and links that relate to video and post production.

I get a lot of calls from people within the video industry in Jamaica about all sorts of problems and issues they have when shooting or editing HD video. A lot of times directors call and ask me how to shoot a music video in slow motion and still have the artist synced to the music track. Since the video is in slow motion, the music track needs to be sped up to a certain percentage so that in editing the two of them match up accurately. There are several ways to speed up a music track, but the easiest method for me is using Final Cut Pro. Just drop the music track on an empty timeline in FCP and use the ‘Change Speed’ tool which is under the ‘Modify’ option, or using ‘Command – J’ for the shortcut. Now the percentage depends on the speed at which you want to shoot your video and also the frame-rate of your project (24p, 29.97, 25p, etc.) Listed below is a formula by Barry Green which I found on dvxuser.com, in which he lists several frame rates and percentages that can be used to speed up or slow down music to match certain frame rates. Once you have chosen the speed that matches the frame rate at which you want to shoot, input that percentage in the ‘Change Speed’ option in FCP, and export the audio. Burn that new track to a CD or put it on an iPod for playback on set. It would be wise to let the artist familiarise themselves with the new speed of the song, because if they can’t get it right you might end up in trouble. Also, it goes without saying that you should do some tests to make sure that the song will match up to your video before you go on set and shoot your video.

Article by Barry Green
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

Thanks to Barry for making such extensive calculations which i am sure too several hours to compile and to DVXUSER for posting pretty much everything you need to know about video and editing.

Feel free to comment or ask any questions, or if you have any alternate solutions to the same issues please feel free to share. See you next week.

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2 Responses to TECH TUESDAY: Speeding up a song to shoot a slow motion music video

  1. Maurice Christian Garcia says:

    Thanks for the info. I would also recommend Twixtor as a third party plugin for after effects users. I haven’t used it yet but it seems to render smooth results especially with different frame rate conversions. Check out this link from creative cow

    Also the best option for shooting slow motion on a budget right now seems to be a Canon 7D SLR 1080p @ 60 frames a sec. Just my two cents. Love the site though.

  2. Ceejayanthirium says:

    I remember seeing the making of a Jennifer Love-Hewitt music video for her song : “Barenaked”, back in 02′ which was shot in slowmo, with her singing the song faster to achieve the effect. Im guessing its an old technique but who said Jamaica is up to speed, lol

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