changing the bpm within a video

[williama39539046]

I am assuming this an after effects question, if not, please direct me to the correct forum. I have 2 different videos containing the same song but they are 2 different iterations. The first video is 3:19 with the song starting 7 seconds in at 178bpm, the second video is 3:15 with the song starting at 4 seconds in and is 173bpm. I would like to speed the second video up to 178 bpm. Once I have the second sped up, I will pull the sound out and sync them together. This for Halloween project where I will be using multiple projectors. Can this be done and how hard is it going to be?

Thank you in advance

William

[Mylenium]

You can speed up the video using a simple tiem stretch, time-remapping or the timewarp effect. Audio is another matter. AE is not an audio tool. You need to do that stuff in Audition or another fully fledged audio software.

Mylenium

[williama39539046]

Well keep in mind I won't be using the audio, I just need the video to more or less sync up. . So I am assuming  I can do a linear ratio then. 3:11@173 = x@179 and then once I have the ratio, apply it to the whole video. Thank you very much for a quick answer.

[Rick Gerard · Accepted solution]

You can do this without math by putting the video you want to change on one layer and the video you want to keep on the second. Now change the position of the videos so you can see both of them at the same time, make sure your composition is longer than the longest video, apply time remapping to the video you want to change then put the CTI to the point where the first beat is supposed to be in sync for both videos. Put a marker on the video you don't want to change, slide the second video in the timeline until the beats line up, insert a new keyframe in the time remapped layer where you want the first beat to sync up, move to the end of the timeline where the last beat is in the video you are not changing. Now click and drag the last keyframe in the time remapped layer until the beats line up.

If the waveform is good (press LL to reveal it) you can use the waveform to match things up but it may be easier to just look for the cut or animation in the time remapped layer. If the tempo is consistent this will take you about 2 minutes. Now check the sync of both layers by dragging or previewing segments of the video, reposition the layers as necessary and you're done.