My machines are a few Android tablets (not the newest, but not too old either) as well as a Mac running OS X 10.9.5 (not about to upgrade the OS - long and irrelevant story why). Sometimes I do a presentation where I record separately the video track and the audio track - and then selectively speed-and-slow parts of the video track to sync with the audio --- thereby producing something similar to whiteboard animation.

Here's my question. The current way I do the speeding-up and slowing-down is through iMovie -- where I load the video, strip the audio that comes with me (which is just the sounds that are in the room at the time) load the audio that it is meant to go with --- and then I split the video clip at the right places, and for each segment, adjust the speed manually, thereby getting the video to sync with the audio. It's a slightly tedious process --- and I'd like something a tad more efficient. Say, something that would allow me to select key points where I map the audio track to a corresponding key point in the video track -- and maybe let the program then automatically speed-up and slow-down the video segments between those key-points so that things sync. Would make the process much less tedious.

Here's the thing though -- I am on a very limited budget -- and therefore, if the only options for something like this are too expensive, I probably will then just go on doing it the way I'm currently doing it through iMovie (which is tedious - but gets the job done). I can spend a little money, but something expensive is just out-of-the-question for me - and will remain so for a while it looks like. I'd like to have more money to spend on expensive tools (and if I had such money, I would have been using FinalCut Pro rather than iMovie for example) but the reality of the situation is that I don't have much money to spend.

So --- any suggestions what tool I can use to more-easily speed-slow the segments of the video track to sync with the audio track?


5 Answers 5


Well you could download a trial 30 day copy of the legacy version of Adobe After Effects CS6. It allows a full unrestricted 30 day install trial.

From there, you could take your footage in, place the master clip in a composition, and instead of cutting it, use the the time warp feature, which will give you smooth keyframes where you can adjust up the speed to X, then place a keyframe if you notice it begin to slip, and set a keyframe to slow it down a bit. This will provide ramping, which basically "cuts" the clip in half over and over again, and does all the math for you, to make the smooth changes in speed. Then render it out. Premiere might also have that function- it's also included in the CS6 Production Premium Bundle, google the download link, and you can install and try for 30 days without purchase.

  • Depends how much it would cost after those 30 days are up.
    – Sophia_ES
    May 31, 2016 at 11:33


  • Hitfilm 3 Express (free after registration)
  • Lightworks (free with some limitations)
  • Adobe Premiere elements (about 100$)
  • Blackmagic da-vinci resolve (free - but with steep learning curve and heavy systems requirements)

In HitFilm Express 4 (not 3) it is very easy to slow or accelerate your video. Give it a try. It is free.

You can use keyframes to change the speed of the movie. And you can use a pitch effect to prevent your audio to become too distorted.

Another nice app to accelerate or slow your video, is the video editor of GoPro cameras, now called Quik. I stopped using it because it used to be very buggy, but this new version looks a lot better.


Your problem is not necessarily a software problem, it is a workflow planning and logistics problem.

The following steps should help you sync your external audio to your video easier and more efficiently saving you time.

Note how step one is all about methodology and should resolve your issue provided your software has the assumed functionality.

  1. Prior to recording each scene, you need to make a loud clap sound that both the audio input of your video camera, and the external audio recorder can pick up at the same time. Typically, a clapper or hand claps are used for this purpose. A clapper is a framed chalkboard or whiteboard with scene information that is recorded by the video camera, and has an arm that is raised and clapped down to make the needed sound. The clap, when recorded, creates a spike in the audio of both the video camera's audio and the external sound recorder audio. These spikes are illustrated in the sounds waveform view with larger spikes if the sound is loud enough. When you align these two waveform spikes in your time line, the video and external sound are aligned and synced perfectly.

If you record your audio and video in one setting without breaks and without stopping the camera and the audio recorder, there is no need for you to have multiple claps during the recording, a single one will do. However, you will need to insure that when you edit out unwanted portions, you delete both the video and external audio portions at the same time otherwise, your external audio and video will cease to be synced.

  1. Once you have aligned your audio and video; rather than delete the video audio, mute the video's audio track. If the video editing software you are using does not allow you to mute the audio track on your video, then you do have a software problem and you may want to look for a different program. I have been looking at OpenShot.org. It appears to be a full featured open source cross platform video editor which I am currently downloading and have yet to try out.

This should help you refine and simplify your video production.



Almost instant and Free Trial available: http://www.redgiant.com/products/pluraleyes/ .

I use AviSynth, but it is also tedious to get frame perfect results.

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