stretching or shrinking a video track to match length of another track

Peeteey wrote on 4/25/2023, 9:40 PM

Hi kids,

I filmed a concert using two identical cameras, have done for years with these cameras, but for some reason, one of the output files seems to play slightly faster than the other.

Lets imagine there's a clap for syncing at the beginning of the video and another one at the end of the video. both cameras filmed the whole thing with the same settings but for some reason, if I match up the clap in the two videos at the beginning of the track, by the clap at the end, they're out of sync. It's as if one video track is playing minutely faster than the other.

Is there a function to automatically stretch or shrink (speed up or slow down I guess) the second clip to match the first clip?

In a free editor I used to use years ago, it had a function where I could mark a point at the beginning of both videos, say the hand clap, and then mark a point at the end of both videos, say the second hand clap which is now out of sync but *should* be in sync, and the program would adjust one clip so that they're both now synchronised all the way through.

Can MEP '22 Premium do anything like this?

If not, how do I do it other than manually stretching or shrinking the second clip and getting it to match by trial and error?

Thanks!

Pete

Comments

CubeAce wrote on 4/26/2023, 2:23 AM

@Peeteey

Hi Pete.

Are the cameras on remote controls and can both be started at the same time? Are there significant distances between the two ant the subject matter?

Did you check on the mediainfo that both cameras used the same video format and frame speed?

Yes there is a frame speed adjustment available in MEP 2022 for manual adjustment and it may be possible to sync the videos in Multi-cam mode.

If however you recorded one or both cameras that allowed for a variable speed frame rate you may have to convert those files to constant frame rates first.

Again that information should be available in the MediaInfo programs' text view.

Ray.

AAProds wrote on 4/26/2023, 2:41 AM

@Peeteey

how do I do it other than manually stretching or shrinking the second clip

It's unclear whether you mean using Object Stretch mouse mode. If you're not, this mode allows you to stretch an object at will:

The left end is fixed, drag the right end of an object to stretch it.

johnebaker wrote on 4/26/2023, 5:52 AM

@Peeteey

. . . . I filmed a concert using two identical cameras . . . .

What is the make/model of the cameras ?

@CubeAce commented '. . . a variable speed frame rate .... information should be available in the MediaInfo programs' text view. . . .

To add to this - see this tutorial on how to setup MediaInfo, which Ray linked to, and analyse a video clip to get the data required.

In the Video section of the analyses, if you see this line:

Framerate mode: Variable

Then as Ray has commented you will need to convert them to Constant framerate.

John EB
Forum Moderator

browj2 wrote on 4/26/2023, 6:55 AM

@AAProds

Hi Al,

The left end is fixed, drag the right end of an object to stretch it.

Actually, you can drag either end of an object to stretch it.

The Object Stretch button is linked to the Effects/Video effects/Speed effect. Adjusting the slider/input box there will only adjust the right end with the left end fixed.

John CB

AAProds wrote on 4/26/2023, 7:17 AM

@browj2

JohnCB, yes, technically you're correct but it would rarely work like that in practice. I cannot envisage a scenario where the audio is in-sync at the end but out at the start.

browj2 wrote on 4/26/2023, 8:17 AM

@AAProds

Hi Al,

True. I was just pointing out that it can be done.

Also, if there is uneven drift over a long duration (this has happened to me with S8 sound files), Speed can be keyframed. Alternatively, make cuts at scene changes and realign each part.

@Peeteey

Once you have the beginning lined up, go to some obvious point towards the end of the clips that you can use for alignment. Put a Snap marker (Ctrl+P) on each (obviously different locations) and then stretch the one where the snap marker is to the left, until the snap markers line up.

John CB

Peeteey wrote on 4/27/2023, 4:39 AM

Thanks everybody, I should've been a bit clearer re the settings. The cameras are 2 (actually 4) Samsung S7 phones recording in 4k, all set to the exact same settings 25fps, same bitrate etc.

I use them to record music concerts from multiple angles. I've been using then like this for years with no issues ever, until this one file.

I thought the frame rate must've got changed somehow but nope, all settings identical.

Anyhoo, thanks for the comments and help, I did experiment with the mouse dragging type stretch thing but I was just wanting to find out I if MEP had some automated way of doing it, like the snap markers mentioned above, but automated.

I'll give that method a go, thanks so much again!

johnebaker wrote on 4/27/2023, 5:33 AM

@Peeteey

. . . . Samsung S7 phones recording in 4k, all set to the exact same settings 25fps, same bitrate etc . . . .

Did the MediaInfo data show if they are Variable framerate ?

If so it should tell you what the minimum and maximum framerates are. I suspect the one causing the issue has a wider range than the others, particularly if there was less 'action' in the area it was recording.

John EB

CubeAce wrote on 4/27/2023, 5:59 AM

@Peeteey @johnebaker

Hi.

I agree strongly with John.

Both my wife and I have Samsung phones and you have to set the frame rate manually at 4K not to get a variable frame rate on ours. Yes you set a frame rate that the phone will then uses as a base frame rate. Most phones will do that at higher resolutions to save storage space.

You may have achieved this but it is best to check the data with MediaInfo as Windows cannot supply that information. It is very unlikely that two phones will keep to the same frame rates at the same time if they have different viewpoints.

Ray.

Peeteey wrote on 4/27/2023, 3:14 PM

... is very unlikely that two phones will keep to the same frame rates at the same time if they have different viewpoints.

Thanks, i know, that's why I use a 3rd party app that lets me lock all the settings and also so I can record with the screen turned off. That way they can record for about 3 hours straight.

Anyhoo, thanks again everyone!

johnebaker wrote on 4/27/2023, 5:02 PM

@Peeteey

. . . . I use a 3rd party app that lets me lock all the settings . . . .

What is the app?

The apps I have tried on my Samsung phone do not have the capability of specifying a Constant framerate mode.

John EB

Peeteey wrote on 4/28/2023, 1:59 AM

What is the app?

The apps I have tried on my Samsung phone do not have the capability of specifying a Constant framerate mode.

John EB

Hey John,

It's not made anymore unfortunately. I forget it's name off the top of my head but it was a slightly dodgy spy cam type app, hence the ability to record with the screen off. It can set Resolution, Frame rate, Bitrate etc and many other things. As I've said, it's always been consistent, until just this one anomalous file.

The previous and subsequent files recorded by the same camera during the same session are perfectly fine, just this one in the middle. May have just got a little corrupted somehow.

johnebaker wrote on 4/28/2023, 6:27 AM

@Peeteey

Thanks for the info - there are still many of these apps that allow screen off recording. Just the one file in a sequence is an 'odd' behaviour.

John EB