Video Editor: Sound track length doesn't match imported movie length?

Am I doing something wrong, or is there something wrong with my install of blender? I’m trying to use the video compositor for the first time. I imported two clips that I want to crossfade to start learning how to use it, but apparently the sound track is imported separately…and it came in SHORTER than the video part of the movie.

First question: Why did this happen?

Second Question: How do I re-sync the sound with the video? Is there a way to lock the sound track in sync with it’s original video so I can move them around together instead of having to fiddle with them separately?

Third Question: Is this a bug, or just a weird feature that I don’t understand yet?

Before you add the clips, ensure that the fps in the render settings matches the fps of your imported clips.

Unfortunately, “Blender for dummies” is useless…it must have been a much earlier version of blender…pressing the space bar doesn’t pull up an Add Sequence Strip menu, for example.

OK, so where can I find these settings? Like I said, I only just now opened the thing, and this program is massively hotkey driven.

“Shift A” brings up the add menu

Still can’t find a FPS setting…under properties there’s a lot of info on the clip, but FPS isn’t one of em.

Click on the camera picture in the properties panel. It’s where you set up your project size, render resolution, etc. FPS is there.

You should also check out some tutorials on the Video Sequence Editor (VSE)

There’s probably tons more on youtube.

Good advanced info and helpful tips about the VSE


I presume that once a strip is imported, you’re locked into that framerate and can’t resample, thus no “FPS” settings in the VSE clip properties pane?

I believe that is correct, but to be honest, I’m not 100% sure, as I haven’t used the VSE extensively.

Frame rate is not resasmpled for video. If you use a speed effect to do that all you get is missing frames or stretched frames. You need to set up a scene to match the frame rate of the source video. Check the properties of the clip in your OS first. The audio is imported at a frequency setting which doesn’t vary (it can be remapped automatically 48k or 44.1k etc).

Check out my blog in the sig below for more VSE info.

Actually, By resampling I meant, if I got the framerate wrong, thus resulting in a video clip that was no longer sound-synchronised, I can’t just select the clip and, using the same frames that are there, tell the clip that it’s actually, say, 30FPS instead of 22FPS or whatever. no actual resampling involved, just fixing the frame rate when it was imported incorrectly.

You can do that but the changes will be effected next time you import a clip. The current clip is not automatically affected. It would also have to be deleted and re-imported.

Blender does import the frame rate acurately, it’s just that 30 frames in a second will be mapped over a larger time in a scene that runs at 25 frames per second. You do get a slo motion effect if you place 50fps footage in a 25 fps scene.

Hi everyone !

I had the same problem and found that thread. Now, i understand that you have to specify the frame rate of your imported strip in the render panel. (I find it strange to be honest, i view the Render panel more as an “output” kind of thing…)

But imagine you want to import multiple strips that have different frame rates ?
Or you want to work on a 50fps strip and export as 25 fps ?

Is that possible ?

Gwenouille the point, I think, is that you must match the input and output resolution. For mixed frame rate you have 2 choices.

  1. Play the input video at the scene frame rate. A 50fps video in a 25fps scene will play at 1/2 speed. Whereas a 25fps video in a 50fps scene will play at double speed.
  2. Import the video at mismatched frame rate, then apply a Speed Effect to it. You can stretch the video strip to any length, but it does this by either - duplicating frames or- discarding frames. The speed effect only performs smoothly if you divide frames evenly eg 50/2=25

@3point: In my experience, that works well in theory or in ideal situations (e.g. 50 fps–>25fps). In all other situations it’s going to be a big royal mess! :frowning:
My students are expected to make short videos using all sorts of input materials they could get their hands on. This means using videos from common videosharing sites such youtube/vimeo as well as from other sources (e.g. cell phones cameras, web cameras etc). Trying to figure out how to combine the various frame rates (ranging from 10 fps cell phone cameras to 60 fps or more) is really asking for trouble especially when the audio has to be synced as well. Each file has to be treated separately before it can be imported into a single fps VSE project for editing.

Things are looking brighter when the audio tracks are not needed or no sincing is required but you can never bet on it due to Murphy’s law.

@Gwenouille: yes, in principle, it can be done but be prepared to fiddle with it. In most cases this requires some experimentation to get it to work. I would advise against it really, esp if you’re on a deadline.

Alternatively, I would strongly recommend using Avidemux to pre-process sources before using the VSE for editing and rendering. It has an excellent resample fps filter and if you render out to a lossless codec then there is no image quality degradation. I have found it to be a great compliment to Blender’s VSE esp for fps tasks. Not to mention, of course, the fact that you can very easily trim a video and save the file without the need to re-encode it! :slight_smile:

+1 avidemux or vdub too (but it makes big AVI files).