1 Topic by jryan15

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Before I start, I just want to say how great this software is!

I've got two videos that I'm trying to synchronize and compare.  The problem that I'm having is that one video is was filmed at a regular 30 frames per second while the second video was downloaded off of the web and is from a high speed camera in super slow motion.  When I synchronize the two videos, the first video play much faster than the 2nd video (which is in slow motion).  When I try and using the speed setting for the 1st video, the speed of both videos changes so I can slow the 1st video down independently.

If however I open the 1st video and slow it down to say 30% and then open a new session with the 2nd video.  The 2nd video will import at 100%.  I can then play both videos and they are roughly the same rate, but as soon as I click the speed setting of one video to tweak it a bit both videos change to the same speed setting.

Any help would be greatly appreciated!

2 Reply by joan

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Hello,
Yes, it is a known side effect of the slow motion being locked between videos.
Haven't gotten around to implement a work around yet.

3 Reply by jryan15

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Thanks for the reply.  So is the bug that the 2nd video opens at 100% while the 1st remains in slow motion (ie 30%), or is the bug that once two videos are open, the speed between the two are locked together (change one speed, both speeds change)?

4 Reply by joan

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jryan15 wrote:

So is the bug that the 2nd video opens at 100% while the 1st remains in slow motion (ie 30%), or is the bug that once two videos are open, the speed between the two are locked together (change one speed, both speeds change)?

It's not a bug it's a feature !™
Haha, always wanted to say that one smile

The issue is the locking. Previously the sliders were free from each other, and it was a feature request to have as many things as possible locked together while comparing.
And it does make sense in the context of comparing two videos that have the same capture speed. Similar concept that when you press F6 to create a key image, it creates it in both videos at once. (ok, I'm might be the only person to know about this one).

The fact that you can open one video, slow it down, and then open a second one and have different slow motions is a little trick I hadn't thought about. I would consider this an unrelated bug.
Anyway, the workaround might be to provide a CTRL or Shift modifier to deactivate the locking when changing the speed (if possible/practical).

It will not be by default, because having two videos with differing capture speed is still not the most common scenario. Unless most people think it's an annoyance anyway, in which case it can certainly be disabled. (Feedback please).

Just to be clear for all readers, this is about videos with different capture speed (say one normal video and one 1000fps video). Videos with different playback frame rates (e.g: 30fps vs 24.97fps) are supported out of the box.

5 Reply by jryan15

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Boy is my face red, lol!  Upon reading your last post, I see that indeed locking the speeds would be a desired effect, and as matter of fact once my two videos are synchronized in speed, I beleive that I would also like for them to be locked together.  It would be difficult however since percentage based speed changes would affect each videos differently.

Let me preface my suggestion below with the following: This software is awesome, and my comments below are from a completely novice point of view.

Would there be a way to automatically sync the video speeds based on the frame rates of the video?  The software did seem to be "aware" of the two different frame rates of the sources.  It might be neat if could automatically speed up or slow down the second clip to match that of the first.  Further if there were a single speed slider on the bottom, it may be able to automatically adjust both video speeds according to their frame rates.  The scale factor between the two frame rates may also be able to be tied to the frame advance buttons were the frame advance buttons would react to a single frame movement of the slowest video.  A sync lock button could enable or disable the scale factor accomodations between the two videos.

All of this would of course depend on how often and accurately the software is able to detect the frame rates of incoming videos.  From my limited experiance, it seems to do very well. 

Thanks again, awesome support!

6 Reply by joan

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jryan15 wrote:

Would there be a way to automatically sync the video speeds based on the frame rates of the video?

There are two kinds of synchronization in Kinovea. (I refer to them as static and dynamic but the distinction is not named in the interface).
Static sync is when you use the common frame tracker, common "next", common "prev", "first", etc. buttons. It's purely frame-based. When you ask "next", it advances one frame in each vid. This one is sensitive to frame rate.

Dynamic sync is when you use the common "Play" button. It is not sensitive to differing frame rate. You can compare a 50fps video with a 10fps video, if they both last ten seconds, they will end in unison. It's just as if you'd press play on both. It is however sensitive to differing capture speed (your problem) and this information is not exposed in the file so we can't fix it automatically.

I just realized that I have already tried to address the issue of synchronizing one high speed video with a normal video a few month ago roll
Are you using 0.8.15 or 0.8.16 (the fix being only in the latter).

In 0.8.16: open both videos, then specify the capture speed of the high speed camera.  (motion > high speed camera).
The slow motion sliders will be locked on the value of the high speed video (the normal video will play in slow motion).

7 Reply by jryan15

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hello again joan!  sorry it took me so long to get back to this.  i'm running the experimental version 0.8.16.

ok, i tried changing the capture speed of one of the videos, but it really didn't seem to change the speed of the video relative to the 2nd video.  the speed slider bar did change from a max speed of 195% to a max speed of 16.67%, but at the 16.67% setting the video appears to play at the same speed that it did previously with the slide bar at 100% (in the middle).  i'm still not able to synchronize speeds since the slider bar positions are still locked together (even though they display different percentages).

i hope that makes sense.  i did not state specific capture rates as they appear to be skewed due to my editting.

thanks