Topic: Playback speed automatically changes

A student wrote to me with this problem:

When I try to configure the video timing to 240 fps (iPhone slow-motion) the video play speed drops down to 0% and when I try to move it to get the video to play it will change automatically drop back down to 0% so the video will not play.

Upon troubleshooting (restarting and not bothering to adjust video timing settings)

When I try that the video plays at 10% speed but I filmed it in slow mo to begin with so it is really slow now.

So I started trying it out myself. I had a slo-mo video of myself kicking a soccer ball and at first it seemed to work fine. However, as it played through the video a couple times, the playback speed started to decrease to 90%, to 80%, played a few more times and eventually got to 50% playback speed. If I set the playback speed to 1.5x it almost immediately slows it down to 1x and as it repeats through the video again goes down to slower speeds.

I'm guessing this has to do with memory allocation, but I'm not entirely sure and I'm not at all sure what to tell my students to do to troubleshoot this issue.

Re: Playback speed automatically changes

Hi,
The automatic slow down happens when the program can't playback the video at the expected framerate because it's too much processing.
What version is this with? On recent versions (after ~0.8.20 or something) there is an optimization that should help a lot with this. Please test with 0.9.1 and let me know if you reproduce the issue.

Going all the way to 0% is strange though, I imagine the original is at 240 fps and the program detects it's missing a ton of frames repeatedly.

Regarding memory allocation: if you reduce the working zone enough that it fits in the allocated memory it will decompress the frames in advance and you shouldn't have the problem.

Re: Playback speed automatically changes

joan wrote:

Hi,
The automatic slow down happens when the program can't playback the video at the expected framerate because it's too much processing.
What version is this with? On recent versions (after ~0.8.20 or something) there is an optimization that should help a lot with this. Please test with 0.9.1 and let me know if you reproduce the issue.

Going all the way to 0% is strange though, I imagine the original is at 240 fps and the program detects it's missing a ton of frames repeatedly.

Regarding memory allocation: if you reduce the working zone enough that it fits in the allocated memory it will decompress the frames in advance and you shouldn't have the problem.

This was with 9.1 - it was on a student's computer which has a high chance of being run on a Mac via VirtualApps at our institution. When I tried on my PC, it slowed a bit, but wasn't too bad. I'll share the thought about trimming the working region.

Thank you for the fast reply!

Re: Playback speed automatically changes

I had this problem on 0.8.15 with 60 fps  2704x1520 video from a GoPro.  It went away on 0.8.27 and 0.9.3.