Rendering slow motion


#1

Experimenting with rendering slow motion, I came across an interesting bug.

Input: 11 sec video @ 60fps

Export 1: speed 0.400x, output 60fps
Result: slow motion, appears to be 24fps.
Export 2: speed 0.400x, output 24fps
Result: slow motion, appears to be 24fps.

The issue:
To compare video quality, I did a “Save Frame” of Export 1. I selected the frame at 07.32sec for its quality. This choice led to an accidental discovery of a bug.
I then attempted a “Save Frame” of Export 2. When I tried to scroll to 07.32sec, it was not possible. I could scroll to 07.23sec, then the next frame was 08.00sec.
The intervening frames had disappeared.


#2

Are you sure you mean “7.23sec”? Shotcut doesn’t show time in seconds + fractions of seconds. It shows time in timecode which is seconds + frames. That means at 24 fps, the counter goes:

---
00:20
00:21
00:22
00:23 <- last frame (24th) of second #1
01:00 <- first frame (1st) of second #2
01:01
...

At 60 fps, the frame counter will go up to 59 before rolling over.


#3

Thank you for setting me straight on the numbers.
Whatever the number system, the fact remains that a segment of the video disappeared and therefore the precise location could not be replicated.


#4

Hmmm. OK. I’m not able to reproduce this. Can you submit a sample MLT project that demonstrates the problem?


#5

Thanks for getting back to me.
I am in the midst of some other projects so it may take me some time to replicate the problem.