openshot.bugs team mailing list archive

[Oliver Schonrock <520941@xxxxxxxxxxxxxxxxxx>]

PROBLEM SOLVED!! ...at least for me!

I too have been plagued by this issue. When adding many clips to a
project the clips would start not to line up properly and then blank
frames started appearing and the fades/transitions would "skip" / show
the wrong frames at the start of the transition...in short all of the
symptoms described above...it was driving me mad...and it was happening
in every 2nd project.

BTW I am using Ubuntu Oneiric with Openshot 1.4 and melt 0.7.4 (i also
tried 0.7.6, but no joy).

So I took a "broken" project and started reducing it to a minimal version. The clearest example I had were 4 clips with 2  transitions about 20 seconds apart using the same 2 Tracks.ie like this (hope that's readable):
            
                22222222                            444444444444
                ^^^                                       ^^^^
1111111111                          333333333

The project had nothing else in it just 4 clips and 2 transitions..and
it was still "broken"..ie the second transition would display an
incorrect frame at the start of the transition (makes it look like it
"jumps/flickers").

I made a new project and added the same 4 clips and 2 transitions. The
new project worked! so now I had a good and a bad copy. I started
exporting the XML and comparing the 2 versions (I am a software
developer so this stuff comes easily..only very amateur with video
though).

The only significant differences in the xml were the paths the producer
Ids and the "in/out" timings (because I had created them "by hand" in
the new project).

So I opened 2 copies of openshot and copy/pasted the in/out timings for
all 4 clips and 2 transitions from the broken project to the new one.
and....the new project broke! Then I played with the in/out setting of
each piece and figured out it was clip 2 (see ascii diagram). It had an
out timeof 17.02s when broken, but if I set it to 17.00 it worked fine.
All this time I kept thinking "rounding error", because that happens a
lot when you add lots of floating point number together. At first I
thought openshot was introducing the rounding error..then I stumbled
upon the key. 29.97 is almost 30 but not quite and might be introducing
this "rounding error".

So I checked the manual of my video camera (Panasonic HX-WA10). It says
30fps. Both projects were 30fps (1080p blah blah). So I ran

ffmpeg -i filename

which allows you to inspect what ffmpeg says is in the raw file direct
from the camera. It said 29.97fps!!!

mplayer -endpos 0 filename

also said 29.97fps. They also reported 510 frames exactly (there is no
such thing as a half frame!), and 510 / 29.97 = 17.02!

I know that you are supposed to match the project profile to the raw
source material so I re-saved the project as 29.97fps 1080p and voila!
All the problems went away. The clips lined up nicely, the black frames
were gone and the transitions worked as expected, first time. Without
spreading them over many tracks etc...

Openshot was missing the odd frame on its timeline and that was breaking
the transitions etc...

So the moral of the story is:
a) don't trust your camera manual's frame rate! check it with ffmpeg!
b) be very very sure that your project profile matches the raw material


Questions to the developers of openshot
---------------------------------------
I don't understand enough about video editors to know if openshot could compensate for this. 

- Should it be possible to edit "wrong frame rate" source material
reliably?

- What if you are mixing different source material?

- Could openshot at least warn you if you try to add source material
with the wrong frame rate..ie "don't do this because your transitions
will turn purple!"

I did check and on a previous project the final exported file was
faithfully turned into 30fps eventhough the raw source was 29.97 as I
now know. This meant that openshot/ffmpeg must have interpolated the odd
frame here and there or just sped them up slightly (or slowed the sound
track down).

So maybe this is a genuine bug that can be fixed..maybe not.

Anyway, for me, fortunately the problem appears to be solved.

Hope this helps someone...

Oliver

-- 
You received this bug notification because you are a member of OpenShot
Bugs, which is subscribed to OpenShot Video Editor.
https://bugs.launchpad.net/bugs/520941

Title:
  Fade in/out glitches

Status in OpenShot Video Editor:
  In Progress

Bug description:
  Hi,

  I don't know if anyone else has experienced this, but now and again
  (not all the time) my fades in and out glitch at the outer end: before
  a fade in, the image or video appears momentarily (probably just for
  one frame) then disappears, and the fade starts normally. Similarly at
  the end, with the final frame flashing up full brightness.

  It also seems to some extent to happen on audio - it's like OpenShot
  realises a moment too late that it's not meant to be playing the
  audio, or that a fade is meant to be happening.

  Sometimes it doesn't happen, and sometimes it fixes itself...
  unfortunately not on a 'quick' project I've been doing this morning!

  Anyway. It's absolutely great work - I'm so impressed! Something as
  good as this, and non-linear (I can't understand what you can even do
  with linear editing!) is a joy to have!

  Ubuntu 8.04
  DEB 1.0.0

  Again - great application. I've already done some stuff I'm really
  pleased with!

  Cheers,

  Mike

To manage notifications about this bug go to:
https://bugs.launchpad.net/openshot/+bug/520941/+subscriptions