Black thumbnail problem on timeline
I have my timeline preferences set for video track to display thumbnails. Recently I encountered a problem in which some clips brought to the timeline start with just one or a few thumbnails visible, and the rest of the clip duration shown on the timeline is just black. Playing such a clip normally is OK, but if I pause over the backed out area, and say reverse or forward in single frames, the image in the composition window goes black. I have also had other examples of a clip showing no thumbnails at all, the video track is just all black and I can see no image at all in the composition window when playing it normally. When I have played these video clips in a Linux video player or VLC, the playback has been fine, so I don't think there is anything essentially wrong with the clips themselves. So I wonder what is tripping Cinelerra up with those clips -- other clips that are the same format and codec are fine on the timeline, it is only a few that are affected.
I also had the problem once and reported it as a bug. It turned out that certain video files are not editable and therefore not suitable for seeking. This is a problem with these files. If you activate the proxies, then you can use the proxy file and everything works fine again.
Here is the post about it:
Try it with proxies, then you can be sure that it is because of the files.
Also, along with what Sam said, recently Andrew just re-encoded this type of "only a single keyframe at the beginning of the file" with ffmpeg, and then it opens ok.
Since I do not have a smaller file to test, GG and I were wondering if when you proxy this file and work on it, do the edit results actually get applied to the original file when you un-proxy it? I would like to know so I can add this to the manual section 17.2.3 Seeking Issues.