This is the discussion thread for the request in the issue tracker.
Vote for it here:
http://forum.cockos.com/project.php?issueid=4295
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For the video thumbnail view of an item containing video, I propose we have a default image size of
160 by 90 pixels. This gives you a good overview and plenty of frames.
A comparison of 320x180 versus 160x90 versus 80x45 from a specific frame.
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An example of how much memory and file space is used:
Video length: 7:02 16:9 ratio
@ 1 thumbnail-frame per second that's 422 thumbnail images
JPEG Quality 85 - average of 5337 bytes per thumbnail - 320 kBytes per minute of video
JPEG Quality 75 - average of 4167 bytes per thumbnail - 250 kBytes per minute of video(best compromise IMHO)
JPEG Quality 65 - average of 3353 bytes per thumbnail - 200 kBytes per minute of video
This would look a bit like this (with 4 pixels of padding on either side of every frame, which would change depending on zoom level):
Technically this simple overview could be stored in one file, just like a waveform overview is.
This simple approach does not take scene changes in to account, and we have to remember that live-calculation of overview data is exceptionally expensive in terms of CPU, especially for H264 compressed video. Thus this overview should be all the thumbnail overview ever shows, i.e. no additional frames by default. Perhaps a zoom threshold after which missing frames are added as the user can make proper use of an actual frame-by-frame overview of the video. That would have ot be live-generated however, and kept in memory.
Should Reaper in fact try to detect scene and angle changes, which is just a severe change in screen content and prioritize thumbnails like that or would this simplistic approach give a good enough overview ?
One thumbnail per second of video is pretty good since most people only strive to find scenes or locations with such an overview. Anything else could be handled by following the video window.
Advanced Functionality
That stuff up there is the stuff everyone does. How about something NOBODY in the DAW world does.
Mouse-Over-Scrub ala iMovie/FCPX.
When the mouse cursor hovers over the video item, the thumbnail it hovers over changes to display the preview-thumbnail frame that is closest to the time-position the mouse cursor is currently hovering at.
It's important to state that the preview-thumbails are used, not the actual video because FFMPEG is crrrrap at fast seeking. Reaper is fast.