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Maniphest T41165

Prefetch frames does not seem to take effect on playback
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Description

System Information
Mac OS X 10.9.4

Blender Version
Broken: 2.71

Short description of error
Editing a multi-strip project on VSE, I am not able to playback smoothly the sequence.

No matter if I change the value in Blender preferences (System - Seuqnecer/Clip Editor: Prefetch Frames), the playback hangs and even Blender become unresponsive.

By the way, the documentation (http://wiki.blender.org/index.php/Doc:2.6/Manual/Preferences/System) says that there is a limit on "System - Sequencer/Clip Editor" values. If the documentation is updated and this is still applicable, I think the controls of UI should limit the numbers. Should I open another bug for this UI issue?

Event Timeline

Jonata Bolzan (jonata) created this task.Jul 24 2014, 2:43 PM
Jonata Bolzan (jonata) raised the priority of this task from to 90.
Jonata Bolzan (jonata) updated the task description. (Show Details)
Jonata Bolzan (jonata) added a project: Video Sequencer.
Jonata Bolzan (jonata) edited a custom field.
Jonata Bolzan (jonata) added a subscriber: Jonata Bolzan (jonata).
Bastien Montagne (mont29) added a project: BF Blender.Jul 24 2014, 7:55 PM
Bastien Montagne (mont29) added a subscriber: Bastien Montagne (mont29).
Sergey Sharybin (sergey) assigned this task to Antonis Ryakiotakis (psy-fi).Jul 28 2014, 12:47 PM
Sergey Sharybin (sergey) added subscribers: Antonis Ryakiotakis (psy-fi), Sergey Sharybin (sergey).

@Antonis Ryakiotakis (psy-fi), afair this isn't fully ported since 2.49. Mind having a glance?

Sergey Sharybin (sergey) lowered the priority of this task from 90 to Normal.Jul 28 2014, 12:47 PM
Antonis Ryakiotakis (psy-fi) triaged this task as 30 priority.Aug 4 2014, 1:14 PM

Quick test with two strips here looks OK...I'd like a test file to investigate if possible.

Jonata Bolzan (jonata) added a comment.Aug 4 2014, 3:08 PM

Well, it is not that hard to reproduce. Just add a lot of strips with common effects like alpha over. The link is for a screen record of some strips playing with some video. The FPS goes to 4-7 - definitely not smooth - and you can note that when you move a strip and play, you can see... how can I say... "residual" frames that, as I understand, is a consequence of blender not pre-"fetching" the frames.

https://www.dropbox.com/s/qbceph71k2xvwot/blender-vse-test.mov

Thanks for the attention.

Antonis Ryakiotakis (psy-fi) added a comment.Aug 4 2014, 3:38 PM

This looks like latency due to computation time rather than a hang. Scaling and translating an image just takes time. This is normal.

Jonata Bolzan (jonata) added a comment.Aug 4 2014, 3:47 PM

I see. So, what is "prefetch" for?

Antonis Ryakiotakis (psy-fi) changed the task status from Unknown Status to Archived.Aug 4 2014, 4:05 PM

Prefetch fetches the frames of the movie itself in memory, it doesn't influence computation time due to transform operations. In the uploaded video you can clearly see that the delay occurs only while those transforms are active, not due to the movie itself.

Jonata Bolzan (jonata) added a comment.Aug 4 2014, 4:07 PM

Ok, thanks.