Problem with Alpha Channel video in Sequencer and textures #29295

New Issue

Kassandra · 2011-11-16T18:03:27+01:00

Kassandra commented

2011-11-16 18:03:27 +01:00

%%%The alpha channel appears to not be working correctly for alpha channel videos in the sequencer and also on surfaces and materials. I have tested this in 2.6a r41226. Attached is RAR with example blend file for 2.49b and 2.6, and a simple alpha channel Quicktime Animation mov file, and a jpeg as a background image. In 2.49b it shows up properly, in 2.6 the alpha channel only is properly affecting AlphaOver blending for a few frames. In another file I tested, it was not properly showing the alpha channel for about 10 frames at the start and end of the file, again working perfectly in 2.49b (the alpha channel video was rendered with 2.49b as well). I also have tried with motion png in a mov container - same results.

Here are 2 youtube videos showing the problem in 2.6, and how it works correctly in 2.49b:

http://www.youtube.com/watch?v=h9b7X45SsFs - Shows the problem in viewport glsl textured and in sequencer
http://www.youtube.com/watch?v=w_ix8DR9hOY - Shorter, shows just sequencer, different alpha channel video file

Windows 7 64-bit
Phenom II x6 2.8
8GB
Radeon 6670 1GB
Blender 2.6a r41226
%%%

%%%The alpha channel appears to not be working correctly for alpha channel videos in the sequencer and also on surfaces and materials. I have tested this in 2.6a r41226. Attached is RAR with example blend file for 2.49b and 2.6, and a simple alpha channel Quicktime Animation mov file, and a jpeg as a background image. In 2.49b it shows up properly, in 2.6 the alpha channel only is properly affecting AlphaOver blending for a few frames. In another file I tested, it was not properly showing the alpha channel for about 10 frames at the start and end of the file, again working perfectly in 2.49b (the alpha channel video was rendered with 2.49b as well). I also have tried with motion png in a mov container - same results. Here are 2 youtube videos showing the problem in 2.6, and how it works correctly in 2.49b: http://www.youtube.com/watch?v=h9b7X45SsFs - Shows the problem in viewport glsl textured and in sequencer http://www.youtube.com/watch?v=w_ix8DR9hOY - Shorter, shows just sequencer, different alpha channel video file Windows 7 64-bit Phenom II x6 2.8 8GB Radeon 6670 1GB Blender 2.6a r41226 %%%

Kassandra commented

2011-11-16 18:03:27 +01:00

Changed status to: 'Open'

Sergey Sharybin commented

2011-11-16 20:33:21 +01:00

%%%AFAIR, it was a bug in swscale which used to set alpha channel incorrectly, so it's getting reassigned to 1.0 (full non-transparent) after decoding frame. It's tricky check for alpha channel of first pixel on frame (think it's bottom left corner), which describes why your video behaves in such way.
Need to check if bug still present in swscale and probably this hack could be removed.%%%

%%%AFAIR, it was a bug in swscale which used to set alpha channel incorrectly, so it's getting reassigned to 1.0 (full non-transparent) after decoding frame. It's tricky check for alpha channel of first pixel on frame (think it's bottom left corner), which describes why your video behaves in such way. Need to check if bug still present in swscale and probably this hack could be removed.%%%

Sergey Sharybin commented

2011-11-17 19:33:29 +01:00

%%%Kassandra, are you familiar with applying patches? I've attached possible fix in attachments here, looks like it works fine, but more tests would be welcome.%%%

Kassandra commented

2011-11-17 20:51:56 +01:00

%%%I could give it a try maybe, I'm not a programmer though and I don't have any compilers installed or setup etc, nor have I ever used version control things, but if it wouldn't be too difficult I can give it a try and do some more experiments on the results, I use alpha video quite a lot so I'd love to try and help test :)%%%

Sergey Sharybin commented

2011-11-20 17:27:59 +01:00

%%%Pardon for the delay. Discussed patch with Peter and think it can go into trunk.
Your issue should be resolved in svn rev42017. Thanks for the report, closing it now.%%%

%%%Pardon for the delay. Discussed patch with Peter and think it can go into trunk. Your issue should be resolved in svn rev42017. Thanks for the report, closing it now.%%%

Sergey Sharybin commented

2011-11-20 17:27:59 +01:00

Changed status from 'Open' to: 'Resolved'

Sergey Sharybin closed this issue

2011-11-20 17:27:59 +01:00

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Problem with Alpha Channel video in Sequencer and textures #29295