VSE: Faster processing of alpha-over strip at the bottom of strip stack #127310

Aras Pranckevicius · 2024-09-08T15:59:50+02:00

2024-09-08 15:59:50 +02:00

When a strip with alpha-over blend mode (which is default) has an alpha
channel and is at the bottom of the whole stack, there's no point in
blending it with black color; the result will be identical.

So stop doing that. Also, whenever some other case happens at the bottom
of the stack (e.g. some other blend mode), create the fake "black input"
image at the needed color type (float or byte) and with the correct
color space already applied. Otherwise, especially for floats, VSE
spends much time converting this fake black input from byte to float,
and then converting it to sequencer color space.

Test case of two EXR files blended over each other, at 4K resolution,
on Ryzen 5950X (Win10/VS2022):

whole sequencer_preview_region_draw 115ms -> 75ms
seq_render_give_ibuf part: 64ms -> 24ms

i.e. this saves 40ms per frame, which was done but is not really needed:

allocate a 4K byte image,
clear it to black,
convert it to float,
convert that to linear space,
blend it with the bottom exr file,
free the black image.

When a strip with alpha-over blend mode (which is default) has an alpha channel and is at the bottom of the whole stack, there's no point in blending it with black color; the result will be identical. So stop doing that. Also, whenever some other case happens at the bottom of the stack (e.g. some other blend mode), create the fake "black input" image at the needed color type (float or byte) and with the correct color space already applied. Otherwise, especially for floats, VSE spends much time converting this fake black input from byte to float, and then converting it to sequencer color space. Test case of two EXR files blended over each other, at 4K resolution, on Ryzen 5950X (Win10/VS2022): - whole sequencer_preview_region_draw 115ms -> 75ms - seq_render_give_ibuf part: 64ms -> 24ms i.e. this **saves 40ms per frame**, which was done but is not really needed: - allocate a 4K byte image, - clear it to black, - convert it to float, - convert that to linear space, - blend it with the bottom exr file, - free the black image.

👍 2 ❤️ 1

Aras Pranckevicius added 1 commit 2024-09-08 15:59:56 +02:00

VSE: Faster processing of alpha-over strip at the bottom of strip stack

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978d065b6b

When a strip with alpha-over blend mode (which is default) has an alpha
channel and is at the bottom of the whole stack, there's no point in
blending it with black color; the result will be identical.

So stop doing that. Also, whenever some other case happens at the bottom
of the stack (e.g. some other blend mode), create the fake "black input"
image at the needed color type (float or byte) and with the correct
color space already applied. Otherwise, especially for floats, VSE
spends much time converting this fake black input from byte to float,
and then converting it to sequencer color space.

Test case of two EXR files blended over each other, at 4K resolution,
on Ryzen 5950X (Win10/VS2022):
- whole sequencer_preview_region_draw 115ms -> 75ms
- seq_render_give_ibuf part: 64ms -> 24ms

i.e. this saves 40ms per frame, which was:
- allocate a 4K byte image,
- clear it to black,
- convert it to float,
- convert that to linear space,
- blend it with the bottom exr file,
- free the black image.

Aras Pranckevicius commented

2024-09-08 16:00:23 +02:00

@blender-bot build

Aras Pranckevicius requested review from Sergey Sharybin 2024-09-08 16:15:19 +02:00

Sergey Sharybin approved these changes 2024-09-09 12:41:16 +02:00

Aras Pranckevicius merged commit 5c259a1bae into main

2024-09-09 13:16:27 +02:00

Aras Pranckevicius referenced this issue from a commit

2024-09-09 13:16:28 +02:00

VSE: Faster processing of alpha-over strip at the bottom of strip stack

Aras Pranckevicius deleted branch vse_alphaover_at_bottom

2024-09-09 13:16:30 +02:00

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VSE: Faster processing of alpha-over strip at the bottom of strip stack #127310