VSE patch affects scaling of CbCr planes #47766

New Issue

Paul R · 2016-03-11T22:09:59+01:00

Paul R commented

2016-03-11 22:09:59 +01:00

System Information
SUSE Linux Leap 42.1
NVidia GTX 560ti (official drivers)

Blender Version
Broken: 2.77 606f6b79ea
Worked:

Short description of error
The patch for #47724 now causes the video chroma planes to be scaled differently to the Y channel.

Colours look aligned on the left, but get progressively shifted towards the right. Especially noticeable on the green bars (bottom of the three images):

^ This happens even if the src video and project dimensions are divisible by 16, eg 720x480.

*As a side issue, the CbCr channels are now upscaled with interpolation instead of nearest neighbour. Interpolation obviously looks more pleasing for previewing (and might make green-screen keying easier), but might not be wanted for simple 'pass through' work like editing/grading as it will end up softening the image a bit.

Exact steps for others to reproduce the error

open F289048 .blend
load 854x480_vertical_rgb_grid2.mp4
video is 854x480, h.264, 25fps, 4:2:0 (encoded with ffmpeg 2.8.4)

The test video can be created from scratch using:
with:
ffmpeg -loop 1 -i 854x480_vertical_rgb_grid2.png -pix_fmt yuv420p -crf 20 -t 4 854x480_vertical_rgb_grid2.mp4

**System Information** SUSE Linux Leap 42.1 NVidia GTX 560ti (official drivers) **Blender Version** Broken: 2.77 606f6b79ea Worked: **Short description of error** The patch for #47724 now causes the video chroma planes to be scaled differently to the Y channel. Colours look aligned on the left, but get progressively shifted towards the right. Especially noticeable on the green bars (bottom of the three images): ![blender_vse_colour_scaling_vertical_rgb_bars_alignment.png](https://archive.blender.org/developer/F289531/blender_vse_colour_scaling_vertical_rgb_bars_alignment.png) ^ This happens even if the src video and project dimensions are divisible by 16, eg 720x480. *As a side issue, the CbCr channels are now upscaled with interpolation instead of nearest neighbour. Interpolation obviously looks more pleasing for previewing (and might make green-screen keying easier), but might not be wanted for simple 'pass through' work like editing/grading as it will end up softening the image a bit. **Exact steps for others to reproduce the error** - open [F289048](https://archive.blender.org/developer/F289048/vse_video_resolution_crop.blend) .blend - load [854x480_vertical_rgb_grid2.mp4](https://archive.blender.org/developer/F289533/854x480_vertical_rgb_grid2.mp4) - video is 854x480, h.264, 25fps, 4:2:0 (encoded with ffmpeg 2.8.4) The test video can be created from scratch using:![854x480_vertical_rgb_grid2.png](https://archive.blender.org/developer/F289535/854x480_vertical_rgb_grid2.png) with: ffmpeg -loop 1 -i 854x480_vertical_rgb_grid2.png -pix_fmt yuv420p -crf 20 -t 4 854x480_vertical_rgb_grid2.mp4

Paul R commented

2016-03-11 22:09:59 +01:00

Changed status to: 'Open'

Paul R commented

2016-03-11 22:09:59 +01:00

Added subscriber: @intracube

Sergey Sharybin commented

2016-03-14 10:55:35 +01:00

Added subscriber: @Sergey

Sergey Sharybin self-assigned this 2016-03-14 10:55:35 +01:00

Sergey Sharybin commented

2016-03-14 10:55:35 +01:00

Will check later, but perhaps only real fix is to implement alignment form Blender side make damn FFmpeg happy..

Paul R commented

2016-03-14 15:09:17 +01:00

After running through some test charts at various sizes, it looks like the horizontal resolution needs to be divisible by 32 to avoid any colour shift.

So common HD resolutions (1920 and 1280) are OK.

For other resolutions, this is going to cause some headaches for people colour keying and wondering why their mattes don't line up properly :/

After running through some test charts at various sizes, it looks like the horizontal resolution needs to be divisible by 32 to avoid any colour shift. So common HD resolutions (1920 and 1280) are OK. For other resolutions, this is going to cause some headaches for people colour keying and wondering why their mattes don't line up properly :/

Sergey Sharybin commented

2016-03-15 11:09:18 +01:00

Changed status from 'Open' to: 'Resolved'

Sergey Sharybin closed this issue

2016-03-15 11:09:18 +01:00

Sergey Sharybin commented

2016-03-15 11:09:18 +01:00

This issue should now be fixed in Git. Thanks for the report!

Paul R commented

2016-03-16 17:41:23 +01:00

Can confirm it's now working. Thanks for the fix :)

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VSE patch affects scaling of CbCr planes #47766