Video Sequencer, Aspect Ratio issue #39785
Labels
No Label
Interest
Alembic
Interest
Animation & Rigging
Interest
Asset Browser
Interest
Asset Browser Project Overview
Interest
Audio
Interest
Automated Testing
Interest
Blender Asset Bundle
Interest
BlendFile
Interest
Collada
Interest
Compatibility
Interest
Compositing
Interest
Core
Interest
Cycles
Interest
Dependency Graph
Interest
Development Management
Interest
EEVEE
Interest
EEVEE & Viewport
Interest
Freestyle
Interest
Geometry Nodes
Interest
Grease Pencil
Interest
ID Management
Interest
Images & Movies
Interest
Import Export
Interest
Line Art
Interest
Masking
Interest
Metal
Interest
Modeling
Interest
Modifiers
Interest
Motion Tracking
Interest
Nodes & Physics
Interest
OpenGL
Interest
Overlay
Interest
Overrides
Interest
Performance
Interest
Physics
Interest
Pipeline, Assets & IO
Interest
Platforms, Builds & Tests
Interest
Python API
Interest
Render & Cycles
Interest
Render Pipeline
Interest
Sculpt, Paint & Texture
Interest
Text Editor
Interest
Translations
Interest
Triaging
Interest
Undo
Interest
USD
Interest
User Interface
Interest
UV Editing
Interest
VFX & Video
Interest
Video Sequencer
Interest
Virtual Reality
Interest
Vulkan
Interest
Wayland
Interest
Workbench
Interest: X11
Legacy
Blender 2.8 Project
Legacy
Milestone 1: Basic, Local Asset Browser
Legacy
OpenGL Error
Meta
Good First Issue
Meta
Papercut
Meta
Retrospective
Meta
Security
Module
Animation & Rigging
Module
Core
Module
Development Management
Module
EEVEE & Viewport
Module
Grease Pencil
Module
Modeling
Module
Nodes & Physics
Module
Pipeline, Assets & IO
Module
Platforms, Builds & Tests
Module
Python API
Module
Render & Cycles
Module
Sculpt, Paint & Texture
Module
Triaging
Module
User Interface
Module
VFX & Video
Platform
FreeBSD
Platform
Linux
Platform
macOS
Platform
Windows
Priority
High
Priority
Low
Priority
Normal
Priority
Unbreak Now!
Status
Archived
Status
Confirmed
Status
Duplicate
Status
Needs Info from Developers
Status
Needs Information from User
Status
Needs Triage
Status
Resolved
Type
Bug
Type
Design
Type
Known Issue
Type
Patch
Type
Report
Type
To Do
No Milestone
No project
No Assignees
3 Participants
Notifications
Due Date
No due date set.
Dependencies
No dependencies set.
Reference: blender/blender#39785
Loading…
Reference in New Issue
No description provided.
Delete Branch "%!s(<nil>)"
Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?
System Information
Linux bubastis 3.10.25-gentoo #10 SMP Thu Jan 30 22:17:35 UTC 2014 x86_64 Intel(R) Core(TM) i7-4800MQ CPU @ 2.70GHz GenuineIntel GNU/Linux
NVIDIA Corporation GK107GLM [Quadro K1100M]
Blender Version
Broken: blender-2.70-linux-glibc211-x86_64
Short description of error
The video sequence editor's preview window does not match up with
the rendered output when a video strip refers to a blender scene
with an aspect ratio different from the aspect ratio of the
compositing scene.
Exact steps for others to reproduce the error
Create first scene with 40x40 resolution. fill it with 3d objects
Create second scene with 1920x1080 resolution. put some text on the right side.
Create third scene with 1920x1080 resolution. This is a VSE project. Incorporate the first scene on top of the second scene.
render
Check the Image Offset option on the 40x40 scene
render
Add a transform strip to the 40x40 scene and set the scale and position parameters so it fills the left side of the composite scene with the text from the second scene visible on the right.
render
Notice how at each stage the rendered output is different from the view in the preview window. This discrepancy confounds new users as they attempt to construct a mental model of how blender works and delays understanding and competence.
I am pretty sure this relates to the TODO regarding a rewrite of the Video Sequence Editor, but I'm going to incorporate my narrative from the sample .blend because I don't want the issues relating to pixel_aspect_ratio to fall through the cracks when this TODO transitions to a todone.
Changed status to: 'Open'
Added subscriber: @mutantbob
I do not have any applications on this linux box that would allow me to drag and drop a .blend file here, so I'll just use pasteall.org:
http://www.pasteall.org/blend/28546
Here is my narrative I composed in a text buffer which also appears in that .blend file. Consider it an RFE:
This .blend file contains a test suite for VSE strips based on scenes. There are some bugs and shortcomings in the VSE's handling of scenes with aspect ratios that differ from the aspect ratio of the VSE scene.
"credits" is a scene with matching aspect ratio. It has a text object and a yellow square that is a "placeholder" which should be obscured by the square video from the "square test pattern" scene.
"square test pattern" is a simple scene designed to make it easy to tell when the scene has been cropped.
In all the compositing scenes we have to change the Blende menu to "over drop". Why this is not the default I have no idea.
"vse 1" illustrates a surprise:
I had hoped the preview window and the rendered output would incorporate the scene at its true aspect ratio. Special care should be taken to respect the pixel aspect ratio specified by the linked scene and the compositing scene. (Consider the case where you take a 4:3 352x480 mpeg video and incorporate it into a 16:9 720x480
compositing scene)
"vse 2" is derived from "vse 1" but adds a transform effect strip which scales the "square test pattern" by 9/16 and offsets it by <-22,0>
The preview window matches the rendered output.
We're getting closer to the desired effect, but are still frustrated by blender's failure to respect the shape of the original scene.
"vse 3" is derived from "vse 1" but we activate the "Image Offset" checkbox on the strip referring to "square test pattern". This is the first stage of a workaround suggested by blender.stackexchange.com and triggers a number of strange things
The mismatches between the preview window and the rendered output are a serious problem that will confuse users, but should take a back seat to fixing the rest of the bugs surrounding scene-based video strips.
Exactly what the Image Offset checkbox does is mentioned at:
http://wiki.blender.org/index.php/Meta:Sanbox/Doc:2.6/Manual/Sequencer/Usage
I suspect that it would be a little less confusing to users if auto-scaling were controlled by its own appropriately named checkbox.
"vse 4" is where we have achieved the desired effect of incorporating the square scene filling the left side of the composite scene and have the text on the right side.
The way we accomplished this was by adding a strip for the scene "square test pattern" and activating the "image offset" checkbox. Then we scale up the scene from its 40 pixel starting version using a Transform strip. To fill its target space we scale it by a factor of 27, and adjust its position by 1300% of the original pixel size (which corresponds to (27-1)/2 ).
As you might notice, the preview window is horribly wrong.
I suspect most of this confusion comes from the fact that there are a myriad of ways you can describe the size of a video
When both scenes have the same resolution there is no confusion. When they differ, I'm sure you could find people whose intent varies. The primary problem is that their intent does not directly correspond to labels on any user interface element.
I have identified the following theoretical options for incorporating source video of different resolution:
I am open to suggestions for other scaling modes, but I suspect these will provide a solid non-confusing base for accomplishing any use case.
An option to align video to top/bottom/left/right of composite scene frame would be gravy, but without that option you can accomplish the effect using a transform strip.
Right now the only options are 1 (the default) and 3 (with Image Offset checked). Accomplishing any of the suboptions from section 2 requires a transform strip. Additionally, since the preview window is very buggy, you also need either
*) a lot of experimentation or
*) a solid understanding of the mathematical model that governs the transform strip's scale and position parameters.
I propose that the Image Offset checkbox be replaced by a menu that makes the scaling mode explicit rather than being a NiceTip on the wiki.
Additionaly, the preview window should be updated to better reflect the rendered output since new users rely on its display to help them build a mental model of how the various options work. When the preview window does not match the rendered output, users come to defective conclusions that can take a while to straighten out.
the video sequence editor's preview pane does not correspond to rendered output when using video strips from a scene with a different aspect ratio. this leads to user confusion.to Video Sequencer, Aspect Ratio issueWill have a look.
This issue was referenced by blender/blender-addons-contrib@e7c5931990
This issue was referenced by
e7c5931990
Changed status from 'Open' to: 'Resolved'
Closed by commit
e7c5931990
.