This forwards on a few more parameters from the GUI to FFMPEG for rendering the animation. I also added a scale slider, so it is easier to scale the entire dimensions down by percentage. Blender does this and I thought it is a good idea. The aspect ratio is always locked with these actions. Making it unlocked created complications with the scale slider.
I talked with Bollebib and these were the use cases:
- faster to encode videos with smaller image sizes
- sometimes clients like to see animations slowed down (changing the FPS)
For point one, right now the only way to do this is to directly modify the image size. This has a negative effect of you forgetting you did it and potentially saving over the file.
Note: it is possible that the dimensions don't follow the aspect ratio exactly. In this case, ffmpeg will tweak the values to make sure it works. I thought this was a better solution than the render giving an error.