Module ladder 

ABR ladder computation — derive a sensible set of Rungs from a source resolution.

Callers who want full control build Rungs by hand and skip this module entirely. standard_ladder is the convenience path: it snaps to standard short-side quantizations (2160/1440/1080/720/480/360/240), preserves the source aspect ratio, even-aligns every dimension, and caps the top rung.

Constants

DEFAULT_MAX_SHORT_SIDE

Default cap on the short side of any rung. Sources above this have their top rung clamped down (aspect preserved); rungs above it never appear.

Functions

standard_ladder

Build a standard ladder for a source clip, every rung at default quality.

standard_ladder_with_quality

Same as standard_ladder but stamps every rung with quality.