matroska: Support seeking to nearest keyframe
Add support for KEY_UNIT seeks to nearest keyframe
Right now matroskademux
only supported either SNAP_BEFORE
or SNAP_AFTER
seek flags when doing KEYINT seeks.
When user requested a SNAP_NEAREST
it always used SNAP_BEFORE
which is not what user wanted.
This MR adds support for SNAP_NEAREST
seeks and changes the KEY_UNIT
seeks behavior to also default to nearest keyframe when neither SNAP_BEFORE
or SNAP_AFTER
were requested.
Edited by Rafał Dzięgiel