parity shouldn't be reset when using bob or
assumeframebased, but it should be kept the same as the
Finally caught this long time slip through the cracks.
avisynth/src/filters/field.cpp; revision 1.19; date: 2013/04/22 07:00:36; author: ianb1957;
Bob now preserves IT_BFF and IT_TFF values. Parity is passed through from the source clip.
Available in AviSynth 2.6.0 Alpha5, Sep 18th, 2013
AssumeFrameBased() behaviour is to entrenched to change safely.