Interlacing is detected upstream (PAL DVD -> R576i) but was dropped in
two places: the video label hardcoded a 'p' suffix, and the muxer never
wrote any scan-type flag, so MediaInfo inferred progressive and reported
576p for a 576i source.
- Add Resolution::is_interlaced() for the R*i variants.
- generate_video_label now branches i/p for the heights that can be
interlaced (1080, 576, 480) instead of always emitting 'p'.
- MkvTrack carries interlaced + field_order; the video serializer emits
FlagInterlaced (0x9A; 1=interlaced, 2=progressive) and, for interlaced
content, FieldOrder (0x9D) - bottom-field-first for PAL 576i,
top-field-first otherwise. Adds the EBML constants.
Matthew Jackson
e0ce035765