The start of MPEG-2 encoding in craft_video::mpeg2 (feature
mpeg2-encode): progressive frame pictures, closed I/P GOPs, 4:2:0 Main
Profile and 4:2:2 Profile, constant quantiser or single-pass average
bitrate with adaptive quantisation, half-sample motion search.
The encoder shares the decoder's code tables, IDCT, dequantisation and
motion compensation, so the decoder outputs exactly the encoder's
reconstruction. B pictures, a VBV guarantee, interlaced coding and DVD
or broadcast presets are later steps of #1133.
The mpeg2 feature is split into mpeg2-decode and mpeg2-encode; mpeg2
still turns on both.
