int mode_blocksize[64]
window size mapping for each mode
int blocksize[2]
short and long window sizes
int prev_mask
bitmask used to get the previous mode flag in each packet
int valid_extradata
extradata is valid, so we can calculate duration
int mode_mask
bitmask used to get the mode in each packet
int extradata_parsed
we have attempted to parse extradata
main external API structure.