webmask is identified by 4 bytes = MASK.
MASK <> VERSION <> kI <> vU <> Ly
4D 41 53 4B <> 00 00 00 01 <> 02 <> 02 00 00 00 <> 00 00 00 0B
MASK must equal "MASK". kI must equal 2.
version = 1
kI = 2
vU = 33554432
Ly = 11 (I think these may be timing segments? perhaps, keyframes?)
version = int32 at offset 4 kI = int8 at offset 8 vU = int32 at offset 8 Ly = int32 at offset 12
c == "header length" c = 16
b == "timing info length?" b = 16 * Ly (11) = 176
Looks like the file has 3 parts. 1: Header 2: Timing Data 3: SVG Data
MK function
frames = []
l = 0
loop through 0..Ly
if 0 == int32(timing_data[l]) && 0 == int32(timing_data[l + 8]) { time = int32(l + 4) offset = int32(l + 12) l = l + 16
frames.push({ time: time, offset: offset }) }
number_of_frames = frames.length l = 1000 * duration # not sure where duration comes from. l > frames[number_of_frames - 1].time && frames.push({ time: l, offset: -1 })
if (last_frame.time < total_length) { frames.push({ time: l, offset: -1 }) }
This is probably a data saving method, if last frame specified is not last frame in the video: use first frame as last frame?
Frame Data
frame: data = []; data_len = int32 time (g) = int32 at offset 8
frame_length = 12 + data_len
frameData.push({ start: b, end: c, data: data })