start = find_next_marker(start, end); // in WVC1 extradata first byte is its size, but can be 0 in mkv
next = start;
for (; next < end; start = next) {
start = find_next_marker(start, end); // in WVC1 extradata first byte is its size, but can be 0 in mkv
next = start;
for (; next < end; start = next) {