Inconsistancy.  The number of frames per region is not constant.
 1         11         52

 1         11         27
 2         28         52

 1       3358         11         23         35         47
 1       3357         12         24         36         48
 1       3356         13         25         37         49
 1       3355         14         26         38         50
 1       3475         15         27         39         51
 1       3593         16         28         40         52
 1       3594         17         29         41
 1       3476         18         30         42
 1       3477         19         31         43
 1       3595         20         32         44
 1       3596         21         33         45
 1       3478         22         34         46