This applies to NetCam SC, NetCam XL, Express 4 and Express 2.
The motion detection information is stored in an APP10 marker in each JPEG.
For firmware 1.1.61 and later
2-byte APP10 marker (0xff, 0exa)
2-byte length (big endian)
4-byte type marker (0x53, 0x44, 0x4d, 0x30, or "SDM0")
32-byte motion grid (16x16); 0=no motion, 1=motion
For firmware 1.1.60 and earlier
2-byte APP10 marker (0xff, 0xea)
2-byte length (big endian, always 0x00, 0x22)
32-byte motion grid (16x16); 0=no motion, 1=motion
The motion grid is ordered consecutively from the top left to bottom right; there are 16 rows from top to bottom, each row is 16 columns from left to right. So if the first two bytes of motion data are "0x80 0x00" then there is motion in the upper left grid cell.
Note that there may be other APP10 markers in the JPEG data, such as timestamp information, etc.
