File format
===========

The image data is stored raster-scanned in the following format.
QCIF = 176x144 luma resolution with 4:1:1 chroma subsampling.

           176
     +-------------+
     |             |
     |     Y       | 144
     |             |
     |             |
     +-------------+
     |  U   |
     |  88  |72
     +------+
     |  V   |
     |  88  |72
     +------+

The Y, U and V components are concatenated together, scan-lines after
scan-lines in one big file.