Ah ha--got the full resolution of the sensor. (Within 1 pixel of the y axis.)
Shoot a full resolution silent picture, either dng or mlv converted to dng with mlv_dump --dng, and run dcraw -4 -E on the dng. The resulting .pgm file will be the full size of the sensor. For the EOSM/650D it is 5280x3529. The extra pixels are on the top and left, just like on the simple silent picture showing the video raw buffer.
So going back to the exiftool report on the full res silient picture:
Default Crop Origin : 0 0
Default Crop Size : 5208 3477
Active Area : 52 72 3529 5280
5208 + 72 = 5280 width -- Check
The height is completely off:
3477 + 52 = 3549 height -- Wrong!
Taking a close look in Photoshop:
It appears to confirm that 72 pixels are taken off the x axis at the left but 50 pixels are taken off the top. Yet the image measures a total of 3529 high so that's what we can probably assume to be true.
That brings up the issue of what is going on with CR2 files? Running dcraw -4 -E on a CR2 file results in:
Image Size : 5280x3528
Both exiftool and Photoshop agree on this size. So where is the row shaved off on CR2 files, the top or the bottom? The only way to find out for sure is through more tests but we are close, very close and if you think about it--it doesn't really matter for raw video but as long as we're examining the full sensor we might as well find out.
Canon 100D / SL1 and Canon 700D / T5i testers, are you following along? What does exiftool report as the full sensor size of a CR2 and the image size of a full resolution silent picture (for DNG files) or mlv_dump -m -v (for mlv files) ? Are you also seeing a 1 pixel discrepancy in the vertical resolution?
BTW, I know that I mix things up a bit to keep it interesting but:
Vertical resolution = Y axis = Height
Horizontal resolution = X axis = Width