Hi,
You need to check following points b4 chose any FPGA.
1. How much is the frame size?
2. What is the resolution has been targeted?
3. How much BRAM in the FPGA to process frames? --> Though you are using external memories like DDR/SRAm/Flash etc.
You atleast need 2-3 frames to be stored in BRAM. keep this in mind.
4. What all soft/hard core IPs available with the FPGA vendors? --> Like Line buffers/framing/color space converter/deinterlacer/scalar/LCD.VGA timing controller etc.
Hope this helps.
Regards,
Sachin