Is there a high speed video encoder with a compression ratio of 2:1?

The target chip is DM648-900MHz, and I need to encode a video of 640X480 resolution and 8bit gray color. Since the application only requires a compression ratio of 2:1 and a very high frame rate, so what kind of encoder could I choose?

I check the H.264 and MPEG2/4 encoders, but they could only offer 30FPS encoding speed which is not acceptable. I only need 2:1 compression, could I reduce the compression rate to increase the frame rate? Or is there any high speed data compression algorithm instead of video compression algorithm to meet my need?

Thanks!