Hi Lakshit,
You can use -b command line switch to change the bit rate of the compressed video.
Higher bit rate will reduce the compression and increase the output video quality and vice versa.
Usage -
-b <bit rate>
For example,
-b 1000000 for 1Mbps bit rate.
Other option is changing the quantization parameter using the command line switch.
Refer to demo guide for details.