Some I get, some I don't. Frame rate, video codec & dimensions, aspect ratio, min & max video bitrate, audio codec, audio bitrate, sample rate & number of channels are pretty self-explanatory. What's the rest of it mean?

For example

-r 23.97 -vcodec h264 -s 1280x720 -aspect 16:9 -flags +loop -cmp +chroma -deblockalpha 0 -deblockbeta 0 -b 3500k -maxrate 4000k -bufsize 4M -bt 256k -refs 1 -bf 3 -coder 1 -me umh -me_range 16 -subq 7 -partitions +parti4x4+parti8x8+partp8x8+partb8x8 -g 250 -keyint_min 25 -level 30 -qmin 10 -qmax 51 -qcomp 0.6 -trellis 2 -sc_threshold 40 -i_qfactor 0.71 -acodec aac -ab 256k -ar 44100 -ac 2


Further is it possible - or even desirable to specify a constant bitrate on the video and/or audio?

Thanks for all assistance.