gource and ffmpeg reduce video size
-preset

Use the slowest preset that is fast enough that it does not drop frames. You can see if ffmpeg is dropping frames in the console output (if I recall correctly). Presets are: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow.

-crf

Use the highest -crf value that still provides an acceptable quality level. Range is 0-51. 0 is lossless, 18 is generally considered to be visually lossless or nearly so, 23 is default, and 51 is worst quality. Using a value of 1 will likely result in a huge file.

Also see:


FFmpeg H.264 Video Encoding Guide