Without fully understanding how the bitrate calculator function in ffmpegX works, I'm wondering if it's accurate for H.264 encodes. For video parameters of 1280x720, 16:9, 30fps with the x264 codec, (audio of 128 kbit/s) it recommends a "Best" bitrate of 3240 kbit/s. Most similar clips I can find on the net are between 5000-6000 kbit/s.