All notes
Avidemux

Intro

Avidemux tutorial on batch processing.

REM pity that we could not specify filters here such as Rotating.
set avidemux="C:\Program Files\Avidemux 2.5\avidemux2.exe"
set videocodec=Xvid
set audiocodec=MP3
for %%f in (*.mp4) do %avidemux% --video-codec %videocodec% --audio-codec %audiocodec% --force-alt-h264 --load "%%f" --save "%%f.avi" --quit

Video Compression

ezs3.

About containers

Among MP4, MOV, FLV, WMV and AVI containers, MP4 is the best option.

Screencast example
Assume your video is a low motion 5fps screen cast in a 1280 x 720 frame size you would have a formula like this: (1 = Low Motion, multiply by 0.07 to get the bit rate in bps)
(1280 x 720 x 5) x 1 x 0.07 = 322,560 bps / 1000 = 322 kbps bitrate

High action video example
Another example on the other side of the spectrum would be a 24 fps high action shot of an action scene with multiple quick cuts in a 1920 x 1080 frame size: (4 = High Motion)
(1920 x 1080 x 24) x 4 x 0.07 = 13,934,592 bps / 1000 = 13,934 kbps bitrate

Audio encoders

Avidemux.org ref.

Video encode

Avidemux guide to encoding types.

ffmpeg

# bitrate of 1000000 bits/sec.
ffmpeg -i input.mp4 -b 1000000 output.mp4

# slhck.
# Basically, the CRF ranges from 0 (lossless, best) to 51 (worst). Steps of ±6 roughly egal double or half the bitrate.
# The default for x264 is 23.
ffmpeg -i input.mp4 -vcodec libx264 -crf 20 output.mp4

# SuperUser.
for i in $(seq 0 5 51); do 
	ffmpeg -i input.mkv -c:v libx264 -crf $i -c:a copy output-$i.mkv
done