avconv

convert video to jpeg with good quality

avconv -i input_video.mp4 -qmax 1 -qmin 1 images_%05d.jpg

crop video

avconv -i input.avi -vf crop=<width>:<height>:<x>:<y> output_%05d.png


create gif using http://gifmaker.me/

ffmpeg(avconv) jpeg quality

conversion with good jpeg quality:

avconv  -i ./input.avi -q:v 1 output_frame_%05d.jpg