A little script that uses Mac OS X's screencapture, ImageMagick and ffmpeg to capture a bunch of screenshots with instructions for making an MPEG movie

screencap.py

#!/usr/bin/python
import os
import sys
import time
from datetime import datetime
from AppKit import NSWorkspace

# This will be a movie
process_filter = None
if len(sys.argv) >= 2:
    process_filter = sys.argv[1]
if len(sys.argv) >= 3:
    sleep_time = int(sys.argv[2])

print 'try: convert -quality 100 snapshot-*.png outvideo.mpeg'
print 'then: rm snapshot-*.png'
print 'when you want to stop recording: Ctrl-C'

while True:
    time.sleep(5)
    active_app_name = NSWorkspace.sharedWorkspace().activeApplication()['NSApplicationName']
    if process_filter and active_app_name.lower().find(process_filter) == -1:
        continue
    filename = 'snapshot-{}'.format(datetime.now().strftime('%Y-%m-%d-%H-%M-%S.%f.png'))
    # print 'Capturing screen because {} is the active application. {}'.format(active_app_name, process_filter)
    os.system('screencapture -mxrC {}'.format(filename))