Exporting a Movie using the 'Motion JPEG A' Codec

While there are many different video codecs (compressor-decompressors) to choose from in QuickTime, it may come as a surprise that one of the older codecs works quite well for use in screensavers. We encourage you to test the 'Motion JPEG A' codec, because it has some notable benefits: Video quality is extremely high, it requires a low amount of CPU to decode (making it suitable for older machines), and playback starts and stops smoothly (making it ideal for short looping movies). It also is a relatively simple codec, which means the number of options is lower than other codecs, which reduces complexity when you are authoring. The main disadvantage to MJA is large file size, often 2 to 5 times larger than other codecs. However, in the age of DVD distribution and broadband download speeds, screensavers that are 10 or 100 megabytes in size are not unreasonable. Thus, the trade-offs of using MJA may be right for you. Read on for instructions for proper use of the 'Motion JPEG A' codec.

Important: QuickTime 7.4 and later considers Motion JPEG as a 'legacy encoder' which must be specifically enabled within the QuickTime Preferences' Advanced tab. If you are creating for newer versions of QuickTime, it might be preferable to use H.264 or another modern codec.

Note that there are several buttons labelled 'Settings' or 'Options' within these cascading dialog boxes. Yes, it can be confusing at first!

In this example, we created a sample 640x480-sized movie (other sizes are fine). When saving the movie under QuickTime, choose 'Export' from the 'File' menu, choose 'Movie to QuickTime Movie', then choose 'Settings' to bring up the 'Movie Settings' dialog:

Movie Settings : We turned off 'Sound' (since we like silent screensavers) but you have the option of leaving it on. Our suggested audio settings are 22.0 KHz, 16-bit mono, which will preserve audio quality, but reduce the file size. Turn off 'Internet Streaming'. QuickTime allows adding different image filters with the 'Filter' button. If you wish to resize the image size of your screensaver, you can change it with the 'Size' button (but do not use a larger size, since this will waste bytes with no increase in quality). Click 'Settings' to bring up the 'Standard Video Compression Settings' dialog:



Standard Video Compression Settings : Choose the 'Motion JPEG A' as the Compression Type. Fifteen (15) frames per second (fps) is a good starting point, remembering that the higher the FPS - the larger the final file size - plus, older machines might have problems with smoothly playing the higher frame rates. With Motion JPEG, there are no options for key frames or data rate, as each frame is saved as a key frame, but the 'Quality' slider is available (we suggest somewhere between Medium or High). Click 'Options' to bring up the 'Motion JPEG A Options' dialog.



Motion JPEG A Options : Make sure to set 'Number of fields' to One, and turn off 'Optimize for streaming', if on.



Of course, experiment as you see fit. Have fun and good luck!

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