Thursday, July 31, 2008

Video Compression Workshop – 10 Steps to Better Compression

1.) De-interlace your video: Most video files are interlaced, which means that half of one image is blended with half of the next.  On a Television this produces smoother motion, on a computer it produces junk.

2.) Lower your audio standards: Most users are listening to computer audio on tiny speakers.  Cutting your sample rate to 22 or 11 kHz and the sample size to 8-bit will often produce unnoticeable audio changes but huge space saving.

3.) Shrink the window: While you don’t need to make video postage stamps sized.  But reducing the window to half size creates a file that is 25% the file size of the original.  That’s a BIG savings in space.

4.) Reshape the video: Most likely you are working with a video file that is sized 720 X 480 (or 486) pixels.  You need to resize this to 640 X 480 for it to properly display on the computer monitor.

5.) Restore the washed-out picture: Video signals operate between an RGB value of 16 thru 235.  Computers use an RGB value of 0 thru 255.  You will need to restore the back and white point of your image.  Many applications have this option.

6.) Improve the saturation: A video file displayed on a computer will also need the saturation turned up a bit.  This is to compensate for what I call the Wal-Mart effect.  Consumer TVs have their reds over-cranked to make skin tones appear richer on their cheap tubes.

7.) Frame Rate:  Your video file is likely recorded at approximately 30 fps.  This is needed for a television display, but not important for most web video.  Reducing your frame rate to 15 or even 10 fps will result in a 50 - 66% savings in file size.

8.) Codecs: The file architecture you pick will often have its own codec chosen.  However some file formats support a variety of codecs.  Be sure to keep compatibility and audience requirements in mind.  Newer codecs offer a significant advantage over older formats.

9.) Don’t use a Conduit: For faster compression, don’t run web compression through a conduit like Final Cut Pro to your compression utility.  Instead, save a flattened, self-contained movie and then compress.

10.) Test it: Before you compress a lot of video, create a small test file.  Try compressing 10 seconds of video with different settings.  Find the ones that work best for you.

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