Digital Video Optimization
Optimizing video for distribution over the Internet is becoming an absolute necessity in a world where YouTube and other online media sites are amongst some of the most popular and heavily-trafficked web sites on the planet. While improperly optimizing graphical imagery can result in files that are hundreds of Kilobytes to process, improperly optimized video can result in files that are hundreds of Megabytes in size.
There are several common methods which are available to all of us which can dramatically reduce the size of one's files, including:
- Reducing the resolution/dimensions (frame size) of the file. A 600x400 pixel video will be roughly four-times larger in size than that same video being displayed at 300x200 pixels. If you do not need as large of a display within your site, reducing those dimensions as much as possible will pay huge dividends. Both proportional scaling and the cropping off of the outer edges of one's footage are options that are available to consider.
- Reducing the frame rate in your videos. Digital television in the United States has a frame rate of 30 frames per second (fps), while motion picture films in movie theatres are typically displayed at 24 fps. 10-15 fps is much more common within content that is displayed over the Internet. With that information as a backdrop, it is important to understand that reducing the frames per second in your files will dramatically reduce a file's size. Going from 15 fps to 10 fps, as an example, can reduce the size of your file by 50 to 65 percent! Be careful though: reducing your frames per second will reduce the smoothness in transitioning from frame to frame, so weigh file size savings against how a reduced quality in on-screen appearance will be received by your audience.
- Increase your key frame rates. Key frame rate define how often full frames ("key frames") are saved, with all frames in between each key frame not being saved as complete images. Only the differences between the frames are saved. This technique is sometimes referred to as interframe compression. Having a higher frame rate though will make it harder to seek within a file, so be aware of that trade-off.
- Reduce the bit depth (color depth) used in your footage. As is the case with graphical files, you can reduce a file's size if you are able to reduce the number of colors contained in the file. Going from 24-bit color to 16-bit or even 8-bit color can make a BIG difference...both in file size (positive) and potentially in image quality (negative).
- Changing your CODEC (Compressor-Decompressor). Different CODECs can result in dramatically different results, so experimenting with different CODECs is worthwhile. However, keep in mind that the CODEC used on your files must be the same CODEC that is being used by the viewers of your content.
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