The file size of video displayed online is as important as its quality. Uncompressed video impacts the speed and performance for the viewer and greatly increases your storage capacity.
There are many methods of video compression. The format dictates how the audio and video is compressed, the quality and file size, as well as its support across devices (such as mobile smartphones).
H.264 video is currently the best compression formats for online content. H.264 is supported across most browsers (including HTML 5), players, and mobile devices (including the iPhone, which doesn’t support Flash and its FLV format). If you’d like lots more information about H.264, start with the H.264 Wikipedia page.
Simply explained, video compression works by saving a key frame and then only saving changes that occur in following frames until another key frame is required. A video with a talking head and very few cuts can be compressed well without impacting the quality. A lot of action and cuts in a video mean more frames are required during compression. The file size will be bigger or else quality will be compromised.
Most video compression software includes preset compression for video to MP4 format using H.264 video and AACaudio.
Set the size of the video to a standard such as 320W x 240H, 480W x 360H, or 640W x 480H. Standard YouTube videos are 320×240. Remember that larger sizes take longer to download and view.
Some programs also include settings for H.264 quality. A quality setting between 50-60% is usually quite good and means that you don’t need to set the bit rate. If you do, try a two-pass bit rate of 400 kbps for the smallest size video and up to 500 kbps for the larger size. The AAC audio encoder bit rate produces good results from 64 (poor) to 192 kbps (excellent).
For more information, see the Adobe site.