All videographers have to deal with the reality of compression. Compression is used to reduce the file size of a video image to fit it more easily into an available space. Even the Mini DV format uses a compressed data format that allows an hour or so of digital video to fit on a small tape. DVD video is even more compressed to fit on optical discs. To pass through the small data pipeline, video distributed on the Web has to be compressed to an extreme degree. This is commonly achieved by lowering resolution (image size) and decreasing frame rate (speed) to eliminate significant amounts of data.
Highly compressed video tends to exhibit some common problems. Reducing the number of frames will reduce the file size, but can result in video that jitters and stutters. Reducing the resolution of your video too much causes pixelization when displayed at full-screen (which many viewers prefer).
Perhaps it is easiest to post video that is blocky and jerky and curse the limitations of the Web, but there are ways to improve your results. With careful shooting, you can create videos that compress easier and stream better on the Web. In this article we’ll discuss how to shoot video for compression.
A tendency of many videographers is to use pans and zooms, especially to take in the expansive scenery. While this might look fine on a television, camera moves do not compress well for the Web. When you move the camera, every pixel in every frame changes constantly, and this is very hard to compress. MPEG encoders recreate only the pixels that change from frame to frame and reuse those that don’t. The more pixels that are repeated, the smaller the size of the file. By limiting movement, you can increase the efficiency of compressing your footage, and reduce the file size for faster playback. Even subtle camera movement, like handheld footage, creates a problem. If you’re shooting video for the Web, use a tripod and lock your camera in position when you record.
Busy backgrounds are as bad as camera moves. Avoid shooting your on-camera narrator in front of a crowd of people, a busy road or leafy tree. This type of motion gives compression programs a lot of trouble. While the better compressors will handle this situation, you will typically see blurry and pixilated artifacts that will reduce the effectiveness of the shot and annoy the viewer.
Lighting is very important as well. Low-lit video looks grainy and gray. The resulting grain is interpreted as movement by the MPEG codec and the video has to be processed as much as if every shot were a pan or zoom. Good lighting can greatly decrease file size and playback speeds.
Set a Soft Focus
Another technique to incorporate when shooting for compression is to decrease the depth of field as much as possible, in order to throw the background out of focus. Manually focus the camera on your subject and allow the background to go soft. This allows the compression technology to do most of its work on your subject, instead of on a detailed background.
Because you will likely display your image in a window the size of a Wheat Thin, prefer to shoot closeups – especially when shooting people. Keep wide head-to-toe shots of people short as they will not display detail well at low resolutions. Instead, favor head-and-shoulders shots.
The secret to successful streaming is to shoot your footage with compression in mind. Lock your camera down for solid shots, avoid busy backgrounds, light well and set a soft focus. These simple shooting tips will help you reduce file sizes to give your Web viewers a better viewing experience.
Stream or Download
Streaming video requires some kind of interaction between the viewer and the Internet server that is transmitting the video. Streaming video servers cost money and you may have to pay to use one for your video. The primary advantage of streaming is that your viewers will have random access to the program. There really isn’t any disadvantage to the old fashioned method of downloading a file before you view it, except for the inconvenience of waiting, and there certainly isn’t any loss of quality. Streaming is nice, but it isn’t magical.
Editing for Compression
When editing, use cuts, not fades or transition effects. Fades do not compress well. Cuts look clear and distinct between shots and allow compression to be more efficient, which means smaller file sizes for upload and download.
Make it a Slideshow
Still images stream very well. Instead of using full-motion video, consider creating a streaming slideshow from digital stills captured to the memory card in your camcorder. Add some music and narration to create a slick show.