Flash Video Fundamentals

Any video file you want to add to your web page must first be converted to the Flash Video (FLV) format to make the file smaller so that it would generally load faster. The original raw format and properties of your video clips generally affect the capability of the video encoder and the user’s experience of the video playback on his computer.

There are two fundamental factors that directly affect the video encoding procedure, source quality and frame motion of the video clip.

As soon as you press the REC button of your video camera, the video clip source quality is established. To guarantee that you will always have high quality compressed video clips to improve your website, always keep the following in mind:

- Always use a tripod when you shoot video clips to reduce camera shake and movement. Camera movements always cause excessive amounts of pixels to adjust unnecessarily from frame to frame which results to higher data rates.

- Avoid using unnecessary light filters. Make sure that you have adequate lighting. Shooting in low light conditions and the use of light gain filters invariably produce video noise on each video frame making good quality compression more difficult.

All types of cameras have the capability to capture high quality videos if you use good lighting and a tripod as you shoot. Most models in the last three years also have anti-shake technology embedded in their firm ware since it is not always the case that you can take along a tripod. However, this is not always possible. The rule of thumb is a high quality video source produces lower data rates that render a good quality playback.

As much as possible, avoid the following:

- People, vehicles or objects that come between the lens and the subject.

ý Special camera effects like pan, zoom or extreme close-ups.

ý Postproduction effects such as dissolves, fades or complex video effects.

These avoidable and sometimes superfluous effects create motions (more pixel changes from frame to frame) in your video clip, resulting to more data that has to be compressed.

Video compression requires that you achieve the perfect balance between several variables such as file size, target bandwidth, frame rate, key frame interval, and pixel dimensions of the video.

The following are general guidelines to follow when compressing raw video to Flash Video for delivery over the Internet:

- A higher target bandwidth allows for more motion in the video, better frame rates and larger pixel dimensions but an equally larger file size.

þ The lesser the motion there is in your video, the smaller the file size and the lower a target bandwidth you can reach.

- As the target bandwidth decreases reduce the key frame rate. Lower key frame rates reduce bandwidth demand.

- As motion increases the key frame rate must be increased.

Action clips (skateboarding, children playing) require more information to be handled by the video player and are not good for low bandwidth delivery because additional uncompressed key frames to be encoded in the file.