Best Practices for On-Demand Streaming
Part 3a. - Shooting video for streaming
The mechanics of streaming
When streaming video is encoded it will use the available amount of information (defined by the chosen bitrate) to create the highest quality video possible. Unlike film, each ‘frame’ in a streaming video is not a complete image, it is simply an update of the image to show any changes that were made between frames (generally movement). The only complete updates are what is known as ‘key frames’, which are inserted at regular intervals and also for scene changes.
In a video with very little movement, only a small portion of the available data for each frame needs to go to these ‘updates’, the rest is available to enhance the picture’s quality. In a video with frequent movement, the available data needs to be used to update large portions of the image, resulting in less data available for image quality.
If it is possible to minimize the amount of change between frames, you can deliver a high quality stream at a lower bitrate, or increase the quality of your stream without increasing the bitrate.
If you are shooting the video you intend to stream, you should attempt to minimize unnecessary movement in your video. Try to focus on your subject and keep the background either simple, or softly out of focus. If you are not producing your own content you will have to rely on compression techniques to optimize the video for streaming.
