Scalable video encoding allows the creation of video bitsreams for video receivers with different resolutions (HDTV, SDTV, Mobile Devices etc.) and channels with varying quality levels.
The input of a scalable video encoder is high resolution video. The video resolution is scaled down and the scaled video is encoded into a low bitrate stream. The low bitrate stream is then decoded, preprocessed by compression artifact filters and scaled up by a high quality scaler. The difference of the input HD video sequence and scaled video sequence is encoded as a high bitrate stream.
Low resolution devices receive only the low bitrate stream. High resolution devices receive both the low bitrate and high bitrate streams. Low bitrate streams for broadcasting should use more robust methods of modulation and error-correction coding than high bitrate streams since low resolution channels usually introduce more noise and distortions.
Using similar approach, scalable video encoding may generate a greater number of bitstreams to cover a greater number of possible resolutions.