Constant quality video encoding

Lossy video compression algorithms, such as those used in the H.261 and MPEG standards, result in quality degradation seen in the form of tiling, edge business, and mosquito noise. The number of bits required to encode a scene so as to achieve a given quality objective depends on the scene content; the more complex the scene is, the more bits are required. Therefore, in order to achieve a given video quality at all times, the encoder parameters must be appropriately adjusted according to the scene content. The authors propose a video encoding scheme which maintains the quality of the encoded video at a constant level. This scheme is based on a quantitative video quality measure, and it uses a feedback control mechanism to control the parameters of the encoder. The authors evaluate this scheme by applying it to test sequences, and compare it with constant bit rate and open-loop variable bit rate schemes in terms of quality and rate. They show that their scheme achieves better quality than the other two schemes for a given total number of bits, particularly when the content has scene changes over time.