Encoding at a higher quality level based on mixed image prediction factors for different quality levels

摘要

Image encoder 500 comprises a first encoder 504 for a signal representing an image at a first quality level, and a second encoder 506 for encoding a signal representing an image at a second, higher, quality level. Mixer 346 mixes a factor of a signal representing a prediction of the image at the first quality level and a factor of a signal representing a prediction of the image at the second quality level, producing a mixed signal. The second encoder 506 encodes the image signal at a second quality level based on the mixed signal, and factors are selected based on a measure of noise introduced by the first and second encoders when producing the predictions; corresponding decoders and decoding / encoding methods are also claimed. Further independent claims relate to encoding the second, higher quality signal based on a weighted sum and encoder quantization factors, or on a frequency domain representation of the predicted images.