Reduced resolution update mode extension to the H.264 standard

In this paper we present an extension of the reduced resolution update mode, originally supported by H.263, into the H.264 (MPEG-4 AVC/JVT) video coding standard. This new mode provides the opportunity of increasing the coding picture rate, while maintaining subjective quality. This is done by encoding an image at a reduced resolution, while performing prediction using a high resolution reference. This allows the final image to be reconstructed at full resolution and with good quality, although the required bitrate for encoding the image is reduced considerably. In our paper, considering that H.264 contains several new improved motion compensation tools compared to its counterpart, this concept had to be adapted accordingly to fit within the specifications of the new standard or its extensions. This includes new syntax elements, and certain semantic and encoder/decoder architecture modifications to inter and intra prediction modes.