Temporal signal energy correction and low-complexity encoder feedback for lossy scalable video coding
In this paper, we address two problems found in embedded implementations of Scalable Video Codecs (SVCs): the temporal signal energy distribution and frame-to-frame quality fluctuations. The unequal energy distribution between the low- and high-pass band with integer-based wavelets leads to sub-optimal rate-distortion choices coupled with quantization-error accumulations. The second problem is the quality fluctuation between frames within a Group Of Pictures (GOP). To solve these two problems, we present two modifications to the SVC. The first modification aims at a temporal energy correction of the lifting scheme in the temporal wavelet decomposition. By moving this energy correction to the leaves of the temporal tree, we can save on required memory size, bandwidth and computations, while reducing floating/fixed-point conversion errors. The second modification feeds back the decoded first frame of the GOP (the temporal low-pass) into the temporal coding chain. The decoding of the first frame is achieved without entropy decoding while avoiding any required modifications at the decoder. Experiments show that quality fluctuations within the GOP are significantly reduced, thereby significantly increasing the subjective visual quality. On top of this, a small quality improvement is achieved on average.