The objective of scalable video coding is to enable the generation of a unique bitstream that can adapt to various bitrates,
transmission channels and display capabilities. The scalability is categorised in terms of temporal, spatial, and
quality. Effective Rate Control (RC) has important ramifications for coding efficiency, and also channel bandwidth and
buffer constraints in real-time communication.
The main target of RC is to reduce the disparity between the actual and target bit-rates. In order to meet the target bitrate,
a predicted Mean of Absolute Difference (MAD) between frames is used in a rate-quantisation model to obtain the
Quantisation Parameter (QP) for encoding the current frame.
The encoding process exploits the interdependencies between video frames; therefore the MAD does not change abruptly
unless the scene changes significantly. After the scene change, the MAD will maintain a stable slow increase or
decrease. Based on this observation, we developed a simplified RC algorithm. The scheme is divided in two steps;
firstly, we predict scene changes, secondly, in order to suppress the visual quality, we limit the change in QP value
between two frames to an adaptive range. This limits the need to use the rate-quantisation model to those situations
where the scene changes significantly.
To assess the proposed algorithm, comprehensive experiments were conducted. The experimental results show that the
proposed algorithm significantly reduces encoding time whilst maintaining similar rate distortion performance,
compared to both the H.264/SVC reference software and recently reported work.