Most of existing rate control schemes in the literature focus on the bit allocation under the assumption of constant frame rate. As a result, the distortion of consecutive frames varies in a great extent, which may result in low temporal quality (e.g. flickering effect). In this work, we design rate control with two control parameters (i.e. quantization factor and frame rate) to achieve better tradeoff between spatial quality and temporal quality in low complexity. Our optimization gives two suggested quantization step sizes. One is used to change the frame rate in order to allocate how many bits used in the current frame. Another one is used to change the quantization factor in order to quantize MBs to achieve target bit rates. The experimental results suggest that our scheme can achieve more consistent quality while keeping high spatial quality.
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