Adaptive downsampling/upsampling for better video compression at low bit rate

To transmit video contents over limited bandwidth network, video bitstreams may need to reduce the bit rate by encoding with coarse quantization parameters at the expense of degrading quality. At low bit rates, better coding quality can be achieved by downsampling the video prior to compression and upsampling later after decompression. In this paper, we present an adaptive downsampling/upsampling video coding scheme in order to achieve better video quality at low bit rates in terms of both measure and visual quality. In particular, appropriate downsampling directions/ratios and quantization step sizes are adaptively decided for encoding different regions of video frame with the consideration of local contents. Experimental results have shown the better performance of the proposed scheme over the regular coding and downsampling-based coding scheme with fixed downscaling ratio. In addition, the proposed scheme significantly raises the critical bit rate below which a downsampling-based coding scheme outperforms the regular coding.