Guided Transcoding Using Deflation and Inflation

This paper analyzes and improves an existing guided transcoding scheme called deflation and inflation. By adding three new coding tools, required storage is reduced by 4.2 percentage points on a test set defined by the Moving Picture Experts Group. The first tool predicts coefficient signs, the second tool reorders coefficients using a dynamic scanning order, and the third tool uses new contexts for the binary coder to encode whether coefficients are non-zero or not. All three tools are based on a new method for estimating the likelihood of a coefficient being non-zero. Furthermore, the paper introduces a modified test configuration using a fast transcoder based on the x265 encoder for comparisons. Using this configuration, the three proposed tools provide a storage reduction of 4.4 percentage points with a transcoding complexity of around 5% of a transcoder based on x265.