No reference PSNR estimation for compressed pictures

Abstract

Many user-end applications require an estimate of the quality of coded video or images without having access to the original, i.e. a no-reference quality metric. Furthermore, in many such applications the compressed video bitstream is also not available. This paper describes methods for using the statistical properties of intra coded video data to estimate the quantization error caused by compression without accessing either the original pictures or the bitstream. We derive closed form expressions for the quantization error in coding schemes based on the discrete cosine transform and block based coding. A commonly used quality metric, the peak signal to noise ratio (PSNR) is subsequently computed from the estimated quantization error. Since quantization error is the most significant loss incurred during typical coding schemes, the estimated PSNR, or any PSNR-based quality metric may be used to gauge the overall quality of the pictures.