No-reference image quality assessment based on DCT domain statistics

  • Authors:

  • Tomás Brandão;Maria Paula Queluz

  • Affiliations:

  • IT - Instituto de Telecomunicaçíes, Torre Norte, Piso 10, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal and ISCTE - University Institute of Lisbon, Av. Forças Armadas, 1649-026 Lisb ...;IT - Instituto de Telecomunicaçíes, Torre Norte, Piso 10, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal and Instituto Superior Técnico - Technical University of Lisbon, Av. Rovisco ...

  • Venue:
  • Signal Processing
  • Year:
  • 2008

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Abstract

This paper proposes a no-reference quality assessment metric for images subject to quantization noise in block-based DCT (discrete cosine transform) domain, as those resulting from JPEG or MPEG encoding. The proposed method is based on natural scene statistics of the DCT coefficients, whose distribution is usually modeled by a Laplace probability density function, with parameter @l. A new method for @l estimation from quantized coefficient data is presented; it combines maximum-likelihood with linear prediction estimates, exploring the correlation between @l values at adjacent DCT frequencies. The resulting coefficient distributions are then used for estimating the local error due to lossy encoding. Local error estimates are also perceptually weighted, using a well-known perceptual model by Watson. When confronted with subjective quality evaluation data, results show that the quality scores that result from the proposed algorithm are well correlated with the human perception of quality. Since no knowledge about the original (reference) images is required, the proposed method resembles a no-reference quality metric for image evaluation.