Method and apparatus for video quality measurement
AssigneeThomson Licensing
InventorsFan Zhang, Ning Liao, Kai Xie, Zhibo Chen
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Abstract
Accuracy and efficiency of video quality measurement are major problems to be solved. According to the invention, a method for accurately predicting video quality uses a rational function of the quantization parameter QP, which is corrected by a correction function that depends on content unpredictability CU. Exemplarily, the correction function is a power function of the CU. Both QP and CU can be computed from the video elementary stream, without full decoding the video. This ensures high efficiency.
Claims15
A method for estimating video quality of an encoded video stream, the encoded video stream comprising macroblock prediction residuals, wherein the method is performed by and configured to be executed on a video quality measurement processor, the method comprising:
- performing quantization parameter (QP) parsing and averaging QPs within a macroblock for determining an average quantization parameter, QP, of frames of a video sequence;
- calculating, for the video sequence comprising a plurality of frames, an overall quality score Q from a basic quality score Qb multiplied by a correction factor Qc,
- wherein the basic quality score Qb is obtained from the average quantization parameter QP of the frames of the video sequence, and wherein the correction factor Qc is obtained from an average pixel variance within the prediction residuals of macroblocks in the video sequence, and
- wherein the method further comprises:
- determining said basic quality score Qb according to a function of a form xb/(1+xb), where in xb is a parameter depending on said average quantization parameter QP;
- and
- determining said correction factor Qc according to a rational function of a form b2·xc+b3, with b2, b3 being constants and xc being a power function of said average pixel variance within the prediction residuals.
An apparatus for estimating video quality of an encoded video stream, the encoded video stream comprising macroblock prediction residuals, the apparatus comprising:
- a processing element for
- detecting and averaging quantization parameters of macroblocks for determining an average QP, QP, of frames of a video sequence;
- providing the quantization parameters of the macroblocks and said average quantization parameter value;
- calculating, for the video sequence comprising a plurality of frames, an overall quality score Q from a basic quality score Qb multiplied by a correction factor Qc,
- wherein the basic quality score Qb is obtained from the average quantization parameter value over the frames of the video sequence, and wherein the correction factor Qc is obtained from an average pixel variance within the prediction residuals of macroblocks in the video sequence, and
- wherein said basic quality score Qb is determined according to a function of a form xb/(1+xb), wherein xb is a parameter depending on said average quantization parameter QP;
- and
- said correction factor Qc is determined according to a rational function of a form b2·xc+b3, with b2, b3 being constants and xc being a power function of said average pixel variance within the prediction residuals.
Dependencies are inferred from the claim text.