System and method for quality-aware selection of parameters in transcoding of digital images
First Claim
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1. A method for selecting transcoding parameters and transcoding an input image into an output image for a terminal having terminal constraints including a maximum device file size, the method comprising:
- (a) determining a file size, and an encoding quality factor QF(I) of the input image;
(b) providing an array of relative file size prediction values and predicted quality metric values characterizing a measure of distortion of an image introduced by transcoding, the array being indexed by encoding quality factor QF(I), output encoding quality factor QFT and a resolution scaling factor zT;
(c) computing a maximum relative file size as the maximum device file size divided by the file size of the input image;
(d) selecting, from the array, a set of feasible transcoding parameters, yielding those predicted relative file size values not exceeding the maximum relative file size, which correspond to the file size and the encoding quality factor QF(I) of the input image;
(e) obtaining, from the array, predicted quality metric values corresponding to the set of feasible transcoding parameters; and
(f) selecting those transcoding parameters from the set of feasible transcoding parameters, which yield the highest predicted quality metric value.
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Abstract
Several quality-aware transcoding systems and methods are described, in which the impact of both quality factor (QF) and scaling parameter choices on the quality of transcoded images are considered in combination. A basic transcoding system is enhanced by the addition of a quality prediction look-up table, and a method of generating such a table is also shown.
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Citations
30 Claims
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1. A method for selecting transcoding parameters and transcoding an input image into an output image for a terminal having terminal constraints including a maximum device file size, the method comprising:
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(a) determining a file size, and an encoding quality factor QF(I) of the input image; (b) providing an array of relative file size prediction values and predicted quality metric values characterizing a measure of distortion of an image introduced by transcoding, the array being indexed by encoding quality factor QF(I), output encoding quality factor QFT and a resolution scaling factor zT; (c) computing a maximum relative file size as the maximum device file size divided by the file size of the input image; (d) selecting, from the array, a set of feasible transcoding parameters, yielding those predicted relative file size values not exceeding the maximum relative file size, which correspond to the file size and the encoding quality factor QF(I) of the input image; (e) obtaining, from the array, predicted quality metric values corresponding to the set of feasible transcoding parameters; and (f) selecting those transcoding parameters from the set of feasible transcoding parameters, which yield the highest predicted quality metric value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A system for selecting transcoding parameters and transcoding an input image into an output image for a terminal having terminal constraints including a maximum device file size, the system comprising:
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a processor; and a computer readable storage medium having computer readable instructions stored thereon for execution for the processor, forming; an image feature extraction module, determining a file size, and an encoding quality factor QF(I) of the input image; an array of relative file size prediction values and predicted quality metric values characterizing a measure of distortion of an image introduced by transcoding, the array being indexed by encoding quality factor QF(I), output encoding quality factor QFT and a resolution scaling factor zT; a quality and file size prediction module being configured to; compute a maximum relative file size as the maximum device file size divided by the file size of the input image; select from the array, a set of feasible transcoding parameters, yielding those predicted relative file size values not exceeding the maximum relative file size, which correspond to the file size and the encoding quality factor QF(I) of the input image; and obtain, from the array, predicted quality metric values corresponding to the set of feasible transcoding parameters; and a quality-aware parameter selection module, selecting those transcoding parameters from the set of feasible transcoding parameters, which yield the highest predicted quality metric value. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification