Quantization method and system for video MPEG applications and computer program product therefor
First Claim
1. A method of converting digital signals between a first and a second format, the method comprising:
- generating coefficients representative of said digital signals;
subjecting said coefficients to a first quantization to generate an undithered quantized coefficient;
checking if said undithered quantized coefficient is equal to zero, such thatwhen said undithered quantized coefficient is equal to zero, taking said undithered quantization coefficient as a quantized signal, andwhen said undithered quantized coefficient is different from zero, generating a dither signal, and adding said dither signal to said coefficients before said first quantization to generate a dithered coefficient and subjecting said dithered coefficient to a quantization step to generate a dithered quantized signal.
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Abstract
Digital signals are converted between a first and second format by a conversion process including generating coefficients representing the digital signals. The coefficients may be discrete cosine transform coefficient generated during encoding/transcoding of MPEG signals. The coefficients are subject to quantization by generating a dither signal that is added to the coefficients before quantization to generate a quantized signal. Preferably, each coefficient is first subject to a first quantization in the absence of any dither signal added to generate an undithered quantized coefficient. If the undithered quantized signal is equal to zero the undithered quantized coefficient is taken as the output quantized signal. If the undithered quantized coefficient is different from zero, the dither signal is added and the dithered coefficient thus obtained is subject to quantization to generate the output quantized signal.
54 Citations
39 Claims
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1. A method of converting digital signals between a first and a second format, the method comprising:
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generating coefficients representative of said digital signals; subjecting said coefficients to a first quantization to generate an undithered quantized coefficient; checking if said undithered quantized coefficient is equal to zero, such that when said undithered quantized coefficient is equal to zero, taking said undithered quantization coefficient as a quantized signal, and when said undithered quantized coefficient is different from zero, generating a dither signal, and adding said dither signal to said coefficients before said first quantization to generate a dithered coefficient and subjecting said dithered coefficient to a quantization step to generate a dithered quantized signal. - 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 converting digital signals between a first and second format, the system being configured for generating coefficients representative of said digital signals comprising:
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a first quantizer for subjecting each said coefficient to a first quantization step to generate an undithered quantized coefficient; a control module for checking if said undithered quantized coefficient is equal to zero; an output element for taking said undithered quantization coefficient as a quantized signal when said undithered quantized coefficient is equal to zero; a source of a dither signal; an adder for adding said dither signal to said coefficient when said undithered quantized coefficient is different from zero; and a second quantizer for subjecting said dithered coefficient to a quantization step to generate said quantized siqnal for feeding to said output element. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A computer program product directly loadable in the internal memory of a digital computer and including software code portions for performing, when the product is run on a computer, a method of converting digital signals between a first and a second format, the method comprising:
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generating coefficients representative of said digital signals; subjecting said coefficients to quantization; generating a dither signal; and checking if said quantized coefficient is equal to zero, such that when said quantized coefficient is equal to zero, taking said quantization coefficient as a quantized signal, and when said quantized coefficient is different from zero, adding said dither signal to said coefficients before said quantization to generate a dithered coefficient and subjecting said dithered coefficient to quantization to generate a dithered quantized signal.
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31. A method of converting digital signals between a first and second format, the method comprising:
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subjecting said digital signals to a discrete cosine transform to generate coefficients representative of said digital signals; generating a dither signal; adding said dither signal to said coefficients and subjecting said coefficients to which said dither signal has been added to quantization to generate a quantized signal; subjecting such quantized signal to inverse quantization; and leaving said signal subjected to inverse quantization exempt from subtraction therefrom of dither signal, wherein said signal subjected to inverse quantization contains artifacts due to the non-linear characteristic of said quantization. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39)
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Specification