QUANTIZATION AND DIFFERENTIAL CODING OF ALPHA IMAGE DATA
First Claim
1. One or more computer-readable media containing computer-executable instructions which, when executed by a computer, cause the computer to perform a method for decoding an alpha image encoded in a bit stream, the method comprising:
- entropy decoding encoded data from the bit stream to produce differential residual data for the image, the differential residual data encoded in a modulo domain;
differential decoding the residual data to produce quantized data for the alpha transparency image, the quantized data represented in a continuous domain; and
dequantizing the quantized data from the continuous domain to produce reconstructed data for the alpha image such that a quantized data value representing a full encoded alpha image value is dequantized to result in a full reconstructed alpha image value.
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Abstract
Alpha images are efficiently encoded for inclusion in video bitstreams. During encoding, alpha image data is quantized as a first step before differential encoding. The quantized alpha image data is then differential encoded and represented in a modulo domain before entropy encoding to take advantage of certain distribution features of typical alpha image data. During decoding, a decoder performs differential decoding of encoded alpha image data before dequantization. During differential decoding, the data is converted from a modulo domain to a continuous domain. Dequantization is performed using a technique which results in reconstructed alpha image values which include 0 and maximal values within the acceptable alpha image data range so that the process preserves these values for reconstructed alpha images.
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Citations
20 Claims
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1. One or more computer-readable media containing computer-executable instructions which, when executed by a computer, cause the computer to perform a method for decoding an alpha image encoded in a bit stream, the method comprising:
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entropy decoding encoded data from the bit stream to produce differential residual data for the image, the differential residual data encoded in a modulo domain; differential decoding the residual data to produce quantized data for the alpha transparency image, the quantized data represented in a continuous domain; and dequantizing the quantized data from the continuous domain to produce reconstructed data for the alpha image such that a quantized data value representing a full encoded alpha image value is dequantized to result in a full reconstructed alpha image value. - View Dependent Claims (2)
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3. A method for encoding an alpha transparency image in a video sequence, the method comprising:
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representing data for the alpha transparency image in a modulo domain; transmitting the data in the modulo domain in a video bit stream. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for decoding an alpha transparency image in a video sequence, the method comprising:
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receiving a video bit stream containing alpha image data in a modulo domain; transforming the modulo domain alpha image data into quantized data in a continuous domain; and dequantizing the quantized data to produce reconstructed alpha transparency data. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification