Method and apparatus for compressing image data using a tree structure
First Claim
1. A method of encoding an input set of data bits by a codec comprising hardware, the method comprising:
- arranging said input set of data bits into a plurality of first groups of data bits, wherein said input set of data bits comprises a two-dimensional array of data bits;
dividing each of said first groups of data bits into a plurality of first subgroups of data bits;
logically combining said data bits within each of said first subgroups of data bits using a first logical operation to generate a first output data bit for each said first subgroup of data bits;
logically combining said first output data bits for said first subgroups of data bits of each of said first groups of data bits using a second logical operation to generate a second output data bit for each of said first groups of data bits, by forming a plurality of second subgroups of said second output data bits and logically combining said second subgroups of said second output data bits;
logically combining said second output data bits for said first groups of data bits to generate a final output data bit for said input set of data bits;
generating an encoded output set of data bits for said input set of data bits, said encoded output set of data bits comprising said final output data bit and, if said final output data bit is not equal to a first predetermined value, said encoded output set of data bits further comprising one or more of said output data bits and one or more of said data bits of said input set of data bits, in dependence on at least a first exclusion condition that if a given output data bit is equal to a second predetermined value, then said data bits and said output data bits used to generate said given output data bit are excluded from said encoded output set of data bits,wherein said two-dimensional array of data bits comprises a bit plane of a block of image data that has been transformed using a multi-level wavelet transform and said second output data bits are grouped to form said second subgroups of said second output bits according to levels of said multi-level transform to which they relate.
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Abstract
Methods of data encoding using trees formed with logic gates are described which lead to spatial compression of image data. Data encoding is achieved using a five-level wavelet transform, such as the Haar or the 2/10 transform. A dual transform engine is used, the first and engine being used for the first part of the first-level transform, the second part of the first-level transform and the subsequent-level transforms being performed by the second transform engine within a time interval which is less than or equal to the time taken by the first transform engine to effect the part-transform. Each bit plane of the resulting coefficients is then encoded by forming a tree structure from the bits and OR logical combinations thereof. Redundant data are removed from the resulting tree structure, and further data can be removed by using a predetermined compression profile. The resulting blocks of compressed data are of variable length and are packaged with sync words and index words for transmission so that the location and identity of the transformed data blocks can be determined from the received signal.
65 Citations
16 Claims
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1. A method of encoding an input set of data bits by a codec comprising hardware, the method comprising:
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arranging said input set of data bits into a plurality of first groups of data bits, wherein said input set of data bits comprises a two-dimensional array of data bits; dividing each of said first groups of data bits into a plurality of first subgroups of data bits; logically combining said data bits within each of said first subgroups of data bits using a first logical operation to generate a first output data bit for each said first subgroup of data bits; logically combining said first output data bits for said first subgroups of data bits of each of said first groups of data bits using a second logical operation to generate a second output data bit for each of said first groups of data bits, by forming a plurality of second subgroups of said second output data bits and logically combining said second subgroups of said second output data bits; logically combining said second output data bits for said first groups of data bits to generate a final output data bit for said input set of data bits; generating an encoded output set of data bits for said input set of data bits, said encoded output set of data bits comprising said final output data bit and, if said final output data bit is not equal to a first predetermined value, said encoded output set of data bits further comprising one or more of said output data bits and one or more of said data bits of said input set of data bits, in dependence on at least a first exclusion condition that if a given output data bit is equal to a second predetermined value, then said data bits and said output data bits used to generate said given output data bit are excluded from said encoded output set of data bits, wherein said two-dimensional array of data bits comprises a bit plane of a block of image data that has been transformed using a multi-level wavelet transform and said second output data bits are grouped to form said second subgroups of said second output bits according to levels of said multi-level transform to which they relate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification