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US 5,629,737 AGranted
Method and apparatus for subband coding video signals
AssigneeInternational Business Machines Corporation
InventorsJean Menez, Michele Rosso, Paolo Scotton
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Abstract
Technique for coding video images by filtering the original input image into subband images using successive high-pass and low-pass filterings over a tree-shaped filter bank. Each subband image is then submitted to activity detection and coded with a different number of levels depending on the activity detected and on the subband involved.
Claims10
A method for digitally coding video signals using subband decomposition of the video signals, said method comprising:
- filtering each video signal using a tree-structured filter bank into a plurality of subband video signals;
- generating a plurality of predicted subband images from said plurality of subband video signals using a differential pulse code modulation loop;
- determining a plurality of subband error prediction images by subtracting from each of said plurality of subband video signals a corresponding predicted subband image from said plurality of predicted subband images;
- for each of a first set of said plurality of subband error prediction images, performing an activity detection operation based on a plurality of threshold values to separate each subband error prediction image into a plurality of subband active blocks in which interframe motion is detected, and a plurality of subband background blocks in which no interframe motion is detected;
- and
- for each of a second set of said plurality of subband error prediction images, determining a plurality of subband active blocks by correlation with the plurality of subband active blocks in said first set of subband error prediction images;
- for each of said plurality of subband error prediction images, quantizing the plurality of subband active blocks and the plurality of subband background blocks separately with a multi-resolution quantizer that encodes each of said plurality of subband active blocks and each of said plurality of subband background blocks using a number of bits associated with encoding each active block and each background block in the corresponding subband wherein each video signal is filtered into seven subband video signals and said activity detection step comprises:
- performing an activity detection step on subband one using a first plurality of threshold values to determine the active blocks and background blocks in said subband one;
- and
- performing a joined activity detection on subbands two to four using a second plurality of threshold values to determine the active blocks and background blocks in said subbands two to four, wherein a block is determined to be active if it is active in at least one of subbands two to four.
7 more elements
A coding system for digitally coding video signals wherein each video signal is scanned to derive a digital video signal represented by an array of pixels, said coding system comprising:
- a tree-structured filtering means for decomposing said digital video signal into a plurality of subband video signals;
- down sampling means for down sampling each of said plurality of subband video signals by a factor of two after each decomposition step performed by said tree-structured filtering means;
- means for generating a corresponding plurality of predicted subband images from said plurality of subband video signals, said means for generating including a differential pulse code modulation loop;
- means for determining a plurality of subband error prediction images from said plurality of subband video signals and said corresponding plurality of predicted subband images;
- means for performing an activity detection operation based on a plurality of threshold values for each of a first set of said plurality of subband error prediction images to separate each subband error prediction image into a plurality of subband active blocks in which interframe motion is detected and a plurality of subband background blocks in which no interframe motion is detected;
- means for determining a plurality of subband active blocks in a second set of said plurality of subband error prediction images by correlation with the plurality of subband active blocks in said first set of subband error prediction images;
- and
- means for quantizing each of said plurality of subband active blocks and each of said plurality of subband background blocks using a number of bits associated with encoding each active block and each background block in the corresponding subband wherein each video signal is filtered into seven subband video signals and said means for performing an activity detection operation comprises:
- means for performing an activity detection operation on subband one using a first plurality of threshold values to determine the active blocks and background blocks in said subband one;
- and
- means for performing a joined activity detection operation on subbands two to four using a second plurality of threshold values to determine the active blocks and background blocks in said subbands two to four, wherein a block is determined to be active if it is active in at least one of subbands two to four.
8 more elements
Dependencies are inferred from the claim text.