Reduced complexity IDCT decoding with graceful degradation
AssigneePhilips Electronics North America Corporation
InventorsTse-Hua Lan, Zhun Zhong, Yingwei Chen
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Abstract
Data compressed according to a lossy DCT-based algorithm, such as the MPEG or MPEG2 algorithms, is decompressed according to a dynamically-selected set of DCT coefficients, with unused coefficients masked out. A macroblock of the data exhibiting little motion is decompressed with a small subset of DCT coefficients, while a macroblock exhibiting more motion is decompressed using a larger subset of DCT coefficients up the full set of DCT coefficients. Average computational complexity is thus kept low, enabling the use of inexpensive equipment, while degradation is minimized.
Claims14
A method of decoding DCT-encoded blocks of a data signal, the method comprising:
- (a) predetermining a plurality of subsets of DCT coefficient positions;
- (b) receiving a set of DCT coefficients obtained from DCT-encoding a corresponding portion of a data signal;
- (c) selecting one of said subsets of DCT coefficient positions according to a value of a predetermined one of the received DCT coefficients;
- (d) performing IDCT decoding on the selected subset of DCT coefficients to recover a representation of the corresponding portion of the data signal;
- and
- (e) repeating steps (b), (c), and (d) for successive sets of DCT coefficients.
Apparatus for decoding DCT-encoded blocks of a data signal, the apparatus comprising:
- a data store for storing a predetermined plurality of subsets of DCT coefficient positions;
- a receiver for receiving a set of DCT coefficients obtained from DCT-encoding a portion of said data signal;
- computation means for:
- selecting one of said subsets of DCT coefficient positions according to a value of a predetermined one of the received DCT coefficients;
- and
- performing IDCT decoding on the selected subset of DCT coefficients to recover a representation of the corresponding portion of the data signal;
- and
- control logic for routing successive sets of DCT coefficients through the receiver and computation means.
Dependencies are inferred from the claim text.