JPEG Decoder Scaling Through Selective IDCT Processing
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Solution Overview
Problem
Conventional JPEG decoders for mobile devices require a separate scaling block, which increases product size and slows down decoding speed, making real-time image output impossible due to the need for equal pixel weighting and discarding of pixels during scaling.
Innovation Solution
A JPEG decoder with an integrated inverse discrete cosine transform (IDCT) block that selectively performs IDCT on partial pixel data of a macroblock, allowing for image scaling without a separate scaling block, by reordering and dequantizing data according to a scaling control signal and performing IDCT only on selected pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate scaling block is used to scale the image output from the JPEG decoder, then the image can be output at the desired resolution, but the product size increases and the decoding speed decreases
Solution Approach 1:
The patent combines the scaling function with the existing IDCT block by selectively performing IDCT on only the necessary pixel data based on the target resolution. This merging eliminates the need for a separate scaling block while maintaining the desired output resolution, thereby improving decoding speed without sacrificing product quality.
Solution Approach 2:
The patent extracts and processes only the necessary pixel data required for the target resolution by selectively applying IDCT to specific portions of the macroblock. This extraction approach reduces the amount of data processing needed, thereby increasing decoding speed while still achieving the desired output resolution.
2Measurement precision
If a separate scaling block is used to scale the image, then the image resolution can be adjusted, but the time required for processing increases making real-time output impossible
Solution Approach 1:
The patent applies partial action by performing IDCT only on the necessary pixel data corresponding to the target resolution rather than processing the entire image data. This selective processing significantly reduces the processing time while still achieving the desired output resolution, enabling real-time image output.
Solution Approach 2:
The patent determines the target resolution in advance and uses this information to selectively process only the necessary pixel data from the beginning of the decoding process. This preliminary determination of processing requirements eliminates unnecessary computations, reducing processing time and enabling real-time output.
3Ease of operation
If conventional scaling schemes are used that equalize pixels with equal weighting, then the scaling can be performed uniformly, but a separate functional block is required increasing the device complexity
Solution Approach 1:
The patent makes the IDCT block multi-functional by enabling it to perform both its traditional inverse discrete cosine transform function and the scaling function simultaneously. By selectively applying IDCT based on target resolution, the same block achieves uniform scaling without requiring a separate scaling functional block, thereby reducing device complexity.
Data Source
AI summary
A JPEG decoder having a scaling function includes an inverse discrete cosine transform block, wherein the JPEG decoder selectively performs an inverse discrete cosine transform on a part of pixel data of a macroblock through the inverse discrete cosine transform block and outputs a scaled image file. The JPEG decoder and the scaling method using the JPEG decoder increase a decoding speed, thereby enabling an image to be output in real time, especially when the JPEG decoder and/or the scaling method are applied to a mobile field. Also, the JPEG decoder and the scaling method using the JPEG decoder can achieve an efficient scaling, even without a separate circuit for scaling, thereby reducing a circuit size and the number of components.