A reconstruction technique for block-based transform-coded images transmitted over lossy packet networks is proposed and demonstrated. Lost blocks of transform coefficients are reconstructed via linear interpolation using the same coefficients from adjacent blocks, thus preserving high frequency details and local image characteristics. Determination of the interpolation coefficients, or weights, is combined with vector quantization in a single step at the encoder, and the resulting quantized weights are transmitted as overhead information. The required transmission overhead is less than 10% for typical JPEG-coded images, and the computation for reconstruction of a block is less than that required for simply decoding a block using an inverse discrete cosine transform. This technique is applicable to both luminance and chrominance components, and the reconstructed images maintain good visual quality at loss rates as high as 30%. >
['Sheila S. Hemami', 'Robert M. Gray']
Image reconstruction using vector quantized linear interpolation