Image encoding apparatus
Provided is a moving picture coding apparatus for increasing a compression ratio of a moving picture signal while maintaining high image quality. To minimize the number of bits required for a residual block, quantized transform coefficients are adaptively divided into a plurality of subsets according to a size of a transform block, and non-zero quantized transform coefficients of each subset are scanned and encoded. Also, an intra prediction mode of the current block is determined using reference pixels obtained by filtering reference pixels of the current block. Accordingly, it is possible to minimize the amount of data required for the residual block of the current block.
1. An image encoding method, comprising:
determining, by a coding mode determiner, a size and a prediction mode of a predictive coding block for image or video data;
transforming and quantizing, by a transform/quantization unit, a residual block of a prediction block generated by intra prediction to generate a quantized block;
inversely quantizing and inversely transforming, by an inverse quantization/transform unit, the quantized block;
applying, by a de-blocking filtering unit, a de-blocking filter to an image data received from the inverse quantization/transform unit;
determining, by an intra prediction unit, an intra prediction mode;
generating, by the intra prediction unit, the prediction block according to the intra prediction mode; and
entropy-coding, by an entropy coder, quantized coefficients of the quantized block,
wherein, when a size of the quantized block is equal to 8×8, the coefficients of the quantized block are divided into a plurality of subsets, and the plurality of subsets are scanned using a scan pattern determined according to the intra prediction mode,
wherein a scan pattern for scanning non-zero coefficients of each subset is same with the scan pattern for the plurality of subsets,
wherein a scan pattern for scanning flags indicating non-zero coefficients of each subset is same with the scan pattern for scanning non-zero coefficients of each subset.
2. The method of claim 1 , wherein the quantized coefficients of each subset are scanned in a reverse direction according to a scan pattern determined by the intra prediction mode.
3. The method of claim 1 , wherein the plurality of subsets are scanned in a reverse direction.
4. The method of claim 1 , wherein when the intra prediction mode is a vertical mode, the scan pattern is a horizontal scan.
5. The method of claim 1 , wherein when the intra prediction mode is a horizontal mode, the scan pattern is a vertical scan.
6. The method of claim 1 , further comprising generating, by the intra prediction unit, reference pixels when unavailable reference pixels exist.
7. The method of claim 1 , wherein the intra prediction mode is encoded using an upper intra prediction mode and a left intra prediction mode.
8. The method of claim 7 , wherein when the upper intra prediction mode is unavailable, the upper intra prediction mode is set to a DC mode.