Scan conversion apparatus, image encoding apparatus, and methods of controlling them

An image encoding apparatus comprising:

• an image dividing unit constructed to divide an image into unit blocks each having n rows×m columns;
• an orthogonal transform unit constructed to perform orthogonal transform of each unit block output from the image dividing unit and to output transform coefficients;
• a quantization unit constructed to quantize the transform coefficients output from the orthogonal transform unit and to output quantized transform coefficients;
• a parallel scan conversion unit constructed to sort the quantized transform coefficients output from the quantization unit in each unit block and to output the quantized transform coefficients;
• and
• an entropy encoding unit constructed to entropy-encode the quantized transform coefficients output from the parallel scan conversion unit and to output a code stream,
• wherein the parallel scan conversion unit comprises:
• a scan status holding unit constructed to update and to hold a current scan status in accordance with a status of the data in the block;
• a scan order holding unit constructed to update and to hold a scan order in accordance with the scan status;
• a significant data position information generation unit constructed to generate position information of significant data that exists in the block;
• a parallel number determination unit constructed to instruct to perform scan conversion processing of N (N is an integer:
• N≧2) blocks as M-parallel processing (M is an integer:
• 1≦M≦N) in accordance with the position information output from the significant data position information generation unit;
• and
• a scan conversion unit constructed to sort, in accordance with the instruction from the parallel number determination unit, the data in the block based on the scan order held by the scan order holding unit.

A method of controlling a scan conversion apparatus for sorting data in a block having n rows×m columns based on a predetermined scan order, comprising:

• a scan status holding step of updating and holding a current scan status in accordance with a status of the data in the block;
• a scan order holding step of updating and holding a scan order in accordance with the scan status;
• a significant data position information generation step of generating position information of significant data that exists in the block;
• a parallel number determination step of instructing to perform scan conversion processing of N (N is an integer:
• N≧2) blocks as M-parallel processing (M is an integer:
• 1≦M≦N) in accordance with the position information output in the significant data position information generation step;
• and
• a scan conversion step of sorting, in accordance with the instruction in the parallel number determination step, the data in the block based on the scan order held in the scan order holding step.

A method of controlling an image encoding apparatus, comprising:

• an image dividing step of dividing an image into unit blocks each having n rows×m columns;
• an orthogonal transform step of performing orthogonal transform of each unit block output in the image dividing step and outputting transform coefficients;
• a quantization step of quantizing the transform coefficients output in the orthogonal transform step and outputting quantized transform coefficients;
• a parallel scan conversion step of sorting the quantized transform coefficients output in the quantization step in each unit block and outputting the quantized transform coefficients;
• and
• an entropy encoding step of entropy-encoding the quantized transform coefficients output in the parallel scan conversion step and outputting a code stream,
• the parallel scan conversion step comprising:
• a scan status holding step of updating and holding a current scan status in accordance with a status of the data in the block;
• a scan order holding step of updating and holding a scan order in accordance with the scan status;
• a significant data position information generation step of generating position information of significant data that exists in the block;
• a parallel number determination step of instructing to perform scan conversion processing of N (N is an integer:
• N≧2) blocks as M-parallel processing (M is an integer:
• 1≦M≦N) in accordance with the position information output in the significant data position information generation step;
• and
• a scan conversion step of sorting, in accordance with the instruction in the parallel number determination step, the data in the block based on the scan order held in the scan order holding step.

A scan conversion apparatus which scans data in two-dimensionally arrayed blocks to convert the data into one-dimensionally arrayed data for run-length encoding, comprising:

• a setting unit constructed to set initial sorting information in which positions of data in the two-dimensional arrayed scan target blocks and statistical appearance frequency values of nonzero at the data positions are paired, and the pairs are arranged in descending order of appearance frequency value;
• a plurality of scan conversion units, each scan conversion unit constructed to sequentially read out and to output the data in the two-dimensionally arrayed blocks in an order of data positions based on the sorting information, and if the readout data is nonzero, to increase the appearance frequency value at the position of the data;
• an information generation unit constructed to scan, based on the sorting information, data in blocks of two-dimensionally arrayed data that is a scan target of one of the plurality of scan conversion units, and to generate information representing nonzero/zero for each data;
• and
• a control unit constructed to control, based on the information generated by the information generation unit and representing nonzero/zero, whether to allow execution of parallel processing of the plurality of scan conversion units.

A method of controlling a scan conversion apparatus which includes a plurality of scan conversion units, each scan conversion unit constructed to sequentially read out and to output data in two-dimensionally arrayed blocks in an order of data positions based on sorting information, and if the readout data is nonzero, to increase an appearance frequency value at the position of the data, and to scan the data in the two-dimensionally arrayed blocks to convert the data into one-dimensionally arrayed data for run-length encoding, comprising:

• a setting step of setting initial sorting information in which positions of data in the two-dimensional arrayed scan target blocks and statistical appearance frequency values of nonzero at the data positions are paired, and the pairs are arranged in descending order of appearance frequency value;
• an information generation step of scanning, based on the sorting information, data in blocks of two-dimensionally arrayed data that is a scan target of one of the plurality of scan conversion units, and generating information representing nonzero/zero for each data;
• and
• a control step of controlling, based on the information generated in the information generation step and representing nonzero/zero, whether to allow execution of parallel processing of the plurality of scan conversion units.