Image compressing apparatus

An image compressing apparatus for compressing an image in a unit of a macroblock composed of a plurality of blocks including image information, comprising;

• a predictive coding unit for obtaining a predictive error between each input image signal and each predictive signal for each block and obtaining a predictive error sum for each macroblock, which is an absolute value sum of the obtained predictive errors;
• an orthogonal transform unit for effecting an orthogonal transform on each predictive error obtained by said predictive coding unit to produce and output an orthogonal transform signal;
• a coding control unit for supplying a quantization parameter;
• a quantization unit for quantizing each orthogonal transform signal output from said orthogonal transform unit using said supplied quantization parameter to produce and output a quantizing signal;
• a variable length coding unit for effecting variable length coding on each quantizing signal to output a compressed signal;
• and
• a start decision unit for providing a start control signal for controlling operations of said orthogonal transform unit, quantization unit and variable length coding unit,
• wherein said start decision unit produces said start control signal from said predictive error sum for each macroblock and said supplied quantization parameter.

An image compressing apparatus for compressing an image in a unit of a macroblock composed of a plurality of blocks including image information, comprising;

• a predictive coding unit for obtaining a predictive error between each input image signal and each predictive signal for each block and obtaining a predictive error sum for each macroblock, which is an absolute value sum of the obtained predictive errors;
• an orthogonal transform unit for effecting an orthogonal transform on each predictive error obtained by said predictive coding unit to produce and output an orthogonal transform signal;
• a coding control unit for supplying a quantization parameter;
• a quantization unit for quantizing each orthogonal transform signal output from said orthogonal transform unit using said supplied quantization parameter to produce and output a quantizing signal;
• a variable length coding unit for effecting variable length coding on each quantizing signal to output a compressed signal;
• and
• a start decision unit for providing a start control signal for controlling operations of said orthogonal transform unit, quantization unit and variable length coding unit,
• wherein said start decision unit sets said start control signal to a logic value 1 if said predictive error sum for each block or macroblock is at least equal to a predetermined value and to a logic value 0 if said predictive error sum is less than the predetermined value and
• wherein said orthogonal transform unit, quantization unit and variable length coding unit are activated to operate only if they receive the logic value 1 and are not activated to operate if they receive the logic value 0.

An image compressing apparatus for compressing an image in a unit of a macroblock composed of a plurality of blocks including image information, comprising;

• a predictive coding unit for obtaining a predictive error between each input image signal and each predictive signal for each block and obtaining a predictive error sum for each macroblock, which is an absolute value sum of the obtained predictive errors;
• an orthogonal transform unit for effecting an orthogonal transform on each predictive error obtained by said predictive coding unit to produce and output an orthogonal transform signal;
• a coding control unit for supplying a quantization parameter;
• a quantization unit for quantizing each orthogonal transform signal output from said orthogonal transform unit using said supplied quantization parameter to produce and output a quantizing signal;
• a variable length coding unit for effecting variable length coding on each quantizing signal to output a compressed signal;
• and
• a start decision unit for providing a start control signal for controlling operations of said orthogonal transform unit, quantization unit and variable length coding unit, and
• restoring means for obtaining restored image signal, wherein said restoring means is also controlled by said start control signal from said start decision unit.