Picture processing apparatus, picture processing method, picture processing program and recording medium
First Claim
1. A picture processing apparatus, comprising:
- transforming means for performing a transforming process for picture data in the unit of a transforming block and outputting transformed coefficients as a result of the transforming process;
sub block forming means for forming a sub block from the transforming block, said sub block having a dimension, in pixels by lines, smaller than that of a conventional block;
activity detecting means for calculating an activity in the unit of a plurality of sub blocks contained in the transforming block of the picture data and outputting an activity of a block composed of the plurality of transforming blocks with the activity of each of the sub blocks; and
quantizing means for deciding a quantizer scale of the block according to the activity output from the activity detecting means and quantizing the transformed coefficients output from the transforming means with the quantizer scale.
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Abstract
Occurrence of mosquito noise of a macro block that contains even a small plain region is suppressed. One macro block is subdivided into sub blocks each of which is composed of four pixels×four lines. The average value of luminance levels of each sub block is calculated. The absolute values of the difference values between the luminance levels and the average value are obtained for each sub block. The minimum value of the average difference values of the 16 sub blocks of one macro block is selected and decided as an activity of the macro block. Corresponding to the decided activity, a quantizer scale of the macro block is decided. With the decided quantizer scale, the macro block is quantized. According to this method, since the size of each sub block is smaller than the size of a conventional sub block of eight pixels×eight lines, the average difference value of each sub block is more emphasized. Since the minimum value of the average difference values is designated as an activity of the macro block, an activity of a macro block that contains even a small plain portion can be more suppressed. As a result, a quantizer value of a macro block that contains an edge can be decreased. Thus, mosquito noise of a macro block that contains an edge portion of a picture can be suppressed.
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Citations
12 Claims
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1. A picture processing apparatus, comprising:
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transforming means for performing a transforming process for picture data in the unit of a transforming block and outputting transformed coefficients as a result of the transforming process; sub block forming means for forming a sub block from the transforming block, said sub block having a dimension, in pixels by lines, smaller than that of a conventional block; activity detecting means for calculating an activity in the unit of a plurality of sub blocks contained in the transforming block of the picture data and outputting an activity of a block composed of the plurality of transforming blocks with the activity of each of the sub blocks; and quantizing means for deciding a quantizer scale of the block according to the activity output from the activity detecting means and quantizing the transformed coefficients output from the transforming means with the quantizer scale. - View Dependent Claims (2, 3, 4, 5)
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6. A picture processing method, comprising the steps of:
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performing a transforming process for picture data in the unit of a transforming block and outputting transformed coefficients as a result of the transforming process; forming a sub block from the transforming block, said sub block having a dimension, in pixels by lines, smaller than that of a conventional block; calculating an activity in the unit of a plurality of sub blocks contained in the transforming block of the picture data and outputting an activity of a block composed of the plurality of transforming blocks with the activity of each of the sub blocks;
deciding a quantizer scale of the block according to the activity output at the activity detecting step and quantizing the transformed coefficients output at the transforming step with the quantizer scale; andoutputting picture data transformed based upon the calculated activity in the plurality of sub blocks.
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7. A computer-readable medium having stored thereon a program for causing a computer apparatus to execute a picture processing method for quantizing input picture data in the unit of a transforming block, the picture processing method comprising the steps of:
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forming a sub block from the transforming block, said sub block having a dimension, in pixels by lines, smaller than that of a conventional block; calculating an activity in the unit of a plurality of sub blocks contained in the transforming block of the picture data and outputting an activity of a block composed of the plurality of transforming blocks with the activity of each of the sub blocks; and deciding a quantizer scale of the block according to the activity output at the activity detecting step and quantizing the transformed coefficients output at the transforming step with the quantizer scale.
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8. A picture processing apparatus, comprising:
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a transforming device configured to perform a transforming process for picture data in the unit of a transforming block and outputting transformed coefficients as a result of the transforming process; a sub block forming device configured to form a sub block from the transforming block, said sub block having a dimension, in pixels by lines, smaller than that of a conventional block; an activity detecting device configured to calculate an activity in the unit of a plurality of sub blocks contained in the transforming block of the picture data and outputting an activity of a block composed of the plurality of transforming blocks with the activity of each of the sub blocks; and a quantizing device configured to decide a quantizer scale of the block according to the activity output from the activity detecting device and quantizing the transformed coefficients output from the transforming device with the quantizer scale. - View Dependent Claims (9, 10, 11, 12)
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Specification