Image processing device, image processing method, image processing program and recording medium

• US 20040114686A1
• Filed: 09/25/2003
• Published: 06/17/2004
• Est. Priority Date: 03/28/2001
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Sugiyama, Akira, Togashi, Haruo
• Granted Patent: US 7,502,414 B2
• Time in Patent Office: Days
• US Class Current: 375/240.03
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/42 characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation H04N19/635 takes precedence
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness
• CPC Class Codes: H04N 19/98 Adaptive-dynamic-range coding [ADRC]

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.

Claims

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;

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.

2. The picture processing apparatus as set forth in claim 1,

wherein the transforming means performs DCT for the picture data in the unit of one DCT block and output DCT coefficients, and

wherein the transforming block is the DCT block.

3. The picture processing apparatus as set forth in claim 2,

wherein the block is a macro block according to MPEG2.

4. The picture processing apparatus as set forth in claim 1,

wherein the block has a block size of X pixels×

Y lines, and

wherein the sub block has a block size of (X/2ⁿ) pixels×

(Y/2^m) lines where n and m are predetermined integers.

5. The picture processing apparatus as set forth in claim 1,

wherein the activity is calculated by replacing each frame of the picture data with data in the unit of one field and dividing the data in the unit of one field into the sub blocks.

6. The picture processing apparatus as set forth in claim 1,

wherein the activity calculating means comprises:

means for obtaining an average value of levels of pixels for each sub block;

means for obtaining an absolute value of a difference value between the level of the pixel and the average value for each pixel;

means for obtaining an average difference value of the absolute values of the difference values for each sub block; and

means for selecting a minimum value from the average difference values of the block and using the selected minimum value as the activity of the block.

7. A picture processing method, comprising the steps of:

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;

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.

8. A picture processing program for causing a computer apparatus to execute a picture processing method for quantizing input picture data in the unit of one block, the picture processing method comprising the steps of:

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.

9. A recording medium on which a picture processing program for causing a computer apparatus to execute a picture processing method for quantizing input picture data in the unit of one block is recorded, the picture processing method comprising the steps of:

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.