Block noise removal device

• US 20070242896A1
• Filed: 04/18/2007
• Published: 10/18/2007
• Est. Priority Date: 04/18/2006
• Status: Active Grant

• Current Assignee: Pioneer Corporation
• Original Assignee: Pioneer Corporation
• Inventors: Honda, Hirofumi, Okumichi, Kenji
• Granted Patent: US 8,023,765 B2
• Time in Patent Office: Days
• US Class Current: 382/268
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• 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 19/176 the region being a block, e.g. a macroblock
• 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

Abstract

A block noise removal device classifies, into separate pixel groups, interpixel differential values by using a block size N (where N is an integer) of the decoded video signal or by using M which is an integer multiple of the block size N. The block noise removal device accumulates the interpixel differential values in the pixels disposed in the nth position (where n is 1 to N or 1 to M) in the respective pixel groups. This accumulation is performed for each of the first to Nth positions or the first to Mth positions in all the pixel groups. The results of the accumulation provide first to Nth block noise values or first to Mth block noise values. Then, the largest block noise value among the first to Nth block noise values or the first to Mth block noise values is found. A block boundary position signal is produced that represents, as a block boundary position, the pixel position in the pixel group that corresponds with the largest block noise value. The larger of two block noise values of the adjacent pixels on both sides of the pixel having the largest block noise value is taken as the phase error block noise value. A phase error signal is then generated on the basis of the ratio between the phase error block noise value and the largest block noise value. Block noise removal processing is effected on the basis of a phase correction pixel sample value. The phase correction pixel sample value is obtained by performing phase correction processing based on the phase error signal on the decoded video signal.

Claims

1. A block noise removal device for removing block noise from within a decoded video signal obtained by encoding and decoding an input video signal for each pixel block having a plurality of pixels, the block noise removal device comprising:

an interpixel differential value calculator for calculating, as an interpixel differential value, a differential value between each two adjacent pixels in the decoded video signal;

an accumulation unit for classifying, into separate pixel groups, the interpixel differential values by using a block size N (where N is an integer) of the decoded video signal or by using M which is an integer multiple of the block size N, and accumulating the interpixel differential values of the pixels disposed in the respective nth position (where n is 1 to N or 1 to M) in the respective pixel groups, thereby obtaining first to Nth block noise values or first to Mth block noise values;

a block boundary detector for detecting the largest block noise value among the first to Nth block noise values or the first to Mth block noise values to generate a block boundary position signal that represents the pixel position having the largest block noise value in the pixel group, and detecting, as a phase error block noise value, the larger of the block noise values of the adjacent pixels on both sides of the pixel having the largest block noise value, so as to generate a phase error signal on the basis of a ratio between the phase error block noise value and the largest block noise value;

a phase correction unit for obtaining a phase correction pixel sample value that is produced by performing phase correction processing based on the phase error signal on the decoded video signal; and

a signal output unit for generating a noise-removed video signal by performing block noise removal processing on the basis of the phase correction pixel sample value.

2. The block noise removal device according to claim 1, wherein a correction position of the block noise is between a position of the largest block noise value and a position of the phase error block noise value, and is decided by a ratio between the phase error block noise value and the largest block noise value.

3. The block noise removal device according to claim 1, further comprising a unit block noise detection unit for detecting a center value of each m consecutive interpixel differential values and calculating, as a unit block noise value, the difference between the center value and the interpixel differential value associated with the center value, wherein the accumulation unit uses the unit block noise values instead of the interpixel differential values to obtain the first to Nth block noise values or the first to Mth block noise values.

4. A block noise removal device for removing block noise from within a decoded video signal obtained by encoding and decoding an input video signal for each pixel block having a plurality of pixels, the block noise removal device comprising:

an interpixel differential value calculator for calculating, as an interpixel differential value, a differential value between each two adjacent pixels in the decoded video signal;

an accumulation unit for classifying, into separate pixel groups, the interpixel differential values by using M which is an integer multiple of a block size N (where N is an integer) of the decoded video signal and a resized block size L estimated from the decoded video signal, and accumulating the interpixel differential values of the pixels disposed in the respective nth position (where n is 1 to M) in the respective pixel groups, thereby obtaining first to Mth block noise values;

a cycle judgment unit for determining whether the cycle of the consecutive first to Mth block noise values is N or L;

a block boundary detector for detecting the largest block noise value among the first to Nth block noise values or the first to Mth block noise values to generate a block boundary position signal that represents the pixel position having the largest block noise value in the pixel group, and detecting, as a phase error block noise value, the larger of the block noise values of the adjacent pixels on both sides of the pixel having the largest block noise value, so as to generate a phase error signal on the basis of a ratio between the phase error block noise value and the largest block noise value;

a phase correction unit for obtaining a phase correction pixel sample value that is produced by performing phase correction processing based on the phase error signal on the decoded video signal; and

a signal output unit for generating a noise-removed video signal by performing block noise removal processing on the basis of the phase correction pixel sample value and the cycle detected by the cycle judgment unit.

5. The block noise removal device according to claim 4, wherein the correction position of the block noise is between a position of the largest block noise value and a position of the phase error block noise value and decided by a ratio between the phase error block noise value and the largest block noise value.

6. The block noise removal device according to claim 4 further comprising a center value detector for detecting a center value of each m consecutive interpixel differential values and calculating, as a unit block noise value, the difference between the center value and the interpixel differential value associated with the center value, wherein the accumulation unit uses the unit block noise values instead of the interpixel differential values to obtain the first to Mth block noise values.

7. A block noise removal device that removes block noise from within a decoded video signal of N (horizontal direction) pixels×

N (vertical direction) pixels obtained by encoding and decoding an input video signal for each pixel block having a plurality of pixels or from within a resized decoded video signal obtained by resizing resolution of the decoded video signal using a factor of Q, the block noise removal device comprising;

an interpixel differential value calculator for calculating, as an interpixel differential value, a differential value between each two adjacent pixels in the decoded video signal or the resized decoded video signal;

an accumulation unit for classifying pixels of one screen into separate pixel groups, each pixel group having M continuous pixels (M is a common multiple of N·

Q and N) in a horizontal direction or a vertical direction, and accumulating the unit block noise values of the pixels disposed in the respective nth position (where n is 1 to M) in the respective pixel groups, thereby obtaining first to Mth block noise values;

a convolution unit for cyclically allocating first to Nth labels to the first to Mth block noise values in order of the first to Mth block noise values and accumulating the block noise values to which the same labels have been allocated, thereby obtaining first to Nth convolution block noise values;

a first block boundary detector for detecting the largest convolution block noise value among the first to Nth convolution block noise values to generate a first block boundary position signal that represents the pixel position having the largest convolution block noise value, and detecting, as a phase error convolution block noise value, the larger of the convolution block noise values of the adjacent pixels on both sides of the pixel having the largest convolution block noise value to generate a first phase error signal on the basis of a ratio between the phase error convolution block noise value and the largest convolution block noise value;

a second block boundary detector for detecting the largest block noise value among the first to Mth block noise values to generate a second block boundary position signal that represents the pixel position having the largest block noise value, and detecting, as a phase error block noise value, the larger of the block noise values of the adjacent pixels on both sides of the pixel having the largest block noise value to generate a second phase error signal on the basis of a ratio between the phase error block noise value and the largest block noise value;

a selector for selecting one of the first phase error signal and the second phase error signal to issue the selected phase error signal as a phase error signal, and for selecting one of the first block boundary position signal and the second block boundary position signal to issue the selected block boundary position signal as a block boundary position signal; and

a signal output unit for generating a noise-removed video signal by performing block noise removal processing on the basis of the block boundary position signal on the decoded video signal or the resized decoded video signal after performing phase correction processing on the basis of the phase error signal on the decoded video signal or the resized decoded video signal.

8. The block noise removal device according to claim 7, wherein the selector comprises:

a first unit for calculating the difference between the largest convolution block noise value and the convolution block noise value which is the largest among the first to Nth convolution block noise values except for the largest convolution block noise value and the phase error convolution block noise value, thereby generating a first boundary judgment value;

a second unit for calculating the difference between the largest block noise value and the block noise value which is the largest among the first to Mth block noise values except for the largest block noise value, the phase error block noise value, a next largest block noise values disposed in each resizing cycle starting from the position of the largest block noise value, and a next largest phase error block noise which is the larger of the block noise values of the adjacent pixels on both sides of the pixel having the next largest block noise value, thereby generating a second boundary judgment value; and

a third unit for selecting the first phase error signal and the first block boundary position signal when the first boundary judgment value is greater than the second boundary judgment value to generate the first phase error signal and the first block boundary position signal as the phase error signal and the block boundary position signal, and for selecting the second phase error signal and the second block boundary position signal when the second boundary judgment value is greater than the first boundary judgment value to generate the second phase error signal and the second block boundary position signal as the phase error signal and the block boundary position signal.