CODING METHOD CONVERSION APPARATUS

• US 20080199090A1
• Filed: 02/14/2008
• Published: 08/21/2008
• Est. Priority Date: 02/16/2007
• Status: Active Grant

• Current Assignee: Godo Kaisha IP Bridge 1 (IP Bridge, Inc.)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: ARIMURA, Koji, ARAKAWA, Hiroshi, SAIGO, Katsuo, MARUYAMA, Yuki, JURI, Tatsuro, OHGOSE, Hideyuki, TASAKA, Kei
• Granted Patent: US 8,045,821 B2
• Time in Patent Office: Days
• US Class Current: 382/233
• 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 19/134 characterised by the element, parameter or criterion affecting or controlling the adaptive coding
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/174 the region being a slice, e.g. a line of blocks or a group of blocks
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take 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 coding method conversion apparatus converts the first coded data coded by the first coding method into the second coded data. The coding method conversion apparatus includes: an H.264 decoder which decodes the first coded data; a deblocking filter strength calculation unit which calculates a filter strength of deblocking filtering of a second coding method, using at least one piece of decoding information except a coding type of the first coded data, the decoding information being obtained by decoding the first coded data; and a deblocking filter which performs the deblocking filtering to reduce noise in a boundary of blocks according to the filter strength calculated by the deblocking filter strength calculation unit.

Claims

1. A coding method conversion apparatus which converts a first coded data into a second coded data, the first coded data being coded by a first coding method, said apparatus comprising:

a decoding unit operable to decode the first coded data;

a deblocking filter strength calculation unit operable to calculate a filter strength of deblocking filtering of a second coding method, using at least one piece of decoding information except a coding type of the first coded data, the decoding information being obtained by decoding the first coded data; and

a deblocking filter unit operable to perform the deblocking filtering to reduce noise in a boundary of blocks according to the filter strength calculated by said deblocking filter strength calculation unit.

3. The coding method conversion apparatus according to claim 1, further comprising a decoding information analysis unit operable to calculate, as the at lest one of the piece of the decoding information, at least one of (i) a coded amount, (ii) an average value of quantization parameters, (iii) the number of intra-predicted macroblocks, and (iv) a sum of absolute values of motion vectors or a simple sum of the motion vectors, using a syntax element and additional information which are obtained by decoding the first coded data,

wherein said deblocking filter strength calculation unit is operable to calculate the filter strength using the piece of the decoding information calculated by said decoding information analysis unit.

4. The coding method conversion apparatus according to claim 3, further comprising

a coding information analysis unit operable to calculate, as coding information, one of (i) an average value of quantization parameters, (ii) a target coded amount, and (iii) a target coding rate, using a syntax element and additional information which are obtained when the second coded data is generated,

wherein said deblocking filter strength calculation unit is operable to calculate the filter strength using at least one of (a) the piece of the decoding information and (b) the coding information.

5. The coding method conversion apparatus according to claim 4,

wherein said decoding information analysis unit is further operable to obtain a block size for which orthogonal transformation is performed on the first coded data,

said coding information analysis unit is further operable to obtain a block size for which orthogonal transformation is performed on the second coded data, and

the coding method conversion apparatus further comprises

a first deblocking filtering position determination unit operable to determine, as a deblocking filtering position on which the deblocking filtering is to be performed, a boundary of blocks whose block size is one of the block size obtained by said decoding information analysis unit and the block size obtained by said coding information analysis unit,

wherein said deblocking filter unit is operable to perform the deblocking filtering on the deblocking filtering position determined by said first deblocking filtering position determination unit.

6. The coding method conversion apparatus according to claim 1,

wherein said deblocking filter strength calculation unit is operable to calculate the filter strength using at least one of deblocking_filter_control present_flag, disable_deblocking_filter_idc, slice_alpha_c0_offset_div2, and slice_beta_offset_div2 which are syntax elements of an H.264/AVC standard, when the first coding method is the H.264/AVC standard.

7. The coding method conversion apparatus according to claim 1, further comprising

a second deblocking filtering position determination unit operable to determine a deblocking filtering position on which the deblocking filtering is to be performed, using deblocking_filter_control_present_flag and disable_deblocking_filter_idc which are syntax elements of an H.264/AVC standard, when the first coding method is the H.264/AVC standard,

wherein said deblocking filter unit is operable to perform the deblocking filtering on the deblocking filtering position determined by said second deblocking filtering position determination unit.

8. The coding method conversion apparatus according to claim 3,

wherein said deblocking filter strength calculation unit is operable to calculate a higher filter strength as the average value of the quantization parameters is larger, the average value being the piece of the decoding information.

9. The coding method conversion apparatus according to claim 3,

wherein said deblocking filter strength calculation unit is operable to calculate a higher filter strength as a value of a complexity is larger, the value of the complexity being calculated by performing an arithmetic operation on (i) the average value of the quantization parameters and (ii) the coded amount each of which is the piece of the decoding information.

10. The coding method conversion apparatus according to claim 3,

wherein said deblocking filter strength calculation unit is operable to calculate a higher filter strength as a ratio of the number of the intra-predicted macroblocks to an image is larger, the number of the intra-predicted macroblocks being the piece of the decoding information.

11. The coding method conversion apparatus according to claim 3,

wherein said deblocking filter strength calculation unit is operable to calculate a higher filter strength as the sum of absolute values of the motion vectors or the simple sum of the motion vectors is larger, the sum or the simple sum being the piece of the decoding information.

12. The coding method conversion apparatus according to claim 1, further comprising:

a filter strength adjustment unit operable to (i) select a quantization parameter which does not change the filter strength and whose value is within a range defined by a standard of the second coding method, (ii) multiply a quantization step which is determined by the selected quantization parameter, by a quantization matrix which is a scale factor of the quantization step, and (iii) adjust the filter strength, by adjusting the multiplied quantization step to have a value corresponding to a quantization parameter corresponding to the filter strength calculated by said deblocking filter strength calculation unit, when the quantization parameter corresponding to the filter strength is beyond the range; and

a coding unit operable to code the quantization parameter which is selected by said filter strength adjustment unit, and a value of the quantization matrix which is used in the multiplying,

wherein said deblocking filter unit is operable to perform the deblocking filtering with the filter strength adjusted by said filter strength adjustment unit.

13. The coding method conversion apparatus according to claim 12,

wherein said filter strength adjustment unit is operable to select the quantization parameter so that a difference is minimized, when the quantization parameter corresponding to the filter strength is beyond the range, the difference being a difference between (i) a quantization parameter which corresponds to the quantization step to be multiplied by the quantization matrix and (ii) a quantization parameter which has been coded immediately prior to the quantization parameter, and

said coding unit is operable to code the difference.

2. The coding method conversion apparatus according to Claim wherein said deblocking filter strength calculation unit is operable to perform a weighted addition on evaluation values by weighting the respective evaluation values and adding the weighted evaluation values together, and calculate a single filter strength corresponding to a result of the weighted addition, each of the evaluation values being used for evaluating a value of a corresponding piece of the pieces of the decoding information.

14. A coding method conversion method of converting a first coded data into a second coded data, the first coded data being coded by a first coding method, said method comprising:

decoding the first coded data;

calculating a filter strength of deblocking filtering of a second coding method, using at least one piece of decoding information except a coding type of the first coded data, the decoding information being obtained by decoding the first coded data; and

performing the deblocking filtering to reduce noise in a boundary of blocks according to the filter strength calculated in said calculating.

15. A program used in a coding method conversion apparatus which converts a first coded data into a second coded data, the first coded data being coded by a first coding method, said program causing a computer to execute

decoding the first coded data;

calculating a filter strength of deblocking filtering of a second coding method, using at least one piece of decoding information except a coding type of the first coded data, the decoding information being obtained by decoding the first coded data; and

performing the deblocking filtering to reduce noise in a boundary of blocks according to the filter strength calculated in said calculating.