Image encoding apparatus, image encoding method, and image encoding program

1. An image encoding apparatus configured to perform image encoding based on a gradual decoder refresh scheme, the image encoding apparatus comprising:

a pre-processor configured to receive a video signal obtained by slicing one screen into a plurality of sub-screens and perform pre-processing; and

an image encoder configured to receive output of the pre-processor, perform an encoding process, and generate stream data,

wherein the image encoder is configured to acquire information of a first Intra-slice corresponding to a target Intra-slice in a first sequence with respect to the target Intra-slice in a second sequence, in which encoding is performed, after the first sequence; and is configured to estimate an Intra-slice line number and an Inter-slice line number of the second sequence not to exceed a target information amount based on the acquired information of the first Intra-slice, and

wherein:

the image encoder is configured to acquire information of an Intra-generated information amount of the first sequence and an Intra-slice line number of the first sequence as the information of the first Intra-slice, and

the image encoder is configured to obtain the Intra-slice line number N and the Inter-slice line number M of the second sequence by a following expression:

N×I intra /L intra +M×I inter /L inter =P total ,

N+M=L total

where I intra denotes an Intra-generated information amount of the first sequence, I inter denotes an Inter-generated information amount of the first sequence, L intra denotes an Intra-slice line number of the first sequence, L inter denotes an Inter-slice line number of the first sequence, L total denotes a line number per one picture, and P total denotes a target information amount per one picture.

2. The image encoding apparatus as claimed in claim 1 , the image encoding apparatus further comprising:

a buffer for first information configured to hold the Intra-generated information amount of the first sequence, the Intra-slice line number of the first sequence, and Intra-activity of the first sequence.

3. The image encoding apparatus as claimed in claim 2 , the image encoding apparatus further comprising:

a buffer for second information configured to hold an Intra-generated information amount of the second sequence, an Intra-slice line number of the second sequence, and Intra-activity of the second sequence.

4. The image encoding apparatus as claimed in claim 3 , wherein the image encoder is configure to further detect a difference between the Intra-activity of the first sequence and the Intra-activity of the second sequence.

5. The image encoding apparatus as claimed in claim 3 , wherein when the Intra-activity of the second sequence is larger than the Intra-activity of the first sequence, the image encoder is configure to decrease the Intra-slice line number N of the second sequence obtained from the calculation formula; and is configure to increase the Inter-slice line number M of the second sequence according to the decrease in the Intra-slice line number N of the second sequence.

6. The image encoding apparatus as claimed in claim 1 , wherein the image encoder is configured to:

acquire Intra-activity of the first sequence with respect to the first Intra-slice;

acquire Intra-activity of the second sequence with respect to the target Intra-slice; and

detect a difference between the Intra-activity of the first sequence and the Intra-activity of the second sequence.

7. The image encoding apparatus as claimed in claim 1 , wherein the image encoder is configured to:

acquire Intra-activity of the first sequence with respect to the first Intra-slice; is configured to acquire Intra-activity of the second sequence with respect to the target Intra-slice;

decrease the Intra-slice line number N of the second sequence obtained from the calculation formula when the Intra-activity of the second sequence is larger than the Intra-activity of the first sequence; and

increase the Inter-slice line number M of the second sequence according to the decrease in the Intra-slice line number N of the second sequence.

8. The image encoding apparatus as claimed in claim 1 , wherein when the Intra-slice line number N of the second sequence is smaller than an encoded line number of the target Intra-slice, the image encoder is configured to:

perform an encoding process corresponding to the Intra-slice line number N of the second sequence; and

perform an encoding process corresponding to a difference between the Intra-slice line number N of the second sequence and the encoded line number of the target Intra-slice.

9. The image encoding apparatus as claimed in claim 1 , wherein:

the first Intra-slice is included in a first picture, in which an information amount of the first Intra-slice exceeds the target information amount, in the first sequence in which encoding for a plurality of pictures is performed, and

the target Intra-slice is included in a second picture corresponding to the first picture in the second sequence in which encoding for a plurality of pictures is performed.

10. An image encoding method that performs image encoding based on a gradual decoder refresh scheme, the image encoding method comprising:

acquiring, by an image encoder, information of a first Intra-slice corresponding to a target Intra-slice in a first sequence with respect to the target Intra-slice in a second sequence, in which encoding is performed, after the first sequence; and

estimating, by the image encoder, an Intra-slice line number and an Inter-slice line number of the second sequence such that a target information amount is not exceeded, based on the acquired information of the first Intra-slice,

wherein the Intra-slice line number N and the Inter-slice line number M of the second sequence are obtained by calculation formulas below,

N×I intra /L intra +M×I inter /L inter =P total

N+M=L total

where I intra denotes an Intra-generated information amount of the first sequence, I inter denotes an Inter-generated information amount of the first sequence, L intra denotes an Intra-slice line number of the first sequence, L inter denotes an Inter-slice line number of the first sequence, L total denotes a line number per one picture, and P total denotes a target information amount per one picture.

11. The image encoding method as claimed in claim 10 , wherein the image encoding method further comprises:

acquiring Intra-activity of the first sequence with respect to the first Intra-slice;

acquiring Intra-activity of the second sequence with respect to the target Intra-slice;

decreasing the Intra-slice line number N of the second sequence obtained from the calculation formula when the Intra-activity of the second sequence is larger than the Intra-activity of the first sequence; and

increasing the Inter-slice line number M of the second sequence according to the decrease in the Intra-slice line number N of the second sequence.

12. The image encoding method as claimed in claim 10 , wherein the image encoding method comprises:

performing an encoding process corresponding to the Intra-slice line number N of the second sequence when the Intra-slice line number N of the second sequence is smaller than an encoded line number of the target Intra-slice, and then performing an encoding process corresponding to a difference between the Intra-slice line number N of the second sequence and the encoded line number of the target Intra-slice.

13. A non-transitory computer-readable medium storing an image encoding program that performs image encoding based on a gradual decoder refresh scheme, causing a processing device to execute processes comprising:

acquiring information of a first Intra-slice corresponding to a target Intra-slice in a first sequence with respect to the target Intra-slice in a second sequence, in which encoding is performed, after the first sequence; and

estimating an Intra-slice line number and an Inter-slice line number of the second sequence such that a target information amount is not exceeded, based on the acquired information of the first Intra-slice,

wherein the processes further comprises:

obtaining the Intra-slice line number N and the Inter-slice line number M of the second sequence by calculation formulas below,

N×I intra /L intra +M×I inter /L inter =P total

N+M=L total

where I intra denotes an Intra-generated information amount of the first sequence, I inter denotes an Inter-generated information amount of the first sequence, L intra denotes an Intra-slice line number of the first sequence, L inter denotes an Inter-slice line number of the first sequence, L total denotes a line number per one picture, and P total denotes a target information amount per one picture.

14. The non-transitory computer-readable medium storing the image encoding program as claimed in claim 13 , wherein the processes further comprises:

acquiring Intra-activity of the first sequence with respect to the first Intra-slice;

acquiring Intra-activity of the second sequence with respect to the target Intra-slice;

decreasing the Intra-slice line number. N of the second sequence obtained from the calculation formula when the Intra-activity of the second sequence is larger than the Intra-activity of the first sequence; and

increasing the Inter-slice line number M of the second sequence according to the decrease in the Intra-slice line number N of the second sequence.

15. The non-transitory computer-readable medium storing the image encoding program as claimed in claim 13 , wherein the image encoding program causes the processing device to execute processes comprising:

performing an encoding process corresponding to the Intra-slice line number N of the second sequence when the Intra-slice line number N of the second sequence is smaller than an encoded line number of the target Intra-slice, and then performing an encoding process corresponding to a difference between the Intra-slice line number N of the second sequence and the encoded line number of the target Intra-slice.