JP6445404B2 - Encoding method and encoding program - Google Patents

Description

  The present invention relates to an encoding method and an encoding program.

  In recent years, with the spread of broadband services, it has become easy to view moving image content via a network. It is said that more than half of the data on the network becomes moving image data by making it easier to view moving image content. The moving image includes a plurality of frames (still images). As a method for improving the subjective image quality of a moving image, there is adaptive quantization using a quantization parameter (see Patent Document 1). In adaptive quantization, the activity of macroblocks constituting a frame is determined according to whether or not the pattern is visually visually noticeable. For example, in a macroblock pattern, a flat portion that is visually noticeably deteriorated is finely quantized. In other words, in a macroblock pattern, a complicated portion that is visually inconspicuous is hardly quantized.

  In addition, there is an image service that gives viewers a high sense of realism by displaying an all-sky image so that the viewing angle is 360 degrees. In the all-sky image, the frames are displayed adjacent to each other so as to have spatial continuity. That is, in the all-sky image, the frame is displayed so that the edge in the frame is adjacent to the edge in the other frame. For example, in the all-sky image, the right end of the frame is displayed so as to be adjacent to the left end of another frame. For example, in the all-sky image, the upper end of the frame is displayed so as to be adjacent to the lower end of another frame.

JP 2004-72143 A

  A conventional encoding device encodes frames in the order starting from the upper left macroblock and ending with the lower right macroblock in the frame. Also, the conventional encoding device improves the subjective image quality of the frame of the all-sky image by using adaptive quantization. However, when a conventional encoding device encodes a frame of a whole sky image, there may be a difference in image quality (encoding distortion) between edges in adjacently displayed frames. If there is a difference in the image quality between the edges of adjacent frames displayed, the subjective image quality of the frame of the all-sky image is lowered.

  In addition, when encoding a frame of the whole sky image for each area (slice) defined in the frame, the conventional encoding device, the left end and the right end of the frame, the upper end and the lower end of the frame, In some cases, a difference occurs in the image quality (encoding distortion) of the whole sky image at the boundary between slices. As described above, the conventional encoding device has a problem in that it cannot reduce the difference in image quality that occurs at the boundary between adjacent images.

  In view of the above circumstances, an object of the present invention is to provide an encoding method and an encoding program that can reduce the difference in image quality that occurs at the boundary between adjacent images.

  One aspect of the present invention is an encoding method in an encoding device, the step of obtaining a moving image including a frame to be encoded, and a block included in an end of the frame of the moving image, And a step of reducing the difference in image quality between the blocks displayed adjacent to each other when the difference in image quality between the blocks displayed adjacent to each other is equal to or greater than a threshold value.

  One aspect of the present invention is the encoding method described above, wherein when the frame of the moving image is divided for each region, the blocks included in the end of the region are displayed adjacent to each other. When the difference in image quality between blocks is equal to or greater than a threshold, the encoding method further includes a step of reducing the difference in image quality between the blocks displayed adjacent to each other.

  One aspect of the present invention is the encoding method described above, wherein a step of obtaining a decoded moving image frame and a block included in an end of the decoded moving image frame are adjacent to each other. And extracting the block whose image quality difference between the displayed blocks is equal to or greater than a threshold, and based on the block extracted from the decoded moving image frame, the block is included in the end of the frame to be encoded. And a step of reducing a difference in image quality between blocks.

  One aspect of the present invention is an encoding program for causing a computer to execute the above encoding method.

  According to the present invention, it is possible to reduce the difference in image quality that occurs at the boundary between adjacent images.

It is a figure which shows the example of a structure of the encoding apparatus in 1st Embodiment. It is a figure which shows the example of the order which encodes the frame which is not divided | segmented for every slice in 1st Embodiment. 4 is a flowchart illustrating a procedure for controlling image quality in the first embodiment. It is a figure which shows the example of the order which encodes the flame | frame divided | segmented for every slice in 2nd Embodiment. 10 is a flowchart illustrating a procedure for controlling image quality in the second embodiment. 12 is a flowchart illustrating a procedure for controlling image quality in the third embodiment. 14 is a flowchart illustrating a procedure for controlling image quality in a fourth embodiment. 14 is a flowchart illustrating a procedure for controlling image quality in a fifth embodiment.

Embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram illustrating an example of the configuration of the encoding device 10. The encoding device 10 includes an acquisition unit 11, a storage unit 12, an encoding unit 13, and an output unit 14. Some or all of the acquisition unit 11, the encoding unit 13, and the output unit 14 are software functions that function when, for example, a processor such as a CPU (Central Processing Unit) executes a program stored in a memory. Part. Some or all of these functional units may be hardware functional units such as LSI (Large Scale Integration) and ASIC (Application Specific Integrated Circuit).

  The acquisition unit 11 acquires a frame (original image) to be encoded that is an all-round image. The image may be a still image or a moving image. Below, the acquisition part 11 acquires a moving image as an example. The moving image includes a plurality of frames (still images). In the all-sky image, the frames are displayed adjacent to each other so as to have spatial continuity. That is, in the all-sky image, the frame is displayed so that the edge in the frame is adjacent to the edge in the other frame. In the first embodiment, the frame is not divided into regions (slices). The acquisition unit 11 transfers a moving image including a frame to be encoded to the encoding unit 13.

  The storage unit 12 includes, for example, a nonvolatile storage medium (non-temporary recording medium) such as a ROM (Read Only Memory), a flash memory, and an HDD (Hard Disk Drive). The storage unit 12 may include, for example, a volatile storage medium such as a RAM (Random Access Memory) or a register. The storage unit 12 may store a program for causing the software function unit to function, for example. The storage unit 12 may store parameters used for the encoding process, for example. The parameter is, for example, a quantization parameter (QP: Quantization Parameter). The storage unit 12 may store, for example, data representing a peak signal to noise ratio (PSNR). The storage unit 12 may store a threshold value.

  The encoding unit 13 acquires a moving image including a plurality of frames from the acquisition unit 11. The encoding unit 13 encodes a plurality of frames. For example, the encoding unit 13 encodes a frame by executing an encoding program. The encoding unit 13 transmits the encoded frame to the output unit 14. The encoding unit 13 may store the encoded frame in the storage unit 12.

  FIG. 2 is a diagram illustrating an example of the order in which frames that are not divided into slices are encoded. In FIG. 2, blocks A1 to A10 are defined at the upper end of the frame. Blocks B1 to B10 are defined at the lower end of the frame.

  In the all-sky image, the upper blocks A1 to A10 in the frame and the lower blocks B1 to B10 in other frames are displayed adjacent to each other. The upper left block A1 in the frame and the upper right block A10 in other frames are displayed adjacent to each other. The lower left block B1 in the frame and the lower right block B10 in other frames are displayed adjacent to each other.

  The encoding unit 13 encodes the frames for each block in the order starting from the upper left block A1 and ending at the lower right block B10. When encoding the second block, the encoding unit 13 determines the quantization parameter QP used in the second block displayed adjacent to the first block based on the quantization parameter QP used in the first block. Determine.

For example, when encoding the block B1, the encoding unit 13 uses the quantization parameter QP used in the block B1 based on the quantization parameter QP (A1) used in the block A1 displayed adjacent to the block B1. Define (B1). When encoding the block B1, the encoding unit 13 sets a difference ΔQP _f between the quantization parameter QP (A1) and the quantization parameter QP (B1) used in the block A1 displayed adjacent to the block B1. calculate. That is, the encoding unit 13 calculates the difference ΔQP _f of the quantization parameter QP of the block for the upper end and the lower end in the frame. The difference ΔQP _f is, for example, (ΔQP _f = | QP (A1) −QP (B1) |).

The encoding unit 13 determines whether or not the difference ΔQP _{f in the} quantization parameter QP is equal to or greater than the threshold value QP _x . The threshold value QP _x is determined in advance as a target value for image quality. Encoding unit 13, when the difference DerutaQP _f of the quantization parameter QP is equal to or larger than the threshold QP _x, adjusts the difference DerutaQP _f of the quantization parameter QP so as to satisfy the equation (1). Thereby, the encoding unit 13 can reduce a difference in image quality (encoding distortion) between blocks displayed adjacent to each other. That is, the encoding unit 13 can control the image quality of the whole sky image.

ΔQP _f <QP _y (1)

Here, QP _y is a threshold value equal to or less than QP _x . The encoding unit 13 may adjust the quantization parameter QP (B1) of the block B1 encoded after the block A1, or the quantization parameter QP of the block A1 encoded before the block B1. (A1) may be adjusted. For example, when the difference ΔQP _f in the quantization parameter QP is equal to or greater than the threshold QP _x , the encoding unit 13 decreases the quantization parameter QP (B1). Note that the encoding unit 13 does not need to adjust the quantization parameter QP when the difference ΔQP _f in the quantization parameter QP is less than the threshold QP _x .

For example, when the encoding unit 13 encodes the block B2, the quantization parameter QP used in the block B2 is based on the quantization parameter QP (A2) used in the block A2 displayed adjacent to the block B2. Define (B2). When encoding the block B2, the encoding unit 13 sets a difference ΔQP _f between the quantization parameter QP (A2) and the quantization parameter QP (B2) used in the block A2 displayed adjacent to the block B2. calculate. That is, the encoding unit 13 calculates the difference ΔQP _f of the quantization parameter QP of the block for the upper end and the lower end in the frame. The difference ΔQP _f is, for example, (ΔQP _f = | QP (A2) −QP (B2) |). The same applies to the other blocks at the upper and lower ends of the frame.

When encoding the block A10, the encoding unit 13 uses the quantization parameter QP (A10) used in the block A10 based on the quantization parameter QP (A1) used in the block A1 displayed adjacent to the block A10. ). When encoding the block A10, the encoding unit 13 sets a difference ΔQP _f between the quantization parameter QP (A1) and the quantization parameter QP (A10) used in the block A1 displayed adjacent to the block A10. calculate. That is, the encoding unit 13 calculates the difference ΔQP _f of the quantization parameter QP of the block for the left end and the right end in the frame. The difference ΔQP _f is, for example, (ΔQP _f = | QP (A1) −QP (A10) |). The same applies to other blocks at the left end and the right end in the frame.

  The output unit 14 outputs the encoded frame to the display device. The display device decodes the encoded frame and displays a moving image including the decoded frame as an all-sky image. That is, the output unit 14 outputs a moving image to the display device so that a plurality of frames are displayed adjacent to each other.

FIG. 3 is a flowchart showing a procedure for controlling the image quality. The encoding unit 13 acquires a frame (original image) to be encoded (step S101). The encoding unit 13 determines that a difference ΔQP ₁₂ between the quantization parameter QP of the first end block in the frame to be encoded and the quantization parameter QP of the second end block in the target frame is the threshold QP. It is determined whether or not _{x is} greater than or equal to _x . For example, when the first end is the upper end, the second end is the lower end that is the end facing the first end. For example, when the first end is the left end, the second end is the right end that is the end facing the first end (step S102).

When the difference ΔQP ₁₂ is less than the threshold value QP _x (step S102: No), the encoding unit 13 ends the process of adjusting the quantization parameter QP. When the difference ΔQP ₁₂ is greater than or equal to the threshold QP _x (step S102: Yes), the encoding unit 13 sets the difference ΔQP ₁₂ to be less than the threshold QP _y (step S103). The encoding unit 13 ends the process of adjusting the quantization parameter QP.

  As described above, the encoding method of the first embodiment is an encoding method in the encoding device 10, in which the acquisition unit 11 acquires a moving image including a frame to be encoded, and a moving image Reducing the difference in image quality between blocks displayed adjacent to each other when the difference in image quality between adjacent blocks among the blocks included in the edge of the frame is equal to or greater than a threshold value. Have. The difference in image quality is, for example, a difference in quantization parameter QP. The difference in image quality is, for example, a difference in coding distortion.

  As a result, the encoding device 10 of the first embodiment can reduce the difference in image quality that occurs at the boundary between adjacent images.

  The encoding apparatus 10 according to the first embodiment allows a frame when a user views an image having continuity (for example, an all-sky image) when ends (opposite ends) facing each other in a frame are displayed. It is possible to reduce the difference in image quality (encoding distortion) between the upper end and the lower end of the video and improve the subjective image quality of a moving image including frames displayed adjacently.

  The encoding device 10 according to the first embodiment, when a user views a moving image having continuity when ends facing each other in a frame are displayed, image quality (coding distortion) at the left end and the right end in the frame. The subjective image quality of a moving image including frames displayed adjacent to each other can be improved.

(Second Embodiment)
The second embodiment is different from the first embodiment in that the frame is divided into a plurality of regions (slices). In the second embodiment, only differences from the first embodiment will be described.

  FIG. 4 is a diagram illustrating an example of the order in which frames divided for each slice are encoded. In FIG. 4, the frame is divided into slices 1 to 4. Slice 1 is defined at the upper left in the frame. Slice 2 is defined at the upper right in the frame. Slice 3 is defined at the lower left in the frame. Slice 4 is defined at the lower right in the frame. Note that the frame may be divided into regions other than a rectangle.

  In FIG. 4, blocks C <b> 1 to C <b> 10 are defined at the upper end in slice 1. Blocks C21 to C30 are defined at the lower end of slice 1. Blocks D <b> 1 to D <b> 10 are defined at the upper end of slice 2. Blocks D21 to D30 are defined at the lower end of the slice 2. Blocks E1 to E10 are defined at the upper end of the slice 3. Blocks E21 to E30 are defined at the lower end of the slice 3. Blocks F1 to F10 are defined at the upper end of the slice 4. Blocks F21 to F30 are defined at the lower end of the slice 4.

  Therefore, the blocks C21 to C30 of the slice 1 are adjacent to the blocks E1 to E10 of the slice 3. The blocks D21 to D30 of the slice 2 are adjacent to the blocks F1 to F10 of the slice 4. The blocks C10, C20, and C30 of the slice 1 are adjacent to the blocks D1, D11, and D21 of the slice 2. The blocks E10, E20, and E30 of the slice 3 are adjacent to the blocks F1, F11, and F21 of the slice 4.

  In the all-sky image, the blocks C1 to C10 of the slice 1 and the blocks E21 to E30 of the slice 3 are displayed adjacent to each other. The blocks D1 to D10 of the slice 2 and the blocks F21 to F30 of the slice 4 are displayed adjacent to each other. The blocks C1, C11, and C21 of the slice 1 and the blocks D10, D20, and D30 of the slice 2 are displayed adjacent to each other. The blocks E1, E11, and E21 of the slice 3 and the blocks F10, F20, and F30 of the slice 4 are displayed adjacent to each other.

  The encoding unit 13 encodes the slice 1 for each block in the order starting from the upper left block C1 in the slice 1 and ending in the lower right block C30. The same applies to slices 2-4. When encoding the second block, the encoding unit 13 determines the quantization parameter QP used in the second block displayed adjacent to the first block based on the quantization parameter QP used in the first block. Determine.

For example, when encoding the block E21, the encoding unit 13 uses the quantization parameter QP used in the block E21 based on the quantization parameter QP (C1) used in the block C1 displayed adjacent to the block E21. (E21) is defined. When encoding the block E21, the encoding unit 13 sets a difference ΔQP _f between the quantization parameter QP (C1) and the quantization parameter QP (E21) used in the block C1 displayed adjacent to the block E21. calculate. That is, the encoding unit 13 calculates the difference ΔQP _f of the quantization parameter QP of the block for the upper end in slice 1 (upper end in the frame) and the lower end in slice 3 (lower end in the frame). The difference ΔQP _f is, for example, (ΔQP _f = | QP (C1) −QP (E21) |).

The encoding unit 13 determines whether or not the difference ΔQP _{f in the} quantization parameter QP is equal to or greater than the threshold value QP _x . The threshold value QP _x is determined in advance as a target value for image quality. Encoding unit 13, when the difference DerutaQP _f of the quantization parameter QP is equal to or larger than the threshold QP _x, adjusts the difference DerutaQP _f of the quantization parameter QP so as to satisfy the equation (1). Thereby, the encoding unit 13 can reduce a difference in image quality (encoding distortion) between blocks displayed adjacent to each other. That is, the encoding unit 13 can control the image quality of the whole sky image.

The encoding unit 13 may adjust the quantization parameter QP (E21) of the block E21 encoded after the block C1, or the quantization parameter QP of the block C1 encoded before the block E21. (C1) may be adjusted. For example, the encoding unit 13 decreases the quantization parameter QP (E21) when the quantization parameter QP difference ΔQP _f is equal to or greater than the threshold QP _x . Note that the encoding unit 13 does not need to adjust the quantization parameter QP when the difference ΔQP _f in the quantization parameter QP is less than the threshold QP _x .

For example, when encoding the block E22, the quantization parameter QP (E22) used in the block E22 is determined based on the quantization parameter QP (C2) used in the block C2 displayed adjacent to the block E22. When encoding the block E22, the encoding unit 13 sets a difference ΔQP _f between the quantization parameter QP (C2) used in the block C2 displayed adjacent to the block E22 and the quantization parameter QP (E22). calculate. That is, the encoding unit 13 calculates the difference ΔQP _f of the quantization parameter QP of the block for the upper end in slice 1 (upper end in the frame) and the lower end in slice 3 (lower end in the frame). The difference ΔQP _f is, for example, (ΔQP _f = | QP (A2) −QP (B2) |). The same applies to the other blocks at the upper end in slice 1 and at the lower end in slice 3. The same applies to the other blocks at the upper end in slice 2 and the lower end in slice 4.

When encoding the block D10, the encoding unit 13 uses the quantization parameter QP (D10 used in the block D10) based on the quantization parameter QP (C1) used in the block C1 displayed adjacent to the block D10. ). When encoding the block D10, the encoding unit 13 sets a difference ΔQP _f between the quantization parameter QP (C1) and the quantization parameter QP (D10) used in the block C1 displayed adjacent to the block D10. calculate. That is, the encoder 13, for the right end (right end in the frame) and in the slice 2 (left end in the frame) left in the slice 1, calculates a difference DerutaQP _f of the quantization parameter QP of the block. The difference ΔQP _f is, for example, (ΔQP _f = | QP (C1) −QP (D10) |). The same applies to other blocks at the left end in slice 3 and the right end in slice 4.

  The same applies to blocks at the boundary between slices (hereinafter referred to as “slice boundary”) when the same frame is divided for each slice.

  For example, for the right end in slice 1 and the left end in slice 2, when encoding block D1, encoding unit 13 uses quantization parameter QP (C10) used in block C10 displayed adjacent to block D1. Based on the above, the quantization parameter QP (D1) used in the block D1 is determined.

When encoding the block D1, the encoding unit 13 sets the difference ΔQP _s between the quantization parameter QP (C10) used in the block C10 displayed adjacent to the block D1 and the quantization parameter QP (D1). calculate. That is, the encoding unit 13 calculates the difference ΔQP _s of the quantization parameter QP of the block for the right end in slice 1 and the left end in slice 2. The difference ΔQP _s is, for example, (ΔQP _s = | QP (C10) −QP (D1) |).

The encoding unit 13 determines whether or not the difference ΔQP _{s in the} quantization parameter QP is equal to or greater than the threshold value QP _x . Encoding unit 13, when the difference DerutaQP _s quantization parameter QP is equal to or larger than the threshold QP _x, adjusts the difference DerutaQP _s quantization parameter QP so as to satisfy the equation (2). Thereby, the encoding unit 13 can reduce a difference in image quality (encoding distortion) of frames. That is, the encoding unit 13 can control the image quality of the whole sky image.

ΔQP _s ≦ ΔQP _y (2)

  The encoding unit 13 compares the difference of the quantization parameter QP of the block at the slice boundary with the difference of the quantization parameter QP of the end block in the frame, and adjusts the quantization parameter QP of the block based on the comparison result May be. For example, when the difference in the quantization parameter QP of the end block in the frame is larger than the difference in the quantization parameter QP of the block at the slice boundary, the encoding unit 13 adjusts the quantization parameter QP of the end block in the frame. .

For example, the encoding unit 13 determines the difference ΔQP _f (= | QP (C1) −QP (D10) |) between the quantization parameter QP of the block C1 at the end of the frame and the quantization parameter QP of the block D10, and the slice boundary The difference ΔQP _s (= | QP (C10) −QP (D1) |) between the quantization parameter QP of the block C10 and the quantization parameter QP of the block D1 is compared.

When the difference ΔQP _f based on the quantization parameter QP of the end block in the frame is equal to or larger than the difference ΔQP _s based on the quantization parameter QP of the block at the slice boundary, the encoding unit 13 reduces the difference ΔQP _f . The quantization parameter QP (C1) or the quantization parameter QP (D10) is adjusted. That is, when Expression (3) is satisfied, the encoding unit 13 adjusts the quantization parameter QP (C1) or the quantization parameter QP (D10) so as to reduce the difference ΔQP _f .

ΔQP _f ≧ ΔQP _s (3)

For example, the encoding unit 13 determines the difference ΔQP _f (= | QP (C11) −QP (D20) |) between the quantization parameter QP of the block C11 at the end of the frame and the quantization parameter QP of the block D20, and the slice boundary The difference ΔQP _s (= | QP (C20) −QP (D11) |) between the quantization parameter QP of the block C20 and the quantization parameter QP of the block D11 is compared.

When the difference ΔQP _f based on the quantization parameter QP of the end block in the frame is equal to or larger than the difference ΔQP _s based on the quantization parameter QP of the block at the slice boundary, the encoding unit 13 reduces the difference ΔQP _f . The quantization parameter QP (C11) or the quantization parameter QP (D20) is adjusted. That is, when Expression (3) is satisfied, the encoding unit 13 adjusts the quantization parameter QP (C11) or the quantization parameter QP (D20) so as to reduce the difference ΔQP _f . The same applies to the other blocks.

  FIG. 5 is a flowchart showing a procedure for controlling the image quality. The encoding unit 13 acquires a frame (original image) to be encoded (step S201). The encoding unit 13 determines whether the target frame to be encoded is divided for each slice (step S202). When the frame to be encoded is not divided for each slice (step S202: No), the encoding unit 13 ends the process of adjusting the quantization parameter QP.

When the frame to be encoded is divided for each slice (step S202: Yes), the encoding unit 13 determines the quantization parameter QP of the third end block in the slice for the frame to be encoded, and It is determined whether the difference ΔQP ₃₄ with the quantization parameter QP of the block at the fourth end in another adjacent slice is equal to or greater than the threshold QP _x . For example, when the third end is a lower end, the fourth end is an upper end that is an end facing the third end. For example, when the third end is the right end, the fourth end is the left end that is the end facing the third end (step S203). If the difference ΔQP ₃₄ is greater than or equal to the threshold QP _x (step S203: Yes), the encoding unit 13 sets the difference ΔQP ₃₄ to be less than the threshold QP _y (step S204). The encoding unit 13 ends the process of adjusting the quantization parameter QP.

  As described above, the encoding method according to the second embodiment is an encoding method in the encoding device 10, and is included in the end of a region when a moving image frame is divided into regions (slices). If the difference in image quality between adjacent blocks among the displayed blocks is greater than or equal to the threshold value, the method further includes a step of reducing the difference in image quality between adjacent blocks.

  As a result, the encoding device 10 of the second embodiment can reduce the difference in image quality that occurs at the boundary between adjacent images.

(Third embodiment)
The third embodiment is different from the first embodiment in that a difference in image quality (encoding distortion) is extracted using a quantization parameter such as a decoded frame (decoded image). In the third embodiment, only differences from the first embodiment will be described.

  The acquisition unit 11 acquires a frame (original image) to be encoded that is an all-round image. The acquisition unit 11 is an all-sky image and further acquires a decoded frame.

  The encoding 13 acquires the decoded frame from the acquisition unit 11. The encoding 13 extracts a quantization parameter QP difference ΔQP (encoding distortion difference) in each block of the decoded frame for each block. The encoding 13 detects a block in which the difference ΔQP is equal to or greater than a threshold in a frame to be encoded based on the difference ΔQP extracted for each block from the decoded frame.

  Note that the encoding 13 may extract, for each block, the difference ΔQP of the quantization parameter QP in the block of the local decoded image or the prediction image used for encoding, instead of acquiring the decoded frame.

FIG. 6 is a flowchart showing a procedure for controlling the image quality. The acquisition unit 11 acquires a frame (original image) to be encoded and a decoded frame, which are all-sky images, (step S301). The encoding 13 determines whether or not a block having a difference in image quality (encoding distortion) at the first end and the second end in the frame that is equal to or greater than the threshold value QP _x is extracted from the decoded frame. For example, when the first end is the upper end, the second end is the lower end that is the end facing the first end. For example, when the first end is the left end, the second end is the right end that is the end facing the first end (step S302).

When a block whose image quality difference is greater than or equal to the threshold is not extracted (step S302: No), the encoding unit 13 ends the process of adjusting the quantization parameter QP. When a block whose image quality difference is equal to or greater than the threshold is extracted (step S302: Yes), the encoding unit 13 and the quantization parameter QP of the first end block in the target frame to be encoded and the target to be encoded It is determined whether or not the difference ΔQP ₁₂ with respect to the quantization parameter QP of the second end block in the frame is equal to or greater than the threshold value QP _x (step S303).

If the difference DerutaQP ₁₂ is less than the threshold QP _x (Step S303: No), the encoding unit 13 terminates the process of adjusting the quantization parameter QP. When the difference ΔQP ₁₂ is equal to or larger than the threshold QP _x (step S303: Yes), the encoding unit 13 sets the difference ΔQP ₁₂ to be less than the threshold QP _y (step S304). The encoding unit 13 ends the process of adjusting the quantization parameter QP.

  As described above, the encoding method according to the third embodiment is an encoding method in the encoding device 10, and includes a step of obtaining a decoded moving image frame, and an end of the decoded moving image frame. Are extracted based on the block extracted from the frame of the decoded moving image and the step of extracting the block in which the difference in image quality between adjacent blocks among the blocks included in A step of reducing a difference in image quality between blocks included at an end of the frame to be converted.

  As a result, the encoding apparatus 10 according to the third embodiment can accurately reduce the difference in encoding distortion as subjective image quality. Note that the calculation processing amount may be increased.

(Fourth embodiment)
The fourth embodiment is different from the second embodiment in that a difference in image quality (encoding distortion) is extracted using a quantization parameter such as a decoded frame (decoded image). In the fourth embodiment, only differences from the second embodiment will be described.

  The acquisition unit 11 acquires a frame (original image) to be encoded that is an all-round image. The acquisition unit 11 is an all-sky image and further acquires a decoded frame.

  The encoding 13 acquires the decoded frame from the acquisition unit 11. The encoding 13 extracts a quantization parameter QP difference ΔQP (encoding distortion difference) in each block of the decoded frame for each block. The encoding 13 detects a block in which the difference ΔQP is equal to or greater than a threshold in a frame to be encoded based on the difference ΔQP extracted for each block from the decoded frame.

  Note that the encoding 13 may extract, for each block, the difference ΔQP of the quantization parameter QP in the block of the local decoded image or the prediction image used for encoding, instead of acquiring the decoded frame.

  FIG. 7 is a flowchart showing a procedure for controlling the image quality. The acquisition unit 11 acquires a frame (original image) to be encoded and a decoded frame, which are all-sky images, (step S401). The encoding unit 13 determines whether the frame to be encoded is divided for each slice (step S402). If the frame to be encoded is not divided for each slice (step S402: No), the encoding unit 13 ends the process of adjusting the quantization parameter QP.

When the frame to be encoded is divided for each slice (step S402: Yes), the encoding 13 performs image quality (coding distortion) at the third end and the fourth end of the slice of the decoded frame. ) Is extracted whether or not a block having a difference equal to or greater than the threshold QP _x is extracted. For example, when the third end is a lower end, the fourth end is an upper end that is an end facing the third end. For example, when the third end is the right end, the fourth end is the left end that is the end facing the third end (step S403).

When a block having a difference in image quality (encoding distortion) equal to or greater than the threshold value QP _x is not extracted (step S403: No), the encoding unit 13 ends the process of adjusting the quantization parameter QP. When a block having a difference in image quality (encoding distortion) equal to or greater than the threshold value QP _x is extracted (step S403: Yes), the encoding unit 13 determines the quantum of the third end block in the slice for the frame to be encoded. It is determined whether the difference ΔQP ₃₄ between the quantization parameter QP and the quantization parameter QP of the block at the fourth end in another adjacent slice is equal to or greater than the threshold value QP _x . For example, when the third end is a lower end, the fourth end is an upper end that is an end facing the third end. For example, when the third end is the right end, the fourth end is the left end that is the end facing the third end (step S404). When the difference ΔQP ₃₄ is greater than or equal to the threshold QP _x (step S404: Yes), the encoding unit 13 sets the difference ΔQP ₃₄ to be less than the threshold QP _y (step S405). The encoding unit 13 ends the process of adjusting the quantization parameter QP.

  As described above, the encoding method according to the fourth embodiment is an encoding method in the encoding device 10, and includes a step of obtaining a decoded frame and an end in a slice of the decoded frame. Among the blocks that are adjacent to each other, the step of extracting a block in which the difference in image quality between adjacent blocks is equal to or greater than the threshold, and the block extracted from the slice of the frame of the decoded moving image is encoded. A step of reducing a difference in image quality between blocks included at an end of the target frame.

  As a result, the encoding apparatus 10 according to the fourth embodiment can accurately reduce the difference in encoding distortion as subjective image quality. Note that the calculation processing amount may be increased.

(Fifth embodiment)
The fifth embodiment is different from the first embodiment in that the image quality is controlled based on the peak signal-to-noise ratio (PSNR) instead of the quantization parameter QP. In the fifth embodiment, only differences from the first embodiment will be described.

  The encoding unit 13 controls the image quality based on the peak signal to noise ratio (PSNR) instead of the quantization parameter QP. That is, when encoding the second block, the encoding unit 13 uses the second block displayed adjacent to the first block based on the peak signal-to-noise ratio (PSNR) used in the first block. Define the peak signal-to-noise ratio to be used.

  The encoding 13 acquires the decoded frame from the acquisition unit 11. The encoding 13 extracts a peak signal-to-noise ratio difference (encoding distortion difference) in a block of the decoded frame for each block. Encoding 13 detects blocks in which the difference in peak signal to noise ratio is equal to or greater than a threshold value. Note that the encoding 13 may extract, for each block, a peak signal-to-noise ratio difference in a block of a local decoded image or a predicted image used for encoding, instead of acquiring a decoded frame.

  The encoding 13 controls the image quality so as to reduce the difference in the peak signal to noise ratio. For example, the encoding 13 applies a digital filter to a block having a relatively high peak signal to noise ratio. Note that the encoding 13 may apply a digital filter to a block having a relatively low peak signal-to-noise ratio.

FIG. 8 is a flowchart showing a procedure for controlling the image quality. The encoding unit 13 acquires a frame to be encoded (original image) and a decoded frame (step S501). The encoding unit 13 determines that the difference ΔPSNR ₁₂ between the peak signal-to-noise ratio of the first end block in the decoded frame and the peak signal-to-noise ratio of the second end block in the decoded frame is equal to or greater than the threshold PSNR _x. It is determined whether or not. For example, when the first end is the upper end, the second end is the lower end that is the end facing the first end. For example, when the first end is the left end, the second end is the right end that is the end facing the first end (step S502).

When the difference ΔPSNR ₁₂ is less than the threshold PSNR _x (step S502: No), the encoding unit 13 ends the process of adjusting the image quality (PSNR). When the difference ΔPSNR ₁₂ is greater than or equal to the threshold PSNR _x (step S502: Yes), the encoding unit 13 applies a low-pass filter to a portion where the peak signal-to-noise ratio is high in the target frame (original image) to be encoded (step S502). S503). The encoding unit 13 ends the process of adjusting the image quality (PSNR).

  As described above, the encoding method of the fifth embodiment is an encoding method in the encoding device 10, in which the acquisition unit 11 acquires a moving image including a frame to be encoded, and a moving image Reducing the difference in image quality between blocks displayed adjacent to each other when the difference in image quality between adjacent blocks among the blocks included in the edge of the frame is equal to or greater than a threshold value. Have. The difference in image quality is, for example, a difference in peak signal to noise ratio. The difference in image quality is, for example, a difference in coding distortion.

  As a result, the encoding apparatus 10 of the fifth embodiment can reduce the difference in image quality that occurs at the boundary between adjacent images based on the peak signal-to-noise ratio.

  Note that the encoding unit 13 may control the image quality using an encoding parameter other than the quantization parameter QP and the peak signal-to-noise ratio. For example, in HEVC (High Efficiency Video Coding) which is one of the video compression standards, the encoding unit 13 encodes a coding unit (CU) in a maximum coding unit (LCU: Largest Coding Unit) at the first end in a frame. And the configuration of the encoding unit of the maximum encoding unit at the second end in the same frame may be the same. When the first end is the upper end, the second end is a lower end that is an end facing the first end. For example, when the first end is the left end, the second end is a right end that is an end facing the first end.

  You may make it implement | achieve at least one part of the encoding apparatus in embodiment mentioned above with a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Slice, 2 ... Slice, 3 ... Slice, 4 ... Slice, 10 ... Encoding apparatus, 11 ... Acquisition part, 12 ... Memory | storage part, 13 ... Encoding part, 14 ... Output part

Claims (4)

An encoding method in an encoding device, comprising:
Obtaining a moving image including a frame to be encoded;
When the difference in image quality between adjacent blocks among the blocks included at the end of the frame of the moving image is equal to or greater than a threshold value, the difference in image quality between the adjacent blocks displayed is reduced. And steps to
I have a,
In the step of reducing the difference in image quality, the encoding device includes a configuration of a coding unit in a maximum coding unit at a first end in a frame and a coding in a maximum coding unit at a second end in the same frame. An encoding method in which the unit configuration is the same . When the frame of the moving image is divided for each region, among the blocks included in the edge in the region, when the difference in image quality between adjacent blocks is equal to or greater than the threshold, The encoding method according to claim 1, further comprising: reducing a difference in image quality between the displayed blocks. Obtaining a frame of the decoded moving image;
Extracting a block in which the difference in image quality between adjacent blocks among the blocks included at the end of the decoded moving image frame is equal to or greater than a threshold;
Reducing a difference in image quality between blocks included in an end of a frame to be encoded based on a block extracted from the decoded moving image frame;
The encoding method according to claim 1, further comprising:   The encoding program for making a computer perform the encoding method as described in any one of Claims 1-3.

Images