Video encoding method, video decoding method, video encoding apparatus, and video decoding apparatus

1. A video encoding method of performing temporally scalable encoding on video, the video encoding method comprising:

performing the temporally scalable encoding on pictures included in the video and associated with a layer structure, to generate a bitstream; and

determining a total number of layers of the temporally scalable encoding to be a value from 1 to at most a maximum layer count,

wherein the layer structure has as many layers as the total number of layers determined,

the maximum layer count is determined according to a frame rate of the video,

the video encoding method further comprises determining a picture type of a picture included in the video, to make a display latency picture count less than or equal to a maximum picture count determined according to the frame rate, the display latency picture count being a total number of decoded pictures waiting for being outputted in a video decoding apparatus, and

in the performing, the video is encoded as pictures each having the picture type determined.

2. The video encoding method according to claim 1 ,

wherein the maximum layer count is less than or equal to four when the frame rate is less than or equal to 60 frames per second (fps).

3. The video encoding method according to claim 1 ,

wherein the maximum layer count is five when the frame rate is 120 fps.

4. The video encoding method according to claim 1 ,

wherein in the determining of a picture type, the picture type of the picture is determined to make a continuous B-picture count less than or equal to a maximum continuous count determined according to the frame rate, the continuous B-picture count being a total number of pictures in a B-picture group that only includes continuous B-pictures.

5. The video encoding method according to claim 4 ,

wherein the maximum picture count, an encoder output latency from when the video is input to a video encoding apparatus to when the bitstream is output, and the frame rate are defined by

Maximum picture count=int(log 2 (encoder output latency [s]×frame rate [fps])),

the maximum continuous count, the encoder output latency, and the frame rate are defined by

Maximum continuous count=int(encoder output latency [s]×frame rate [fps]−1), and

the maximum layer count, the encoder output latency, and the frame rate are defined by

Maximum layer count=int(log 2 (encoder output latency [s]×frame rate [fps]))+1.

6. The video encoding method according to claim 5 ,

wherein a maximum picture count [i] in each layer, the encoder output latency, and the frame rate are defined by

Maximum picture count [ i ]=int(log 2 (encoder output latency [s]×frame rate [fps]/2 (n−i) )), and

a maximum continuous count [i] in each layer, the encoder output latency, and the frame rate are defined by

Maximum continuous count [ i ]=int(encoder output latency [s]×frame rate [fps]/2 (n−i) −1)

where i is an integer less than or equal to the maximum layer count and represents a layer, and n represents (the maximum layer count−1).

7. A video encoding apparatus that encodes video, the video encoding apparatus comprising:

processing circuitry; and

storage accessible from the processing circuitry,

wherein using the storage, the processing circuitry performs the video encoding method according to claim 1 .

8. A video decoding method of decoding a bitstream obtained by performing temporally scalable encoding on video, the video decoding method comprising:

decoding the video in the bitstream;

decoding first information in the bitstream, the first information indicating a total number of layers of the temporally scalable encoding; and

reordering, using the total number of layers indicated in the first information, pictures included in the video decoded, and outputting the pictures reordered,

wherein the total number of layers is a value from 1 to at most a maximum layer count,

the maximum layer count is determined according to a frame rate of the video,

further in the decoding of first information, second information in the bitstream is decoded, the second information indicating a display latency picture count which is a total number of decoded pictures waiting for being outputted in a video decoding apparatus, and

in the reordering, the pictures included in the video decoded are reordered using the total number of layers indicated in the first information and the display latency picture count indicated in the second information, and the pictures reordered are output.

9. The video decoding method according to claim 8 ,

wherein the maximum layer count is less than or equal to four when the frame rate is less than or equal to 60 fps.

10. The video decoding method according to claim 8 ,

wherein the maximum layer count is five when the frame rate is 120 fps.

11. The video decoding method according to claim 8 ,

wherein further in the decoding of first information, third information in the bitstream is decoded, the third information indicating a continuous B-picture count which is a total number of pictures in a B-picture group that only includes continuous B-pictures, and

in the reordering, the pictures included in the video decoded are reordered using the total number of layers indicated in the first information, the display latency picture count indicated in the second information, and the continuous B-picture count indicated in the third information, and the pictures reordered are output.

12. The video decoding method according to claim 11 ,

wherein a maximum picture count predetermined according to the frame rate, an encoder output latency from when the video is input to a video encoding apparatus to when the bitstream is output, and the frame rate are defined by

Maximum picture count=int(log 2 (encoder output latency [s]×frame rate [fps])),

a maximum continuous count predetermined according to the frame rate, the encoder output latency, and the frame rate are defined by

Maximum continuous count=int(encoder output latency [s]×frame rate [fps]−1), and

the maximum layer count, the encoder output latency, and the frame rate are defined by

Maximum layer count=int(log 2 (encoder output latency [s]×frame rate [fps]))+1.

13. The video decoding method according to claim 12 ,

wherein a maximum picture count [i] in each layer, the encoder output latency, and the frame rate are defined by

Maximum picture count [ i ]=int(log 2 (encoder output latency [s]×frame rate [fps]/2 (n−i) )), and

a maximum continuous count [i] in each layer, the encoder output latency, and the frame rate are defined by

Maximum continuous count [ i ]=int(encoder output latency [s]×frame rate [fps]/2 (n−i) −1)

where i is an integer less than or equal to the maximum layer count and represents a layer, and n represents (the maximum layer count−1).

14. A video decoding apparatus that decodes a bitstream obtained by encoding video, the video decoding apparatus comprising:

processing circuitry; and

storage accessible from the processing circuitry,

wherein using the storage, the processing circuitry performs the video decoding method according to claim 8 .