Moving image distribution server, moving image reproduction apparatus, control method, and recording medium

A control method of a moving image distribution server, comprising:

• causing an acquirer of the moving image distribution server to sequentially acquire viewpoint information to determine a screen to be rendered;
• causing a renderer of the moving image distribution server to render a distribution screen by rendering processing in at least two stages using the viewpoint information acquired by the acquirer, wherein the renderer generates, in rendering processing of a preceding stage, intermediate value maps of specific channels including a Depth map to be referred to in rendering processing of a subsequent stage, and renders, in the rendering processing of the subsequent stage, the distribution screen by referring to the intermediate value maps;
• causing a divider of the moving image distribution server to acquire and divide into a plurality of blocks, during execution of the rendering processing of the subsequent stage for a first screen, the Depth map out of the intermediate value maps generated for the first screen;
• causing a specifier of the moving image distribution server to specify, for each of the plurality of blocks, a corresponding region which corresponds to a block on a Depth map generated for a second screen rendered before the first screen;
• causing a coder of the moving image distribution server to generate, after an end of the rendering processing of the subsequent stage for the first screen, coded moving image data by coding the first screen, wherein for a block, out of the plurality of blocks, whose similarity to the corresponding region specified by the specifier is not less than a threshold, the coder performs inter-frame coding between an image of the block of the first screen and an image of the corresponding region of the second screen, and for a block, out of the plurality of blocks, whose similarity to the corresponding region specified by the specifier is less than the threshold, the coder performs intra-frame coding of the image of the block of the first screen;
• and
• causing a transmitter of the moving image distribution server to send data to an external device,
• wherein in sending the data to the external device, the transmitter
• sends, for the block whose similarity to the corresponding region is not less than the threshold, information which specifies the block and three-dimensional vectors which are used for specifying the corresponding region for the block to the external device before generation of the coded moving image data of each block of the first screen is completed by the coder as specifying information, and
• sends the coded moving image data to the external device after generation of the coded moving image data of each block of the first screen is completed by the coder.

A non-transitory computer-readable recording medium that records a program for causing a computer to function as a moving image distribution server, the moving distribution image server comprising:

• an acquirer which is able to sequentially acquire viewpoint information to determine a screen to be rendered;
• a renderer which is able to render a distribution screen by rendering processing in at least two stages using the viewpoint information acquired by said acquirer, wherein said renderer generates, in rendering processing of a preceding stage, intermediate value maps of specific channels including a Depth map to be referred to in rendering processing of a subsequent stage, and renders, in the rendering processing of the subsequent stage, the distribution screen by referring to the intermediate value maps;
• a divider which is able to acquire the Depth map of the intermediate value maps generated for a first screen and divide the Depth map into a plurality of blocks during execution of the rendering processing of the subsequent stage for the first screen;
• a specifier which is able to specify, for each of the plurality of blocks, a corresponding region which corresponds to a block on a Depth map generated for a second screen rendered before the first screen;
• a coder which is able to generate, after an end of the rendering processing of the subsequent stage for the first screen, coded moving image data by coding the first screen, wherein for a block, out of the plurality of blocks, whose similarity to the corresponding region specified by said specifier is not less than a threshold, said coder performs inter-frame coding between an image of the block of the first screen and an image of the corresponding region of the second screen, and for a block, out of the plurality of blocks, whose similarity to the corresponding region specified by said specifier is less than the threshold, said coder performs intra-frame coding of the image of the block of the first screen;
• and
• a transmitter which is able to send data to an external device,
• wherein said transmitter:
• sends, for the block whose similarity to the corresponding region is not less than the threshold, information which specifies the block and three-dimensional vectors which are used for specifying the corresponding region for the block to the external device before said coder completes generation of the coded moving image data of each block of the first screen as specifying information;
• and
• sends the coded moving image data to the external device after said coder has completed generation of the coded moving image data of each block of the first screen.

A moving image distribution system having a moving image distribution server that transmits coded moving image data into which a distribution screen of one frame that was rendered was coded and a moving image reproduction apparatus that sequentially acquires, decodes and reproduces the coded moving image data,

• wherein the moving image distribution server comprises:
• an acquirer which is able to sequentially acquire viewpoint information to determine a screen to be rendered;
• a renderer which is able to render the distribution screen by rendering processing in at least two stages using the viewpoint information acquired by said acquirer, wherein the renderer generates, in rendering processing of a preceding stage, intermediate value maps of specific channels including a Depth map to be referred to in rendering processing of a subsequent stage, and renders, in the rendering processing of the subsequent stage, the distribution screen by referring to the intermediate value maps;
• a divider which is able to acquire out of the intermediate value maps, and divide into a plurality of blocks, the Depth map, which was generated for a first screen, during execution of the rendering processing of the subsequent stage for the first screen;
• a specifier which is able to specify, for each of the plurality of blocks, a corresponding region which corresponds to a block in a Depth map of a second screen rendered before the first screen;
• a coder which is able to generate, after an end of the rendering processing of the subsequent stage for the first screen, first coded moving image data by performing, for a block, out of the plurality of blocks, whose similarity to the corresponding region specified by said specifier is not less than a threshold, inter-frame coding between an image of the block of the first screen and an image of the corresponding region of the second screen and performing, for a block, out of the plurality of blocks, whose similarity to the corresponding region specified by said specifier is less than the threshold, intra-frame coding of the image of the block of the first screen;
• and
• a transmitter which is able to send data to the moving image reproduction apparatus,
• wherein the moving image reproduction apparatus comprises:
• a first receiver which is able to receive a block for which inter-frame coding has been performed and specific information for specifying reference data to be used for decoding the block for the first coded moving image data;
• a decoding preprocessor which is able to generate, from the second screen obtained by decoding second coded moving image data acquired from the moving image distribution server before the first coded moving image data, the reference data to be used for decoding the first coded moving image data for each block for which the inter-frame coding was performed based on the specific information received by said first receiver;
• a second receiver which is able to receive the first coded moving image data from the moving image distribution server after reception of the specific information;
• and
• a decoder which is able to decode and reproduce the first coded moving image data received by said second receiver using the reference data generated by said decoding preprocessor for each block for which the inter-frame coding was performed, and
• wherein the transmitter
• sends, for the block whose similarity to the corresponding region specified by said specifier is not less than the threshold, information which specifies the block and three-dimensional vectors which are used for specifying the corresponding region for the block to the moving image reproduction apparatus before coding by said coder of each block of the first screen completes as specifying information, and
• sends the first coded moving image data to the moving image reproduction apparatus after coding by said coder of each block of the first screen completes.