Communication apparatus for controlling image compression and control method therefor

1. A communication apparatus wirelessly communicable with another communication apparatus, comprising:

one or more processors; and

at least one memory coupled to the one or more processors, the at least one memory having instructions stored thereon which, when executed by the one or more processors, cause the communications apparatus to:

receive, by wireless communication, a compressed captured image transmitted from the other communication apparatus, wherein the compressed captured image is obtained by compressing a captured image;

decompress the compressed captured image to obtain a decompressed captured image;

generate, based on the decompressed captured image, a CG image to be superimposed and displayed on the captured image;

compress the CG image to generate a compressed CG image;

transmit the compressed CG image to the other communication apparatus by wireless communication;

derive, based on a transmission time point of the compressed captured image in the other communication apparatus and a generation duration measured between a processing start time point and a processing end time point of generating the generated CG image, a time duration from when the compressed captured image is transmitted by the other communication apparatus until when the CG image is generated; and

change a compression ratio of the CG image compression based on whether the derived time duration is longer than a predetermined threshold, wherein the compression ratio is set further based on a transmission time duration of a compressed CG image for a preceding captured image.

2. The apparatus according to claim 1 , wherein in changing the compression ratio, the at least one memory further includes instructions stored thereon which, when executed by the one or more processors, cause the communication apparatus to, if the derived time duration is longer than the predetermined threshold, change the compression ratio of the CG image compression to a compression ratio higher than that if the derived time duration is not longer than the predetermined threshold.

3. The apparatus according to claim 1 , wherein in deriving the time duration, the at least one memory further includes instructions stored thereon which, when executed by the one or more processors, cause the communication apparatus to:

derive a first delay time duration taken for wireless communication of the compressed captured image from the other communication apparatus to the communication apparatus based on the transmission time point of the compressed captured image and a reception time point of the compressed captured image by the communication apparatus, and

derive a second delay time duration taken for generation of the CG image based on the reception time point of the compressed captured image by the communication apparatus and the generation duration of the generated CG image.

4. The apparatus according to claim 3 , wherein the at least one memory further includes instructions stored thereon which, when executed by the one or more processors, cause the communication apparatus to:

change a resolution of the CG image generation based on whether the first delay time duration is longer than a first threshold, and

change the compression ratio of the CG image compression based on whether a sum of the first delay time duration and the second delay time duration is longer than a second threshold.

5. The apparatus according to claim 4 , wherein the at least one memory further includes instructions stored thereon which, when executed by the one or more processors, cause the communication apparatus to:

generate a CG rendering resolution table indicating a relationship between the second delay time duration and a resolution when the compressed CG image is generated,

wherein in generating the CG image, the resolution of the CG image is changed based on the CG rendering resolution table.

6. The apparatus according to claim 3 , wherein the at least one memory further includes instructions stored thereon which, when executed by the one or more processors, cause the communication apparatus to:

derive a third delay time duration taken for wireless communication of the compressed CG image from the communication apparatus to the other communication apparatus based on a transmission time point of the compressed CG image in the communication apparatus and a reception time point of the compressed CG image in the other communication apparatus; and

generate a CG image compression ratio table indicating a relationship between the third delay time duration and a compression ratio when the CG image is compressed,

wherein in compressing the CG image, the compression ratio of the CG image is changed based on the CG image compression ratio table.

7. The apparatus according to claim 1 , wherein

the other communication apparatus is configured as a video see-through type head-mounted display (HMD), and

the at least one memory further includes instructions stored thereon which, when executed by the one or more processors, cause the communication apparatus to receive a captured image obtained by an image capturing unit of the other communication apparatus.

8. A control method for a communication apparatus wirelessly communicable with another communication apparatus, comprising:

receiving, by wireless communication, a compressed captured image obtained by compressing a captured image transmitted from the other communication apparatus, wherein the compressed captured image is obtained by compressing a captured image;

decompressing the compressed captured image to obtain a decompressed captured image;

generating, based on the decompressed captured image, a CG image to be superimposed and displayed on the captured image;

compressing the CG image to generate a compressed CG image;

transmitting the compressed CG image to the other communication apparatus by wireless communication;

deriving, based on a transmission time point of the compressed captured image in the other communication apparatus and a generation duration measured between a processing start time point and a processing end time point of generating the CG image in the generating, a time duration from when the compressed captured image is transmitted by the other communication apparatus until when the CG image is generated by the generating; and

changing a compression ratio of the CG image in the compressing based on whether the time duration derived in the deriving is longer than a predetermined threshold,

wherein the compression ratio is set further based on a transmission time duration of a compressed CG image for a preceding captured image.

9. A non-transitory computer-readable recording medium storing a computer program that, when executed by a computer, causes the computer to function as a communication apparatus wirelessly communicable with another communication apparatus, the program causing the communication apparatus to perform steps comprising:

receiving, by wireless communication, a compressed captured image transmitted from the other communication apparatus, wherein the compressed capture image is obtained by compressing a captured image;

decompressing the compressed captured image to obtain a decompressed captured image;

generating, based on the decompressed captured image, a CG image to be superimposed and displayed on the captured image;

compressing the CG image to generate a compressed CG image;

transmitting the compressed CG image to the other communication apparatus by wireless communication;

deriving, based on a transmission time point of the compressed captured image in the other communication apparatus and a generation duration measured between a processing start time point and a processing end time point of generating the CG image in the generating, a time duration from when the compressed captured image is transmitted by the other communication apparatus until when the CG image is generated by the generating; and

changing a compression ratio of the CG image in the compressing based on whether the time duration derived by the deriving is longer than a predetermined threshold, wherein the compression ratio is set further based on a transmission time duration of a compressed CG image for a preceding captured image.