Transmission method, reception method, transmitting device, and receiving device

1. A reception method, performed by a receiving device, the reception method comprising:

receiving a first content and characteristics information of the first content, the first content conforming to High Dynamic Range (HDR), the characteristics information indicating one of an opto-electrical transfer function (OETF) and an electro-optical transfer function (EOTF);

receiving a second content to be displayed with the first content, the second content conforming to Standard Dynamic Range (SDR), the second content including at least one of a caption or an image;

determining whether a scale factor is received, the scale factor being described in Timed Text Markup Language (TTML);

converting the second content to a first converted content with the scale factor such that the first converted content conforms to HDR if the scale factor is determined to be received; and

converting the second content to a second converted content with a default value such that the second converted content conforms to HDR if the scale factor is not determined to be received, the default value being stored in the receiving device.

2. The reception method according to claim 1 , wherein

the first content and the characteristics information are received from a first network, and

the second content and the scale factor are received from a second network.