Transmission device, transmission method, receiving device, and receiving method

A transmission method comprising:

• generating, by processing circuitry of a transmission device, a video stream with video data;
• generating, by the processing circuitry, a subtitle stream with bitmap data obtained by conversion of subtitle graphics data;
• and
• transmitting, by transmission circuitry, a container containing the video stream and the subtitle stream, wherein
• the subtitle stream contains a first segment that includes a bitmap conversion table with color gamut and/or brightness conversion information,
• the first segment includes first bitmap conversion table conformability information, and
• the first bitmap conversion table conformability information is characteristic information regarding the subtitle graphics data after conversion from the bitmap data.

A receiving device comprising:

• reception circuitry configured to receive a container containing a video stream with video data and a subtitle stream with bitmap data obtained by conversion of subtitle graphics data, the subtitle stream containing a first segment that includes a bitmap conversion table with color gamut and/or brightness conversion information, and
• processing circuitry configured to
• control decoding the video stream to obtain the video data,
• control decoding the subtitle stream to obtain the bitmap data and the bitmap conversion table,
• control converting the bitmap data into the subtitle graphics data based on the bitmap conversion table, and
• control superimposing the subtitle graphics data on superimposition target video data obtained based on the video data, wherein
• the first segment includes bitmap conversion table conformability information, and
• the bitmap conversion table conformability information is characteristic information regarding the subtitle graphics data after conversion from the bitmap data.

A receiving method comprising:

• of receiving, by reception circuitry, a container containing a video stream with video data and a subtitle stream with bitmap data obtained by conversion of subtitle graphics data, the subtitle stream containing a first segment that includes a bitmap conversion table with color gamut and/or brightness conversion information, and
• controlling, by processing circuitry of a receiving device, decoding the video stream to obtain the video data, decoding the subtitle stream to obtain the bitmap data and the bitmap conversion table, converting the bitmap data into the subtitle graphics data based on the bitmap conversion table, and superimposing the subtitle graphics data on superimposition target video data obtained based on the video data, wherein
• the first segment includes bitmap conversion table conformability information, and
• the bitmap conversion table conformability information is characteristic information regarding the subtitle graphics data after conversion from the bitmap data.