Method and apparatus for video encoding/decoding using secondary transform and recording medium storing bitstream

A method of encoding a video, the method comprising:

• obtaining first residual signal for a first chroma component of a current block and second residual signal for a second chroma component of the current block;
• and
• encoding a joint chroma components flag of the current block, the joint chroma components flag indicating whether obtaining residual signal of one of a first chroma component and a second chroma component is dependent to the other chroma component,
• wherein when the joint chroma components flag is encoded with a value indicating that obtaining residual signal of one of the first chroma component and the second chroma component is dependent to the other chroma component, one of the first residual signal and the second residual signal is the same or a half of the other,
• wherein when both a first coded block flag for the first chroma component and a second coded block flag for the second chroma component are encoded as true, the first residual signal and the second residual signal are the same, and
• wherein when one of the first coded block flag and the second coded block flag is encoded as true while the other is encoded as false, one of the first residual signal and the second residual signal is a half of the other.

An apparatus for transmitting compressed video data, the apparatus comprising:

• a processor to obtain the compressed video data which comprising a joint chroma components flag of a current block, a first coded block flag for a first chroma component of the current block and a second coded block flag for a second chroma component of the current block;
• and
• a transmitting unit to transmit the compressed video data,
• wherein the joint chroma components flag indicates whether obtaining residual signal of one of a first chroma component and a second chroma component is dependent to the other chroma component,
• wherein when the joint chroma components flag has a value indicating that obtaining residual signal of one of the first chroma component and the second chroma component is dependent to the other chroma component, one of first residual signal for the first chroma component and second residual signal for the second chroma component is the same or a half of the other,
• wherein when both a first coded block flag for the first chroma component and a second coded block flag for the second chroma component are true, the first residual signal and the second residual signal are the same, and
• wherein when one of the first coded block flag and the second coded block flag is true while the other is false, one of the first residual signal and the second residual signal is a half of the other.