Systems and methods for coding transform data

A method of decoding transform data for video coding based on intra prediction techniques, the method comprising:

• determining the number of zero value transform coefficients generated according to a first transform for a transform unit included in a coding unit;
• and
• determining whether or not to determine whether a secondary transform is applied based on whether the number of zero value transform coefficients being less than a threshold value;
• in a case of determining whether the secondary transform is applied, deriving a coding unit level index syntax element, the coding unit level index syntax element indicating
• (a) whether the secondary transform is applied and (b) which matrix for the secondary transform is used,
• in a case that the coding unit level index syntax element is not equal to 0, the secondary transform is applied,
• in a case that the coding unit level index syntax element is equal to 0, the secondary transform is not applied.