Constant AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL

pub const AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL: u32 = 15; // 15u32

Data found in BlockAdditional element of matroska container. There is no end marker for the data, so it is required to rely on the side data size to recognize the end. 8 byte id (as found in BlockAddId) followed by data.