1. A method of encoding video data, the method comprising: selecting an intra-prediction mode to use to encode a block of video data; determining whether the block includes a sub-block of a size for which multiple transforms are possible based on the size of the sub-block and the selected intra-prediction mode; when the block includes the sub-block of the size for which multiple transforms are possible based on the size of the sub-block and the selected intra-prediction mode: selecting one of the multiple possible transforms; transforming the sub-block using the selected one of the multiple possible transforms; and providing an indication of the selected one of the multiple possible transforms for the size of the block.