The transform operation is performed with a DCT on an 8 × 8 block of pixels or pixel differences. If the motion compensation operation does not provide a close match, then the transform operation is performed on an 8 × 8 block of pixels. If the transform operation is performed on a block level, either a block or the difference between the block and its predicted value is quantized and transmitted to the receiver. The receiver performs the inverse operations to reconstruct the image. The receiver operation is also simulated at the transmitter, where the reconstructed images are obtained and stored in a frame store. The encoder is said to be in intra mode if it operates directly on the input image without the use of motion compensation. Otherwise, it is said to be in inter mode
