ITU-R Recommendation BT.656, sometimes also called ITU656, is a simple digital video protocol for streaming uncompressed PAL or NTSC standard-definition television signals. The protocol builds upon the 4:2:2 digital video encoding parameters defined in ITU-R Recommendation BT.601, which provides interlaced video data, streaming each field separately, and uses the YCbCr color space and a 13.5 MHz sampling frequency for pixels.