ITU-R Recommendation BT.656, sometimes also called ITU656, is a simple digital video protocol for streaming uncompressed PAL or NTSC standard-definition television (625 or 525 lines) signals.
The parallel version of the ITU-R BT.656 protocol is also used in many TV sets between chips using CMOS logic levels.
Typical applications include the interface between a PAL/NTSC decoder chip and a DAC integrated circuit for driving a CRT in a TV set.
SAV codes also contain status bits indicating line position in a video field or frame.
Line position in a full frame can be determined by tracking SAV status bits, allowing receivers to 'synchronize' with an incoming stream.