Automatic detection of HDTV video format

摘要

A method and apparatus for automatically detecting the format of a high-definition television (HDTV) signal at a video encoder to allow proper encoding of the signal, including progressive and interlaced scan, and specific pixel and vertical line resolutions. The system is compatible with video standards such as the SMPTE and MPEG-2 standards. A video sample clock is determined by phase-locking clock pulses in a video signal to one of two or more available reference clocks. An SAV/EAV counter and pixel sample counter determine the horizontaL resolution of the video, e.g., pixels per line. The system discriminates between 24 frames per second video and 30 frames per second video, and between a 720 line progressive scan signal and a 1080 line interlaced scan signal, for example. The system uses PLLs for each reference clock, where a lock range of the PLLs is narrow such that two PLLs will not lock at the same time for one input frequency. F bits in the video signal are used if required to distinguish progressive scan from interlaced scan.