The EL8100 also doubles as the logic signal indicator of active video. The delay timer is a combination of the EL4501 and the EL8100. Keeping the IC count to a minimum, we selected the EL4501 VFE as the level shifter, video buffer and basic interface to the incoming video feed. Ideally, the video amp should be able to double as the logic signal indicator of active video. The delay timer is a combination of this device and a rail-to-rail video amplifier. This device can fulfill the level shifter and video buffer functions and act as a basic interface to the incoming video feed.
This article can serve as a guide to assist in designing such a circuit to fit the designer's objectives it is not offered as an all-inclusive design. The solution is to design a system to detect active video above “blank” and generate a logic level indicating active video present for the entire field. The design must be able to allow for this without indicating a loss of active video.
#COMPOSITE FOR SYNC CHECKER TV#
Second, broadcast TV will insert a blank field just before and just after the inserted advertisement.
They must detect the loss of video at the transmission point in the video broadcast and be notified immediately of such a failure. There are two subtle issues to consider when working with broadcast video and designing an active video detector.įirst, TV transmitters, up link satellite, and commercial video cameras typically will combine the composite sync and the active video just before transmitting and need to insure that the video channel is working. During non-active video, the video feed still supplies H and V syncs but the active video field is black. The challenge is to detect the presence of active video on a NTSC/PAL composite signal when the camera is sending a black or blue screen with no active video present. When video activity is detected in a security system, for example, it needs to automatically switch over to the camera with activity. The need to distinguish between inactive and active cameras or signal feeds is common.
#COMPOSITE FOR SYNC CHECKER PROFESSIONAL#
Security/surveillance and professional broadcast video systems commonly use remote video cameras that output just black screen while there is no activity in front of the camera, and many consumer devices output a blue screen when no signal is present.