Pelco D question
hi,
Can you please let me know how security spy sends the PTZ commands to cameras? Every bit of information I can find about PelcoD says it requires the commands to be sent via a seperate cable (its unclear whether that is only in the case of a coaxial video connection or also in the case of IP cameras) . I have an old camera module that i’m trying to get working and so far i can get the camera to work fine but not the zoom lens. The camera didn’t have any ethernet/power pigtail attached so i’m having to guess the pinout on the interface board. I have the camera working with only two pairs of the ethernet cable connected. There’s two unused pairs and a whole bunch more pins on the interface board that they may or may not connect to.
My question is… are the pelco-d commands being sent by security spy via one of the unused pairs i haven’t connected yet? Or does the fact that i can stream video and access the web interface of the camera mean that the PTZ commands should be getting to the camera and maybe my issue is with the hardware and not the data transmission?
BTW I’m connected to the camera using the ONVIF protocol, RTSP over TCP.
Comments
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The Pelco-D telemetry protocol is firmly rooted in the era of video over co-ax where the remote control commands would have been sent to a remote control receiver from the remote operator position over a twisted-pair cable. This provided control over functions such as pan, tilt, zoom, focus and sometimes lens iris control, floodlight switching and others.
With the advent if IP connected cameras, in order to retain the use and functions of the remote control receiver the camera has a serial data output (usually RS422/485) which can output commands in Pelco-D format which have been sent to the camera over the IP connection using the ONVIF protocol.
In your case it seems that you will need a controller for the lens that can receive Pelco-D commands and translate these into voltages to drive the lens, if this is the case then I've seen "lens decoders" on Aliexpress which should fulfil this function.
It is also possible the camera module internally decodes the commands and outputs the lens drive signals on the interface board.
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You legend. Thanks for the detailed reply. I did wonder if the modules in the pan/tilt housing this camera came from, might have facilitated the zoom functionality also. There was a board still in the housing that had connectors with pins marked RS485 + / - . Maybe i’ll be able to find a similar speed dome housing with the decoder built in.
thanks again for your help!
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Generally, SecuritySpy uses ONVIF to control cameras' PTZ functionality. For cameras that don't support ONVIF, SecuritySpy has a number of built-in camera profiles that have been set up with the custom PTZ commands required by that manufacturer. Pelco-D is not used: ONVIF has its own format for PTZ commands, which consists of XML data sent over TCP/IP.
