Tivo as a security recorder (long ramble)

["Kevin Hawkins" <lists@xxxxxxx>]

    Following an offline chat with one of our members I just though I'd post some thoughts about using Tivo as a video security recorder in case others are interested. It's something I'm playing with at the moment. In a dedicated scenario like this you don't need a subscription to Tivo so you get a great alternative to a Time-Lapse recorder for your £200, the big plus being you have full speed/quality recordings.

 

    Tivo per say doesn't have an 'AUX'  video input that is easy to record from on an ad hoc basis - it obviously has a range of RF channels over it's standard aerial input and it has a Scart input capable of either composite video or RGB recording. Normally your decoder box is connected in here.

 

    I had originally tried to convince Tivo Inc. to incorporate a time lapse type recording ability into the software allowing a low frame rate and / or poor quality. My idea was that on some sort of trigger condition (alarm) the Tivo could step up to highest quality & full frame rate. That way you would have hundreds of hours of time lapse and still space for highest quality in alarm conditions. I had imagined the trigger to be either (preferably) a serial input to Tivo or a remote IR keypress and that the buffer could be retained at full frame rate. But no luck and no one else seemed to want this feature.. So a review of my options and I am thinking about the following....

 

    My camera will be connected directly to the Scart input and just appears to the Tivo as any channel that would have been on an external decoder. In a multi camera situation then either you go through a multiplexer (optionally with auto alarm triggered full screen selection at the mux) or you modulate your cameras onto the aerial input on different channels and select accordingly. The first is preferable for reasons that become apparent*.

 

    It would seem there are two options for recording depending on recording history needs.

 

        1) You leave Tivo set to the channel and when an alarm condition is generated you send an IR command forcing the recorder on (*at the right channel) - unfortunately I suspect the buffer will not be recorded - this is really because there is no program guide in Tivo (as you have no subscription) and although the buffer is now intelligently copied in v 2.5 of the software the problem is the intelligence goes back to the scheduled program start which is not available. I have yet to try this as I need my guide info to run out. *If a channel change occurred the buffer would be cleared anyway. Using this method you probably lose a couple of seconds at the critical time which is vital so probably a better solution is ....

 

        2) You set up a series of manual recordings. The length of the recordings here is dependent on a few things. How much activity you have that is generating an alarm condition, the size of the hard disks in your Tivo (recording time available) and what quality you want to capture 'alarm' recordings at. I have upgraded to large disks and I have chosen to record at Medium quality. There's also no point in recording at too high a quality if the cameras are not up to it. So I have manually set up 48 recordings each of exactly 30 mins. in length. I might move to 96*15 mins.. I can record about 1 weeks continuous video at this rate. The simple way now is to log the exact time of any intrusion on you home PC (from say a triggered PIR or motion detection software) and then cross reference to the recordings to pick out the segment that contains your video clip. Tivo by itself will purge oldest recordings first to make way for the new ones so in my setup you have a week before they get deleted.

 

        There are better ways though that increase your ''weeks' recordings by orders of magnitude ! Firstly you don't need to set up full 24hour recording if there are times when you are not monitoring for alarm conditions using your alarm triggers (e.g. PIR's in an office during office hours or when the alarm isn't set). Secondly you only need to keep clips that have alarm conditions associated, so we can introduce some intelligence. Two solutions spring to mind.

You could immediately delete a recorded clip if the next segment has started and no alarm condition was logged during its recording. However Tivo will do this eventually for you anyway so you may feel more comfortable having it left there just in case it contains something that your sensors missed, or perhaps delete it after an hour if no later alarms occurred. An even better option seems to be to mark any recording that contains an alarm condition as 'keep indefinitely, this way the required clips are never deleted and the adjacent clips if required stay around for at least a week. Perhaps you should keep immediately adjacent clips as well just for good measure.

 

        The control side for this is done through infra red - it would be nice to use the serial port but I haven't unearthed any information yet on this protocol. I use motion detection software over several cameras to select which to record, supplemented by PIR's. These will probably go through a mux to allow single or split screen selection in multi trigger situations. The alarm trip signalling goes to Comfort &/or HomeVision which creates a log file of the times and to generate the various IR signals to update the Tivo. A nice feature is that the Tivo is 'fail safe' to a recording condition and so should something not work or be interfered with then recording is still there. Also there is no time critical IR interaction as I am only altering the flagging on previously saved files.

 

        I haven't actually done all this yet as I was waiting for my second dedicated Tivo to arrive but now it has I shall be giving it a go. Food for thought perhaps... if anyone else is interested get in touch with me...

 

 

        Kevin

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