Monday 5 May 2014

BirdBoxPiCam2014: inside & outside

I put together a portable RaspberryPi camera system a few days ago, so here are a few video clips outside the box.

Inside the box things are not looking great.

I don't think the female has been feeding the chicks at a high enough rate, and it looks like we may have lost a few more chicks.

Portable Pi

The portable RaspberryPi camera unit has a PIR sensor, uses my Pi NoIR camera and runs from a 12V battery.

I've attached a small IR filter to the face of the box, covering the lens, using BlueTak. This gave an interesting fault earlier today when the sun shone down through a gap at the top of the filter, creating a purple vertical band.

Anyway, nothing that could not be fixed with another blob of BlueTak.

Recorded at 90fps, encoded at 25fps

You may be able to guess from the size of the image that this unit needs to be very close for the PIR to trigger from the heat generated by a small garden bird. The PIR should be less than 12" (300mm) and probably nearer to 8" (200mm) for reliable operation with a fairly slow moving bird.

With a fast moving bird, the system does not trigger reliably. So with the camera mounted outside the great tit bird box I found it tended to trigger when a bird left the nest, but not when arriving.

However, I still managed to capture some useful video by allowing the system to record for several minutes after it was triggered.

Bad News From The Nest

The number of visits made by our lone female dropped off yesterday, and it doesn't look like today has been any better.

We did start the day with at least 6 chicks still fighting for the best position in the box.

But by this evening we could only see 3 beaks opening eagerly when mum entered the nest with food. Maybe this is a more manageable clutch for the female to feed.


  1. Could you do a brief post about how you do the 90fps to 25fps conversion sometime?

    1. Well I don't actually do anything. As mentioned in an earlier post ( when you use the RaspiCam at 90fps, the system seems to encode it to produce a 25fps file (i.e. it runs slower, at about 28% of original speed).

      But if you have a video file where you would like change the frame rate, a video editor like Avidemux (which is cross-platform) will do it for you. So for the video which shows the bird approaching the nest, then (apparently) going inside, the start and end sequences were shot at 90fps giving a 25fps result. The video clip inside the box was at 30fps, which I had to convert to 25fps for compatibility with the outside shots.

      If I haven't understood your question, please push me for a better answer.