Sunday, 30 March 2014

Raspi-Cam @90 frames per second

The latest RaspberryPi firmware has added an interesting new camera mode allowing 90fps recording.


Video recorded with this mode is encoded at approximately one quarter of the original speed, producing an interesting slow-motion video.


If you have a RaspberryPi and a RaspiCamera you can start using this, and other new modes, by updating firmware from the terminal:-


sudo rpi-update

...once update is complete, reboot.

And for good measure, update & upgrade your software:-

sudo apt-get update
sudo apt-get upgrade


Camera on a Stick


My hastily constructed set-up included a RaspberryPi model B, a PiNoIR camera, assorted Lego, Blu-Tack and an aluminium rod.

Please don't let it Rain!

The camera gave an interesting purple cast to everything until I remembered I had a spare iR filter taken from a Sony iToy camera. With this Blu-Tacked onto the front of the camera lens, colour was restored! (Ah! Where would we be without Blu-Tack?)

With my system pointing at the bird feeder, I waited...and waited, and waited....
...ready to remotely execute the following command in the RaspberryPi terminal:-

 raspivid -w 640 -h 480 -fps 90 -t 60000 -o video90fps.h264

At last, a bird!


Our resident male robin was the most obliging model, and I've included a few clips below. But first, I had to find some way of editing the 60 second video down to short clips.

The h264 output file is just a video stream, which plays OK on VLC media player, but some applications need this to be wrapped in a container. To do this I installed gpac on my laptop. Then I ran the following on my laptop for each h264 file that I'd transfered from the Pi:-

MP4Box -add filename.h264 filename.mp4

Now I could open these mp4 files in AviDemux, edit them and save in MPEG4-AVC format.

This clip of the robin shows the use of one wing to balance itself on the seed feeder. It hadn't occurred to me before (but its bloody obvious) that he should only flap the wing furthest away from the feeder.

video

Here he is again, this time doing a fly-by...

video

...and we can slow the clip down further in AviDemux (from 25fps to 5fps).

video

Its obviously not as good as one of those expensive BBC cameras used by that nice David Attenborough chappie, but its a start.

This is a poor quality clip, but shows how birds pull their wings in and glide...even during a steep climb like this.

video

Note: these low-res clips look best when viewed in a small window (i.e. NOT full screen).

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