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June 21, 2013 AT 1:00 am

Automatic Exposure Compensation Testing for the Pi Camera #piday #raspberrypi @Raspberry_Pi

Sometimes taking a look at the testing procedures for developing a project can be as useful as the study of the resulting project. Check out Alex Eames’s detailed documentation for how he has been testing the Pi Camera module towards the construction of a RasPiCamcorder.

Automatic Exposure Compensation Testing for the Pi Camera, from RasPi.TV:

In the 4 weeks since the Pi camera came out, I’ve spent a fair amount of time testing and fiddling with different things. I’ve also made two RasPiCamcorders – I hope to document the Mk2 version soon. It’s the reason I haven’t blogged much in the last week. I’ve been working on the hardware and software for it.

One thing I hadn’t done until this week was test out the various settings for exposure compensation and white balance. Previously, I’d only used the automatic settings, which work pretty well. But there are some circumstances where it’s nice to be able to override these manually.

I want a video demo

I wanted to make a video showing each of the settings. But to do that for each of -10 to +10 ev settings and then edit the video seemed like a right royal nuisance. Wouldn’t it be good if we had a computer to do the repetitive boring bit for us? Hold on, we do. 😉

So I wrote a Python program to shoot a short 10s clip at each of the 21 different settings. That was the easy bit.

But I’ve still got to convert them from .h264 to something I can edit. So, using MP4Box, we’re doing that programmatically as well.

Wouldn’t it be nice if we could trim and edit programmatically too?

For each clip, during the first few frames, the camera is setting its exposure levels. So I wanted to be able to trim off the start from each clip and then put them all together in sequence.

I wanted to do all this, along with conversion and filming in one Python program. (This is how software applications grow – just keep adding features.)

I spent a lot of time unsuccessfully messing about with FFMPEG and AVCONV, and then eventually realised that what I needed to do could all be done with MP4Box. (It helps to read the documentation sometimes.) ….

Read more.


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1 Comment

  1. “Sometimes taking a look at the testing procedures for developing a project can be as useful as the study of the resulting project.”

    That was rather kindly put. 😉
    The results were quite boring in this case, but getting there was quite a lot of fun, and I learnt some useful things, like how to shoot, cut up and reassemble video clips programmatically with the Pi.

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