24 hour race prep: part 3, more lights, more camera, more action

Lights

Here’s what the lighted numbers look like at night. Not a bad solution for $25 or whatever. It’s not quite as bright as it looks but it’s very readable.

Camera

Two  weeks ago I talked about the construction of a 64GB camera that can record for at least 24 hours. A YSAR reader suggested that it’s not possible to record for 24 hours on a 64GB card. But of course it is, and I’m sure his meaning was “not possible with acceptable quality”. Not everyone will have the same criteria for acceptable quality. So it’s time to do some real world experiments to explore video quality and file size. As a reference, I checked the Twitch recommendations for streaming video.

  • 1080P 50-60FPS 4.5-6M
  • 1080P 25-30FPS 3.5-5M
  • 720P 50-60FPS 3.5-5M
  • 720P 25-30FPS 2.5-4M
  • 480P 50-60FPS 1.5-3M

I’m not planning on streaming, but rather sharing via YouTube. I had previously determined that a 4M bitrate will let me record for over 28 hours. But what does 4Mbps look like? I scripted a bunch of scenarios and took video in the day and night. I tested over 100 combinations of settings as I was also interested in exposure, brightness, and contrast. Here’s an example of what 720p, 25fps, 4Mbps looks like at 60br 65co.

At 4 MBPs quality at 50fps or 1080p is noticeably worse. This is good enough for my use. However, if you wanted to record at a higher rate, you could either start with a 128G card or have the Pi write to USB flash drives or even a hard disk I suppose. It’s pretty easy when you have programmatic access to the camera.

Video at night never looks that great with this camera. Turning up the brightness helps. But too high and it buggers the daylight shooting. There’s a balance to strike between day and night. If the Pi had an internal clock, I could use that to change camera settings with the time of day. Unfortunately, the Pi doesn’t know what time it is, so date functions can get messed up (this was the cause of several hours of frustration). I could use the length of video previously shot to estimate time of day, but that could become inaccurate if we spend a lot of time in the pits. I think I’m just going with something like 60 brightness 60 contrast.

Action

Once again, there is no action. But next week I promise.

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