[Canberrauav] Raspberry Pi Camera Lag Testing

Jack Pittar jpittar at bigpond.net.au
Sat Feb 3 18:03:22 AEDT 2018

Thanks Bruce. We are avoiding the mobile phone approach is the lack of access to to the data and how it is handled, and the total inability to have any control over it. Jack.

-----Original Message-----
From: Canberrauav [mailto:canberrauav-bounces at canberrauav.org.au] On Behalf Of Bruce Baxter
Sent: Thursday, 1 February 2018 12:58 AM
To: Carlos Peco-Berrocal <carlos.peco at gmail.com>
Cc: canberrauav at canberrauav.org.au
Subject: Re: [Canberrauav] Raspberry Pi Camera Lag Testing

As a side question here,
Has anyone tried using an iPhone and triggering it with a servo on the volume button?
It has its own gps and time tagging and can automatically upload to "cloud" storage via wifi or cell data. 
It may be more accurate being all integrated. 

Also, the flirone clip on for a cellphone may function the same way.

Sent from my iPad

> On 31 Jan 2018, at 11:24 PM, Carlos Peco-Berrocal <carlos.peco at gmail.com> wrote:
> Stephen,
> What about the time it takes the "time" to appear in the video output 
> of the TV? Is that a constant ?
>> On 1/31/18, Stephen Dade <stephen_dade at hotmail.com> wrote:
>> Hi all,
>> I attempted some measurements of the Raspberry PiCam + cuavraw camera lag.
>> It was fairly crude - I pointed the PiCam at my TV, which was 
>> displaying the "time" bash command from the Pi, with cuavraw running 
>> in a screen session in the background.
>> Attached is a (cropped to reduce file size) example image I captured. 
>> From the image, I did have some trouble with the terminal/screen 
>> refresh rate and the PiCam capturing. This meant that I couldn't use 
>> ~20% of the images I captured.
>> For the remaining images where I could pick out the latest timestamp 
>> my results were:
>> Console time lagging the camera time by 600 - 800 milliseconds
>> Given that cuavraw tags the image timestamps after image capture (but 
>> prior to debayering and jpg encoding), this would indicate that 
>> there's a 600-800ms time lag between the camera shutter capturing the 
>> image and the Raspberry Pi downloading the image from the camera.
>> If we were flying at 30m/s, this would equate to a 18-24m error in 
>> our georeferencing.
>> Thanks
>> Stephen
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