Video overlay

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Video overlay is supported in 2.2.0 and later releases.

Contents

Description

The edgertronic camera supports modifying the pixels in each video frame to overlay text and graphics. The video frames with the overlay applied are then encoded into a video file.

There are different overlay features that can be individually enabled or disabled:

  • Overlay frame number
  • Overlay notes text with parameter expansion
  • Overlay settings
  • Overlay logo

The trigger frame is frame zero. Frames prior to the trigger event have a negative frame number and frames after the trigger frame have a positive number. The trigger frame is the frame that occurs coincident or immediately after the trigger input fall edge or trigger event. This delay of zero to one frame time will be recorded in the metadata file. The text overlay can contain parameters, like camera serial number, which are set appropriately when the video is saved.

Settings

Overlay tab
Example video frame with overlays

The Overlay tab in the Settings modal allows on/off setting for each of the 4 overlay features along with a Notes field that can contain a text string. The camera comes with pre-defined layout control for the frame number, settings, and logo. Using the web UI, you can specify the Notes text. The Notes text can contain ampersand & parameters that are expanded when the video is being saved.

The camera ships with 422 x 96 pixel version of the edgertronic logo pre-installed. If you enable logo overlay, you will get the edgertronic logo if no other logo has been installed.

To install a custom logo, you need to provide PNG file named logo.png, store the logo.png file on the big SD card, and power on the camera. If you provide a corrupt PNG file, you will likely need to do a factory reset to get your camera to operate properly again.

When generating the logo PNG file, keep the following in mind:

  • At full camera resolution the logo is overlaid pixel for pixel. For lower resolutions, the camera scales the logo to make it smaller so it covers approximately the same percentage of the overall frame.
  • The camera supports alpha channel if you want the underlying video to show though portions of the logo. Only full transparency / full opacity are supported.
  • The pipelines file that ships with the camera positions the text in the lower left and the logo in the lower right. The text will overlay on top of the logo if the two overlap.
  • If you have loaded one logo file into the camera and then put a second logo file on the big SD card, the new file from the big SD card will replace the previous custom logo.

Notes parameters

The following ampersand parameters can be included in the Notes text. When the file is being saved, the camera will substitute the actual value in place of the ampersand parameter. An overlay preview is displayed in the web UI for a few seconds after calibrate completes. Dummy parameter values are used during overlay preview if the actual value is not available until a video is captured.

Variable Camera Setting
&d Trigger date (DD-MMM-YY)
&t Trigger time (HH-MM-SS)
&T Trigger time (seconds since Jan 1, 1970)
&i Sensitivity (ISO)
&s Shutter
&f Frame rate
&S Sub-sampling
&o Overclock
&e Extended dynamic range
&g Genlock
&b Multishot buffer
&n Serial number
&N Name of file

Preview

When an overlay is enabled, the live preview visible in the web UI for a few seconds after camera calibration completes. This allows you to verify the overlay layout. Some of the Notes parameters, such as trigger time, are only available when the camera is saving the video, so during overlay preview, dummy values are used.

During preview, the camera uses X's instead of the actual value if the actual value is dependent on the trigger time. When the video is saved, the X's are replaced with the correct value. The purpose of the X's are so you can properly frame what is being captured so that the overlay doesn’t cover the important part of the video.

Customization

The pipelines file contains the actual information used by GStreamer to generate the overlay. You can supply our own customized pipelines file if you want to modify the location of the text and logo overlays.

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