Multi-rate capture

From edgertronic high speed video camera

This is a beta feature. Please provide feedback on your experiences and suggestions after trying out the new Multi-rate capture.

Contents

Background

Multi-rate capture allows a video to be captured with three different frame rates, as shown below. Multi-rate capture is intended to provide additional information on what happened before and after the event of interest. For example, imagine a video of a baseball pitch. A pitch can be broken down into a (1) windup, (2) pitch, and (3) follow through. The camera is triggered right as the pitch starts.

Multi-rate capture solves several issues:

  • The need to reduce save time so repetitive events, such as baseball pitches, can all be captured and saved without losing any events of interest.
  • The need to have context around the even of interest, where the context doesn't need to have such fine detail.

Configuring multi-rate capture

Capturing multi-rate videos

Once you have configured multi-rate capture, actually capturing the video is easy; simple trigger the camera. Based on your save mode and multi-shot settings, you can either review the captured video or continue to capture more videos.

Implementation details

Waterfall configuration model

The requested values the user enters into the webUI settings modal follow a waterfall configuration style where a requested value specified higher in the list can change the allowed value of a configuration setting lower in the list.

The camera processes the parameters that affect how a video is captured in the following order:

  • Sensitivity
  • Shutter (exposure)
  • Pre-trigger frame rate
  • Post1-trigger frame rate
  • Post2-trigger frame rate
  • Horizontal resolution
  • Vertical resolution
  • Pre-trigger duration
  • Post1-trigger duration
  • Post2-trigger duration
  • Shot count
  • Overclocking
  • Sub-Sampling
  • Genlock

Handling unspecified configuration values

If you have a setting lower in the waterfall that is more important to you that a value higher in the waterfall, you leave the requested values higher in the waterfall blank/empty/unspecified and then the camera will provide allowed values, doing its best to meet the values you did specify, limited by the camera's hardware capabilities.

For multi-rate capture, the following table describes how unspecified requested values affect allowed values.

Pre-trigger
frame rate
Post1-trigger
frame rate
Post2-trigger
frame rate
Horizontal
resolution
Vertical
resolution
Pre-trigger
duration
Post1-trigger
duration
Post2-trigger
duration
Shot count Description
blank any any any any non-zero any any any Fastest possible frame rate is used for allowed pre-trigger
any blank any any any any non-zero any any Allowed pre-trigger frame rate is used for post1-trigger
any any blank any any any any non-zero any Allowed post1-trigger frame rate is used for post2-trigger

Backward compatibility

The common camera configuration supports specifying a single frame rate, duration, and pre-trigger percentage. When in advanced camera configuration those three common capture configuration parameters are not used. Instead advanced camera configuration displays multi-rate capture settings, which consists of a three sets of (frame rate, duration) values, one set for each of of the pre-trigger, post1-trigger and post2-trigger multi-rate capture regions.

The camera determines if it is in backward compatibility mode by checking if any of the configure_camera() or run() CAMAPI dictionary parameters keys frame_rate, duration, or pretrigger are defined. If any of those three keys are defined, then the camera will be calculate the allowed values based on those keys. When in backward compatibility mode, the six keys related to multi-rate capture are ignored.

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