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cv_opticflow module

Compute optical flow.

Made for Linux video Devices. Computes x and y velocity using optical flow and distance to ground (using sonar).

Example for airframe file

Add to your firmware section:

1 <module name="video_thread"/>
2 <module name="pose_history"/>
3 <module name="cv_opticflow"/>

Module configuration options

Airframe file section

  • section name: OPTICFLOW prefix: OPTICFLOW_
    • name AGL_ID value: ABI_SENDER_ID
      Description: ABI sender id for AGL message (sonar measurement) (default: ABI_BROADCAST)
    • name CAMERA value: bottom_camera|front_camera
      Description: The V4L2 camera device that is used for the calculations
    • name FOV_W value: 0.89360857702
      Description: The field of view width of the bottom camera (Defaults are from an ARDrone 2)
    • name FOV_H value: 0.67020643276
      Description: The field of view height of the bottom camera (Defaults are from an ARDrone 2)
    • name FX value: 343.1211
      Description: Field in the x direction of the camera (Defaults are from an ARDrone 2)
    • name FY value: 348.5053
      Description: Field in the y direction of the camera (Defaults are from an ARDrone 2)
    • name METHOD value: 0
      Description: Method used to calculate optical flow
    • name WINDOW_SIZE value: 10
      Description: Window size used for block matching (pixels)
    • name SEARCH_DISTANCE value: 10
      Description: Maximum search distance for blockmatching (pixels)
    • name SUBPIXEL_FACTOR value: 10
      Description: Amount of subpixels per pixel, used for more precise (subpixel) calculations of the flow
    • name DEROTATION value: 1
      Description: Derotation either turned on or off (depended on gyroscope measurements)
    • name MAX_TRACK_CORNERS value: 25
      Description: The maximum amount of corners the Lucas Kanade algorithm is tracking between two frames
    • name MAX_ITERATIONS value: 10
      Description: Maximum number of iterations the Lucas Kanade algorithm should take
    • name THRESHOLD_VEC value: 2
      Description: TThreshold in subpixels when the iterations of Lucas Kanade should stop
    • name FAST9_ADAPTIVE value: TRUE
      Description: Whether we should use and adapative FAST9 crner detection threshold
    • name FAST9_THRESHOLD value: 20
      Description: FAST9 default threshold
    • name FAST9_MIN_DISTANCE value: 10
      Description: The amount of pixels between corners that should be detected
    • name FAST9_PADDING value: 20
      Description: The outer border in which no corners will be searched

Dependencies

Module functions

Init Functions

These initialization functions are called once on startup.

Periodic Functions

These functions are called periodically at the specified frequency from the module periodic loop.

  • opticflow_module_run()
    • Running at maximum module frequency.
    • Autorun: TRUE
      Periodic function automatically starts after init.

Files

Header Files

The following headers are automatically included in modules.h

Source Files

Raw cv_opticflow.xml file:

<!DOCTYPE module SYSTEM "module.dtd">
<module name="cv_opticflow" dir="computer_vision">
<doc>
<description>
Compute optical flow.
Made for Linux video Devices.
Computes x and y velocity using optical flow and distance to ground (using sonar).
</description>
<!-- Optical flow calculation parameters -->
<section name="OPTICFLOW" prefix="OPTICFLOW_">
<define name="AGL_ID" value="ABI_SENDER_ID" description="ABI sender id for AGL message (sonar measurement) (default: ABI_BROADCAST)"/>
<!-- Video device parameters -->
<define name="CAMERA" value="bottom_camera|front_camera" description="The V4L2 camera device that is used for the calculations"/>
<!-- Camera parameters -->
<define name="FOV_W" value="0.89360857702" description="The field of view width of the bottom camera (Defaults are from an ARDrone 2)"/>
<define name="FOV_H" value="0.67020643276" description="The field of view height of the bottom camera (Defaults are from an ARDrone 2)"/>
<define name="FX" value="343.1211" description="Field in the x direction of the camera (Defaults are from an ARDrone 2)"/>
<define name="FY" value="348.5053" description="Field in the y direction of the camera (Defaults are from an ARDrone 2)"/>
<!-- General optical flow calculation parameters -->
<define name="METHOD" value="0" description="Method used to calculate optical flow"/>
<define name="WINDOW_SIZE" value="10" description="Window size used for block matching (pixels)"/>
<define name="SEARCH_DISTANCE" value="10" description="Maximum search distance for blockmatching (pixels)"/>
<define name="SUBPIXEL_FACTOR" value="10" description="Amount of subpixels per pixel, used for more precise (subpixel) calculations of the flow"/>
<define name="DEROTATION" value="1" description="Derotation either turned on or off (depended on gyroscope measurements)"/>
<!-- Lucas Kanade optical flow calculation parameters -->
<define name="MAX_TRACK_CORNERS" value="25" description="The maximum amount of corners the Lucas Kanade algorithm is tracking between two frames"/>
<define name="MAX_ITERATIONS" value="10" description="Maximum number of iterations the Lucas Kanade algorithm should take"/>
<define name="THRESHOLD_VEC" value="2" description="TThreshold in subpixels when the iterations of Lucas Kanade should stop"/>
<!-- FAST9 corner detection parameters -->
<define name="FAST9_ADAPTIVE" value="TRUE" description="Whether we should use and adapative FAST9 crner detection threshold"/>
<define name="FAST9_THRESHOLD" value="20" description="FAST9 default threshold"/>
<define name="FAST9_MIN_DISTANCE" value="10" description="The amount of pixels between corners that should be detected"/>
<define name="FAST9_PADDING" value="20" description="The outer border in which no corners will be searched"/>
</section>
</doc>
<settings>
<dl_settings NAME="Vision stabilization">
<!-- Optical flow calculations parameters -->
<dl_settings name="vision_calc">
<dl_setting var="opticflow.method" min="0" step="1" max="1" module="computer_vision/opticflow_module" shortname="method" values="LK_Fast9|EdgeFlow" param="METHOD"/>
<dl_setting var="opticflow.window_size" module="computer_vision/opticflow_module" min="0" step="1" max="20" shortname="window_size" param="OPTICFLOW_WINDOW_SIZE"/>
<dl_setting var="opticflow.search_distance" module="computer_vision/opticflow_module" min="0" step="1" max="50" shortname="search_distance" param="SEARCH_DISTANCE"/>
<dl_setting var="opticflow.subpixel_factor" module="computer_vision/opticflow_module" min="0" step="10" max="1000" shortname="subpixel_factor" param="OPTICFLOW_SUBPIXEL_FACTOR"/>
<dl_setting var="opticflow.derotation" min="0" step="1" max="1" module="computer_vision/opticflow_module" values="OFF|ON" shortname="derotation" param="OPTICFLOW_DEROTATION"/>
<dl_setting var="opticflow.median_filter" module="computer_vision/opticflow_module" min="0" step="1" max="1" values="OFF|ON" shortname="median_filter" param="OPTICFLOW_MEDIAN_FILTER"/>
<!-- Specifically for Lucas Kanade and FAST9 -->
<dl_setting var="opticflow.max_track_corners" module="computer_vision/opticflow_module" min="0" step="1" max="500" shortname="max_trck_corners" param="OPTICFLOW_MAX_TRACK_CORNERS"/>
<dl_setting var="opticflow.max_iterations" module="computer_vision/opticflow_module" min="0" step="1" max="100" shortname="max_iterations" param="OPTICFLOW_MAX_ITERATIONS"/>
<dl_setting var="opticflow.threshold_vec" module="computer_vision/opticflow_module" min="0" step="1" max="100" shortname="threshold_vec" param="OPTICFLOW_THRESHOLD_VEC"/>
<dl_setting var="opticflow.fast9_adaptive" module="computer_vision/opticflow_module" min="0" step="1" max="1" values="FALSE|TRUE" shortname="fast9_adaptive" param="OPTICFLOW_FAST9_ADAPTIVE"/>
<dl_setting var="opticflow.fast9_threshold" module="computer_vision/opticflow_module" min="0" step="1" max="255" shortname="fast9_threshold" param="OPTICFLOW_FAST9_THRESHOLD"/>
<dl_setting var="opticflow.fast9_min_distance" module="computer_vision/opticflow_module" min="0" step="1" max="500" shortname="fast9_min_distance" param="OPTICFLOW_FAST9_MIN_DISTANCE"/>
<dl_setting var="opticflow.fast9_padding" module="computer_vision/opticflow_module" min="0" step="1" max="50" shortname="fast9_padding" param="OPTICFLOW_FAST9_PADDING"/>
<!-- Changes pyramid level of lucas kanade optical flow. -->
<dl_setting var="opticflow.pyramid_level" module="computer_vision/opticflow_module" min="0" step="1" max="10" shortname="pyramid_level" param="OPTICFLOW_PYRAMID_LEVEL"/>
</dl_settings>
</dl_settings>
</settings>
<depends>video_thread,pose_history</depends>
<header>
<file name="opticflow_module.h"/>
</header>
<init fun="opticflow_module_init()"/>
<periodic fun="opticflow_module_run()" autorun="TRUE"/>
<makefile target="ap">
<!-- Include the needed Computer Vision files -->
<include name="modules/computer_vision"/>
<file name="image.c" dir="modules/computer_vision/lib/vision"/>
<file name="jpeg.c" dir="modules/computer_vision/lib/encoding"/>
<file name="rtp.c" dir="modules/computer_vision/lib/encoding"/>
<file name="v4l2.c" dir="modules/computer_vision/lib/v4l"/>
<!-- The optical flow module (calculator) -->
<file name="opticflow_module.c"/>
<file name="opticflow_calculator.c" dir="modules/computer_vision/opticflow"/>
<file name="size_divergence.c" dir="modules/computer_vision/opticflow"/>
<file name="linear_flow_fit.c" dir="modules/computer_vision/opticflow"/>
<file name="pprz_algebra_float.c" dir="math"/>
<file name="pprz_matrix_decomp_float.c" dir="math"/>
<!-- Main vision calculations -->
<file name="fast_rosten.c" dir="modules/computer_vision/lib/vision"/>
<file name="lucas_kanade.c" dir="modules/computer_vision/lib/vision"/>
<file name="edge_flow.c" dir="modules/computer_vision/lib/vision"/>
</makefile>
</module>