CameraView

This documentation describes configuration and usage of the CC CameraView component for CODESYS VISU.
General functionality, API documentation and developer guidelines are covered.

Overview

CC CameraView is a control component for CODESYS ActiveX elements. By using the Visu Qt Overlay functionality, it enables GPU accellerated decoding and display of video feeds.

Its primary intended purpose is to show IP camera feeds inside CODESYS Visu applications with good performance in a flexible, easily configurable way. While video feeds from IP cameras are the intended usecase, any video feed with compatible encoding and bitrate can be displayed, for example pre-recorded video files.

Features

Performance

• Native Qt Quick2 GPU rendering, allowing for significantly higher FPS than the CODESYS Visu task itself

• Low CPU overhead

• OS dependent decoding, allowing for additional codecs to be installed independently of CODESYS as needed

Configuration

• Runtime configurable video source

  • Allows for dynamic switching between sources from application

  • Video format support independent of CODESYS, decoding instead deferred to OS native decoding

  • Additional codecs can be added at OS level with no need for updates to this component or CODESYS Visu

• Basic Playback control at GPU level

  • Play

  • Pause

  • Stop

• Runtime configurable Orientation / mirroring control

  • Video transformation handled in GPU with no CPU overhead impact

API documentation

The following method calls are available in the ActiveX component

CameraStatus

Returns the current video reception status.

• Method

  • CameraStatus

• Parameters

• Result parameter

  • INT Operational state

Operational states

Value	Name	Description
0	NoMedia	no media has been set
1	Loading	the media is currently being loaded
2	Loaded	the media has been loaded
3	Buffering	the media is buffering data
4	Stalled	playback has been interrupted while the media is buffering data
5	Buffered	the media has buffered data
6	EndOfMedia	the media has played to the end
7	InvalidMedia	the media cannot be played
8	UnknownStatus	the status of the media is unknown

CameraPlaybackState

Returns the current playback state.

• Method

  • CameraPlaybackState

• Parameters

• Result parameter

  • INT Playback state

Playback states

Value	Name
0	Playing
1	Paused
2	Stopped

CameraSource

Sets the configuration string that defines video source to use.

• Method

  • CameraSource

• Parameters

  • WSTRING Source configuration string

• Result parameter

CameraFlipX

Sets whether video source should be mirrored horizontally.

• Method

  • CameraFlipX

• Parameters

  • BOOL Enabled

• Result parameter

CameraFlipY

Sets whether video source should be mirrored vertically.

• Method

  • CameraFlipY

• Parameters

  • BOOL Enabled

• Result parameter

CameraPortraitMode

Sets whether video source should be rotated 90 degrees clockwise.

• Method

  • CameraPortraitMode

• Parameters

  • BOOL Enabled

• Result parameter

CameraPlay

Starts playback.
NOTE: By default playback is automatically started once loaded. Use this function to resume playing after pausing or stopping.

• Method

  • CameraPlay

• Parameters

• Result parameter

CameraPause

Pauses playback. Current frame remains visible.

• Method

  • CameraPause

• Parameters

• Result parameter

CameraStop

Stops playback. No frame shown.

• Method

  • CameraStop

• Parameters

• Result parameter

Usage guidelines

The CameraView component is a controller for ActiveX elements that exists on the device side only. There is currently no corresponding library installation on the IDE side and thus no API awareness. Keep this documentation at hand when developing as API reference.

Initialization

1. Ensure your CODESYS IDE installation has the correct Visualization library version: Visualization 4.2.0.0
   NOTE: 3.5.17 patch 3 comes with 4.1.0.0 and needs to be manually upgraded to 4.2.0.0

2. Ensure that native overlays are enabled in your project’s Visualization Manager General Settings.
   

3. Add an ActiveX element and assign “CC_CameraView” to its Control property.
   

4. Use method calls (for instance Initial Calls) to configure it as needed.

   • Typically, the only thing that needs to be configured is the CameraSource property, which expects a gstreamer pipeline configuration string. Since these can be very long and contain wide string characters (WSTRING), keep in mind that CODESYS default maximum length for WSTRINGs is 80 characters wich pipeline configs easily exceeds. It is recommended to ensure you have enough space for your config by initializing the WSTRING variable with an explicit sufficent length (for example WSTRING(300)).
     cameraUdpSource: WSTRING(300):=     "gst-pipeline: udpsrc port=62467 ! application/x-rtp, encoding-name=JPEG, payload=26 ! rtpjpegdepay ! jpegdec ! qtvideosink sync=false";
     

   • In the same way, adjust settings for orientation and mirroring as needed.
     The three settings FlipX, FlipY and PortraitMode can be combined to achieve any rotation and mirroring combination.

Interaction

• Control

  • The same method calls that are used for initializing the component are also what are used to control it while running, for example to change video source or switch to portrait orientation.

  • Use Conditional or Cyclic calls as needed.

  • Due to a limitiation in the component its internal state is not kept when switching between different visualizations. Since CODESYS expects the state to be kept it does not re-perform method calls configured as Initial Calls when switching back to a visualization previously shown.
    Instead, you will need to manually ensure this is done, for instance by using Conditional Calls triggered by a visuChanged variable.

• Monitoring

  • Two additional methods exist that reports playback status and video feed reception/decoding status.

  • Calling these cyclicly is a good way to maintain awareness of the overall state of the component.

Examples

• Please refer to the CameraViewExample project.

  It is intended to demonstrate usage of all functionality in the component, including how to ensure the component can cope with visualization switching.
  (It also demonstrates how to handle application window resizing, something that can happen when when inside a compositor environment, which may also be of interest.)

Dependencies

• Runtime

  • CODESYS Visu/Webvisu 3.5.17.30

• IDE

  • Visualization 4.2.0.0

  • VisuUtils 4.2.0.0

• Project configuration

  • Qt Overlay enabled

    • Visualization Manager -> Settings -> General Settings -> Support client animations and overlay of native elements CHECKED

Limitations / Known issues

• The same video source cannot be displayed simultaneously in multiple CameraViews.

• Switching between Visualizations will reset the component to default settings. After switching back to a Visu containing a CameraView settings need to be re-initialized.
  Specifically, this means that configurations done as initial calls will be lost and not re-executed. Conditional calls or similar can be used instead.