GStreamer Pan Tilt Zoom and Rotate Element - GstPTZR Basics

This page describes the fundamentals of RidgeRun's GStreamer digital Pan, Tilt, Zoom and Rotate Element. After reading this page it should be clear if the plug-in meets your application requirements by using any of its different configurations.

PTZR Camera

GstPTZR is a GStreamer plug-in that emulates a PTZR camera using digital image transformations. PTZR stands for Pan, Tilt, Zoom and Rotate. They represent physical degrees of freedom in which the camera may rotate in order to capture different parts of the scene. Pan and Tilt correspond to rotations along the horizontal and vertical axis, respectively. Figures 1 and 2 show these movements.

Figure 2. Tilt movement of a PTZR camera

Similarly, Zoom represents the level of magnification of the image a camera is able to take thanks to different lens configurations. Figure 3 represents graphically this concept. Note that there is no movement of the camera carcass, but a modification in the lens configuration.

Finally, very small amount of cameras may also expose a Rotation factor. This is represented by a rotation in the depth axis. Figure 4 shows this concept.

Figure 4. Rotate movement of a PTZR camera

Digital PTZR Emulation

GstPTZR emulates PTZR by taking a subimage of the input frame. By varying the origin of this subimage a pan and tilt effect is achieved. Figure 5 shows the emulated pan & tilt.

Figure 5. Pan & Tilt digital emulation on Bartok the Dachshund

By taking a bigger/smaller subimage, a zoom-out/zoom-in effect is achieved. Figure 6 shows such concept.

Figure 6. Zoom digital emulation on Bartok the Dachshund

Finally, by rotating the subimage within the input frame, the rotation effect is achieved. Figure 7 exemplifies this rotation.

Figure 7. Rotation digital emulation on Bartok the Dachshund

Index

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