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Strange video artifact with gstreamer & textoverlay, apparently caused by imxvpudec...

Question asked by Ed Sutter on Jun 22, 2017
Latest reply on Jul 6, 2017 by Ed Sutter


I've been working with a Boundary Devices iMX6QP board for a while now.

Recently I added the textoverlay element to my gstreamer pipeline and noticed that it is "affected" by motion around the video area that it overlays...  For example, if I overlay "hello", then swipe my hand over the area within the viewing area of the camera that corresponds to the area over which the text is laying, the text actually "follows" the motion across the screen.

Here are two pipelines, one that works and one that shows the symptom I describe above...

In a simple case everything is fine…

gst-launch-1.0 v4l2src ! textoverlay text=”hello” ! autovideosink

But in a more complex pipeline the “hello” is affected by movement in the video area that it is overlaying..

gst-launch-1.0 v4l2src ! video/x-raw,width=640,height=480 ! videoconvert ! imxvpuenc_h264 bitrate=2048 ! h264parse ! rtph264pay ! queue ! rtph264depay ! h264parse ! imxvpudec ! videoconvert ! textoverlay text=”hello” ! autovideosink

It appears to be related to the use of imxvpudec, but I can't prove that. Has anyone else seen this?  Can one of the imx-gstreamer guys try this out to see if they agree?