imx8 gstreamer artefacts when using textoverlay with glvideomixer

[ondrejbilka]

Hi, 

We want to display output of several cameras with some captions on imx8 eval board. We have problem that if in pipeline below one waves over text there will be artefacts in form of black lines. 

Similar pipeline where we omit glvideomixer renders correctly.

Is this bug or should we add captions in different way?

START='rtspsrc location="rtsp://'$IP'/axis-media/media.amp?videocodec=h264&h264profile=main&resolution='$RX'x'$RY'&fps='$FPS'" latency='$RTSP_LATENCY' ! rtph264depay ! h264parse ! '

gst-launch-1.0 glvideomixer name=m sink_1::xpos=20 sink_1::width=300 sink_1::height=300 sink_1::ypos=20 sink_2::xpos=400 sink_2::width=300 sink_2::height=300 sink_2::ypos=100 ! glimagesink \
$START vpudec ! textoverlay text="foobar" ! m.sink_1 \
$START vpudec ! m.sink_2

[joanxie]

you mean using the glvideomixer in the command is succesful or not?

for how to use current gestreamer in the yocto bsp, pls refer to the i.MX Linux® User's Guide, focus on the chatper 7 Multimedia

[ondrejbilka]

As described in original post pipeline with glvideomixer launches but displays incorrect images. Here probably when glvideomixer is used textoverlay renders directly into buffer that is internally used by h264 decoder, and artefacts are result of decoder deriving frames from modified previous frames.

There is no documentation about glvideomixer in documentation yet, it only contains older imx6 specific g2dcompositor with basically same syntax.