I'm unfamiliar with gstreamer. Can you elaborate on this weird way?

The arguments to the gstreamer binary are encoders,decoders,filters and i/o piped together like commands in a shell (with the ! operator). For example, this is a shell command to show a h264 network stream on a raspberry pi:

    gst-launch-1.0 rtspsrc location=rtsp://192.168.2.112:8080/stream.sdp ! rtph264depay ! h264parse ! omxh264dec ! autovideosink

Gstreamer is more than this, but it'is a neat example.