Useful GStreamer 1.X commands

# view the desktop into a window on Linux
gst-launch-1.0 ximagesrc startx=1920 use-damage=0 \
  ! video/x-raw,framerate=30/1 \
  ! videoscale method=0 \
  ! video/x-raw,width=1920,height=1080 \
  ! ximagesink
  
  
  # view the desktop into a window on MacOS
  gst-launch-1.0 avfvideosrc capture-screen=true \
    ! videoscale \
    ! videoconvert \
    ! video/x-raw,width=640,height=480 \
    ! osxvideosink

# Encode using intel vaapi
# from https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer-vaapi-plugins/html/ch01.html
gst-launch-1.0 -ev videotestsrc num-buffers=60 ! timeoverlay ! vaapih264enc ! mp4mux ! filesink location=test.mp4


# record screen to mkv using hw vaapi (uses <40% CPU on intel i7 8th gen)
gst-launch-1.0 ximagesrc use-damage=0 ! video/x-raw,framerate=30/1 ! videoscale method=0 ! video/x-raw,width=1920,height=1080 ! videoconvert ! vaapih264enc ! matroskamux ! filesink location=record.mkv

# text overlay
gst-launch-1.0 v4l2src ! videoconvert ! textoverlay font-desc="San 32" text="Text" ! ximagesink


# send png stream from browser to node server to stdin and then to gstreamer vaapi264enc
gst-launch-1.0 \
  fdsrc fd=0 ! pngdec ! videoconvert ! videorate  ! video/x-raw,framerate=60/1 ! \
  vaapih264enc ! matroskamux ! filesink location=r.mkv


## Parts 
# encode to x264
queue ! x264enc ! h264parse 
# send via rtp
! rtph264pay ! udpsink


## Interoperability
## OpenCV to GStreamer
cv::VideoWriter writer;
writer.open("appsrc ! autovideoconvert ! v4l2video1h264enc extra-controls=\"encode,h264_level=10,h264_profile=4,frame_level_rate_control_enable=1,video_bitrate=2000000\" ! h264parse ! rtph264pay config-interval=1 pt=96 ! udpsink host=192.168.x.x port=5000 sync=false", 0, 30, cv::Size(640, 480 ), true);