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gstreamer-cheat-sheet/mixing.md
Matthew Clark c48760ecab Move to compositor and add audio example
2018-02-23 08:07:36 +00:00

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Mixing video (GStreamer command-line cheat sheet)

The element compositor allows video to be mixed (overlayed, put side-by-side, etc).

The older videomixer element can be used instead, and takes the same arguments as compositor so it's easy to swap between them. However, videomixer is apparently inferior in some situations, such as for live streams.

Picture in picture

Here we have two source (mp4) files, which should be set as environment variables $SRC and $SRC2

gst-launch-1.0   \
    filesrc location="$SRC2" ! \
    decodebin ! videoconvert ! \
    videoscale ! video/x-raw,width=640,height=360 ! \
    compositor name=mix sink_0::alpha=1 sink_1::alpha=1 !   \
    videoconvert ! autovideosink \
    filesrc location="$SRC" ! \
    decodebin ! videoconvert ! \
    videoscale ! video/x-raw,width=320,height=180! \
    mix.

Put a box around the in-picture using ‘videobox’ e.g.

gst-launch-1.0   \
    filesrc location="$SRC2" ! \
    decodebin ! videoconvert ! \
    videoscale ! video/x-raw,width=640,height=360 ! \
    compositor name=mix sink_0::alpha=1 sink_1::alpha=1 !   \
    videoconvert ! autovideosink \
    filesrc location="$SRC" ! \
    decodebin ! videoconvert ! \
    videoscale ! video/x-raw,width=320,height=180! \
    videobox border-alpha=0 top=-10 bottom=-10 right=-10 left=-10 ! \
    mix.

Choose where the in-picture goes with the ‘xpos’ and ‘ypos’ attributes of videomixer, e.g.

gst-launch-1.0   \
    filesrc location="$SRC2" ! \
    decodebin ! videoconvert ! \
    videoscale ! video/x-raw,width=640,height=360 ! \
    compositor name=mix sink_0::alpha=1 sink_1::alpha=1 sink_1::xpos=50 sink_1::ypos=50 !   \
    videoconvert ! autovideosink \
    filesrc location="$SRC" ! \
    decodebin ! videoconvert ! \
    videoscale ! video/x-raw,width=320,height=180! \
    mix.

Add audio by demuxing the inputs so it can be handled separately. This example does so on the first source (rather than mixing the two together):

gst-launch-1.0   \
    filesrc location="$SRC" ! \
    qtdemux name=demux  demux.audio_0 ! queue ! decodebin ! audioconvert ! audioresample ! \
    autoaudiosink \
    demux.video_0 ! queue ! \
    decodebin ! videoconvert ! \
    videoscale ! video/x-raw,width=640,height=360 ! \
    compositor name=mix sink_0::alpha=1 sink_1::alpha=1 sink_1::xpos=50 sink_1::ypos=50 !   \
    videoconvert ! autovideosink \
    filesrc location="$SRC2" ! \
    decodebin ! videoconvert ! \
    videoscale ! video/x-raw,width=320,height=180! \
    mix.