key_framed_overlay_effect.py

import gi
gi.require_version("Gtk", "3.0")
gi.require_version("GES", "1.0")
gi.require_version("GstController", "1.0")
import signal

from gi.repository import Gtk
from gi.repository import GES
from gi.repository import Gst
from gi.repository import GObject

from gi.repository import GstController


DEFAULT_DURATION = 10 * Gst.SECOND


def handle_sigint(sig, frame):
    Gtk.main_quit()


def bus_message_cb(bus, message):
    if message.type == Gst.MessageType.EOS:
        Gtk.main_quit()


def control_source_value_changed_cb(control_source, value):
    print("value changed")


def effect_control_binding_added_cb(effect, binding):
    control_source = binding.props.control_source
    control_source.connect("value-changed", control_source_value_changed_cb)
    # framepositioner defines:
    # MAX_PIXELS = 100000; MIN_PIXELS = -100000
    # 0.5 -> 0px
    control_source.set(0 * Gst.SECOND, 0.5)
    # 0.5005 -> 100px (100 / 100000 * 0.5 + 0.5)
    control_source.set(4 * Gst.SECOND, 0.5005)


def bg_clip_child_added_cb(clip, track_element):
    if not isinstance(track_element, GES.Effect):
        return

    track_element.connect("control-binding-added",
                          effect_control_binding_added_cb)
    control_source = GstController.InterpolationControlSource()
    control_source.props.mode = GstController.InterpolationMode.LINEAR
    track_element.set_control_source(control_source, "posx", "direct")

if __name__ == "__main__":
    Gst.init(None)
    GES.init()

    timeline = GES.Timeline()
    track = GES.VideoTrack.new()
    timeline.add_track(track)
    
    layer = timeline.append_layer()
    asset = GES.Asset.request(GES.TestClip, None)

    bg_clip = layer.add_asset(asset, 0, 0, DEFAULT_DURATION,
                              GES.TrackType.VIDEO)
    bg_clip.connect("child-added", bg_clip_child_added_cb)
    bg_clip.props.vpattern = GES.VideoTestPattern.WHITE

    effect = GES.Effect.new(
        "videotestsrc ! framepositioner name=positioner ! gescompositor")
    bg_clip.add_top_effect(effect, -1)

    pipeline = GES.Pipeline()
    sink = Gst.ElementFactory.make("xvimagesink", None)
    pipeline.preview_set_video_sink(sink)
    pipeline.set_timeline(timeline)

    bus = pipeline.get_bus()
    bus.connect("message", bus_message_cb)
    bus.add_signal_watch()

    pipeline.set_state(Gst.State.PLAYING)

    signal.signal(signal.SIGINT, handle_sigint)
    Gtk.main()