Kivy/ffpyplayer transparent/alpha background video

transparent_video_test.py

"""
Kivy/ffpyplayer example to read transparent video
=================================================

Right now, VP9/ffmpeg encoder supports alpha channel, under the yuva420p
pixel format. But for decoding, the default libvp9 used by ffmpeg doesn't
support it, so we need to ask for libvpx-vp9 instead.

I was using a set of png image as a source, and got a VP9+alpha video with::

    $ ffmpeg -r 60 -f image2 -s 2000x1500 -start_number 56 \
      -i "perso2expressions%04d.png" -pix_fmt yuva420p -an out.webm

It tells it's a 60 FPS video, the filename starts from
"perso2expressions0056.png".

The Kivy code demonstrate that the background is actually showed.
"""

from os import environ
environ["KIVY_VIDEO"] = "ffpyplayer"
from kivy.app import App
from kivy.factory import Factory as F
from kivy.lang import Builder

import kivy.core.video.video_ffpyplayer as video_ffpyplayer
orig_media_player = video_ffpyplayer.MediaPlayer
def patch_media_player(*largs, **kwargs):
    kwargs["ff_opts"]["vcodec"] = "libvpx-vp9"
    return orig_media_player(*largs, **kwargs)
video_ffpyplayer.MediaPlayer = patch_media_player


KV = """
BoxLayout:
    canvas.before:
        Color:
            rgb: 1, 0, 0
        Rectangle:
            size: self.size
    Video:
        id: video
        source: "out.webm"
        state: "play"
"""


class TestTransparentVideo(App):
    def build(self):
        self.root = Builder.load_string(KV)
        self.video = self.root.ids.video


if __name__ == "__main__":
    TestTransparentVideo().run()

which kivy and ffpyplayer version did you use? it doesn't work on the latest kivy 2.2.1 and ffpyplayer 4.5.0. thanks!

@rostykerei did you ever figure this out?

@jsdir yes, but you'd need to patch kivy.core.video.video_ffpyplayer and comment out the line self._out_fmt = 'yuv420p'. The latest player has a special handling of yuv420p pixel format, but doesn't handle alpha layer.

@rostykerei this worked, thanks a lot!