import vapoursynth as vs
from vapoursynth import core
video = core.std.BlankClip(width = 1920,
                           height = 1080,
                           format = vs.RGB24,
                           length = 100,
                           fpsnum = 60,
                           fpsden = 1,
                           color = [0, 255, 0])
video2 = core.std.BlankClip(width = 1280,
                            height = 720,
                            format = vs.GRAY8,
                            length = 100,
                            fpsnum = 30,
                            fpsden = 1,
                            color = [127])
# video = core.resize.Bicubic(video, format = vs.YUV444P8, matrix_s = '709')
core.std.Splice([video, video2], mismatch = True).set_output()