def METHOD_NAME(cube_r, cube_g, cube_b, prefix, v1, v2, vmin, vmax,
                          ffmpeg_cmd='ffmpeg'):
    """
    Parameters
    ----------
    cube_r, cube_g, cube_b : SpectralCube
        The three cubes to visualize.  They should have identical spatial and
        spectral dimensions.
    prefix : str
        A prefix to prepend to the output png and movie.  For example,
        it could be rgb/sourcename_speciesname
    v1 : Quantity
        A value in spectral-axis equivalent units specifying
        the starting velocity / frequency / wavelength
    v2 : Quantity
        A value in spectral-axis equivalent units specifying
        the ending velocity / frequency / wavelength
    vmin : float
        Minimum value to display (constant for all 3 colors)
    vmax : float
        Maximum value to display (constant for all 3 colors)
    ffmpeg_cmd : str
        The system command for ffmpeg.  Required to make a movie
    """
    import aplpy
    check_ffmpeg(ffmpeg_cmd)
    # Create the WCS template
    F = aplpy.FITSFigure(cube_r[0].hdu)
    F.show_grayscale()
    assert cube_r.shape == cube_b.shape
    assert cube_g.shape == cube_b.shape
    # determine pixel range
    p1 = cube_r.closest_spectral_channel(v1)
    p2 = cube_r.closest_spectral_channel(v2)
    for jj, ii in enumerate(ProgressBar(range(p1, p2+1))):
        rgb = np.array([cube_r[ii].value,
                        cube_g[ii].value,
                        cube_b[ii].value
                       ]).T.swapaxes(0, 1)
        # in case you manually set min/max
        rgb[rgb > vmax] = 1
        rgb[rgb < vmin] = 0
        # this is the unsupported little bit...
        F._ax1.clear()
        F._ax1.imshow((rgb-vmin)/(vmax-vmin), extent=F._extent)
        v1_ = int(np.round(cube_r.spectral_axis[ii].value))
        # then write out the files
        F.refresh()
        F.save('{1}_v{0}.png'.format(v1_, prefix))
        # make a sorted version for use with ffmpeg
        if os.path.exists('{prefix}{0:04d}.png'.format(jj, prefix=prefix)):
            os.remove('{prefix}{0:04d}.png'.format(jj, prefix=prefix))
        os.link('{1}_v{0}.png'.format(v1_, prefix),
                '{prefix}{0:04d}.png'.format(jj, prefix=prefix))
    os.system('{ffmpeg} -r 10 -y -i {prefix}%04d.png'
              ' -c:v libx264 -pix_fmt yuv420p -vf '
              '"scale=1024:768" -r 10' # "scale=1024:768,setpts=10*PTS"
              ' {prefix}_RGB_movie.mp4'.format(prefix=prefix,
                                               ffmpeg=ffmpeg_cmd))