FFMPEG:在视频上叠加图像并保留大小

我正在尝试在视频的顶部"叠加图像(中间有形状的透明背景)，然后重新获得图像.图像尺寸大于视频尺寸.这是我正在使用的命令:

I'm trying to overlay an image (transparent background with shape in the middle) "on top" of the video and get the image back. The image size is bigger then the video. Here is the command that I'm using:

"-i", video.mp4, "-i", image.mp4, "-filter_complex", "[1:v][0:v]scale2ref=iw:ih[ovr][base];[ovr]colorchannelmixer=aa=1.0[ovrl];[base][ovrl]overlay[v]", "-map", "[v]", "-q:v", "2", directoryToStore + "/" + ImageName + ".jpeg"

以上内容将图像缩放为视频的大小.

The above scales the image to the size of the video.

我希望图像和视频保留其大小，并输出2个重叠的图像.

I want the image and the video to retain their size and output an image of the 2 overlaid.

有人可以给我一些建议吗?

Can someone please give me advice on how I can do this?