What video creation parameters should be set so that the quality is not lost on Instagram?

Question

Video

Using ffmpeg, I'm making a short video (10 seconds without an audio track) with a frame size of 1080x1080. I upload it to Facebook - everything is fine, when playing it shows that HD is on. I upload the same video to Instagram - terrible pixelation, the quality is just crap.
And now the most interesting: shitty quality is obtained from the video, where the image gradually appears on a white background. Another video, where the image is immediately opaque, but at the same time moves on a white background, and which was created with the same parameters - this video is played on Instagram with quite acceptable quality. I guess that when transcoding in Insta, some kind of optimization is performed that gives such an effect. But maybe you can somehow overcome it?
Now I have the following settings:
-c:v libx264 -s 1080x1080 -pix_fmt yuv420p -b:v 8M -r 30 -profile:v high -preset veryslow
Actually, the question is - with what parameters should you create a video in order to maximize the quality when uploading to Instagram?
ZY Recommendations of Instagram and FB, of course, I read, but it did not help

Answer 1

By reading all sorts of manuals, articles, forums and a certain number of experiments, I picked up a set of options that gives acceptable quality:
-c:v libx264 -s 1080x1080 -pix_fmt yuv420p -b:v 8M -r 30 -profile:v high -preset veryslow - crf 10 -tune film
I'm not an expert on video at all, but this is how I understand it: thanks to the added options, they give significantly less mpeg-4 compression (the video file is 4 times larger), and therefore, when transcoding by Instagram, we get less loss.
The most amazing thing is that although the uploaded file has become larger, the result recoded by Instagram is 15% -20% smaller with better quality!