Is there a conversion table to stream

Hello,

I wonder if there was a kind of conversiontable of if somebody could explain me the logic…

I have a Foscam camera FI9900EP with a maximum resolution of 1920 x 1080.

I want to stream on my Nest Hub (resolution of 1024 x 600).

To speed up the streaming, I created a proxy camera.

camera:
  - platform: proxy
    entity_id: camera.fi9900ep_voordeur
    name: Camera Voordeur Streamen
    stream_quality: 75
    mode: crop
    max_stream_width: 640
    max_stream_height: 400

This works fine, except that I have black borders left & right.

So I wonder what values I should use to avoid this.