Together with desmonduz and progre55 created a rather successfull (at the time, ~30-50 users a day) Telegram bot -- PreviewBot -- that reduced the size of the forwarded videos to save internet traffic for users in countries where mobile internet was expensive.
This is a code copy (removed sensitive information) of the original PreviewBot for Telegram that was operational in the year of 2018. Here is how it looked like in operation:
