Which formats does Telegram internal video player support?

I know that we can install many applications to support many new video formats. My question is:

1. Does Telegram have an internal video player? (Does the software itself come with a player?)
2. If yes, which formats can be played with that player (audio and video)?

Note: I’ve seen that sometimes mp4 files can be played in Telegram but sometimes they can’t. What’s the difference? Is it related to bitrate?