So what are the file types supported in Google Chromecast? Here is a list, from the official help page for Google Cast (hmm, Chromecast, or Google Cast, I am confused.)

All Google Cast devices at a minimum support the following media types:

• Video codecs: H.264 High Profile Level 4.1, 4.2 and 5, VP8
• Audio decoding: HE-AAC, LC-AAC, CELT/OPUS, MP3
• Containers: MP4/CENC, WebM, MPEG-DASH, SmoothStreaming
• Level 1 DRM support: Widevine, Playready
• Subtitles:
  • TTML – Timed Text Markup Language
  • WebVTT – Web Video Text Tracks

Find more Google Chromecast tips here.