Having issues with playing HEVC/h265 files

[moosespectacles]

Your server ran out of space for the transcode.

Code:

Error writing trailer of C:\Users\amusa\AppData\Local\Jellyfin\transcodes\9f9c53ee2285577dfaebd126e3b6ea9b.mkv: No space left on device

Ah, that makes sense why it suddenly got worse today, since I filled up my hdd. Would you be able to tell me why or what it's transcoding? I thought I transcoded my files to be able to be direct played, but it seems I'm wrong