The video player (mythfrontend::main::internal_play_media()) plays video from any source. For instance Gallery uses it for camera videos and MythBrowser and SetupWizard use it for downloaded videos. So it has to fail in a generic/independent way.
"Try it and handle failure" is a more robust strategy than "Check first, do it and handle unexpected failure" (file disappears between check and play ?). It also avoids having to retrieve a remote file twice.
Recordings are a special case. The UI does extra checks on recording files so that they can be marked as missing in the UI. Therefore, it won't even try to play a recording that it already knows is absent.
