hmm, can say only what docu said.
see return value.
some video formats have sub formats, means .mp4 is not .mp4.
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Quote: "This command loads a video file ready to be played. Only one video file can be loaded at a time so loading a video deletes any existing video. On iOS, Android, and Mac it is recommended that you use .mp4 files with the H264 (MPEG-4 AVC) codec for video. For audio it must be encoded in MP3 or AAC.
On Windows it depends on the codecs installed and although in some cases it will play mp4 files it is recommended that you use wmv on Windows for maximum support.
Returns 1 if successful, 0 if there was an error, -1 if this platform does not support videos. "
AGK 108 (B)19 + AppGameKit V2 Alpha .. : Windows 8.1 Pro 64 Bit : AMD Radeon R7 265