Hi, According to [GCK'S FILE SIGNATURES TABLE](https://www.garykessler.net/library/file_sigs.html), there are three types of file signatures for mp4: ``` [4 byte offset] 66 74 79 70 4D 53 4E 56 [4 byte offset] ftypMSNV MP4 MPEG-4 video file [4 byte offset] 66 74 79 70 69 73 6F 6D [4 byte offset] ftypisom MP4 ISO Base Media file (MPEG-4) v1 [4 byte offset] 66 74 79 70 6D 70 34 32 [4 byte offset] ftypmp42 M4V MPEG-4 video|QuickTime file ``` As only the second one (`66 74 79 70 69 73 6F 6D`) is supported, can you please add support for the other two as well?