If you’re new to the PSP you must remember when copying files video files (created with 3GP converter or PSP Video 9) to your PSP that
M4Vxxxxx.MP4 files go to the
MP_ROOT/100MNV01 dir of the Memory Stick and the
MAQxxxxx.MP4 files go to
M4Vxxxxx files are conventional MPEG-4 files and
MAQxxxxx are MPEG-4 files using AVC codec (recommended).