I created a video of my iOS game using quicktime, processed it & exported it with iMovie iOS App Preview settings. Though I'm able to upload the video to iTunes Connect and successfully play it there, could select poster frame but it says " Your file could not be loaded, try again " & when I save the page, the video doesn't get saved.
I recorded in iPhone 5C at Resolution : 1136 × 640 @ 30fps, Codecs : AAC, H.264, Duration : 0.29 seconds.
I had already followed the handbrake and other approaches mentioned here - Unable to load app preview in iTunes connect but in vain.
Please let me know if there's any sure shot method of uploading App preview video.