I don't know what happened, but suddenly my phone isn't playing mobile-formatted MP4 videos from the internet anymore. I noticed it first with a video on my own site, that I encoded using ffmpeg. I want to make sure it's not just me, so could someone try to load either (or both) of these 2 videos on their phone please: http://infectionist.com/tutorials/after_effects/fire_mobile.mp4 http://infectionist.com/tutorials/sony_vegas/stereoscopic/stereoscopic_mobile.mp4 For me, the first one plays maybe a second and a half, the second one plays maybe 3 seconds, but then they both come up with a popup saying "Sorry, this video cannot be played." I have other mobile-encoded videos elsewhere on my site and they all work fine. I tried re-encoding the videos that weren't working and no matter what I try, it just won't work! The weird thing is, they used to work perfectly. I didn't change anything, so there's no reason it should have stopped working. I use ffmpeg to encode my videos from their original format to 640x360, 256kb/s video, 128kb/s audio, then I use qt-faststart (included with ffmpeg) to relocate the moov atom in the MP4 file to the beginning of the file, so that the video can be streamed over HTTP. This has always worked for me before, and the other videos I've done this to still work fine, so I can't figure out why these two videos specifically won't work. Edit: I should note that I tried downloading the video to my local server and accessing it through my wireless network, and I had the exact same results, so that rules out it being a server issue. I can play the video perfectly fine on my computer, but if I copy it to my phone and try to play it from there, it also doesn't work, which indicates that it's an issue with the way I've encoded the video perhaps. Like I said though, these used to work fine, and the other ones that also used to work still work fine, it's seriously just these 2 videos.