We have a flash web-app that created interactive video, and are using ffmpeg to do some compression/resizing when a user "publishes" their project.

The user can upload flv files and mp4 files, both of which play fine in the Flash UI before publishing. After publishing the flv files work fine, but the mp4 files will not play in the flash player: Audio will play but video won't.

The mp4 files will play fine if I download them and play them in the Quicktime player but if I attempt to open them in the Adobe Media Player it reports "The media file does not contain a supported video track".

If I open the Movie inspector in quicktime it tells me that the original file is an "h264" video and the ffmpeg-processed ones are "mpeg-4".

I have tried forcing it to h264 by adding flags like -f h264 and -vcodec h264 but I get a screenfull of errors (no frame, illegal POC type, sps_id out of range) ending with Could not find codec parameters (Video: h264)

h264 will show up if I run ffmpeg -formats and ffmpeg -codecs, and as I said it will play fine in Quicktime.

Is there anything else I need to do to convince the flash player to play them? Is there anything else I need to tell you about the server that will help?