I had a few problems with some of the videos that were posted on iTunesU, and they lead me to discover some nice tools that may be useful in general.
In first place, the videos took forever to start playing when using the direct access described in the previous post. The problem was that some mp4 files have the index at the end of the file itself – hence in order to be played, the whole file needs to be downloaded first – which may take a looong time.
The solution is easy: one needs to swap the position of the index, by putting it at the beginning of the file. How that can be done? Easy: QTIndexSwapper can do that for you. It’s a plug-in for Adobe AIR developed by Renaun Erickson.
My second problem was that some of my files, when not viewed in iTunes but with the alternative based on JWPlayer (see previous post), were correctly playing the audio, but the video was black. I asked for help on the longtailvideo forum, and the response was that some of my mp4 were coded with MPEG4 Visual (aka MPEG4 Part 2 aka ISO/IEC 14496-2) which is not supported by Flash (and by JWPlayer). Files had to be recoded into H.264 (aka Advanced Video Codec aka MPEG4 Part 10). Nice hint, but how could I get detailed info about a video file on my Mac?
Here it is: Mediainfo, a nice app for the Mac giving plenty of information.
So the last step was how to transcode the files. By using FFmpegX I chose to transcode into “iPod H.264 640w”, and voilà, everything worked well. What I still need to do is to find which set of parameter to use directly from ffmpeg instead of using its GUI wrapper.
BTW, during the whole process I also found a nice reading about HTTP pseudostreming.
Other useful video tools (related to other tasks):