I'm trying to export video for use with the HTML5 tag. I've already created a nice webm encoding but can't create the equivalent mp4 video.
The MP4 option in Pitivi says it's not recommended and produces corrupted MP4 video when I use it. It recommends using mp4mux to render the project instead, but I can't find this option anywhere and Google is failing me.
How do I enable mp4mux rendering of MP4 in Pitivi?
Even if this may not give the right answer to your question, I put my answer here as requested by djeikyb:
Transcoding may be useful for you.
You render your video in whatever lossless format you wish (AVI, MPG, etc.) and transcode it changing the video bit rate in order to make it usable for HTML5 tag. Further information and a GUI I gave when answering this: How can I maximum compress video files? which I paste here for your convenience.
Good Luck!