Code:
#!/bin/bash
ffmpeg -i "$1" -c copy -bsf:a aac_adtstoasc $tname.mp4
Using firefox and VideoDownloadHelper.net plugin (from the FF plugins/extensions store/site). While viewing vid, use the download helper plugin to copy the url of the stream itself. Then pass that into the above shell script as the first/only argument (the "$1" part - need the quotes because the URL will contain control characters).
Haven't met a video that I couldn't capture yet.
Note - for the non-ubergeeks the VideoDownloadHelper.net plugin/extension will also download and save and convert formats BUT it requires a non-Free helper app that I refuse to install on my Linux box, hence the use of my shell script. If you've polluted your life with Microsoft or Apple crap, then go for the add-on to do the conversion etc.