5 or so years later, but for the record a program called yt-dlp can do batch downloads and it has very wide compatibility. See
https://github.com/yt-dlp/yt-dlpIt's command line only. Easiest way is to run a linux vm (Ubuntu etc). Sample command to do a batch download would be: 'yt-dlp -a dl.txt'
dl.txt is a text file with one link per line. Name it whatever you want.
Lots of other instructions and options in the link above, but yt-dlp works on a very high percentage of sites.
If yt-dlp doesn't work, things get harder. Often as Dent has suggested the challenge can be finding the source URL. One app I've found useful for that is a chrome extension called 'Video DownloadHelper'.