youtube-dl can't get something that's obviously there

By default youtube-dl looks for the best available version of a video offered on sites such as youtube or dailymotion. If, however, by some chance, the site seems to claim that the best is available but it isn't then youtube-dl fails with 'HTTP Error 404.' One remedy that works in some circumstances begins with a query to the site for the formats it claims to be available using code like this. youtube-dl -F [video URL] youtube-dl may respond with a report of this kind:

Given that one already knows that the last item in this list is actually unavailable, one can try requesting one of the previous items using, say, height or width. Here's one possibility. youtube-dl -f "[width=512]" [video URL] --recode-video mp4