Thanks for your response, surya987. But when I try each of those three links I just receive the response "Access Denied". Do you know how can I overcome that and obtain those mp4 files?
Two further approaches I will try are 1) to use wireshark to find out what is coming down the line, or 2) make my own simple MPD using the information supplied at
https://www.brendanlong.com/the-stru...-dash-mpd.html
Is either of those likely to succeed?