Simple Java application for downloading segments of a live on-going .mpd stream, and then a little tool for merging results.
java -jar mpd-downloader.jar download https://example.com/stream.mpd output-folder
Will download forever, when the stream is over or you've got all the data you want, you can press Ctrl-C to cancel downloading. You can tell the stream is over when you get continuous download errors for the latest m4s file.
You then end up with a bunch of m4s files in output-folder/audio and output-folder/video. You can then use the merge function to concatinate these m4s (starting with init.m4s, which is like an mp4 header), and then FFMpeg is called to combine the audio m4a and video mp4 into one folder.
java -jar mpd-downloader.jar merge output-folder
Will now output output-folder.mp4 in the current directory. NOTE: requires FFMpeg in path.