Question: .
I am trying to understand how mpd file plays and i am referring to the following data set:
<http://www-itec.uni-klu.ac.at/ftp/datasets/mmsys12/Valkaama/MPDs/Valkaama_1s_act_isoffmain_DIS_23009_1_v_2_1c2_2011_08_30.mpd>

In mpd file format there is segment base consists of mp4 chunk and within it has chunk list with extension .m4s.I downloaded mpd file using :

<http://www-itec.uni-klu.ac.at/ftp/datasets/mmsys12/Valkaama/valkaama_1s/valkaama_1s_50kbit/valkaama_50kbit_dash.mp4>

and m4s chunk by following link:

<http://www-itec.uni-klu.ac.at/ftp/datasets/mmsys12/Valkaama/valkaama_1s/valkaama_1s_50kbit/valkaama_1s1.m4s>

I tried to play both mp4 and m4s in vlc player but not able to play any of these two so i want to ask which of the chunk links in the mpd file forma i can be able to play standalone in vlc player.

Please correct me if any of my observations is wrong:

Regards
Mayank

Answer: 
MPD file is just a index of streams with various formats in order to adapt to your bandwidth, to get more information follow the links of the other answers here.

It's possible to download all streams and merge them into a single file, you could achieve this by using youtube-dl:

```
youtube-dl http://URL/TO/manifest.mpd

```

You can get more information in <https://stackoverflow.com/a/39931712/1522342>.

Also, VLC 3.0.0+ can play that kind of file from a url, just open VLC, use the shortcut CTRL+N, paste the url and enjoy.
you can download init segment (SegmentBase/Initialization@sourceURL) and all media segments (SegmentList/SegmentURL@media) and concatenate everything (e.g. with the copy command on windows). The result should be playable on VLC. This has to be done for audio and video separately. In the next step you can then use MP4Box or similar tools to mux audio and video. 

Alternatively you can use www.dash-downloader.com to download everything in one step. The page will display some log explaining what it's doing. That might be helpfull. 

(full disclosure: that's my website).