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: 
A DASH player plays an MPD by selecting a Period, and in the Period one or more AdaptationSet, and then one Representation per AdaptationSet. For the chosen Representation, it downloads and passes the intialization segment and some media segments to the media engine. As indicated by others you can simulate that by concatenating (simply using `cat`on Linux).

The [MPEG-DASH standard](http://standards.iso.org/ittf/PubliclyAvailableStandards/c065274_ISO_IEC_23009-1_2014.zip) requires that initialization segments (in your case the mp4 file) contain no data. This is because when switching the player might use several times the initialization segment. You can open it in a player but it does not contain any media. 

For m4s files, they contain media data but they cannot be interpreted without the associated initialization segment.
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).