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.
I dont think it is possible to play any of the files in a standalone player. The mp4 is the init segment which is required to decode the .m4s media segments. I dont think there is an option in the vlc player to map an init segment to multiple media segments. Nevertheless you can try a Dash player to play the manifest file. For instance [dash.js](https://github.com/Dash-Industry-Forum/dash.js)

> 
> **Initialization segment:** A sequence of bytes that contain all of the initialization information required to decode a sequence of media segments. This includes codec initialization data, Track ID mappings for multiplexed segments, and timestamp offsets (e.g. edit lists).
> 
> 
> **Media segment:** A sequence of bytes that contain packetized & timestamped media data for a portion of the media timeline. Media segments are always associated with the most recently appended initialization segment.
> 
> 
> 

Source: <http://www.w3.org/TR/media-source/#init-segment>