Thanks for trying out Web Playlists :).
Here are the answers to your question. I would also suggest posting to forums.iis.net as many more people monitor that.
"Is it possible to create the webplaylist.isx file on the fly with asp.net? My iea is to link to a single lets say "mywebsite.com/tvchannel.isx and creating the content of that isx file on the fly with infor coming from a database"
"Currently I am creating .asx palylists on the fly with ASP.NET and it works fine. But I would like to take advantage of your obfuscated URLs."
"Last but not least, how do webplaylists deal with prebuffering of media entries to allow seamless instant (without buffering) between media entries? This is especieally important for me because I intend to link to live streaming sources in between .isx playlist advertisement videos."
Yes, absolutely, Web Playlists allows you to do this. Your ASP page instead of serving asx directly could create isx file (format documented here - learn.iis.net/.../web-playlist---creating-a-simple-playlist) and then serve the link to the isx file instead of asx.
Also, an even better way to do this would be to write a custom provider to Web Playlists (.net providers as well as C++ providers are supported). You can read more about them - http://blogs.iis.net/vsood/archive/2008/04/22/exploring-custom-providers-wrapper-playlists.aspx). Web Playlists offers a very simple interface for you to write custom providers.
For buffering(pre-caching), do you intend to do this on the client side or server side - server side can be done through a custom provider only. For client side, if you are using WMP it would just work. If you are using SL, you will need to do client scripting through multiple layers as SL does not support pre-buffering next content.
"I tested webplaylists in combination with IIS 7.0 Bit Rate Throttling and it seems to work just fine. But I noticed that videos accessed through a webplaylist.isx link do not seem to be cached on the client computers even after watching the whole video. When linking directly to a video.wmv or a palylist.asx file the videos get cached on the client. Can you confirm that behaviour and is there a way to turn on caching?"
This is a security feature, Web Playlist sets the pragma: no-cache and thus the client side caching does not happen. If you really want this, the only way currently is use IIS settings. I don't know the answer right now but will try to find it for you. Is it possible to share the scenario where you would need this?
"Also could I return a file mydynamic.asx playlist to the isx HTTPD request instead of just a relative file link (ad.wmv) as in your example above.
Could I also return a file mydynamic.isx playlist to the isx HTTPD request?"
Currently, httpd entries are just at the entry level, for you to return a complete playlist, once again custom provider is the way to go.
We would be releasing an ASP.net application sample that uses Web Playlists interface with source code in a couple of days. You could take that and use it as an example. Please look out for post on my blog - http://blogs.iis.net/vsood
Jun 06 2008 by