Silverlight streaming structure (control and media protocol), question

06-22-2009 8:04 AM |

Hi all,

I have several questions about Silverlight streaming. What I’m interested in, is exact structure of video streaming, which is accepted by Silverlight.
I’ve made a simple test with video streaming using: Silverlight application as client (MediaElement, source=”http://xxx.xxx.xxx.xxx:8080”), VLC player as streaming server (I’ve set up streaming to certain IP, stream is compressed to wmv), webcam as video source.
Traffic analysis using Network Monitor shows me, that there are two types of packets, which could be related to video:
- HTTP packet (payload: application/octet-stream)
- TCP packets (which NM recognizes as continuation to previous one) with some blob as tcp continuation data (this blob can be decoded as RTP, but I’m not sure that this is true)

Thus, my questions are:
1. How sample is transmitted: does this true that Silverlight uses just RTP over TCP for video streaming or it is more complex, e.g. everything is packed into HTTP (e.g. RTP over HTTP or smth similar, what exactly)? Is it possible to transmit video using RTP over UDP to Silverlight client?

2. What control protocol is used (and supported) by Silverlight (e.g. RTSP, WMSP)?

Thanks in advance for any help.

Re: Silverlight streaming structure (control and media protocol), question

06-26-2009 5:31 AM |

Hi Genli,

Silverlight Streaming wroks depend on Windows Media Services(WMS).   Real Time Streaming Protocol (RTSP) is enabled by default. However, in this condition cache doesn't work any more.  There, most time, we need to change it to HTTP.  For the details, please take a look at this article.

Best regards,

Jonathan 

Re: Re: Silverlight streaming structure (control and media protocol), question

07-03-2009 4:34 AM |

Hi Jonathan,

Thank you for the reply and links. By the way, the last link on 'this article' points to this forum's message. I'm not sure, that this is correct, can you check please?

But, unfortunately, this is not the answer on my question. As I know, Silverlight allows streaming from WMS as far as from any source, which gives the correct stream (as in my example above with VLC). Also, if I disable on WMS server both RTSP and MMS, but enable HTTP only, everything works (I mean I get stream from WMS to Silverlight client).

What I'm asking about, is low-level communication: which protocols are used exactly (is RTP used for samples wrapping?)?

It would be a great help for me, if somebody can give answers on my questions.

Thank you!

Best regards,
genLi

Re: Re: Silverlight streaming structure (control and media protocol), question

07-03-2009 6:14 AM |

Hi Genli,

OK.  I checked the link now.  Below are two links.  Hope it helps.

http://timheuer.com/blog/archive/2008/05/06/streaming-media-in-silverlight.aspx

http://alexzambelli.com/blog/2009/02/04/the-birth-of-smooth-streaming/

Best regards,

Jonathan