Re: [MMUSIC] How to update media information during a streaming session?

[Magnus Westerlund <[e-mail]>]

Hi Christian,

Christian Sageder wrote:
> Hello all,
> 
> I am quite new to this mailing list and I have a question regarding the
> possibility to update media information during a streaming session. 
> 
> The following scenario explains it: 
> 
> - A streaming server sends an audio/video stream to a client. This stream
> contains multiple clips, e.g. as a radio broadcast which includes several
> tracks.
> 
> - In parallel the streaming server should be able to provide additional
> meta data to the client. This meta data has to be in sync with a clip
> within the stream. The meta data we are looking for is some kind of media
> title and some machine readable information like an ID or an URL
> 
> - With this information the client application should be able to provide
> additional information about the currently played stream, e.g. displaying
> the media title which is currently streamed and not only the information
> "live stream" or equaling
> 
> My question is therefore:
> 
> Is there a standard way how a streaming server can pass additional /
> updated information to a client which is in sync with the stream?

Not to my knowledge. It might exist in some of the industry forums that 
has defined streaming related umbrella standards. However in that case I 
would expect them to be limited in usage.

When it comes to handling meta data at all I know that 3GPP has defined 
a asset information SDP Attribute. See chapter 5.3.3.7 in TS 26.234 (PSS).

> 
> I have done some research within the RTSP and SDP standard, but I was not
> able to find something to solve this issue. I think SDP and the future
> extension of SDP allows us to pass all necessary information, but I was
> not able to find anything how a streaming server can pass updated SDP
> information to the client. It seams the SDP information is only send in
> the initial phase, on request from the client (DESCRIBE), to the client.
> There is also a draft about the use of ANNOUNCE, but for me it seams the
> intention of this command was for an other purpose.

There has been discussion in the context of the announce draft:
http://www.ietf.org/internet-drafts/draft-ietf-mmusic-rtsp-announce-01.txt 
about providing updated SDP information.

I think one should consider the meta information as its own media stream 
that needs to be provided in sync with the media. Because publishing new 
SDP would generally mean media level changes which may require update of 
codec, transport or even RTSP state. Thus I don't think the usage of 
announce to distribute meta data is the best.

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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