[Telepathy] telepathy: problem fro accessing stream-engine

Robert McQueen robert.mcqueen at collabora.co.uk
Tue May 22 09:59:13 PDT 2007

Hi Matthieu,

Was it intentional that you replied to me off the list, or are you happy
for me to CC my answers there so they might help others too?

Matthieu LAURENT wrote:
> First of all, thank you for your answer.
> I am new in the world of open source, so thank you for educating me and
> giving me some advises.

Sure, no problem.

> I am also new in the telepathy world. I understand more and more things
> but there are still some interactions between processes
> (telepathy-cilent (tp_caller), connection-manager, stream-engine) that
> are not clear, and some details I don t understand... but I am working
> on it :)

If you start to understand things, you could update documentation on the
Wiki to help other people. :)

> So the telepathy-client (tp_caller, or another on) can directly call
> methods of the stream-engine, without passing through the
> connection-manager. Am I right?

Yes, there are three "directions" of communication.

 Client <---> Stream Engine
   |\           /|
    \           /
  A  \         /  B
     \|       |/
  Connection Manager

A: The client talks to the connection manager to arrange the call, which
streams and their media types, etc
B: The connection mananager talk to stream engine to communicate the
codecs and networking information necessary to establish the call.
C: The client talks to the connection manager to see the state of the
streams, which are

> the example of the duration was just an example.
> I may want to inform the telepathy-client of current delay in
> communication; percentage of rebuffering in the buffer-jitter queue...
> What is the best way to bring this information from the stream-engine to
> the telepathy-client?
> Send regularly signals from the stream-engine that will be caught by the
> telepathy-client (without passing through the connection-manager)?
> If yes, this means, as you said, add some signal to the stream engine's api.

Right, you can add API to stream engine if you want to keep using the
architecture above. For more advanced usages, you might be more
interested in the work in this branch:

Although it's not complete, the plan there is to seperate out the parts
of stream engine which just relay information between Farsight (the
streaming library) and the Telepathy streaming API. These can then be
moved into Farsight or a seperate library, which can be used by a
Telepathy client who wants closer access to the Farsight API, monitoring
the Jitter Buffer, etc.

If you need more control than the stream engine API allows for, this
approach might be more elegant than adding more and more stuff to the
API. Some of what stream engine does is quite specific to the Nokis N800
internet tablets, and we think a library would be far more useful in
other situations.

> Thanks again for your help

No problems.

> Matthieu


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