Questions regarding new Info Service (Cara 6)

[owl102]

The documentation about the new Info Service says:

"Introduced in Cara 6, this service should allow a subscribing control point to report on what is currently being played without having to know which source is currently active."

But I want to know what source is currently active when receiving an event from the Info Service. But how?

Another question: Since there can only be one source playing, why is "TransportState" not part of the Info Service?

[grahamd Linn Staff]

Hi owl102,

Since the Product service is central to establishing the list of sources and the current source in each room, it doesn't seem appropriate to repeat this information in the info service.

But as you suggest, there is certainly a case for including transport state. However, it would then seem reasonable to include some equivalent source-independent method of transport control as well. This needs to be thought about.

Thanks
Graham

[owl102]

(2010-04-06 11:40)grahamd Wrote:  Since the Product service is central to establishing the list of sources and the current source in each room, it doesn't seem appropriate to repeat this information in the info service.

But if I receive an event from the Info Service, how could I determine from which source this event was generated? If I subscribe to the Product Service additionally, I get events about the actual source index. But this event could be delivered right after the event from the Info Service, i.e. too late!?

Quote:But as you suggest, there is certainly a case for including transport state. However, it would then seem reasonable to include some equivalent source-independent method of transport control as well.

Yes, this would be great.

I really love the idea of the new Info Service and immediately started to code some kind of very small DS-Info application which simply displays the most relevant information to the user: Which track is actually playing from which source and what is the current transport state. It would be great if subscribing to the Info Service would be sufficient in the near future - IMHO this would make life much easier for developers.

Same with Leia: I really would like to drop the subscription to the Ds and the Radio service. For Cara I only needed to subscribe to 2 services. For Cara6 I need to subscribe to 5 services instead. (And I'm still struggling with keeping the events from all these services in sync.)

Warm regards,
Axel

[grahamd Linn Staff]

Hi Axel,

I'm afraid that establishing a comprehensive picture of the Hi-Fi system in a house using one service is not really possible.

This is because there may be more than one physical box in a single room, with each box bearing a Product service, and each of those Product services bearing different sources.

That is why the Product service is arranged as it is, with the names of the sources and the names of the products arranged to allow a control point to establish the connections that exist between different products in the same room.

The Product service is concerned with topology. We would like to keep it separate, because we would expect every control point to subscribe to all the Product services in a house all the time.

The control point is then expected to subscribe and unsubscribe from the other services depending on what the current source is.

However, I'm glad you can see the direction we are going in here, and glad that the idea of moving towards a source-independent Info service is in line with what you want.

What I think we should be able to agree on is that a control point author should be able to write a basic control point by subscribing to two services: Product and Info, although if the Info service were to be enhanced in the direction we are discussing here, I would be happier if it were called the Source service, or the CurrentSource service.

Anyway, thank you very much for your feedback. I'm afraid the full implementation of these ideas might take a little while, but with your help in the design we should be able to end up with something that you are happy with.

Best regards
Graham

[owl102]

Hi Graham,

I see your point (and agree that the control point should build up the picture of the hifi-system and not the DS) but I think you have misunderstand me. My basic question was: If I get an event via the Info service from a specific DS, how do I know if it comes from the Playlist or the Radio service inside this particular DS? For example: I get "<e:property><TrackCount>34</TrackCount>...<Uri>http://..." How do I know what service has changed the Uri, the Playlist service or the Radio service?

Warm regards,
Axel

P.S.: Your remarks have helped me a lot to sharpen the picture of the new topology inside my head and how I will (re-)design the next generation of Leia inside. Thanks a lot!