How to regonize a transport-independent Service?

Question

Hi, in the servicecontext.select() of the javatv doc, it said that if the service is transport-independent, the method should transfor it to transport-dependent. But how do I know the service is a ts-independ or not? Besides, what difference between them(ex: different locator format or something else)??

Answer 1

There is no easy way of recognising this, unfortunately. To be honest, it's pretty unclear what is and isn't a transport-dependent locator when we're discussing this in general terms. SInce JavaTV doesn't define its own locator format, we have to look at the standards that use it.
In MHP, all of the locators in the standard form of dvb://<original_network_id>.<transport_stream_id>.<service_id> are transport-independent: by referring ot the original network ID, the locator makes no assumptions about what transport the service is carried on. A transport-dependent locator (used internally by the receiver, for instance) may add the network ID. This would tie it to a specific transport (i.e. the one that carries that network).
For OCAP and ACAP, the situation is a little more confused. OCAP/ACAP locators may include frequency and modulation information, and OCAP locators may include the 'oobfdc' element that defines the OOB forward data channel. Locators that contain physical information (frequency & modulation type) or the 'oobfdc' element are transport-dependent locators. However, to quote the OCAP spec:
"Applications should not include hard-coded values of these. Locators using them are intended to be dynamically constructed in the ocap receiver based on locally accurate information..." (section 16.2.1.1.2.3.3, OCAP 1.0 profile version I16 - the ACAP sepc contains an almost identical statement).
Other OCAP/ACAP locators are transport independent. In other words, all locatoers that should be directly constructed by an application will be transport-independent.
Of course, a locator may only be available on one transport (e.g. a service that's carried on cable but not on a terrestrial network). In this case, the locator is still transport-independent unless it has been specifically transformed into a transport-dependent form.
Steve.