Re: [tvcontrol-api] Why retrieve a list of tuners instead of just one tuner?

@AMorgaut thanks for the feedback.  Most set-top boxes today have 
multiple tuners, and so this is definitely an area that needs careful 
handling.  Experience has shown me that, as you say, trying to be too 
clever with tuner usage leads to unpredictable behaviour and confusion
 for end users (since you can successfully re-use tuners in some cases
 but not others, and the interaction between different use cases is 
complex). This is why I tend to prefer an approach which makes tuner 
management more explicit, like the API currently does: other standards
 that I've been involved with have taken similar approaches for the 
same reason. There is still scope for some optimization by the 
hardware implementer if they want to do so, but it gives 
predictability to the developer and end user.

> Some tuners can sometimes read broadcast stream from different kind 
of sources. So instead of embedding a DVB Terrestrial tuner + a DVB 
Cable Tuner + a ATSC (Cable /Terrestrial) Tuner so your SmartTV or STB
 can be used in more countries on both Terrestrial & Cable signals, a 
constructor might only expose a single Tuner which will switch its 
reception mode depending on the available TVSources.

You're right that this is a good reason to separate TVTuner and 
TVSource, and it is probably worth documenting clearly this in the 
spec.  One of my concerns is that the relationship between the two 
classes is not well specified - re-reading the spec, this is implicit 
but isn't actually stated anywhere..  This may be something that needs
 to go in the introduction (or in the definitions of the TVTuner and 
TVSource classes) so that we have a common understanding between 
implementers of the API and developers using the API.

> You should hardly have in runtime concurrent DVB & ATSC TVSources on
 a TVTuner, but I think that concurrent DVB-T & DVB-C sources is a 
pretty common use cases. As an example an operator client had a 
limitation on the number of channels it could push to its end-users. 
So it wanted to limit cable channels to only those that were not 
available through Terrestrial signal and merge both of the channel 
lists. So having a Tuner that can switch between the 2 TVSources is 
here pretty useful.

Agreed, but I think we need to make sure that the developer can 
distinguish this case from the case where there are two physical 
tuners that are not switchable between different source types: this is
 where we may need some extra text to clarify this.

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Received on Tuesday, 19 July 2016 11:09:55 UTC