[linux-dvb] LinuxDVB V4 API questions (3)

[Ralph Metzler <rjkm@metzlerbros.de>]

Alasdair FARMER writes:
 > 2)  With regard to playback of recordings I am unclear how this will work in the new model...  If a recorded stream were being written to a demux then which instance (given that the handle is actually to a filter rather than a demux itself).  I am not convinced that a memory frontend is the correct or best solution.  The semantic model I am working with is that the frontend is providing a transport stream to a demux which is filtering and passing the appropriate sub streams on to a decoder/storage.  The f
 > rontend is responsible for presenting a single transport stream to the demux, dealing with any issues of source or routing.  I would actually like to see a write interface on the frontend so that a recorded stream could be written to a frontend (rather than the stream come from a tuner).  This neatly maintains a consistent model and removes some complexity at demux level.  In our scenarios, it is not actually possible to 'write' to a demux anyway, a recorded stream would have to be feed back into what is 
 > essentially a frontend - so for our hardware solutions, we would need a write api on a frontend anyway.  This also simplifies CA considerations.

I proposed using frontends with type memory as input before. Somebody
else then thought one should use general input devices (AFAIR 
Florian Schirmer?). Somehow this got dropped again in favor of 
directly writing to demuxes. But I just checked and it is still
mentioned in the dmx.h file. 
 
I also think that using the demux for memory input does not make much 
sense. Usually you have demux unit with several demuxes and several
inputs and each demux can choose the input it wants to use, 
including memory input. 
So, the "frontend" devices, wether there is an actual frontend, 
memory DMA hardware or something else connected to it (other parallel
or serial inputs from other devices), should correspond to these
inputs. 
These devices should then offer calls for rate control as some memory
DMA interfaces offer them and other calls for other hardware like
firewire, etc. The question is how general you want to make
this. Should the device enumerate capabilities and possible settings 
(like e.g. V4L2 devices) or is it enough to support a standard set 
of input devices?


Ralph


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