[linux-dvb] Re: Questions about new API

[Johannes Stezenbach <js@convergence.de>]

Dave Chapman wrote:
> 
> As I understand it, if you want the DVB card to do something with the
> transport stream, then you have to use the demux API, and specify the
> destination of the individual PES packets to be either:
> 
> a) DMX_OUT_DECODER if you want the hardware to decode the data, or
> 
> b) DMX_OUT_TAP / DMX_OUT_TS_TAP if you want your application to process or
> record the data.
> 
> My question concerns doing both of the above at the same time - how can I
> record or otherwise process a live stream whilst also directing it to the
> decoder?
> 
> If I try to set two different filters on the same PID, I get an error message
> saying "Device or resource busy".  I'm using version 0.8.2 of the driver with
> a 2.2.17 Kernel.


I think it is a limitation of the ARM firmware on the Siemens
card which prevents you from setting more than one filter
for the same PID. The driver works around that by implicitly
feeding the video and audio streams to the MPEG decoder when you
set a filter with DMX_OUT_[TS_]TAP. That's OK because the
PCI bridge on the card is also limited, which prevents you
from sending another TS to the MPEG decoder while recording a TS
from the demux.

I have no idea what the driver does for other cards.
The API does not impose any limitations here, though.

If setting two filters with DMX_OUT_[TS_]TAP and DMX_OUT_DECODER
for the same PID works with other cards, then the driver for
the Siemens card should handle that, too (so applications
can be written driver independent).


Regards,
Johannes


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