[linux-dvb] Questions about new API

[Ralph Metzler <rjkm@convergence.de>]

Marcus O.C. Metzler writes:
 > Dave Chapman writes:
 >  > I have been experimenting with the new API, and I have a question about how 
 >  > the new API is supposed to be used which I hope that someone on this list can 
 >  > answer.
 >  > 
 >  > 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?
 > 
 > Try the program test_dmx in the apps/test directory for sending a
 > stream to /dev/ost/dvr and the following (which should also be in the
 > CVS, but isn`t) for recording. The pids here are for n-tv. So you have
 > to be tuned to n-tv in order for it to work, or you have to add some
 > tuning code and set different pids. In any case, if you want to work
 > with the new linux dvb api you should check out the latest sources
 > from http://www.linuxtv.org/cvs.


I want to explain this a little bit more. 

I assumed that it only makes sense to set one PES filter of type
PES_VIDEO, one of type PES_AUDIO, etc. 
(At least nobody at Nokia, who wrote the first versions of the API, 
complained about this interpretation yet).

Those filters are the ones being used as input for the decoder, no
matter what output is specified. Maybe the first input type should
have been call DMX_OUT_DECODER_ONLY instead.
So, for those filters the TAP or TS_TAP for recording through
/dev/ost/demux or /dev/ost/dvr is an additional feature. 
If you want to record more streams (also video or audio) through the
dvr device but do not want them displayed you specify them as PES_OTHER.


Ralph


 


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