[linux-dvb] Re: Reception of raw TS or multiple PIDS

[Marcus Metzler <mocm@metzlerbros.de>]

Gregor Lawatscheck writes:
 > At 20:19 07/02/2003, you wrote:
 > >But I think dvbstream can only handle one video- and one audio-PID.
 > 
 > AFAIK dumping a PS requires one video and one audio PID - if you get TS 
 > from the card you can specify more PIDs (and the special 8192 PID to dump 
 > the entire transponder on the budget cards)....
 > 

The distinction between video and audio PES PIDs is some legacy from
the way the full featured cards are constructed. It is used to define
which PIDs are decoded. In principle one only needs to distinguish
between PES and Section PIDs.

 > > > As far as I know you can do this with budget cards and also with
 > > > full-featured cards when you apply a so called 'budget-patch'.
 > > >
 > > > Searching on this list you can find the link to the budget-patch, but I
 > > > never used it, so I can't say it for sure.
 > >
 > >I've followed the thread of of the patch as I'm interested myself, but
 > >there seem to be problems as this is maintained sporadically.
 > 
 > Hang on, is this a software-only patch? I'm puzzled now, because I'm sure 
 > it looked like you had to use a soldering iron...
 > 

No, you need some soldering.


 > Anyway - it would be great if someone could tell the list the difference 
 > between "filtered" and "unfiltered" TS. If I understand correctly one can 
 > get a so called "filtered" TS (transport stream) from a full featured 
 > DVB-card. Furthermore if I undersand correctly vdr uses these TS streams 
 > (filtered if from a full card, unfiltered when from a budet card) when 
 > recording and pipes them through remux.c to save a PES to the disk.
 > 

The unfiltered TS is the transport stream just as it comes from the
source (sat, cable, ...). The budget hardware just gives you this
unfiltered TS, no filters no changes. The av711x of the full featured
card comes with a firmware that, with the help of the av711x hardware,
takes the TS apart before one can get at it. We can't change this part
of the firmware and we don't know anything about the hardware registers.

 > When doing so it ignores the PTS used for A/V sync -- either because they 
 > are already correct in the "filtered" TS (but then what about unfiltered 
 > streams from budget cards) or because it's reckoned that PTS is not needed. 
 > Could someone please enlighten me on this issue?

It ignores the PCR because we couldn't get at that information with
the full-featured cards. Now we can get the original TS packets, but
the DVB card's mpeg decoder is synching on the PTS only, which should 
still be in the PES. If you want to create a correct MPEG program
stream (PS) you need to include SCR information, which you can only
get from the PCR without analysing the entire stream.
There is also the additional problem that PES in TS can be longer than
the PES in a PS. Which requires you to repack the PES.

Marcus

-- 
/--------------------------------------------------------------------\
| Dr. Marcus O.C. Metzler        |                                   |
|--------------------------------|-----------------------------------|
| mocm@metzlerbros.de            | http://www.metzlerbros.de/        |
\--------------------------------------------------------------------/

 


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