[linux-dvb] Re: how to record?

[Marcus O.C. Metzler <mocm@convergence.de>]

Klaus Schmidinger writes:
 > "Marcus O.C. Metzler" wrote:
 > > 
 > > As before, I meant to write /dev/ost/dvr. The output is a
 > > TS. tuxplayer also uses /dev/ost/dvr, but transforms the output to
 > > muxed PES.
 > 
 > Is that muxed PES the same format as is currently delivered by
 > the 0.8.2 driver via the /dev/video device? In that case, maybe it would be
 > better to make VDR do it just the same way instead of reading separate
 > video and audio streams and multiplexing them?
 > 
 > How is the quality of the resulting muxed PES? Does it have the same
 > glitches as the 0.8.2 recordings when replayed - or is it "clean"?
 > 

It is ok for most transponders. I just tested it with ZDF and it had
some glitches. The TS was fine, so there are either some errors in the
ts_to_pes I use in tuxplayer, or the transformation from TS to PES
results in the known problems (large PES are not as bad in a TS as
they are in a PS/PES stream). It probably is the latter, so I will
have to do some remuxing in tuxplayer. This may be easier, because if
the TS has the right muxing, but only very long PES that destroy it if
one waits until one has the entire PES before writing it, you only
have to set a maxmum PES length and than write the smaller PES before
the larger one is finished. Have a look at this example:


TS:

A1 V1 V1 V1 A1 V1 V1 V1 A2 V1 V1 V1 A2 V2 V2 V2

PES now:

|A1 A1| V1 V1 V1 V1 V1 V1 V1 V1 V1| A2 A2 ...   possible audio buffer underflow
  APES                VPES          APES
better PES:

|A1 A1| V1 V1 V1 V1 V1| A2 A2 | V1 V1 V1 V1| ... better 
  APES    VPES          APES    VPES


I did something similar in the driver for creating the TS for the dvr
device, so that the results are better. Of course, this works much
better, if you have the original TS (budget card).


Marcus

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Dr. Marcus Metzler                             
mocm@netcologne.de                     http://www.metzlerbros.de
mocm@convergence.de                    http://www.convergence.de

Convergence Integrated Media GmbH          
Rosenthaler Str. 51                   
D-10178 Berlin                             
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