[vdr] Some questions

[Dennis Noordsij <dennis.noordsij@wiral.com>]

Hi,

I am currently struggling to get acceptable (2 recordings on 2 cards, 1 
playback on primary card) performance on a P1-133. While it is possible it 
just doesn't have the beef to do this, this machine was hot stuff when I got 
it like 100 years ago, and it would be nice to put it back into service.

If I make a small test program, which tunes the card(s), and then runs the 
equivalent of pesdump it can read the specified streams without any problems 
or any noticable CPU usage (playing with mplayer does show the right stream 
is being correctly recorded).

I imagine the actual work involved in just shuffling data around between cards 
and disks should not really be limited by the CPU. (Disks have DMA enabled, 
and give 12 mbyte/sec in mdma mode (no udma here :-)

Which brings us to my question of what really needs to happen for VDR to do 
it's thing. Video / Audio synchronization I guess needs a kind of elementary 
parsing of the streams in order to line up the correct data so everything is 
in sync. If it is a "read header, read timestamp, read length of packet, skip  
to next header" thing it shouldn't be too hard, but if it needs to scan all 
the data looking for markers it might become a problem. Any docs on this 
issue? Example programs which take care of this and might be quicker to jump 
into than the VDR sourcecode?

In some cases (for example cutting) it is necessary to break down the video 
stream info frames, in order to be able to work on I-frame boundaries. But 
for strict "read a few PID's from transponder A on card 1, read some from 
transponder B on card 2, write a video and audio stream to card 1" type use, 
i.e. basic VDR stuff, how much parsing of the incoming data needs to be done? 
If you disable cutting mode, is there still a need for determining I-frame 
boundaries at all? 

How many (re/de)mux processes occur inside VDR during normal use? Which could 
be simplified to increase performance, while possibly crippling some 
features?

Sorry for all these questions, I am trying to scrape together the info from 
mailing lists and example programs as well. 

Cheers,
Dennis

PS - Klaus, I got the highlight-in-the-program-schedule 
shows-that-are-marked-for-recording thing working, but it's a dirty thing and 
I'll look at it again after I get the VDR box all set up :-) 




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