[linux-dvb] Re: setting voltage takes TONS of time

[Johannes Stezenbach <js@convergence.de>]

On Wed, Jul 31, 2002 at 07:01:01AM -0400, Jeremy Hall wrote:
> It's a Hauppauge DVB/S card.  I can try each patch applied individually,
> instead of all the patches at once and see what the times are, but this
> machine must run LL tasks and they have real-time constraints.
> 
> I need the firm timers patch because I am trying to sleep for 8ms and only
> 8 ms.  Is the line:
> 
> setPIDS (0,0,0,0,0);
> 
> really necessary? I can get under 8ms if I remove that.  But I'm not going
> to do anything until I have a good game plan.  What is the recommended way
> to attack this?

Sorry, I should've read your mail more carefully.

11ms for SEC_SET_VOLTAGE is considered normal, as communication
with the ARM processor on the DVB-S card is required as well as
I2C bus transactions to the QPSK demodulator (which drives the
LNB voltage control).

If you invalidate the transport stream by SEC_SET_VOLTAGE, you must
shut down the PES filters and/or MPEG decoder first, as the ARM
might crash when it gets invalid TS data. The setPIDS(0,0,0,0,0) does
that. So it cannot be omitted, but maybe it might help you to
split the operation in two parts to meet your 8ms contraint?


Johannes


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