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Howto speed up DVB Channel zapping ?
http://forum.linhes.org/viewtopic.php?f=11&t=2776		 Page 1 of 1
Author:  the-FoX [ Mon Oct 25, 2004 3:41 am ]
Post subject:  Howto speed up DVB Channel zapping ?
Hello,

i've just setup a new knoppmyth tv-box withj a dvb-t tuner card. everything works fine, but the sometimes the mythbackend hangs up when watching tv and the time between two channels, when zapping, is very long (nearly 4 seconds). is there a solution to reduce the zapping time with dvb cards ?
Author:  the-FoX [ Wed Nov 03, 2004 2:32 am ]
Post subject: 
there's noone out there, hwo has the same problem or a solution for it to reduce the zap-time between two channels below than 10seconds ?

sometimes my mythbackend hangs. could it be a driver problem ? which driver do you have installed for the hauppauge nova-t ?
Author:  Xsecrets [ Wed Nov 03, 2004 9:30 am ]
Post subject: 
well first post you said 4 seconds, and yes it sucks, but 4 seconds is not out of the norm. Besides I think you will find there are only maybe 3 or 4 people active on the forum who have ever tried to setup a dvb card.
Author:  nigelpearson [ Thu Nov 04, 2004 5:54 pm ]
Post subject: 
1) It depends a lot on whether the card has to retune, or if the channel you want to switch to is on the same transponder. Here in Australia, each network has its own frequency, so it is always slow. In Europe, it is potentially faster if the backend just has to get a different stream from the already tuned card

2) Some cards are a little faster than others. I think I have got it down to 3 seconds

3) It also depends on the signal strength. Stronger means no error correction

4) It is also faster if your frontend and backend are on the same PC. Changing channels from my Mac frontend takes up to 8 seconds

5) There are probably un-needed delays in the backend code, but there aren't many people working on improving the DVB/HDTV stuff. The good thing is that 0.16 is reported to be better than 0.15, and it will just keep improving. Gotta love open source!
Author:  cesman [ Thu Nov 04, 2004 7:00 pm ]
Post subject: 
nigelpearson wrote:
Gotta love open source!
Author:  dilmah [ Tue Dec 28, 2004 9:25 pm ]
Post subject: 
One thing I noticed on my box is that after watching one channel for a long time (1-2 hours) and then changing channels, it would take quite a few seconds (more than normal), during which the hard drive was constantly active.
I eventually figured that it was the live tv buffer that was being flushed which was causing this slowdown, and with a 12GB buffer (on a 200GB drive) it could have potentially taken 10 seconds or more. To resolve the problem I reformatted the /cache partiton as xfs and now the problem is solved. XFS is designed to work well with large files, but be careful of storing important things on there as it uses RAM aggressively to cache transfers and disk writes so if you lose power to the box, you may lose data (moreso than with something like ext3). With the /cache partition though, it's a non-issue.

Note however that you may need to recompile the kernel with XFS support for you to be able to mount the partition after you've formatted it.

I don't know this is related to your problem, but it cetainly helped me. :D
Author:  Xsecrets [ Tue Dec 28, 2004 9:30 pm ]
Post subject: 
And before anyone gets too scared of not having XFS support in the kernel all knoppmyth kernels have XFS support in them, so you only have to worry about this if you are using another distribution, or have compiled your own kernel.
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