[mythtv-users] Why does going to live TV take so long?

Marco Nelissen marcone at xs4all.nl
Sat Mar 11 07:41:59 UTC 2006


>Just shooting from the hip here. Could the long delay have something to do
>with the amount of data thats buffered before writing it to the hard drive?
>If the system buffers 1 meg of data before writing it to the disk then it
>could take several seconds to accumulate the needed data. I know when my
>system is recording a program (pvr-250) the drive light flashes about once
>every 2-3 seconds which means that somewhere the system is buffering large
>amounts of data. I am not linux savy enough to figure out where that might
>be but my system is saving to a LVM group running the XFS file system.

I thought it was something like that too, like the backend doing lots
of buffering to combine writes. There's a 'ringbuffer' setting that seems
to hint at this, but changing (lowering) it didn't appear to have any effect.

>Would it be possible to reduce the amount of info buffered on the write
>cycle? Read buffering is probably a good idea.

If you remove/reduce the buffering for writing, but then add the same
amount of buffering for reading, then live TV will still be equally
slow to start.


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