[mythtv-users] Experimenting with TFW_DEF_BUF_SIZE to minimize HDTV IOBOUND errors

[Yeechang Lee]

Daniel Kristjansson <danielk at cuymedia.net> says:
> However if you are using the DVB recorder or HDTV recorder
> there is a param in Setup:TV Settings:General, on the third
> page called "HD Ringbuffer size".

I've had this setting at the maximum 96MB since about the second day I
started using MythTV. However, didn't 0.18 have a caption on this
setting that implied (to me, at least) that it dealt with LiveTV
rather than recordings? Or am I imagining things?

> (To big a buffer can give you thrashing which destroys performance.)

This is only an issue if the backend starts to swap, right? I now have
1.5GB of RAM and never see any swap use any more.

In an ideal situation the ringbuffer should always be empty, or close
to so, as data flows from the original source, through it, then to
disk, correct?

> BTW you do not have to eliminate the IOBOUND warnings, you just
> have to minimize the length of time they are in effect so that
> you don't fill your HD Ringbuffer in the interval between the
> start and end of the IOBOUND state.

That's good to know. Does two FireWire inputs + one ATSC card =
7.2MB/s = 13.3 seconds grace period for an IOBOUND to end before the
ringbuffer (assuming maximum) overflows?

-- 
Yeechang Lee <ylee at pobox.com> | +1 650 776 7763 | San Francisco CA US