[mythtv-users] HDTV on Myth -- is it a "myth?"
John Patrick Poet
john at BlueSkyTours.com
Wed Oct 13 15:34:54 UTC 2004
On Tue, 12 Oct 2004, Donavan Stanley wrote:
> On Tue, 12 Oct 2004 11:49:37 -0600, Brandon Beattie
> <brandon+myth at linuxis.us> wrote:
> >
> >
> > On Tue, Oct 12, 2004 at 10:45:10AM -0600, John Patrick Poet wrote:
> > >
> > > On Tue, 12 Oct 2004, Brandon Beattie wrote:
> > >
> > > > As for hard drive access causing the audio/video corruption I doubt it,
> > > > because I've rewound and watched the segment again and it is still
> > > > there.
> > >
> > >
> > > I have watched a show just a few minutes behind as it was recording. My
> > > backend was doing lot's of other tasks and I was seeing pixelization. I
> > > could rewind, and see the exact same pixelization.
> > >
> > > I shut down those other tasks, and the pixelization went away. I could
> > > rewind back to the begining and see the pixelization, but once I caught up
> > > to the point where I shut down the other processes, the corruption was gone.
> > >
> > > I never see any errors in the mythbackend log indicating it could not write
> > > to the disk fast enough, but it sure looks like that can happen. Maybe it
> > > is not a problem with myth writing the file, but with myth reading from the
> > > HD-2000 buffer fast enough? Maybe the HD-2000 driver needs a larger buffer?
> > >
> > > John
> >
> > I've wondered about this for some time, but have not had time to prove
> > it. I also thought that the kernel should take care of holding the data
> > in memory until it has the time to write it to disk? Am I wrong with
> > this thought? Adding a buffer may be helpful though.
>
> The data *is* buffered both by Myth and the filesystem (if you're
> using a decent one). In fact the buffering in Myth was recently
> optimized to reduce the disk io for HDTV folks.
Yes, and the new optimizations are effective. Before I actually would
occasionally see messages in the backend log indicating a problem writing
data to the disk.
I have to really *load up* the machine before I have any problems. It would
just be nice if the system could still work flawlessly even with such a
load. If there is something that can be fixed, I am guessing it is in the
HD-2000 driver.
John
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