[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




More information about the mythtv-users mailing list