[mythtv-users] HDTV on Myth -- is it a "myth?"

[Donavan Stanley]

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.