[mythtv] filter updates

Andrew Mahone andrewmahone at eml.cc
Fri Jan 2 23:25:04 EST 2004

On Fri, 2 Jan 2004 22:00:33 -0500, "Isaac Richards" <ijr at po.cwru.edu>
> Applied to CVS -- any idea on the recent problems with the filters?
> (see Michael Sherman's backtrace, for instance)  Memory corruption
> somewhere, but I dunno where..
> Isaac

I've been tracking them on and off, with no real results.  I can't get
valgrind to build on my system.  I set up a test system in a a chroot
that I can run valgrind on, but it dies with a floating point exception
when I use filters.

I've only gotten problems w/ the denoise3d since the most recent rewrite
of the MMX code.  It has a very specific trigger, it will happen reliably
if you enter and exit live tv a couple of times w/ denoise3d in the
filter chain, or after a few recordings are run in the backend.

The new conversion filters I'm working on segfault a few seconds after
loading, with no other filters in the chain, and gdb tells me it happens
in mm_support, which is only used during filter init.

I think that possibly some of function pointers in the VideoFilter
structs are getting corrupted.  I'm going to code up a quick hack where
filters allocate an entire page for the VF struct, and then the
FilterManager mprotects it after it finishes filling it in.  If I'm right
about what's happening, that should make it a lot easier to debug, by
triggering a segfault as soon as something tries to write to those pages.
  Andrew Mahone
  andrewmahone AT eml DOT cc

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