Re: [Audacity-devel] FFmpeg libraries for the Mac

[Leland <le...@au...>]

Gale (Audacity Team) wrote:

 > So Audacity looks for the current major version, which at the moment is
 > libavformat-52.dylib, have I got that right?
 >
Correct.  But, OSX has a bit of a limitation in regards to dynamic 
libraries (this is the reason for the installer) ... you can't just put 
the libraries anywhere since the location of their dependencies is 
determined at build time.  So, the installer puts the libraries in 
/usr/local/lib/audacity.

Search for libs on OSX is a bit convoluted: (from the dlopen() manpage)

SEARCHING
      dlopen() searches for a compatible Mach-O file in the directories
      specified by a set of environment variables and the process's
      current working directory.  When set, the environment variables
      must contain a colon-separated list of directory paths, which can
      be absolute or relative to the current working directory. The
      environment variables are LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, and
      DYLD_FALLBACK_LIBRARY_PATH.  The first two variables have no
      default value. The default value of DYLD_FALLBACK_LIBRARY_PATH is
      $HOME/lib;/usr/local/lib;/usr/lib.  dlopen() searches the
      directories specified in the environment variables in the order
      they are listed.

      When path doesn't contain a slash character (i.e. it is just a leaf
      name), dlopen() searches the following the following until it finds
      a compatible Mach-O file: $LD_LIBRARY_PATH, $DYLD_LIBRARY_PATH,
      current working directory, $DYLD_FALLBACK_LIBRARY_PATH.

      When path contains a slash (i.e. a full path or a partial path)
      dlopen() searches the following the following until it finds a
      compatible Mach-O file: $DYLD_LIBRARY_PATH (with leaf name from
      path), current working directory (for partial paths),
      $DYLD_FALLBACK_LIBRARY_PATH (with leaf name from path).

It's not immediately obvious from that description, but the environment 
variables will override ANY path that the user selects via Preferences. 
  They will also override the compiled in /usr/local/lib/audacity path. 
  So, it's possible that Audacity will get a version of the library that 
wasn't the user's choice.  Not much can be done about that.  I'd wager 
this won't be a problem for most users.  However, it drove me bonkers 
for a bit since I have my macports libraries specified in the 
DYLD_LIBRARY_PATH variable and the ffmpeg libs were being pulled from 
there rather than the ones I was telling Audacity to use.

Leland