Fix log formatting when FFmpeg messages contain newline characters.

git-svn-id: svn://daper.net/moc/trunk@2625 910807d9-36e0-0310-a014-e9ea483e2ba4
Fix frames to duration calculations.

In the first case, it was actually the buffer size in bytes
which was being calculated.  In the second case, there was
potential for integer overflow on 32-bit machines and truncation
in the microsecond range (not that anyone would notice).

git-svn-id: svn://daper.net/moc/trunk@2626 910807d9-36e0-0310-a014-e9ea483e2ba4