use the system binaries for ffmpeg and ffprobe

The library mis-match on ubuntu 18.04 seems impossible to fix, so
revert to using the system binaries.

This makes including a subtitle stream impossible for now, but moving
to the concat *filter* had made that pretty much impossible anyway,
because ffmpeg (even in HEAD) does not set the right PTS when the
input is in matroska format.

.gitignore

@@ -9,3 +9,4 @@
 /ffmpeg.git/
 *.log
 ffmpeg.outoftree
+*~

ffmpeg-myth.scm

@@ -15,8 +15,8 @@
 (define mythtv-db "mythconverg")
 (define mysql-row-sep #\newline)
 (define mysql-col-sep #\tab)
-(define ffmpeg-bin "/usr/local/bin/ffmpeg")
-(define ffprobe-bin "/usr/local/bin/ffprobe")
+(define ffmpeg-bin "/usr/bin/ffmpeg")
+(define ffprobe-bin "/usr/bin/ffprobe")
 (define ffprobe-separator #\page) ;; 
 (define recordings-directory "/var/lib/mythtv/recordings")
 (define working-directory "/mnt/lvraid5/ffmpeg-cut-list.d")

ffmpeg-myth.sh

@@ -4,7 +4,8 @@ set -aex
 export LANG=en_US.UTF-8
 export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin"
 # ugly kludge due to upgrade from 16.04 to 18.04 mismatch
-export LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu:/tmp/root-snap-2020-06-28-21-56-27/usr/lib/x86_64-linux-gnu
+# export LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu:/tmp/root-snap-2020-06-28-21-56-27/usr/lib/x86_64-linux-gnu
+export LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu
 unset -v LANGUAGE
 
 working_dir=${working_dir:-"/mnt/lvraid5/ffmpeg-cut-list.d"}