Fix ffmpeg input bug

diff --git a/fgen.sh b/fgen.sh
index df952fa..f7015ed 100755 (executable)
--- a/fgen.sh
+++ b/fgen.sh
@@ -20,7 +20,11 @@ trames=1
 dry_run=0
 
 SED=sed
-FFMPEG_OPTS="-hide_banner -loglevel error -y"
+
+# When reading a file line by line, if a command inside the loop
+# also reads stdin, it can exhaust the input file.
+# -nostdin: disable ffmpeg interaction on standard input:
+FFMPEG_OPTS="-hide_banner -loglevel error -y -nostdin"
 
 # -limit memory 5000mb -limit disk 5gb
 IM_OPS=""