avformat/concatdec: Enable auto_convert by default

Users have no means to find out from a failure how to make it work
or is it preferred to check and print a warning for h264 concat without auto_convert ?
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/demuxers.texi

@@ -151,6 +151,7 @@ probed and 0 otherwise.
 @item auto_convert
 If set to 1, try to perform automatic conversions on packet data to make the
 streams concatenable.
+The default is 1.
 
 Currently, the only conversion is adding the h264_mp4toannexb bitstream
 filter to H.264 streams in MP4 format. This is necessary in particular if

libavformat/concatdec.c

@@ -627,7 +627,7 @@ static const AVOption options[] = {
     { "safe", "enable safe mode",
       OFFSET(safe), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 1, DEC },
     { "auto_convert", "automatically convert bitstream format",
-      OFFSET(auto_convert), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, DEC },
+      OFFSET(auto_convert), AV_OPT_TYPE_INT, {.i64 = 1}, 0, 1, DEC },
     { NULL }
 };