lavf/image2: extend start_number range to accept zero

Address trac ticket #2884.

doc/muxers.texi

@@ -260,7 +260,7 @@ ffmpeg -i in.avi -f image2 -frames:v 1 img.jpeg
 @table @option
 @item start_number @var{number}
 Start the sequence from @var{number}. Default value is 1. Must be a
-positive number.
+non-negative number.
 
 @item -update @var{number}
 If @var{number} is nonzero, the filename will always be interpreted as just a

libavformat/img2enc.c

@@ -142,7 +142,7 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
 static const AVOption muxoptions[] = {
     { "updatefirst",  "continuously overwrite one file", OFFSET(update),  AV_OPT_TYPE_INT, { .i64 = 0 }, 0,       1, ENC },
     { "update",       "continuously overwrite one file", OFFSET(update),  AV_OPT_TYPE_INT, { .i64 = 0 }, 0,       1, ENC },
-    { "start_number", "set first number in the sequence", OFFSET(img_number), AV_OPT_TYPE_INT,  { .i64 = 1 }, 1, INT_MAX, ENC },
+    { "start_number", "set first number in the sequence", OFFSET(img_number), AV_OPT_TYPE_INT,  { .i64 = 1 }, 0, INT_MAX, ENC },
     { "strftime",     "use strftime for filename", OFFSET(use_strftime), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, ENC },
     { NULL },
 };

libavformat/version.h

@@ -31,7 +31,7 @@
 
 #define LIBAVFORMAT_VERSION_MAJOR 55
 #define LIBAVFORMAT_VERSION_MINOR 14
-#define LIBAVFORMAT_VERSION_MICRO 101
+#define LIBAVFORMAT_VERSION_MICRO 102
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \