libavformat: Use AVFormatContext.probesize in init_input

This was forgotten in the transition from av_open_input_file to
avformat_open_input, see 603b8bc2.

This doesn't change anything for the default case where the
option isn't set, since PROBE_BUF_MAX is 1048576 (which was
used as max probe size earlier) while the default value for
the probesize option is 5000000, which for the probe function
is clipped to PROBE_BUF_MAX anyway.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/utils.c

@@ -480,7 +480,7 @@ static int init_input(AVFormatContext *s, const char *filename, AVDictionary **o
     if (s->pb) {
         s->flags |= AVFMT_FLAG_CUSTOM_IO;
         if (!s->iformat)
-            return av_probe_input_buffer(s->pb, &s->iformat, filename, s, 0, 0);
+            return av_probe_input_buffer(s->pb, &s->iformat, filename, s, 0, s->probesize);
         else if (s->iformat->flags & AVFMT_NOFILE)
             return AVERROR(EINVAL);
         return 0;
@@ -495,7 +495,7 @@ static int init_input(AVFormatContext *s, const char *filename, AVDictionary **o
         return ret;
     if (s->iformat)
         return 0;
-    return av_probe_input_buffer(s->pb, &s->iformat, filename, s, 0, 0);
+    return av_probe_input_buffer(s->pb, &s->iformat, filename, s, 0, s->probesize);
 }
 
 static AVPacket *add_to_pktbuf(AVPacketList **packet_buffer, AVPacket *pkt,