rtpenc: Write a log message if the max packet size is too small

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/rtpenc.c

@@ -108,8 +108,10 @@ static int rtp_write_header(AVFormatContext *s1)
                                  NTP_OFFSET_US;
 
     max_packet_size = s1->pb->max_packet_size;
-    if (max_packet_size <= 12)
+    if (max_packet_size <= 12) {
+        av_log(s1, AV_LOG_ERROR, "Max packet size %d too low\n", max_packet_size);
         return AVERROR(EIO);
+    }
     s->buf = av_malloc(max_packet_size);
     if (s->buf == NULL) {
         return AVERROR(ENOMEM);