From 497431a5b645ffc39cf3acbd333c9ff0f3031adb Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michaelni@gmx.at>
Date: Fri, 9 Apr 2010 22:39:39 +0000
Subject: [PATCH] Dont try to compute AVPacket duration for possibly interlaced
 video codecs when no parser is available. This partly fixes the frame rate
 misdetection in issue1756.

Originally committed as revision 22824 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavformat/utils.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavformat/utils.c b/libavformat/utils.c
index aa779ed80d..eaa912612f 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -739,6 +739,11 @@ static void compute_frame_duration(int *pnum, int *pden, AVStream *st,
             if (pc && pc->repeat_pict) {
                 *pnum = (*pnum) * (1 + pc->repeat_pict);
             }
+            //If this codec can be interlaced or progressive then we need a parser to compute duration of a packet
+            //Thus if we have no parser in such case leave duration undefined.
+            if(st->codec->ticks_per_frame>1 && !pc){
+                *pnum = *pden = 0;
+            }
         }
         break;
     case AVMEDIA_TYPE_AUDIO: