From 99e07a4453732058df90885f80b3db3b4f37cb3c Mon Sep 17 00:00:00 2001
From: anatoly <anatoly.nenashev at>
Date: Tue, 22 Feb 2011 12:04:50 +0300
Subject: [PATCH] Fix crash of interlaced MPEG2 decoding

---
 libavcodec/mpegvideo.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
index 50c99f4a82..6bb35f9f39 100644
--- a/libavcodec/mpegvideo.c
+++ b/libavcodec/mpegvideo.c
@@ -1094,8 +1094,13 @@ int MPV_frame_start(MpegEncContext *s, AVCodecContext *avctx)
         s->pict_type, s->dropable);*/
 
     if(s->codec_id != CODEC_ID_H264){
-        if((s->last_picture_ptr==NULL || s->last_picture_ptr->data[0]==NULL) && s->pict_type!=AV_PICTURE_TYPE_I){
-            av_log(avctx, AV_LOG_ERROR, "warning: first frame is no keyframe\n");
+        if((s->last_picture_ptr==NULL || s->last_picture_ptr->data[0]==NULL) &&
+           (s->pict_type!=AV_PICTURE_TYPE_I || s->picture_structure != PICT_FRAME)){
+            if (s->pict_type != AV_PICTURE_TYPE_I)
+                av_log(avctx, AV_LOG_ERROR, "warning: first frame is no keyframe\n");
+            else if (s->picture_structure != PICT_FRAME)
+                av_log(avctx, AV_LOG_INFO, "allocate dummy last picture for field based first keyframe\n");
+
             /* Allocate a dummy frame */
             i= ff_find_unused_picture(s, 0);
             s->last_picture_ptr= &s->picture[i];