[FFmpeg-cvslog] Fix crash of interlaced MPEG2 decoding

[Anatoly Nenashev]

ffmpeg | branch: master | Anatoly Nenashev <anatoly.nenashev at ovsoft.ru> | Sun Mar 27 21:41:48 2011 +0200| [b44c8ad280c221691560ae9625421416e20c483f] | committer: Reinhard Tartler

Fix crash of interlaced MPEG2 decoding

Problem description, preliminary review discussion at
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/127731

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b44c8ad280c221691560ae9625421416e20c483f
---

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

diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
index f4de8dd..2c0525e 100644
--- a/libavcodec/mpegvideo.c
+++ b/libavcodec/mpegvideo.c
@@ -998,8 +998,13 @@ 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];