decode mpeg-2 closed gop first b frames, fix issue #824

Originally committed as revision 18837 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpeg12.c

@@ -30,6 +30,7 @@
 #include "avcodec.h"
 #include "dsputil.h"
 #include "mpegvideo.h"
+#include "mpegvideo_common.h"
 
 #include "mpeg12.h"
 #include "mpeg12data.h"
@@ -2139,7 +2140,7 @@ static void mpeg_decode_gop(AVCodecContext *avctx,
     int drop_frame_flag;
     int time_code_hours, time_code_minutes;
     int time_code_seconds, time_code_pictures;
-    int closed_gop, broken_link;
+    int broken_link;
 
     init_get_bits(&s->gb, buf, buf_size*8);
 
@@ -2151,7 +2152,7 @@ static void mpeg_decode_gop(AVCodecContext *avctx,
     time_code_seconds = get_bits(&s->gb,6);
     time_code_pictures = get_bits(&s->gb,6);
 
-    closed_gop  = get_bits1(&s->gb);
+    s->closed_gop = get_bits1(&s->gb);
     /*broken_link indicate that after editing the
       reference frames of the first B-Frames after GOP I-Frame
       are missing (open gop)*/
@@ -2160,7 +2161,7 @@ static void mpeg_decode_gop(AVCodecContext *avctx,
     if(s->avctx->debug & FF_DEBUG_PICT_INFO)
         av_log(s->avctx, AV_LOG_DEBUG, "GOP (%2d:%02d:%02d.[%02d]) closed_gop=%d broken_link=%d\n",
             time_code_hours, time_code_minutes, time_code_seconds,
-            time_code_pictures, closed_gop, broken_link);
+            time_code_pictures, s->closed_gop, broken_link);
 }
 /**
  * Finds the end of the current frame in the bitstream.
@@ -2354,8 +2355,17 @@ static int decode_chunks(AVCodecContext *avctx,
                 int mb_y= start_code - SLICE_MIN_START_CODE;
 
                 if(s2->last_picture_ptr==NULL){
-                /* Skip B-frames if we do not have reference frames. */
-                    if(s2->pict_type==FF_B_TYPE) break;
+                /* Skip B-frames if we do not have reference frames and gop is not closed */
+                    if(s2->pict_type==FF_B_TYPE){
+                        int i;
+                        if(!s2->closed_gop)
+                            break;
+                        /* Allocate a dummy frame */
+                        i= ff_find_unused_picture(s2, 0);
+                        s2->last_picture_ptr= &s2->picture[i];
+                        if(alloc_picture(s2, s2->last_picture_ptr, 0) < 0)
+                            return -1;
+                    }
                 }
                 if(s2->next_picture_ptr==NULL){
                 /* Skip P-frames if we do not have a reference frame or we have an invalid header. */

libavcodec/mpegvideo.c

@@ -2107,6 +2107,7 @@ void ff_mpeg_flush(AVCodecContext *avctx){
     s->current_picture_ptr = s->last_picture_ptr = s->next_picture_ptr = NULL;
 
     s->mb_x= s->mb_y= 0;
+    s->closed_gop= 0;
 
     s->parse_context.state= -1;
     s->parse_context.frame_start_found= 0;

libavcodec/mpegvideo.h

@@ -312,6 +312,7 @@ typedef struct MpegEncContext {
     int *lambda_table;
     int adaptive_quant;         ///< use adaptive quantization
     int dquant;                 ///< qscale difference to prev qscale
+    int closed_gop;             ///< MPEG1/2 GOP is closed
     int pict_type;              ///< FF_I_TYPE, FF_P_TYPE, FF_B_TYPE, ...
     int last_pict_type; //FIXME removes
     int last_non_b_pict_type;   ///< used for mpeg4 gmc b-frames & ratecontrol