Revert r19317, "simplify slice_end, return size of output frame".

It returns non decodable B-frames.

Originally committed as revision 19324 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpeg12.c

@@ -1935,7 +1935,7 @@ static int slice_decode_thread(AVCodecContext *c, void *arg){
 
 /**
  * Handles slice ends.
- * @return sizeof(AVFrame) if a frame is output, 0 otherwise
+ * @return 1 if it seems to be the last slice
  */
 static int slice_end(AVCodecContext *avctx, AVFrame *pict)
 {
@@ -1966,7 +1966,6 @@ static int slice_end(AVCodecContext *avctx, AVFrame *pict)
         if (s->pict_type == FF_B_TYPE || s->low_delay) {
             *pict= *(AVFrame*)s->current_picture_ptr;
             ff_print_debug_info(s, pict);
-            return sizeof(*pict);
         } else {
             s->picture_number++;
             /* latency of 1 frame for I- and P-frames */
@@ -1974,11 +1973,13 @@ static int slice_end(AVCodecContext *avctx, AVFrame *pict)
             if (s->last_picture_ptr != NULL) {
                 *pict= *(AVFrame*)s->last_picture_ptr;
                  ff_print_debug_info(s, pict);
-                 return sizeof(*pict);
             }
         }
+
+        return 1;
+    } else {
+        return 0;
     }
-    return 0;
 }
 
 static int mpeg1_decode_sequence(AVCodecContext *avctx,
@@ -2316,7 +2317,10 @@ static int decode_chunks(AVCodecContext *avctx,
                 if (CONFIG_MPEG_VDPAU_DECODER && avctx->codec->capabilities&CODEC_CAP_HWACCEL_VDPAU)
                     ff_vdpau_mpeg_picture_complete(s2, buf, buf_size, s->slice_count);
 
-                *data_size = slice_end(avctx, picture);
+                if (slice_end(avctx, picture)) {
+                    if(s2->last_picture_ptr || s2->low_delay) //FIXME merge with the stuff in mpeg_decode_slice
+                        *data_size = sizeof(AVPicture);
+                }
             }
             s2->pict_type= 0;
             return FFMAX(0, buf_ptr - buf - s2->parse_context.last_index);