avcodec/h264: Partially decode and display single fields try #2

This like the previous attempt does not fully correctly decode this
type of non standard H.264, but it now works fully automatic
requiring no manual filters or flags to be used

See Ticket2254
Reviewed-by: Kieran Kunhya <kierank@obe.tv>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/h264.c

@@ -762,7 +762,10 @@ static void decode_postinit(H264Context *h, int setup_finished)
          * yet, so we assume the worst for now. */
         // if (setup_finished)
         //    ff_thread_finish_setup(h->avctx);
-        return;
+        if (cur->field_poc[0] == INT_MAX && cur->field_poc[1] == INT_MAX)
+            return;
+        if (h->avctx->hwaccel || h->missing_fields <=1)
+            return;
     }
 
     cur->f.interlaced_frame = 0;
@@ -1912,6 +1915,29 @@ static int h264_decode_frame(AVCodecContext *avctx, void *data,
             if (!h->next_output_pic->recovered)
                 h->next_output_pic->f.flags |= AV_FRAME_FLAG_CORRUPT;
 
+            if (!h->avctx->hwaccel &&
+                 (h->next_output_pic->field_poc[0] == INT_MAX ||
+                  h->next_output_pic->field_poc[1] == INT_MAX)
+            ) {
+                int p;
+                AVFrame *f = &h->next_output_pic->f;
+                int field = h->next_output_pic->field_poc[0] == INT_MAX;
+                uint8_t *dst_data[4];
+                int linesizes[4];
+                const uint8_t *src_data[4];
+
+                av_log(h->avctx, AV_LOG_DEBUG, "Duplicating field %d to fill missing\n", field);
+
+                for (p = 0; p<4; p++) {
+                    dst_data[p] = f->data[p] + (field^1)*f->linesize[p];
+                    src_data[p] = f->data[p] +  field   *f->linesize[p];
+                    linesizes[p] = 2*f->linesize[p];
+                }
+
+                av_image_copy(dst_data, linesizes, src_data, linesizes,
+                              f->format, f->width, f->height>>1);
+            }
+
             ret = output_frame(h, pict, h->next_output_pic);
             if (ret < 0)
                 return ret;

libavcodec/h264.h

@@ -740,6 +740,8 @@ typedef struct H264Context {
 
     int has_recovery_point;
 
+    int missing_fields;
+
     int luma_weight_flag[2];    ///< 7.4.3.2 luma_weight_lX_flag
     int chroma_weight_flag[2];  ///< 7.4.3.2 chroma_weight_lX_flag
 

libavcodec/h264_slice.c

@@ -1663,9 +1663,11 @@ int ff_h264_decode_slice_header(H264Context *h, H264Context *h0)
             if (!FIELD_PICTURE(h) || h->picture_structure == last_pic_structure) {
                 /* Previous field is unmatched. Don't display it, but let it
                  * remain for reference if marked as such. */
+                h0->missing_fields ++;
                 h0->cur_pic_ptr = NULL;
                 h0->first_field = FIELD_PICTURE(h);
             } else {
+                h0->missing_fields = 0;
                 if (h0->cur_pic_ptr->frame_num != h->frame_num) {
                     ff_thread_report_progress(&h0->cur_pic_ptr->tf, INT_MAX,
                                               h0->picture_structure==PICT_BOTTOM_FIELD);