h264: Refactor ff_h264_decode_ref_pic_list_reordering

In preparation for MVC support.

libavcodec/h264_refs.c

@@ -237,14 +237,16 @@ int ff_h264_decode_ref_pic_list_reordering(H264Context *h)
                     return -1;
                 }
 
-                if (reordering_of_pic_nums_idc < 3) {
-                    if (reordering_of_pic_nums_idc < 2) {
+                switch (reordering_of_pic_nums_idc) {
+                case 0:
+                case 1: {
                     const unsigned int abs_diff_pic_num = get_ue_golomb(&h->gb) + 1;
                     int frame_num;
 
                     if (abs_diff_pic_num > h->max_pic_num) {
-                            av_log(h->avctx, AV_LOG_ERROR, "abs_diff_pic_num overflow\n");
-                            return -1;
+                        av_log(h->avctx, AV_LOG_ERROR,
+                               "abs_diff_pic_num overflow\n");
+                        return AVERROR_INVALIDDATA;
                     }
 
                     if (reordering_of_pic_nums_idc == 0)
@@ -265,15 +267,18 @@ int ff_h264_decode_ref_pic_list_reordering(H264Context *h)
                     }
                     if (i >= 0)
                         ref->pic_id = pred;
-                    } else {
+                    break;
+                }
+                case 2: {
                     int long_idx;
                     pic_id = get_ue_golomb(&h->gb); // long_term_pic_idx
 
                     long_idx = pic_num_extract(h, pic_id, &pic_structure);
 
                     if (long_idx > 31) {
-                            av_log(h->avctx, AV_LOG_ERROR, "long_term_pic_idx overflow\n");
-                            return -1;
+                        av_log(h->avctx, AV_LOG_ERROR,
+                               "long_term_pic_idx overflow\n");
+                        return AVERROR_INVALIDDATA;
                     }
                     ref = h->long_ref[long_idx];
                     assert(!(ref && !ref->reference));
@@ -284,10 +289,17 @@ int ff_h264_decode_ref_pic_list_reordering(H264Context *h)
                     } else {
                         i = -1;
                     }
+                    break;
+                }
+                default:
+                    av_log(h->avctx, AV_LOG_ERROR,
+                           "illegal reordering_of_pic_nums_idc\n");
+                    return AVERROR_INVALIDDATA;
                 }
 
                 if (i < 0) {
-                        av_log(h->avctx, AV_LOG_ERROR, "reference picture missing during reorder\n");
+                    av_log(h->avctx, AV_LOG_ERROR,
+                           "reference picture missing during reorder\n");
                     memset(&h->ref_list[list][index], 0, sizeof(Picture)); // FIXME
                 } else {
                     for (i = index; i + 1 < h->ref_count[list]; i++) {
@@ -303,10 +315,6 @@ int ff_h264_decode_ref_pic_list_reordering(H264Context *h)
                         pic_as_field(&h->ref_list[list][index], pic_structure);
                     }
                 }
-                } else {
-                    av_log(h->avctx, AV_LOG_ERROR, "illegal reordering_of_pic_nums_idc\n");
-                    return -1;
-                }
             }
         }
     }