h264: Refactor ff_h264_decode_ref_pic_list_reordering

In preparation for MVC support.

libavcodec/h264_refs.c

@@ -237,75 +237,83 @@ 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) {
-                        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;
-                        }
-
-                        if (reordering_of_pic_nums_idc == 0)
-                            pred -= abs_diff_pic_num;
-                        else
-                            pred += abs_diff_pic_num;
-                        pred &= h->max_pic_num - 1;
-
-                        frame_num = pic_num_extract(h, pred, &pic_structure);
-
-                        for (i = h->short_ref_count - 1; i >= 0; i--) {
-                            ref = h->short_ref[i];
-                            assert(ref->reference);
-                            assert(!ref->long_ref);
-                            if (ref->frame_num == frame_num &&
-                                (ref->reference & pic_structure))
-                                break;
-                        }
-                        if (i >= 0)
-                            ref->pic_id = pred;
-                    } else {
-                        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;
-                        }
-                        ref = h->long_ref[long_idx];
-                        assert(!(ref && !ref->reference));
-                        if (ref && (ref->reference & pic_structure)) {
-                            ref->pic_id = pic_id;
-                            assert(ref->long_ref);
-                            i = 0;
-                        } else {
-                            i = -1;
-                        }
+                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 AVERROR_INVALIDDATA;
+                    }
+
+                    if (reordering_of_pic_nums_idc == 0)
+                        pred -= abs_diff_pic_num;
+                    else
+                        pred += abs_diff_pic_num;
+                    pred &= h->max_pic_num - 1;
+
+                    frame_num = pic_num_extract(h, pred, &pic_structure);
+
+                    for (i = h->short_ref_count - 1; i >= 0; i--) {
+                        ref = h->short_ref[i];
+                        assert(ref->reference);
+                        assert(!ref->long_ref);
+                        if (ref->frame_num == frame_num &&
+                            (ref->reference & pic_structure))
+                            break;
                     }
+                    if (i >= 0)
+                        ref->pic_id = pred;
+                    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 (i < 0) {
-                        av_log(h->avctx, AV_LOG_ERROR, "reference picture missing during reorder\n");
-                        memset(&h->ref_list[list][index], 0, sizeof(Picture)); //FIXME
+                    if (long_idx > 31) {
+                        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));
+                    if (ref && (ref->reference & pic_structure)) {
+                        ref->pic_id = pic_id;
+                        assert(ref->long_ref);
+                        i = 0;
                     } else {
-                        for (i = index; i + 1 < h->ref_count[list]; i++) {
-                            if (ref->long_ref == h->ref_list[list][i].long_ref &&
-                                ref->pic_id   == h->ref_list[list][i].pic_id)
-                                break;
-                        }
-                        for (; i > index; i--) {
-                            COPY_PICTURE(&h->ref_list[list][i], &h->ref_list[list][i - 1]);
-                        }
-                        COPY_PICTURE(&h->ref_list[list][index], ref);
-                        if (FIELD_PICTURE(h)) {
-                            pic_as_field(&h->ref_list[list][index], pic_structure);
-                        }
+                        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");
+                    memset(&h->ref_list[list][index], 0, sizeof(Picture)); // FIXME
                 } else {
-                    av_log(h->avctx, AV_LOG_ERROR, "illegal reordering_of_pic_nums_idc\n");
-                    return -1;
+                    for (i = index; i + 1 < h->ref_count[list]; i++) {
+                        if (ref->long_ref == h->ref_list[list][i].long_ref &&
+                            ref->pic_id   == h->ref_list[list][i].pic_id)
+                            break;
+                    }
+                    for (; i > index; i--) {
+                        COPY_PICTURE(&h->ref_list[list][i], &h->ref_list[list][i - 1]);
+                    }
+                    COPY_PICTURE(&h->ref_list[list][index], ref);
+                    if (FIELD_PICTURE(h)) {
+                        pic_as_field(&h->ref_list[list][index], pic_structure);
+                    }
                 }
             }
         }