From fc268542a3df935294f7319f785b08dcaeab86c9 Mon Sep 17 00:00:00 2001
From: Francois Savard <46498565+fsavard-eai@users.noreply.github.com>
Date: Tue, 29 Oct 2019 13:24:48 +0000
Subject: [PATCH] Fixing issue #1530 by starting ann_id to 1 in
 convert_to_coco_api

---
 references/detection/coco_utils.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/references/detection/coco_utils.py b/references/detection/coco_utils.py
index efbbdd3f4ea..26701a2cbee 100644
--- a/references/detection/coco_utils.py
+++ b/references/detection/coco_utils.py
@@ -145,7 +145,8 @@ def _has_valid_annotation(anno):
 
 def convert_to_coco_api(ds):
     coco_ds = COCO()
-    ann_id = 0
+    # annotation IDs need to start at 1, not 0, see torchvision issue #1530
+    ann_id = 1
     dataset = {'images': [], 'categories': [], 'annotations': []}
     categories = set()
     for img_idx in range(len(ds)):