From 32cb43f74ff60d37e809e2e70e751574d6c286b2 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Thu, 2 Dec 2021 20:16:02 +0100
Subject: [PATCH] Fix possible incorrect eye mapping with 3D-alternate sources.

---
 src/lib/video_decoder.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib/video_decoder.cc b/src/lib/video_decoder.cc
index cee4bcdc6..8d6f7e6c7 100644
--- a/src/lib/video_decoder.cc
+++ b/src/lib/video_decoder.cc
@@ -105,7 +105,7 @@ VideoDecoder::emit (shared_ptr<const Film> film, shared_ptr<const ImageProxy> im
 
 		if (vft == VideoFrameType::THREE_D_ALTERNATE) {
 			frame = decoder_frame / 2;
-			eyes = (decoder_frame % 1) ? Eyes::RIGHT : Eyes::LEFT;
+			eyes = (decoder_frame % 2) ? Eyes::RIGHT : Eyes::LEFT;
 		} else {
 			frame = decoder_frame;
 			if (vft == VideoFrameType::THREE_D) {
-- 
2.30.2