Fix keyframe flag

remove +1 offset.

Bug: webrtc:42225151
Change-Id: Ib735fddfd82f0ae9cfb433648950d936647614a9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/356820
Commit-Queue: Erik Språng <sprang@webrtc.org>
Auto-Submit: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#42616}
diff --git a/modules/video_coding/codecs/test/video_codec_test.cc b/modules/video_coding/codecs/test/video_codec_test.cc
index 3d07a3d..2b144ac 100644
--- a/modules/video_coding/codecs/test/video_codec_test.cc
+++ b/modules/video_coding/codecs/test/video_codec_test.cc
@@ -582,7 +582,8 @@
   uint32_t timestamp_rtp = 90000;
   std::map<uint32_t, EncodingSettings> frame_settings;
   for (int frame_num = 0; frame_num < num_frames; ++frame_num) {
-    encoding_settings.keyframe = (frame_num % (key_interval + 1) == 0);
+    encoding_settings.keyframe =
+        (key_interval > 0 && (frame_num % key_interval) == 0);
     frame_settings.emplace(timestamp_rtp, encoding_settings);
     timestamp_rtp += k90kHz / framerate;
   }