diff --git a/demos/video-capture-simple.py b/demos/video-capture-simple.py
index 086dbaa..298e628 100755
--- a/demos/video-capture-simple.py
+++ b/demos/video-capture-simple.py
@@ -76,8 +76,10 @@ def main() -> None:
             # the video, as well as possibly audio and more.  These are each called "streams".  We only create one
             # stream here, since we're just recording video.
             video_stream = avmux.add_stream(CODEC, rate=FPS, options=CODEC_OPTIONS)
-            video_stream.width = monitor["width"]
-            video_stream.height = monitor["height"]
+            # Width and height must be divisible by 2, otherwise the encoder will fail.
+            # Round down to the nearest even number.
+            video_stream.width = monitor["width"] // 2 * 2
+            video_stream.height = monitor["height"] // 2 * 2
             # There are more options you can set on the video stream; the full demo uses some of those.
 
             # Count how many frames we're capturing, so we can log the FPS later.
diff --git a/demos/video-capture.py b/demos/video-capture.py
index 18ff9f0..03c0210 100755
--- a/demos/video-capture.py
+++ b/demos/video-capture.py
@@ -476,8 +476,10 @@ def main() -> None:
                 # so some video encoders will tag it as AVCOL_TRC_BT709 (1) instead.
                 video_stream.color_trc = 13
 
-            video_stream.width = monitor["width"]
-            video_stream.height = monitor["height"]
+            # Width and height must be divisible by 2, otherwise the encoder will fail.
+            # Round down to the nearest even number.
+            video_stream.width = monitor["width"] // 2 * 2
+            video_stream.height = monitor["height"] // 2 * 2
             # There are multiple time bases in play (stream, codec context, per-frame).  Depending on the container
             # and codec, some of these might be ignored or overridden.  We set the desired time base consistently
             # everywhere, so that the saved timestamps are correct regardless of what format we're saving to.