diff --git a/app.py b/app.py
index 4f96d7b..0dbd257 100644
--- a/app.py
+++ b/app.py
@@ -128,7 +128,8 @@ def process_video():
         scale_percentage = data.get('scale_percentage', 100)
         if scale_percentage != 100:
             # Scale based on percentage - ffmpeg will apply this after crop
-            scale_filter = f"scale=iw*{scale_percentage/100}:ih*{scale_percentage/100}"
+            # Force dimensions divisible by 2 for H.264 compatibility
+            scale_filter = f"scale=trunc(iw*{scale_percentage/100}/2)*2:trunc(ih*{scale_percentage/100}/2)*2"
             filters.append(scale_filter)
         
         # Apply filters if any
diff --git a/templates/index.html b/templates/index.html
index 6a8b54c..5cd7383 100644
--- a/templates/index.html
+++ b/templates/index.html
@@ -845,8 +845,9 @@
             const cropWidth = parseInt(document.getElementById('crop-width').value) || videoInfo.width;
             const cropHeight = parseInt(document.getElementById('crop-height').value) || videoInfo.height;
             
-            const outputWidth = Math.round((cropWidth * scalePercentage) / 100);
-            const outputHeight = Math.round((cropHeight * scalePercentage) / 100);
+            // Round to nearest even number for H.264 compatibility
+            const outputWidth = Math.round((cropWidth * scalePercentage) / 100 / 2) * 2;
+            const outputHeight = Math.round((cropHeight * scalePercentage) / 100 / 2) * 2;
             
             outputResolution.textContent = `${outputWidth}x${outputHeight}`;
         }