diff --git a/pack-vid b/pack-vid
index ce71466..96ff723 100755
--- a/pack-vid
+++ b/pack-vid
@@ -122,12 +122,25 @@ function convert( $src, $dest, $options ) {
         $frameHeight = 1080;
     }
 
-    if ( $options['letterbox'] ) {
-        $scaleWidth = $frameWidth;
-        $scaleHeight = evenize( $height * $frameWidth / $width );
+    $aspect = $width / $height;
+    $wide = $aspect > ( $frameWidth / $frameHeight );
+    $pad = boolval( $options['letterbox'] );
+    if ( $pad ) {
+        if ( $wide ) {
+            $scaleWidth = $frameWidth;
+            $scaleHeight = evenize( $frameWidth / $aspect );
+        } else {
+            $scaleHeight = $frameHeight;
+            $scaleWidth = evenize( $frameHeight * $aspect );
+        }
     } else {
-        $scaleHeight = $frameHeight;
-        $scaleWidth = evenize( $width * $frameHeight / $height );
+        if ( $wide ) {
+            $scaleHeight = $frameHeight;
+            $scaleWidth = evenize( $frameHeight * $aspect );
+        } else {
+            $scaleWidth = $frameWidth;
+            $scaleHeight = evenize( $frameWidth / $aspect );
+        }
     }
 
     $peakNits = 2000;
@@ -142,10 +155,11 @@ function convert( $src, $dest, $options ) {
     }
     $filters[] = "format=yuv420p";
     if ( $options['letterbox'] ) {
-        $offset = round( ( $frameHeight - $scaleHeight) / 2 );
-        $filters[] = "pad=h=$frameHeight:y=$offset";
+        $offsetX = round( ( $frameWidth - $scaleWidth) / 2 );
+        $offsetY = round( ( $frameHeight - $scaleHeight) / 2 );
+        $filters[] = "pad=w=$frameWidth:h=$frameHeight:x=$offsetX:y=$offsetY";
     } else {
-        $filters[] = "crop=w=$frameWidth";
+        $filters[] = "crop=w=$frameWidth:h=$frameHeight";
     }
     $vf = implode( ',', $filters );