diff --git a/pack-vid b/pack-vid
index d3634c1..d8e36f1 100755
--- a/pack-vid
+++ b/pack-vid
@@ -355,7 +355,11 @@ function convert( $src, $dest, $options ) {
     $fps = $options['fps'];
 
     if ( $options['preset'] ) {
-        $preset = [ '-preset', $options[ 'preset' ] ];
+        if ( $options['vcodec'] === 'libvpx' || $options['vcodec'] === 'libvpx-vp9' ) {
+            $preset = [ '-speed', $options['preset'] ];
+        } else {
+            $preset = [ '-preset', $options[ 'preset' ] ];
+        }
     } else {
         $preset = [];
     }
@@ -369,7 +373,16 @@ function convert( $src, $dest, $options ) {
         $format = [];
     }
 
-    $vcodec = $options['vcodec'];
+    $vcodec = [
+        '-vcodec', $options['vcodec']
+    ];
+    switch ( $options['vcodec'] ) {
+        case 'libvpx-vp9':
+            $vcodec[] = '-row-mt';
+            $vcodec[] = 1;
+            break;
+        default:
+    }
 
     $tempPrefix = 'pack-vid-passlog' . rand(0,1 << 31);
     $passlog = tempnam( '.', $tempPrefix );
@@ -379,7 +392,7 @@ function convert( $src, $dest, $options ) {
             '-f', 'mp4',
             '-fpsmax', $fps,
             '-vf', $vf,
-            '-c:v', $vcodec,
+        ], $vcodec, [
             '-b:v', $bitrate,
         ], $preset, [
             '-pass', '1',
@@ -394,7 +407,7 @@ function convert( $src, $dest, $options ) {
             '-i', $src,
             '-vf', $vf,
             '-fpsmax', $fps,
-            '-c:v', $vcodec,
+        ], $vcodec, [
             '-b:v', $bitrate,
         ], $preset, [
             '-pass', '2',