diff --git a/pack-set b/pack-set
index 40dbe44..7357af7 100755
--- a/pack-set
+++ b/pack-set
@@ -8,7 +8,7 @@ do
     SPEED_SMALL="veryslow"
     SPEED_LARGE="medium"
 
-    SMALL="$COMMON --size=4m --preset=$SPEED_SMALL --quality=0.75"
+    SMALL="$COMMON --size=4m --preset=$SPEED_SMALL"
     LARGE="$COMMON --size=25m --preset=$SPEED_LARGE"
 
     pack-vid $SMALL "$INFILE" "${INFILE%.mp4}-small.mp4"
diff --git a/pack-vid b/pack-vid
index e18e7e4..207dbe9 100755
--- a/pack-vid
+++ b/pack-vid
@@ -26,6 +26,7 @@ $options = [
     'fps' => '60000/1001',
     'size' => $maxBytes,
     'quality' => 1.0,
+    'hdr' => false,
 ];
 
 while ( count( $args ) > 0 && substr( $args[0], 0, 2 ) == '--' ) {
@@ -51,7 +52,8 @@ if ( count ( $args ) < 2 ) {
         "  --preset=key   set h.264 encoding preset\n" .
         "  --fps=n        frame rate limit\n" .
         "  --size=n       target file size in bytes (default 3.5M)\n" .
-        "  --quality=n    fraction of base bitrate to break on (deafult 0.75)\n"
+        "  --quality=n    fraction of base bitrate to break on (deafult 0.75)\n" .
+        "  --hdr          force HDR input processing on\n"
     );
 }
 [ $src, $dest ] = $args;
@@ -97,7 +99,7 @@ function ffprobe( $path ) {
 }
 
 function evenize( $n ) {
-    $n = ceil( $n );
+    $n = round( $n );
     if ( $n & 1 ) {
         $n++;
     }
@@ -140,7 +142,7 @@ function convert( $src, $dest, $options ) {
     $duration = floatval( $track->duration );
     $width = $track->width;
     $height = $track->height;
-    $hdr = $track->color_primaries === 'bt2020'; 
+    $hdr = $track->color_primaries === 'bt2020' || $options['hdr'];
     $keyframeInt = ceil( $duration * 60 );
 
     $bitrate = floor( $maxBits / $duration );
@@ -161,6 +163,7 @@ function convert( $src, $dest, $options ) {
 
     $mbits = 1000 * 1000;
     $base = intval( $mbits * floatval( $options['quality'] ) );
+    /*
     if ( $bitrate < 1 * $base || $height < 480 ) {
         $frameWidth = 640;
         $frameHeight = 360;
@@ -182,8 +185,49 @@ function convert( $src, $dest, $options ) {
         $frameHeight = 1080;
         $bitrate = min( $bitrate, $base * 8 );
     }
+    */
 
     $aspect = $width / $height;
+    $pixels = $width * $height;
+
+    // canonical base rate is 1 megabit at 480p
+    $bitrate = min( $bitrate, 4 * $base );
+
+    $minWidth = 640;
+    $minHeight = 360;
+
+    $baseWidth = 854;
+    $baseHeight = 480;
+    $pixelsPerBit = ( $baseWidth * $baseHeight ) / $base;
+
+    $maxWidth = 1920;
+    $maxHeight = 1080;
+    $maxrate = $base * ( $maxWidth * $maxHeight ) / ( $baseWidth * $baseHeight );
+
+    $pixels = $bitrate * $pixelsPerBit;
+    $frameHeight = evenize( sqrt( $pixels / $aspect ) );
+    $frameWidth = evenize( $frameHeight * $aspect );
+
+    if ( $aspect > 16 / 9 ) {
+        if ( $frameWidth < $minWidth ) {
+            $frameWidth = $minWidth;
+            $frameHeight = evenize( $frameWidth / $aspect );
+        } elseif ( $frameWidth > $maxWidth ) {
+            $frameWidth = $maxWidth;
+            $frameHeight = evenize( $frameWidth / $aspect );
+            $bitrate = min( $bitrate, $maxrate );
+        }
+    } else {
+        if ( $frameHeight < $minHeight ) {
+            $frameHeight = $minHeight;
+            $frameWidth = evenize( $frameHeight * $aspect );
+        } elseif ( $frameWidth > $maxWidth ) {
+            $frameHeight = $maxHeight;
+            $frameWidth = evenize( $frameHeight * $aspect );
+            $bitrate = min( $bitrate, $maxrate );
+        }
+    }
+
     $wide = $aspect > ( $frameWidth / $frameHeight );
     $crop = boolval( $options['crop'] );
     $letterbox = boolval( $options['letterbox'] );