peak to 10k and allow setting exposure and peak

pack-vid

@@ -14,19 +14,29 @@ $self = array_shift( $args );
 $options = [
     'letterbox' => false,
     'audio' => false,
+    'exposure' => '0',
+    'peak' => '10000'
 ];
 
 while ( count( $args ) > 0 && substr( $args[0], 0, 2 ) == '--' ) {
     $option = substr( array_shift( $args ), 2 );
+    $parts = explode( '=', $option, 2 );
+    if ( count( $parts ) == 2 ) {
+        [ $key, $val ] = $parts;
+        $options[$key] = $val;
+    } else {
         $options[$option] = true;
     }
+}
 
 if ( count ( $args ) < 2 ) {
     die(
         "Usage: $self [options...] <srcfile.mp4> <destfile.mp4>\n" .
         "Options:\n" .
         "  --letterbox    pad instead of cropping\n" .
-        "  --audio        include audio\n"
+        "  --audio        include audio\n" .
+        "  --exposure=n   adjust exposure\n" .
+        "  --peak=n       set HDR peak nits\n"
     );
 }
 [ $src, $dest ] = $args;
@@ -143,13 +153,17 @@ function convert( $src, $dest, $options ) {
         }
     }
 
-    $peakNits = 2000;
+    $exposure = floatval( $options['exposure'] );
+    $peakNits = floatval( $options['peakNits'] );
     $sdrNits = 80;
     $peak = $peakNits / $sdrNits;
 
     $filters = [ "scale=w=$scaleWidth:h=$scaleHeight" ];
     if ( $hdr ) {
         $filters[] = "zscale=t=linear:p=bt709";
+        if ( $exposure ) {
+            $filters[] = "exposure=$exposure";
+        }
         $filters[] = "tonemap=hable:peak=$peak";
         $filters[] = "zscale=t=bt709:m=bt709:r=full";
     }