make size configurable

pack-vid

@@ -11,12 +11,17 @@
 
 $args = $_SERVER['argv'];
 $self = array_shift( $args );
+
+$maxBytes = 4000 * 1000; // fit in 4MB
+$maxBytes = $maxBytes * 7 / 8; // leave some headroom
+
 $options = [
     'letterbox' => false,
     'audio' => false,
     'exposure' => '0',
     'peak' => '10000',
     'fps' => '60',
+    'size' => $maxBytes,
 ];
 
 while ( count( $args ) > 0 && substr( $args[0], 0, 2 ) == '--' ) {
@@ -38,7 +43,8 @@ if ( count ( $args ) < 2 ) {
         "  --audio        include audio\n" .
         "  --exposure=n   adjust exposure\n" .
         "  --peak=n       set HDR peak nits\n" .
-        "  --fps=n        set frame rate\n"
+        "  --fps=n        frame rate limit\n" .
+        "  --size=n       target file size in bytes (default 3.5M)\n"
     );
 }
 [ $src, $dest ] = $args;
@@ -91,9 +97,25 @@ function evenize( $n ) {
     return $n;
 }
 
+function sizify( $str ) {
+    $matches = [];
+    if ( preg_match( '/^(\d+(?:\.\d+)?)([kmgt]?)$/i', $str, $matches ) ) {
+        [ , $digits, $suffix ] = $matches;
+        $n = floatval( $digits );
+        switch ( strtolower( $suffix ) ) {
+            case 't': $n *= 1000; // fall through
+            case 'g': $n *= 1000; // fall through
+            case 'm': $n *= 1000; // fall through
+            case 'k': $n *= 1000; // fall through
+            default: return $n;
+        }
+        return $n;
+    }
+    die( "Unexpected size format '$str'\n" );
+}
+
 function convert( $src, $dest, $options ) {
-    $maxBits = 4000 * 1000 * 8; // fit in 4Mb
-    $maxBits = $maxBits * 7 / 8; // leave some headroom
+    $maxBits = 8 * sizify( $options['size'] );
 
     $probe = ffprobe( $src );