add --letterbox and --audio options

pack-vid

@@ -2,8 +2,8 @@
 <?php
 
 // Squishes given video input into sub-4000kb .mp4
-// Crops to 16:9
+// Crops or pads to 16:9 (crop default; --letterbox to pad)
-// Strips audio
+// Strips audio (to override, pass --audio for 96 kbps AAC)
 // HDR to SDR tonemapping
 // Picks bitrate to match
 // Picks resolution based on bitrate target
@@ -11,12 +11,26 @@
 
 $args = $_SERVER['argv'];
 $self = array_shift( $args );
+$options = [
+    'letterbox' => false,
+    'audio' => false,
+];
+
+while ( count( $args ) > 0 && substr( $args[0], 0, 2 ) == '--' ) {
+    $option = substr( array_shift( $args ), 2 );
+    $options[$option] = true;
+}
 
 if ( count ( $args ) < 2 ) {
-    die( "Usage: $self <srcfile.mp4> <destfile.mp4>\n" );
+    die(
+        "Usage: $self [options...] <srcfile.mp4> <destfile.mp4>\n" .
+        "Options:\n" .
+        "  --letterbox    pad instead of cropping\n" .
+        "  --audio        include audio\n"
+    );
 }
 [ $src, $dest ] = $args;
-convert( $src, $dest );
+convert( $src, $dest, $options );
 exit(0);
 
 //
@@ -65,7 +79,7 @@ function evenize( $n ) {
     return $n;
 }
 
-function convert( $src, $dest ) {
+function convert( $src, $dest, $options ) {
     $maxBits = 4000 * 1000 * 8; // fit in 4Mb
     $maxBits = $maxBits * 7 / 8; // leave some headroom
 
@@ -84,18 +98,34 @@ function convert( $src, $dest ) {
 
     $bitrate = floor( $maxBits / $duration );
 
+
+    if ( $options[ 'audio' ] ) {
+        $audioBitrate = 96 * 1000;
+        $audio = [ '-b:a', $audioBitrate ];
+        $bitrate -= $audioBitrate;
+    } else {
+        $audio = [ '-an' ];
+    }
+
     $mbits = 1000 * 1000;
     if ( $bitrate < 2 * $mbits ) {
-        $cropWidth = 854;
+        $frameWidth = 854;
-        $scaleHeight = 480;
+        $frameHeight = 480;
     } else if ( $bitrate <= 4 * $mbits ) {
-        $cropWidth = 1280;
+        $frameWidth = 1280;
-        $scaleHeight = 720;
+        $frameHeight = 720;
     } else {
-        $cropWidth = 1920;
+        $frameWidth = 1920;
-        $scaleHeight = 1080;
+        $frameHeight = 1080;
+    }
+
+    if ( $options['letterbox'] ) {
+        $scaleWidth = $frameWidth;
+        $scaleHeight = evenize( $height * $frameWidth / $width );
+    } else {
+        $scaleHeight = $frameHeight;
+        $scaleWidth = evenize( $width * $frameHeight / $height );
     }
-    $scaleWidth = evenize( $width * $scaleHeight / $height );
 
     $filters = [ "scale=w=$scaleWidth:h=$scaleHeight" ];
     if ( $hdr ) {
@@ -104,7 +134,12 @@ function convert( $src, $dest ) {
         $filters[] = "zscale=t=bt709:m=bt709:r=full";
     }
     $filters[] = "format=yuv420p";
-    $filters[] = "crop=w=$cropWidth";
+    if ( $options['letterbox'] ) {
+        $offset = round( ( $frameHeight - $scaleHeight) / 2 );
+        $filters[] = "pad=h=$frameHeight:y=$offset";
+    } else {
+        $filters[] = "crop=w=$frameWidth";
+    }
     $vf = implode( ',', $filters );
 
     run( 'ffmpeg', [
@@ -119,7 +154,8 @@ function convert( $src, $dest ) {
         '-an',
         '-y', '/dev/null'
     ] );
-    run( 'ffmpeg', [
+    run( 'ffmpeg',
+        array_merge( [
             '-i', $src,
             '-vf', $vf,
             '-c:v', 'libx264',
@@ -127,9 +163,10 @@ function convert( $src, $dest ) {
             '-preset', 'veryslow',
             '-pass', '2',
             '-g', $keyframeInt,
-        '-an',
+        ], $audio, [
             '-y', $dest
-    ] );
+        ] )
+    );
 }
 
 /*