From 2a55fc989f07e4ddd26f0f1d34c43e6febaa4cb7 Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@pobox.com>
Date: Sat, 14 Jan 2023 17:20:35 -0800
Subject: [PATCH] initial commit

---
 pack-vid | 163 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 163 insertions(+)
 create mode 100755 pack-vid

diff --git a/pack-vid b/pack-vid
new file mode 100755
index 0000000..cb2907c
--- /dev/null
+++ b/pack-vid
@@ -0,0 +1,163 @@
+#!/usr/bin/env php
+<?php
+
+// Squishes given video input into 4000kb .mp4
+// Crops to 16:9
+// Picks bitrate to match
+// Picks resolution based on bitrate target
+// 2-pass encoding with libx264 veryslow
+
+$args = $_SERVER['argv'];
+$self = array_shift( $args );
+
+if ( count ( $args ) < 2 ) {
+    die( "Usage: pack-vid.php <srcfile.mp4> <destfile.mp4>\n" );
+}
+[ $src, $dest ] = $args;
+convert( $src, $dest );
+exit(0);
+
+//
+
+function run( $cmd, $args ) {
+    $commandLine = implode( ' ',
+        array_merge(
+            [ escapeshellcmd( $cmd ) ],
+            array_map( 'escapeshellarg', $args )
+        )
+    );
+
+    echo "$commandLine\n";
+    $output = shell_exec( $commandLine );
+    if ( $output === false ) {
+        throw new Error( "Failed to run $cmd" );
+    }
+
+    return $output;
+}
+
+function ffprobe( $path ) {
+    $output = run( 'ffprobe', [
+        '-hide_banner',
+        '-show_format',
+        '-show_streams',
+        '-print_format',
+        'json',
+        '--',
+        $path
+    ] );
+
+    $data = json_decode( $output );
+    if ( $data === null ) {
+        throw new Error( "Failed to read JSON from ffprobe: $output" );
+    }
+
+    return $data;
+}
+
+function evenize( $n ) {
+    $n = ceil( $n );
+    if ( $n & 1 ) {
+        $n++;
+    }
+    return $n;
+}
+
+function convert( $src, $dest ) {
+    $maxBits = 4000 * 1000 * 8; // fit in 4Mb
+    $maxBits = $maxBits * 7 / 8; // leave some headroom
+
+    $probe = ffprobe( $src );
+
+    $videoTracks = array_filter( $probe->streams, function ( $stream ) {
+        return $stream->codec_type === 'video';
+    } );
+    $track = $videoTracks[0];
+
+    $duration = floatval( $track->duration );
+    $width = $track->width;
+    $height = $track->height;
+    $hdr = $track->color_primaries === 'bt2020'; 
+    $keyframeInt = ceil( $duration * 60 );
+
+    $bitrate = floor( $maxBits / $duration );
+
+    $mbits = 1000 * 1000;
+    if ( $bitrate < 2 * $mbits ) {
+        $cropWidth = 854;
+        $scaleHeight = 480;
+    } else if ( $bitrate <= 4 * $mbits ) {
+        $cropWidth = 1280;
+        $scaleHeight = 720;
+    } else {
+        $cropWidth = 1920;
+        $scaleHeight = 1080;
+    }
+    $scaleWidth = evenize( $width * $scaleHeight / $height );
+
+    $filters = [ "scale=w=$scaleWidth:h=$scaleHeight" ];
+    if ( $hdr ) {
+        $filters[] = "zscale=t=linear:p=bt709";
+        $filters[] = "tonemap=hable";
+        $filters[] = "zscale=t=bt709:m=bt709:r=full";
+    }
+    $filters[] = "format=yuv420p";
+    $filters[] = "crop=w=$cropWidth";
+    $vf = implode( ',', $filters );
+
+    run( 'ffmpeg', [
+        '-i', $src,
+        '-f', 'null',
+        '-vf', $vf,
+        '-c:v', 'libx264',
+        '-b:v', $bitrate,
+        '-preset', 'veryslow',
+        '-pass', '1',
+        '-g', $keyframeInt,
+        '-an',
+        '-y', '/dev/null'
+    ] );
+    run( 'ffmpeg', [
+        '-i', $src,
+        '-vf', $vf,
+        '-c:v', 'libx264',
+        '-b:v', $bitrate,
+        '-preset', 'veryslow',
+        '-pass', '2',
+        '-g', $keyframeInt,
+        '-an',
+        '-y', $dest
+    ] );
+}
+
+/*
+# <18s
+ffmpeg \
+  -i "yikes.mp4" \
+  -f null \
+  -vf "zscale=t=linear:p=bt709,\
+       tonemap=hable,\
+       zscale=w=1146:h=480:t=bt709:m=bt709:r=full,format=yuv420p,\
+       crop=w=854" \
+  -vcodec libx264 \
+  -b:v 1250k \
+  -preset veryslow \
+  -pass 1 \
+  -g 1080 \
+  -an \
+  -y /dev/null && \
+ffmpeg \
+  -i "yikes.mp4" \
+  -vf "zscale=t=linear:p=bt709,\
+       tonemap=hable,\
+       zscale=w=1146:h=480:t=bt709:m=bt709:r=full,format=yuv420p,\
+       crop=w=854" \
+  -vcodec libx264 \
+  -b:v 1250k \
+  -pass 2 \
+  -preset veryslow \
+  -g 1080 \
+  -ab 96k \
+  -movflags +faststart \
+  -y yikes-small-compat.mp4
+*/