transcode a toxbox archive webm file containing variable dimensions to an mp4

transcode.php

#!/usr/bin/env php
<?php
	$input = isset($argv[1]) ? $argv[1] : null;
	$output = isset($argv[2]) ? $argv[2] : null;

	if (!$input || !file_exists($input)) {
		die("No valid input file specified.\n");
	}

	if (!$output) {
		die("No output file specified.\n");
	}

	function getMaxSize($input) {
		$largestDimension = [
			'width' => null,
			'height' => null
		];

		// Find the max width/height of the video
		$dimensionList = shell_exec("ffprobe -loglevel quiet -show_entries frame=width,height -of compact=p=0:nk=1 " . $input . "|sort|uniq");
		foreach (explode("\n", $dimensionList) as $dimension) {
			list($width, $height) = array_pad(explode("|", $dimension), 2, null);
			if ($width && $height &&
				($largestDimension['width'] == null ||
				 $largestDimension['width'] < $width ||
				 $largestDimension['height'] < $height
				)
			) {
				$largestDimension['width'] = $width;
				$largestDimension['height'] = $height;
			}
		}
		return $largestDimension;
	}

	function transcode($input, $output, $width, $height) {
		shell_exec("ffmpeg -y -i ".$input." -vf \"scale=".$width.":-1,pad=".$width.":".$height.":(".$width."-iw)/2:(".$height."-ih)/2\" -strict -2 ".$output);
	}

	$size = getMaxSize($input);
	transcode($input, $output, $size['width'], $size['height']);