PHP-FFMPEG possible ExtractMultipleFramesFilter bug

php-ffmpeg.php

<?php

require 'vendor/autoload.php';
use \FFMpeg\Filters\Video\ExtractMultipleFramesFilter;

/**
 * @param $fromUrl
 */
function getIGOriginalVideoUrl($fromUrl) {
    $html = file_get_contents($fromUrl);

    $doc = new \DOMDocument();
    libxml_use_internal_errors(TRUE); //disable libxml errors

    if ($html) {
        $doc->loadHTML($html);
        libxml_clear_errors(); //remove errors for yucky html

        $xpath = new \DOMXPath($doc);

        $query = '/html/head/meta[@property="og:video"]/@content';
        $row = $xpath->query($query);
        if ($row->length > 0) {
            foreach ($row as $row) {
                return $row->nodeValue;
            }
        }
    }
}
$url = getIGOriginalVideoUrl('https://www.instagram.com/p/BdmpyJFFPQB/?taken-by=shaked.klein.orbach');

$dir = '/tmp/test_dir';
@mkdir($dir, 0777, true);

$ffmpeg = \FFMpeg\FFMpeg::create();
$video = $ffmpeg->open($url);
$video
    ->filters()
    ->extractMultipleFrames(
        ExtractMultipleFramesFilter::FRAMERATE_EVERY_60SEC,
        $dir
    )
    ->synchronize();

$path = sprintf('%s/output_%s.png', $dir, '%d');
$format = new \FFMpeg\Format\Video\X264();
$format->on('progress', function ($video, $format, $percentage) {
    echo 'percentage: ' . $percentage . PHP_EOL;
});

$video
    ->save($format, $path);

die(PHP_EOL . 'DONE' . PHP_EOL);