MP4 streaming class only streaming one file at a time

Question

The issue is that I have multiple HTML5 videos that are autoplaying at the same time on a page, for some reason the second one doesn't start until the first one has fully buffered. I need them both to start at the same time.

I'm not sure if this is related to the PHP script, or possibly something to do with the HTML5 video player.

How can I get both videos to begin streaming at the same time?

I have a page with multiple HTML5 videos, eg:

<video src="api/group_video.php?id=1" loop controls muted autoplay></video>
<video src="api/group_video.php?id=2" loop controls muted autoplay></video>

My group_video.php script streams the videos. Here is the relevant part:

$path = "../../user_uploads/videos/post-{$_GET['id']}.mp4";
$stream = new VideoStream($path);
$stream->start();

I am using this simple VideoStream class by Rana at CodeSamplez:

/**
 * Description of VideoStream
 *
 * @author Rana
 * @link http://codesamplez.com/programming/php-html5-video-streaming-tutorial
 */
class VideoStream
{
    private $path = "";
    private $stream = "";
    private $buffer = 102400;
    private $start  = -1;
    private $end    = -1;
    private $size   = 0;
 
    function __construct($filePath) 
    {
        $this->path = $filePath;
    }
     
    /**
     * Open stream
     */
    private function open()
    {
        if (!($this->stream = fopen($this->path, 'rb'))) {
            die('Could not open stream for reading');
        }
         
    }
     
    /**
     * Set proper header to serve the video content
     */
    private function setHeader()
    {
        ob_get_clean();
        header("Content-Type: video/mp4");
        header("Cache-Control: max-age=2592000, public");
        header("Expires: ".gmdate('D, d M Y H:i:s', time()+2592000) . ' GMT');
        header("Last-Modified: ".gmdate('D, d M Y H:i:s', @filemtime($this->path)) . ' GMT' );
        $this->start = 0;
        $this->size  = filesize($this->path);
        $this->end   = $this->size - 1;
        header("Accept-Ranges: 0-".$this->end);
         
        if (isset($_SERVER['HTTP_RANGE'])) {
  
            $c_start = $this->start;
            $c_end = $this->end;
 
            list(, $range) = explode('=', $_SERVER['HTTP_RANGE'], 2);
            if (strpos($range, ',') !== false) {
                header('HTTP/1.1 416 Requested Range Not Satisfiable');
                header("Content-Range: bytes $this->start-$this->end/$this->size");
                exit;
            }
            if ($range == '-') {
                $c_start = $this->size - substr($range, 1);
            }else{
                $range = explode('-', $range);
                $c_start = $range[0];
                 
                $c_end = (isset($range[1]) && is_numeric($range[1])) ? $range[1] : $c_end;
            }
            $c_end = ($c_end > $this->end) ? $this->end : $c_end;
            if ($c_start > $c_end || $c_start > $this->size - 1 || $c_end >= $this->size) {
                header('HTTP/1.1 416 Requested Range Not Satisfiable');
                header("Content-Range: bytes $this->start-$this->end/$this->size");
                exit;
            }
            $this->start = $c_start;
            $this->end = $c_end;
            $length = $this->end - $this->start + 1;
            fseek($this->stream, $this->start);
            header('HTTP/1.1 206 Partial Content');
            header("Content-Length: ".$length);
            header("Content-Range: bytes $this->start-$this->end/".$this->size);
        }
        else
        {
            header("Content-Length: ".$this->size);
        }  
         
    }
    
    /**
     * close curretly opened stream
     */
    private function end()
    {
        fclose($this->stream);
        exit;
    }
     
    /**
     * perform the streaming of calculated range
     */
    private function stream()
    {
        $i = $this->start;
        set_time_limit(0);
        while(!feof($this->stream) && $i <= $this->end) {
            $bytesToRead = $this->buffer;
            if(($i+$bytesToRead) > $this->end) {
                $bytesToRead = $this->end - $i + 1;
            }
            $data = fread($this->stream, $bytesToRead);
            echo $data;
            flush();
            $i += $bytesToRead;
        }
    }
     
    /**
     * Start streaming video content
     */
    function start()
    {
        $this->open();
        $this->setHeader();
        $this->stream();
        $this->end();
    }
}