如何在此代码中执行ffmpeg命令

Question

想知道如何执行ffmpeg命令以在此代码中执行屏幕截图。我无法弄清截图是在什么时候创建，通过哪个函数或通过哪一行完成的。

$ffmpeg = '/usr/bin/ffmpeg'; 
     $video = $sourceUrl;// the input video file 
     $thumbId = uniqid(); 
     $thumbId .= ".jpg"; 
     // where you'll save the image 
     $image = "uploads/$thumbId"; 
     // default time to get the image 
     $second = 1; 
     // get the duration and a random place within that 
     $cmd = "$ffmpeg -i $video 2>&1"; 
     if (preg_match('/Duration: ((\d+):(\d+):(\d+))/s', `$cmd`, $time)) { 
      $total = ($time[2] * 3600) + ($time[3] * 60) + $time[4]; 
      $second = rand(1, ($total - 1)); 
     } 

     // get the screenshot 
     $cmd = "$ffmpeg -i $video -deinterlace -an -ss $second -t 00:00:01 -r 1 -y -s 120x90 -vcodec mjpeg -f mjpeg $image 2>&1"; 
     $return = `$cmd`; 
     $thumbLink = ""; 

Answer 1

此行执行您存储在变量$cmd命令：

$return = `$cmd`; 

在PHP中，倒引号是execution operator，它的使用是相同的主叫shell_exec。