server/lib/private/preview/movies.php

<?php
/**
 * Copyright (c) 2013 Frank Karlitschek frank@owncloud.org
 * Copyright (c) 2013 Georg Ehrke georg@ownCloud.com
 * This file is licensed under the Affero General Public License version 3 or
 * later.
 * See the COPYING-README file.
 */
namespace OC\Preview;

// movie preview is currently not supported on Windows
if (!\OC_Util::runningOnWindows()) {
	$isShellExecEnabled = !in_array('shell_exec', explode(', ', ini_get('disable_functions')));
	$whichAVCONV = ($isShellExecEnabled ? shell_exec('which avconv') : '');
	$isAVCONVAvailable = !empty($whichAVCONV);

	if($isShellExecEnabled && $isAVCONVAvailable) {

		class Movie extends Provider {

			public function getMimeType() {
				return '/video\/.*/';
			}

			public function getThumbnail($path, $maxX, $maxY, $scalingup, $fileview) {
				$absPath = \OC_Helper::tmpFile();
				$tmpPath = \OC_Helper::tmpFile();

				$handle = $fileview->fopen($path, 'rb');

				$firstmb = stream_get_contents($handle, 1048576); //1024 * 1024 = 1048576
				file_put_contents($absPath, $firstmb);

				//$cmd = 'ffmpeg -y  -i ' . escapeshellarg($absPath) . ' -f mjpeg -vframes 1 -ss 1 -s ' . escapeshellarg($maxX) . 'x' . escapeshellarg($maxY) . ' ' . $tmpPath;
				$cmd = 'avconv -an -y -ss 1 -i ' . escapeshellarg($absPath) . ' -f mjpeg -vframes 1 ' . escapeshellarg($tmpPath);

				shell_exec($cmd);

				$image = new \OC_Image($tmpPath);

				unlink($absPath);
				unlink($tmpPath);

				return $image->valid() ? $image : false;
			}
		}

		\OC\Preview::registerProvider('OC\Preview\Movie');
	}
}