$re = '/(?<=\)\s\().+(?=\s\/)/m';
$str = '1)Video: h264 (High) (avc1 / 0x31637661), yuv420p, 452x360 [SAR 1:1 DAR 113:90], 297 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc (default)
2)Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 76 kb/s (default)';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php