Using exec(): Program sends output to STDERR instead of STDOUT

[World Wide Weird]

I am using exec() and ffmpeg to generate thumbnails from video files. ffmpeg apparently sends its output to STDERR instead of STDOUT because the output appears in my Apache error log instead of the $out array. How can I make it send the output to STDOUT? Here's my code:

<?php

$out = array();
exec('path/to/ffmpeg.exe -i "path/to/some_movie.avi" -ss 00:00:10 -vframes 1 -vcodec mjpeg -f image2 "path/to/screenshot.jpg"',$out,$ret);
echo "<pre>";
print_r($out);
echo "</pre>";
echo "Return: " . $ret;

?>

This echoes:

Array
(
)

Return: 0

[stereofrog]

add 2>&1 to your command

[World Wide Weird]

add 2>&1 to your command

That worked. Thanks a million!