I created a valid MP4 file (without the progressive download fix) and a test script and put them in the main folder.
My test script looks exactly like this:
And the output of this script:
$command = escapeshellcmd('qt-faststart input.mp4 output.mp4');
echo($command.'<br /><br />');
echo('<br /><br />'.$return_value);
Not sure yet what that 127 means; I'm guessing "fail" because 'output.mp4' was not created.
qt-faststart input.mp4 output.mp4
Array ( )
However, executing the same line of code in the SSH (same username/directory) results in a successful 'output.mp4'.