I had to migrate a few thousand flv and mp4 videos. I ended up just migrating the file name into a field, uploading the videos files to s3 and then using a custom node.tpl.php to render the player:
<?php
//display legacy videos
$mediaid = $content['field_mediaid']['#items'][0]['value'];
if ($mediaid != '') {
$video2 = '<a href="http://mydomain.s3.amazonaws.com/videos/ka/'.$mediaid.'.mp4" id="player" class="flowplayer"></a>';
flowplayer_add('#player', array(
'clip' => array(
'autoPlay' => TRUE
),
));
print $video2;
}
//hide the mediaid field from display
hide($content['field_mediaid']);
?>
Not very elegant but it got the job done. I used migrate 7.x-2.2 back then, maybe 2.5 has better video and/or file import features.