I’m encountering this as well. The method I’ve used with a previous technique is this…
$video = $custom_fields['videoid'];
if ( $video ) :
$embeded = wp_oembed_get( $video );
$output .= apply_filters( 'embed_oembed_html', $embeded );
endif;
but it’s not working here. I see the FluidVideoEmbed filter is listed as being regesistered with the embed_oembed_html hook, so am scratching my head.
I suppose I could do it using the shortcode, but I’d rather do it with filters if I can.
I ended up using FitVids for WordPress plugin with the code I mentioned above.
http://wordpress.org/plugins/fitvids-for-wordpress/