Post Specific Uploader

I have played around with filters for uploading files. The closest I have gotten is to have the files uploaded to the directory, but after the file uploads, I get a series of errors:
Undefined index: post_id
I think the issue is as simple as not having access to the current post id. I have tried $wp_query->post->ID; and $post->ID and neither seem to work.
These files would always be associated with a post.

The last iteration of the code I am using:

// filter for uploads
    function ml_media_upload_dir($upload) {

    $id = $_REQUEST['post_id'];
    $parent = get_post( $id )->post_parent;

        if (isset($_REQUEST['post_id'])) {
            $upload['path']    = "/foo/www/folder/blog/wp-content/uploads/" . $id;
            $upload['url']     = "http://foo.com/blog/wp-content/uploads/" . $id;
            $upload['basedir'] = "/foo/www/folder/blog/wp-content/uploads/" . $id;
            $upload['baseurl'] = "http://foo.com/blog/wp-content/uploads/" . $id;

            if (!file_exists("/foo/www/folder/blog/wp-content/uploads/" . $id)) {
                mkdir("/foo/www/folder/blog/wp-content/uploads/" . $id, 0777);
            }
        }


        return $upload;
    }
    add_filter('upload_dir', 'ml_media_upload_dir');

I even tried adding another ‘insert media’ link with the post_action=1 param to test.
(http://foo.com/blog/wp-admin/media-upload.php?post_id=571&TB_iframe=1&post_action=1&width=640&height=567)

How can I ensure that if there is a post_id, that the file gets loaded into the specific folder?

Any help..

cheers!
Bo