How to filter posts by format and category via url?

I am doing something similar, but for member pages. I was able to use the code in my answer linked here which parses the information in the URL which can be manipulated within WordPress.

https://wordpress.stackexchange.com/a/91399/12920

Here’s a snippet of the URL handling portion which perhaps will get you started? Granted you’re doing something different than me, but the underlying function should be very similar.

// Catch the URL and redirect it to a template file
function userpage_rewrite_catch() {
    global $wp_query;

    if ( array_key_exists( 'member', $wp_query->query_vars ) ) {
        // Do something if member is in the URL
        include (TEMPLATEPATH . '/user-profile.php');
        exit;
    }
}
add_action( 'template_redirect', 'userpage_rewrite_catch' );