Replace media ID with the media title in URL

functions.php

<?php

// Add this code into theme's functions.php

function custom_get_rtmedia_permalink( $permalink, $media, $id ) {
	$post = get_post( $media[0]->media_id );
	$title = isset( $post->post_name ) ? $post->post_name : '';
	if ( ! empty( $title ) ) {
		$permalink = str_replace( '/' . $id , '/' . $title, $permalink );
	}
	return $permalink;
}
function custom_rtmedia_action_query_modifier_type( $modifier_type, $raw_query ) {
	$allowed_types = rtmedia_get_allowed_types();
	$allowed_types = array_keys( $allowed_types );
	if ( is_array( $raw_query ) && array_key_exists( '0' , $raw_query ) ) {
		$post = custom_get_page_by_slug( $raw_query[0], OBJECT, 'attachment' );
		$post_album = custom_get_page_by_slug( $raw_query[0], OBJECT, 'rtmedia_album,rtmedia_playlist', 'publish,hidden' );
		$post = $post ? $post : $post_album;
		if ( $post ) {
			$modifier_type = 'id';
		}
	}
	return $modifier_type;
}
function custom_rtmedia_action_query_modifier_value( $modifier_value, $raw_query ) {
	global $is_album, $global_media_id;
	$allowed_types = rtmedia_get_allowed_types();
	$allowed_types = array_keys( $allowed_types );
	if ( is_array( $raw_query ) && array_key_exists( '0' , $raw_query ) ) {
		$post = custom_get_page_by_slug( $raw_query[0], OBJECT, 'attachment' );
		$post_album = custom_get_page_by_slug( $raw_query[0], OBJECT, 'rtmedia_album,rtmedia_playlist', 'publish,hidden' );
		$post = $post ? $post : $post_album;
		if ( $post ) {
			$modifier_value = rtmedia_id( $post->ID );
			$is_album = is_rtmedia_album( $modifier_value );
			$global_media_id = $modifier_value;
		}
	}
	return $modifier_value;
}
function custom_rtmedia_pre_template() {
	global $rtmedia_query, $rtmedia_interaction, $is_album, $global_media_id;
	if ( isset( $rtmedia_query->media_query ) && array_key_exists( 'id' , $rtmedia_query->media_query ) ) {
		$media_id = $rtmedia_query->media_query['id'];
		$rtmedia_interaction->routes['media']->query_vars['0'] = $media_id;
	} elseif ( $is_album ) {
		$rtmedia_interaction->routes['media']->query_vars['0'] = 'album';
		$rtmedia_interaction->routes['media']->query_vars['1'] = $global_media_id;
	}
}
function custom_get_page_by_slug( $page_slug, $output = OBJECT, $post_type = 'page', $post_status = 'inherit' ) {
	global $wpdb;
	$post_type = str_replace( ',', '\',\'', $post_type );
	$post_status = str_replace( ',', '\',\'', $post_status );

	$page = $wpdb->get_var( "SELECT ID FROM $wpdb->posts WHERE post_name = '$page_slug' AND post_type IN ( '$post_type' ) AND post_status IN ( '$post_status' )" );
	if ( $page ) {
		return get_post( $page, $output );
	}
	return null;
}

if ( class_exists( 'RTMedia' ) ) {
	add_filter( 'get_rtmedia_permalink', 'custom_get_rtmedia_permalink', 10, 3 );
	add_filter( 'rtmedia_action_query_modifier_type', 'custom_rtmedia_action_query_modifier_type', 10, 2 );
	add_filter( 'rtmedia_action_query_modifier_value', 'custom_rtmedia_action_query_modifier_value', 10, 2 );
	add_action( 'rtmedia_pre_template', 'custom_rtmedia_pre_template' );
}