optional<DCPTime>
-Player::content_time_to_dcp (shared_ptr<const Content> content, ContentTime t)
+Player::content_time_to_dcp (shared_ptr<const Content> content, ContentTime t) const
{
boost::mutex::scoped_lock lm (_mutex);
optional<ContentTime>
-Player::dcp_to_content_time (shared_ptr<const Content> content, DCPTime t)
+Player::dcp_to_content_time (shared_ptr<const Content> content, DCPTime t) const
{
boost::mutex::scoped_lock lm (_mutex);