That vessel is the R.M.S Olympic. From a quick glimpse at the exterior, the major differences in the ships is that on the Olympic, who A-deck promenade was open right across, while Titanic is enclosed at the forward end. Also on B-deck Olympic has a different configuaration of windows, ie most of the windows are all spaced evenly as this was Olympic's equilvent to Titanic's enclosed deck on A-deck. Titanic's B-deck windows are not evenly spaced in formation as her sister ship. Also you can also see in the above picture just under A-deck, aft you can see the B-deck second-class promenade deck. On Olympic this deck was opened for a greater length than Titanic's as hers was slightly shorter to accomondate a french cafe. Olympic would also recieved this after Titanic sank in her next refit in 1913.
It looks like the Olympic departing the Ocean Dock in Southampton on 14th June 1911 on her maiden voyage, judging by this photos similarlity with one I saw in Simon Mills' book "RMS Olympic: The Old Reliable"