This allows a user to download {HEAD ~ only a difference} between {TAIL ~ quality levels}, saving time and resources, rather than downloading the entire multimedia stream afresh 
between
This allows a user to download { HEAD ~ only a difference } between { TAIL ~ quality levels } , saving time and resources , rather than downloading the entire multimedia stream afresh
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH