Upfront Intra-Refresh Decision forLow-Complexity Wireless VideoTelephony (2006)

An adaptive intra-refresh (IR)technique ispro-inter modesaresupported than everbefore, andoptimal mode posed forlow-complexity video encoding onresource-constrained selection usually involves exhaustive searches thatarequite wireless platforms. TheIRdecision ismadeupfront withoutcomputationally intensive. Forreal-time applications suchas requiring anypre-encoding, whichsignificantly reduces thecom- plexity andpowerconsumption inreal-time communication. To videotelephnly onhadeld deics,rsuh thgh comlexity Si allow upfront modedecision, anovel closed-form solution ispro-usually formidable considering their constraints inprocessing vided requiring noalgorithmic iteration orexhaustive searches. capability, poweretc.Forthese reasons, manyrecentworks TheIRscheme adapts tomultiple factors including thecontenthavebeenfocusing onhowtoreduce thecoding complexity texture information, theframe-to-frame pixel-value variation, without notable degradation incoding quality orefficiency (5), andtheestimated channel lossprobability. Themacroblock-(6)(7). basedrefresh canbeperformed usingvarious patterns (i.e.,IR (7). cyclic, randometc.). Experimental results demonstrate superiorIRdecision being part ofthemodedecision process, howto performance oftheadaptive schemeoverfixed schemes atallnarrow downthecoding modesinthefirst place, before actual channel loss rates. encoding, becomes verycritical foradvanced video coding on resource-constrained devices, andisthefocus ofthis work. Themajor contribution ofthis workistheupfront IRmode Transmission ofvideo overwireless networks canbeun- selection, before anyactual encoding isperformed, whichcan reliable duetochannel losses. Errors resulting fromchannelsignificantly reduce thecomplexity andpowerconsumption losses canadversely impact thequality ofthevideo presented forencoding onlight devices intherealworld. Thedeci- totheuser. Inparticular, channel errors canimpair notonlysioncouldeliminate theneedofintensive motion estimation thequality ofacurrent frame, butalsosubsequent inter-coded onceanintra-mode isselected. Thisrequires aclosed-form (P)frames that depend onthecurrent frameduetotheuse solution thatisnotfoundinprevious literature. Theclosed- ofmotion estimation andcompensation techniques. Tolimitformsolution hastobeobtained without requiring anyoutput thepropagation ofchannel-induced errors fromoneframefromactual encoding, suchasthenumberofbits, measured toanother, theencoder typically employs intra-refresh (IR)distortion etc. Thisallows encoding onmobile devices under techniques tocombat errors. Tomeetthestringent target bitrate stringent real-time constraints withsatisfactory performance. andtoavoid high ratefluctuations invideo telephony applica-Thispaper isstructured asfollows: Section IIstarts withan tions, intra-coded (I)frames cannotbefrequently employed. introduction oftheIRprocess, withSubsection 11-A onhowto Instead, macroblock (MB)intra-refresh isconsidered amore determine theIRrate, andSubsection 11-B onhowtoactually feasible wayinsuchapplications. Intra-coded MBs help to determine themodeforaparticular MB.Experimental results improve error-resilience , butusually require anincrease in arepresented inSection IIItodemonstrate theperformance of