Methods of Handling Packet Loss for Multimedia ApplicationsContentsIntroductionSender-Based RepairForward Error CorrectionInterleavingRetransmissionError ConcealmentInsertion-based repairInterpolation-based repairRegeneration-based repairInteractive modesMethods of Handling Packet Loss for Multimedia Applicationsby Hansen BowContents•Introduction•Sender Methods•Receiver Methods•Interactive MethodsIntroduction•Channels can introduce bit and erasure errors•Variable length coding can be desynchronized •MPEG-2–15 pictures in GoP–loss in one frame messes up rest of frames in group•cannot really use TCP protocol because results in sawtooth patterns in transmission rateSender-Based Repair•Forward Error Correction•Interleaving•RetransmissionForward Error Correction•Media independent–block or algebraic codes•Media dependent–primary and secondary encoding–multiple description coding–joint source and channel coding–robust waveform and entropy coding•Congestion Control–layered encoding sent to different groupsInterleaving•Prerequisite: –Unit size smaller than packet size•Units interleaved at encoder and returned to order at decoder•Disperses effect of packet lossesRetransmission•only host closest to failure issues request•subsidiaries repress request to avoid implosionError Concealment•Insertion-based repair•Interpolation-based repair•Regeneration-based repairInsertion-based repair•Splicing together of streams•Silence substitutions•Noise substitution•RepetitionInterpolation-based repair•Account for changing characteristics of signal•Motion-compensated temporal prediction•maximally smooth recovery•Time scale modificationRegeneration-based repair•Based on compression algorithm–one way: DC and lowest five AC coefficients estimated from top and bottom of neighboring blocks – rest forced to zeroInteractive modes•Adjusting transmission rate according to feedback information–withdraw congestion before packet loss•Selective encoding–tell encoder locations of damaged parts–encoder adapts encoding strategy to match with prediction•Retransmission without waiting–interpolation at decoder during retransmission–reverse calculate what current scene is when encoder information
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