H.264視訊編碼之同步式逆向錯誤追蹤演算法

摘要

關鍵字 –多媒體，無線網路，錯誤追蹤，H.264，錯誤隱藏，回授通道，抗誤性機制。

隨著視訊編碼、數位視訊媒體製作和網際網路技術的蓬勃發展，在無線網路上資料的種類與特性已有逐漸從非即時性數據資料演進至即時性視訊多媒體服務的趨勢。然而，在網際網路或無線網路中均具有可用頻寬高變動性及欠缺服務品質保證的特性，對於視訊多媒體服務的提供將造成十分負面的影響。除此之外，近年來視訊多媒體傳輸於無線環境之應用已經相當廣泛。本論文的目標是要在高錯誤率、可用頻寬高變動性、頻寬資源有限與欠缺服務品質(Quality of Service, QoS)保證的無線通信網路中，同時適用H.264且增進視訊品質的抗誤性機制為目的。

除了解該視訊壓縮標準所擁有的抗誤性機制，並參考其他抗誤性機制(如錯誤追蹤、參考畫面的選擇、自動重傳機制)。本論文主要是讓編碼端藉由迴授通道得知解碼端的狀態，並搭配錯誤追蹤演算法來使的編碼端與解碼端的狀態一致，最後再由原先的機制來決定編碼結果，而藉由實驗數據得知所提方式相較於傳統方式來的好，而我們也提到了一些降低運算量及記憶體使用量的方式。

Synchronous Backward Error Tracking algorithm in H.264 video coding

Abstract

Keyword - multimedia, wireless networks, error tracking, H.264, error concealment, feedback channel, error resilience.

With the prosperous development of efficient video coding and widespread Internet accessing, real-time multimedia applications over cellular mobile networks and wireless local area networks are becoming popular. However, video of multimedia service will be harmfully influenced from high variation of usable bandwidth and lack of QoS guarantee over widespread Internet and wireless network. Besides, transmission of multimedia over wireless environment is applied extensively in recent years. The objective of this thesis is to provide effective mechanism of error resilience for enhancing video quality in H.264 over wireless networks that usually come with high bit error rate.

Based on encoder process of H.264 standard to analyze internal error resilience tools and research other valid solutions such as error tracking, selection of reference frames, and automatic re-sending mechanism for error resilience. The method proposed is that the encoder can know the state of decoder and reconstruct that of decoder by utilizing backward error tracking, then the original criteria of mode decision is applied. By the simulation result, the approach proposed is always better than the conventional one and some resolution about reducing calculation and memory requirement are also mentioned.