整合式多媒體串流平台的發展與實作

Abstract

摘要 多媒體串流技術，使消費者在下載多媒體檔案的同時可以觀賞到已收到的部份，此項技術使得使用者不需要花費下載時間與硬體空間來儲存多媒體檔案。 多媒體串流技術，包括三個部份：1、檔案包裝格式，舉例來說*.avi 、*.mp4、*.wmv、*.mpg，這些都是包裝格式的一種，包裝格式的檔頭會說明如何從這些檔案格式中拆解出解碼器所需要的聲音流與影像流。2影音壓縮解壓縮技術，舉例來說 mpeg-4、mp3、AAC等都是影音壓縮解壓縮的一種，藉由這些影音壓縮技術可以把原始影音檔案大小壓縮成原來的數十分之ㄧ，３、網路串流技術，利用網路讓遠端接收到多媒體檔案並播放，所要求的為檔案播放的及時性與平順性。因此，一個完美的多媒體串流平台，基本上必須看得懂所有的檔案包裝格式與網路串流格式，同時必須準備各種影音壓縮技術來對影像流與聲音流進行編碼及解碼，這種看似複雜的串流平台在自由軟體基金會及全球軟體工程師的努力下正逐漸的建構當中，本論文的第三章將探討一個開放原碼的自由軟體FFmpeg。 多媒體串流的一項重要應用為安全監控，本論文將建構一套雙攝影機模組的即時遠端安全監控系統，利用VFW SDK擷取雙攝影機影像並將其壓縮成mpeg-4 simple profile，再利用串流平台串流播放之，由於將即時影像來源壓縮成mpeg-4 simple profile將會消耗大量cpu資源，本論文嘗試使用硬體代替軟體進行mpeg-4 simple profile的壓縮，至於解壓縮部份由於銷耗cpu資源有限因此仍以軟體進行解壓縮，而研究中也發現雖然軟、硬體皆是使用mpeg-4 simple profile但會因為codec tool 的差異而造成解碼錯誤，本論文將解決差異所造成的解碼錯誤，並成功的串流由硬體所壓縮出來的影音檔案。

Abstract Streaming technology allows people to enjoy the multimedia contents while downloading them. With the advantages of this technology, users don’t need to spend extra hours on downloading multimedia contents or spare memory space to save them. Streaming technology consists of three components. 1. File Format, for example, *.avi, *.mp4, *.wmv, and *.mpg. Decoder can parse video stream and audio stream via analyzing the header of a file format. 2. Codec, for example, mpeg-4, mp3, and AAC. By using Codec, users can compress original file several folds. 3. Network Streaming Technology. User can present smooth and real-time multimedia contents via network. In order to develop a perfect multimedia streaming platform, one have to realize all kinds of file formats and network streaming technology. In addition, the perfect platform has to possess all kinds of Codec to decode or encode multimedia contents. This complex perfect multimedia streaming platform is being built gradually by global software engineers. We will introduce an open source software which is produced by free software foundation in chapter 3. Surveillance system is an important application in streaming technology, we will build a real-time two camera model multimedia streaming surveillance system in this thesis, we use VFW SDK to capture this two camera image and encode image to mpeg-4 simple profile, and stream the mpeg-4 video stream via internet. In order to decrease the cpu loading, we try to use hardware mpeg-4 simple profile encoder to replace the software one. Although both hardware encoder and software decoder are mpeg-4 simple profile codec, the difference of codec tool will cause decoder error, we will resolve this problem in this thesis and successfully streaming multimedia contents which is made by hardware encoder.