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    Please use this identifier to cite or link to this item: http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/35769


    Title: H.264影像傳輸使用緩衝器管理之研究
    Other Titles: The reaseach of buffer management in H.264 video transmission
    Authors: 張倢銘;Chang, Chien-ming
    Contributors: 淡江大學電機工程學系碩士班
    李維聰;Lee, Wei-tsong
    Keywords: H.264;MPEG-2;SMP8634;IPTV;H.264;MPEG-2;SMP8634;IPTV
    Date: 2007
    Issue Date: 2010-01-11 07:07:59 (UTC+8)
    Abstract: 影音編碼已經成為數位家庭中,最主要的角色,隨著科技的進步,網路影音出現了多種格式和壓縮法,目前最熱門的莫過於H.264,H.264具有MPEG-1及MPEG-2所沒有的高壓縮率、高抗誤性、頻寬適應性等技術特性,他可以利用超低資料傳輸速率提供令人驚豔的畫質。由於H.264具有低資料傳輸的特性,很適合用在IPTV的應用,因為MPEG-2在傳送影音的時候,需要非常高的頻寬,所以並不適合應用於遠端傳送。
    本文探討H.264的資料傳送至遠端時,網路很容易發生各種現象而讓影音資料有延遲的狀況發生,為了改善此種現象,在經過H.264晶片解碼之前,會先把H.264的資料放在SDRAM 裡的緩衝器中暫存,但若緩衝器開很大的時候,因為要等待資料下載至緩衝器後再播放影片的時間,可能會等待很久,甚至超過一分鐘以上,每次播放影片要等待太久的時間是讓人覺得煩悶的,而且也很浪費記憶體的配置,但在頻寬不足或是受到干擾的網路環境中,緩衝器最大的優點就可以讓播放影片在頻寬較不穩定的狀態下,仍舊可以很穩定的播放影片,降低影片斷斷續續的情況發生,本文所要探討的就是影像傳輸使用緩衝器的管理之研究,並透過網路分析儀模擬各種網路狀態時,調整緩衝器大小的配置和網路發生干擾或頻寬不足時,H.264的檔案資料播放情形,可以最有效率的使用緩衝器,是我們實驗的目的,不但可以讓H.264播放的更順暢,也可以節省嵌入式系統的記憶體配置。
    本文使用 Sigma Design發表的SMP8634媒體處理晶片,是一個適合用在IP TV用途的STB,8634同時支援MPEG-2/MPEG-4/H.264/VC-1,執行處理方面使用300MHz的MIPS核心,我們架設了一台Linux的Server 用來傳送H.264的資料給SMP8634。透過實驗平台,模擬各種網路可能發生的因素,並調整SMP8634 緩衝器的大小,我們發現,若緩衝器調整的太小,雖然可以節省記憶體的配置,但是在播放影片時,常會因為網路狀態不穩定而導致播放的品質不穩定,若緩衝器太大,比較會浪費記憶體的配置,嵌入式系統中的RAM,因為較不像PC的RAM那麼普及,成本也較貴,所以節省記憶體是目前最重要的課題,我們將可以了解,該如何去設置Buffer的大小,不但可以讓H.264播放的更順暢,也可以進一步的達到緩衝器管理的目的 。
    Media encorder has play an important role in the digital media home. The technology have develop fast, the network media have appear many different format and compress way. The most popular format is H.264. The H.264 have high compression ratio, high , Scalability ...etc which MPEG-1 and MPEG-2 does not have. It is can be used for low data rate transmit to provide the beautiful (high solution) pictures for it. Since the H.264 have low data transmit specialty, its very suitable to use on the IPTV, because during the MPEG2 convey the imagine, its require very high bandwidth which is not suit to use on the far transmission. This paper is to discuss during the H.264 transmit the data to far side, the Internet is very easy to appear the phenomenon that will delay the media data. In order to improve this situation, the H.264 data will store in the SDRAM’s buffer temporary before passing through the H.264 chipset. However, if the buffer temporary open very big, its may wait too long for the data to download into the bumper to broadcast the film, the timing may wait over a minute which cause inconvenient to people and waste the memory allocation. However, the biggest advantage of the bumper is to stable broadcast while the broadcast condition is not stable, in order to avoid the film intermittently.
    This paper mainly discuss how media data transmit by using buffer management study through the Internet to analysis and simulation each status, adjust the bumper’s size allocation and internet interference and limit bandwidth of H.264 file data broadcast situation, in order to use the bumper more efficiently, this is the main purpose of this experiments. It can help H.264 broadcast more frequently, also save the embedded system’s memory allocation. This paper use Sigma Design’s SMP8634 media process chipset. It is used on the IPTV STB .8634 also support the MPEG-2/MPEG-4/H.264/VC-1, CPU 300mhz MIPS core. We set up a linux server which use to transmit the H.264 data to SMP8634. Through the experiment platform, we simulate each situation may happen while transmit the data through the Internet. We have found out, if the bumper adjust too small, its can save the memory size allocation, but it caused the inernet condition unstable which influence the broadcast quality unstable. If the bumper too big, it’s waste memory size allocation, also have to wait too long too broadcast. The embedded system is not like PC’s RAM popular and the cost is too high, so how to save the memory size is the main problem. From this experiement, we can understand how to set up the bumper’s size and broadcast the H.264 more frequently, also to achieve the buffer management purpose.
    Appears in Collections:[電機工程學系暨研究所] 學位論文

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