現(xiàn)代通信網(wǎng)絡(luò)課件2(參考版)
2025-01-05 01:00本頁(yè)面
【正文】 作業(yè)： 1. 在 MPEG4協(xié)議中，是如何描述場(chǎng)景組和 Composition of Scenes ？ 2. 為什么可以對(duì)原始視頻和音頻信息進(jìn)行壓縮編碼？主要有哪些壓縮編碼方法？ 3. 在 電視信號(hào)頻譜結(jié)構(gòu)中，為什么圖像信號(hào)采用殘留邊帶調(diào)幅，而伴音信號(hào)使用調(diào)頻方法？ 4. 在 MPEG2中， 專門定義了 4個(gè) PSI（ Program Specific Information），請(qǐng)問(wèn)：在單路 TS節(jié)目復(fù)用過(guò)程中， PSI和 PID是 如何加入的？ 謝謝觀看 /歡迎下載 BY FAITH I MEAN A VISION OF GOOD ONE CHERISHES AND THE ENTHUSIASM THAT PUSHES ONE TO SEEK ITS FULFILLMENT REGARDLESS OF OBSTACLES. BY FAITH I BY FAITH 。 ? 前臺(tái)服務(wù)器可以從不同的子網(wǎng)接收和發(fā)送直播服務(wù)。 ? 前臺(tái)服務(wù)控制器 web service管理一組前臺(tái)服務(wù)器。 ? 它監(jiān)視一或多股從電視直播后臺(tái)子系統(tǒng)傳出的 RTP流，并且傳送直播服務(wù)給客戶端。 ?然后將 key發(fā)給 Delivery Server子系統(tǒng)以便客戶端可以播放這些視頻流。 ? 其主要特點(diǎn)在于交互性和實(shí)時(shí)性。 ? 編碼 : 即編碼器將源端的電視信號(hào)數(shù)據(jù)進(jìn)行編碼處理，轉(zhuǎn)化成適合 IP網(wǎng)絡(luò)傳輸?shù)臄?shù)據(jù)形式 ? 通過(guò) IP網(wǎng)絡(luò)傳送 ? 接收端進(jìn)行解碼，再通過(guò)電腦或是電視播放?！? IPTV: 業(yè)務(wù)類型 ? 廣播電視：利用 IP組播技術(shù)，使用戶通過(guò)寬帶網(wǎng)絡(luò)可以觀看到直播電視節(jié)目： ? 個(gè)人視頻錄制 /網(wǎng)絡(luò)個(gè)人視頻錄制 (PVR/nPVR) ? 互動(dòng)電視 (iTV)－ RDP (遠(yuǎn)程桌面協(xié)議 ) ? 視頻點(diǎn)播 (VOD) ? 家居銀行 /電視商務(wù) (TCommerce) ? 遠(yuǎn)程教育 (eTV) ? 即時(shí)信息 (IM)和電視短信 /聊天 (TV Chat ) ? 視頻通信 (Video Communication) ? 網(wǎng)絡(luò)游戲 (GAME) ? Inter訪問(wèn) /電子郵件：高級(jí)的數(shù)字 IP機(jī)頂盒 (帶有鍵盤 )可以充當(dāng)用戶訪問(wèn)電子郵件和瀏覽 Inter的途徑。 ?國(guó)際電信聯(lián)盟給出的 IPTV的官方定義：“ IPTV是指通過(guò)可控、可管理、安全傳送并具有 QoS保證的無(wú)線或有線 IP網(wǎng)絡(luò)，提供包含視頻、音頻 (包括語(yǔ)音 )、文本、圖形和數(shù)據(jù)等業(yè)務(wù)在內(nèi)的多媒體業(yè)務(wù)。 ?與 MPEG－ 4相比， MPEG－ 1和 MPEG－ 2則采用一種類Ｃ語(yǔ)言的描述， MPEG－ 4描述語(yǔ)言反映了面向?qū)ο蠹夹g(shù)來(lái)描述對(duì)象。 MPEG：數(shù)字 【 AVO對(duì)象 】 描述 SD Integration of Natural and Synthetic Content MPEG4: SD Scene Description ?A ‘positor’ poses objects in a scene (AV, 23D) creating a posite scene ?A scene description defines how AVOs appear on End User screen (position view) ?With the scene description an End User can ? change the position of individual video object ? Zoom in/out interesting object ? Choose different audio track (language, music) ? Turn on/off individual object ?Binary Format for Scene Description : ‘BIFS’ MPEG4: Object Streams 【 目標(biāo)碼流 】 MPEG4： Decoder Model 【 解碼模式 】 MPEG4 Standard ?Part 1: System ?Part 2: Visual ?Part 3: Audio ?Part 4: Conformance Testing ?Part 5: Reference Software ?Part 6: Delivery Multimedia Integration Framework (DMIF) MPEG4 systems part: ? Addresses the description of the relationship between the audiovisual (AVs)ponents that constitute a scene. ?The relationship is described at two main levels: ? Binary Format for Scenes (BIFS) ? Object Descriptors (ODs) Binary Format for Scenes (BIFS) ?BIFS describes the spatiotemporal (時(shí)空的 ) arrangements of the objects in the scene. ?Viewers may have the possibility of interacting with the objects, . by rearranging them on the scene or by changing their own point of view in a 3D virtual environment. ?The scene description provides a rich set of nodes for 2D and 3D position operators and graphics primitives. Object Descriptor (OD) ? At a lower level, ODs define the relationship between the Elementary Streams pertinent to each object ( the audio and the video stream of a participant to a videoconference) ? Entity Groups a set of Elementary streams (ESs) associated with a particular object as a single entity ? Transported in object descriptor stream ? Object descriptors can be updated dynamically over time Examples of Object Descriptors:ODs MPEG4 語(yǔ)法描述 ?MPEG－ 4定義了一個(gè)句法描述語(yǔ)言來(lái)描述 AV對(duì)象比特流表示和場(chǎng)景描述信息。 Video Compression: Deficiencies of existing standards ? Designed for specific usage ? cannot be stored (no random access) ? MPEG1 MPEG2: not optimized for IP transport ? No universal file format for both local storage and work streaming ? Output cannot be reused efficiently after position encoded once, no versatility The solution: MPEG4 standard The solution: MPEG4 ?Inter in the future ?Not only text and graphics, but also audio and video ?Fast and versatile (多功能 ) interactivity ?Zoom in, zoom out (remote monitoring) ?Fast forward and fast backward (video on demand) ?Change viewing point (online shopping, sports) ?Trigger a series of events (distance learning) ?On the fly position ?Virtual environments ?Support both low bandwidth connections (wireless/mobile) and high bit rates (fixed/wireline) MPE
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