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MPEG-4影音串流伺服器之設計與實作

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行政院國家科學委員會專題研究計畫成果報告

MPEG-4 影音串流伺服器之設計與實作

The Design and Implementation of

an MPEG-4 Media Streaming Server

計畫編號:NSC 90-2213-E-002-091

執行期限:90 年 8 月 1 日至 91 年 7 月 31 日

主持人:陳文進 教授 國立臺灣大學資訊工程研究所

一、中文摘要 隨著寬頻網路的蓬勃發展,影音串流服務 (video streaming)不再遙不可及,影音串流技術 發展的目的在於如何在複雜的網路媒介下傳送影 音資料,用戶端能夠即時接收資料後立刻播放,不 需等待整個影片下載完畢,用戶端便不再浪費冗長 的等待時間,並且能降低用戶端暫存空間需求。 此計劃的研究課題分為兩類:(1)如何藉由影 音串流技術傳送影音資料、(2)如何在有限的頻寬限 制下,傳送高品質的影音內容。由於 MPEG-4 標準 為了適應網路傳輸的需求,整體的設計已經包含了 網路傳輸的各種技術,需要的傳輸頻寬也大大減 少,所以本計劃將採用 MPEG-4 標準的各種技術做 為發展的主軸, 並實作出以下各個相關模組: (1) MPEG-4 檔案編輯器、(2)MPEG-4 媒體格式轉換 器、(3)MPEG-4 影音串流伺服器。 關鍵詞:多媒體, MPEG-4, 串流, 網路, 伺服器, 實 作。 Abstract

MPEG-4(ISO/IEC 14496) is the state-of-the-art standard for describing the presentation and composition of multimedia contents. It enables the integration of different media data in an objected-based way. The specification of MPEG-4 includes media data access framework, video/audio codec, and synthetic object presentation and integration method of different media data.

The research topics of this project are: (1) how to stream video data in internet, (2) how to send high quality media in the internet with low bandwidth. The design of the MPEG-4 standard includes the needs of streaming media in the network, so in this project we implement the streaming park of the MEPG-4 standard and develop some tools, which are: (1) The MPEG-4 file format editor, (2) The MPEG-4 video format transformer, (3) The MPEG-4 streaming server.

Keywords: MPEG-4, Multimedia, Streaming, Network, Server, Implementation.

二、緣由與目的

Following the great success of MPEG-1 and MPEG-2 in the Audio/Video market, the ISO MPEG

group continues to develop their next standard – MPEG-4. MPEG-4 targets on several issues: authoring and encoding of object-oriented scenes, encoding of natural and synthetic media, media streaming, uniform transmission interface in the heterogeneous network environments, and fancy human-machine interactions. Therefore, MPEG-4 is designed to be applicable for a wide spectrum of the presentation applications.

The MPEG-4 standard comes in several parts. The definition of the binary scene description and the management information of the elementary streams are specified in part 1: System. The scene description is based on VRML and specifies the spatial-temporal composition of a MPEG-4 presentation, and the elementary streams convey the coded representation of audiovisual data to the receiver. Then these media objects will be composed into an integrated audiovisual presentation at the receiver. Compression techniques of visual and audible media objects are specified in part 2 and part 3. Other parts of MPEG-4 describe reference software and conformance procedure (part 4 and 5). In part 6, the delivery multimedia integration framework (DMIF) is introduced, which standardizes the transport services features which are available for the MPEG-4 applications.

In this project, our purpose is to research the streaming technologies and to develop some useful systems:

2.1 The MPEG-4 video format transformer

To facilitate MPEG-4 video content creation, we propose our architecture for MPEG-4 video content creator. For the quality and availability of video inputs, we choose the MPEG-2 video clips and captured video to be our video source. This encoder can convert MPEG-2 video clips into MPEG-4 compliant video clips, or capture video frames and convert them into MPEG-4 video clips.

2.2 The MPEG-4 file format editor

The MPEG-4 standard proposes MP4 file format to be media data storage format. According to MP4 specification, media bitstream can be divided into two parts: media description information (metadata) and media data. The media description information is stored in a “moov” atom, and the media data is stored in a “mdat” atom. Without any GUI application assistance, we can not create MP4 file in an instinctive way.

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2 To facilitate the MP4 file creation and management, we implemented an MP4 file editor. The encoded MPEG-4 video data can be transformed into MP4 file track easily. The media samples of the media track can be analyzed and the statistical information can be used to schedule the media samples streaming plan.

2.3 The MPEG-4 Streaming Server

Conforming to the MPEG-4 file format and media data streaming definition, we propose the architecture design and implementation of a MPEG-4 streaming server. In the streaming server, we propose the design and implementation of media data segmentation, SL packet generation, user commands, and the access unit timing information. In the client site, we propose the design and implementation of the access unit reconstruction, SL packet lost detection mechanism, and integration with open source ISO MPEG-4 video decoder. With media streaming, users can review the media presentation at the streaming client in real-time.

三、結果與討論

3.1 The MPEG-4 video format transformer 3.1.1 System introduction

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3 The architecture of the MP4 file editor is illustrated in Figure 3. To extract the access unit in the media stream, we implemented the packetizer module to segment access units from the media streams. Our packetizer module can recognize the MPEG-4 video, MPEG-1 Layer-3 audio and OD command encoded bitstream. After access units are extracted from the media stream, we put these access units in the sample buffer. Then we update the MP4 file sample table information and store these samples in the media data atom (‘mdat’ atom). The user interface of the MP4 file editor is shown as Figure 4. The atom information is displayed in the right Information window. The left window is the tree structure of the MP4 file.

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4 of the MPEG-4 streaming and develop some useful tool to facilitate the process of creating the MPEG-4 video and streaming the media via the internet. Currently, our system is useful to process the video only MPEG-4 media, but we cannot stream the scene data with network. We will still work on some advanced research topics about the MPEG-4 streaming technology.

五、參考文獻

[1] 劉登榮, “MPEG-4 媒體伺服器架構設計”, 國立台灣大學資

訊所博士班論文, July 1992.

[2] International Standard ISO/IEC 14496-1, Information Technology – Generic Coding of Audio-Visual Objects – Part 1: System, International Organization for Standardization, 1999.

[3] International Standard ISO/IEC 14496-2, Information Technology – Generic Coding of Audio-Visual Objects – Part 2: Visual, International Organization for Standardization, 1999.

[4] International Standard ISO/IEC 14496-3, Information Technology – Generic Coding of Audio-Visual Objects – Part 3: Audio, International Organization for Standardization, 1999.

[5] International Standard ISO/IEC 14496-6, Information Technology – Generic Coding of Audio-Visual Objects – Part 6: DMIF, International Organization for Standardization, 1999.

[6] International Standard ISO/IEC 14772-1:1997 – VRML 97: The Virtual Reality Modeling Language.

[7] ISO/IEC IS 11172, Information Technology – Coding of Moving Pictures and Associated Audio for Digital Storage Media up to about 1.5 Mbit/s – Part 2: Coding of Moving Picture Information, Part 3: Audio, International Organization for Standardization, 1991.

[8] ISO/IEC IS 13818, Information Technology – Generic Coding of Moving Pictures and Associated Audio Information – Part 2: Video, Part 3: Audio, International Organization for Standardization, 1994.

參考文獻

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