Download WhatNOW: A System to Enable Videostream in a Mobile Network

WhatNOW: A System to Enable
Videostream in a Mobile
Network
Alexandre Martini, Sandro Mourão, Wesley Silva
Nokia Technology Institute, Manaus, Brazil
報告者：劉源蔁
1
Introduction

Communication graphic
2
Software Architecture

Mobile Client Software

Server Description and Theory
3
Mobile Client Software


Symbian platform
Controllers
 CVideoPlayerUtility
 CVidePlayerUtility2
 CVideoRecordingUtility
4
Mobile Client Software-Codecs

Codecs As shows, the codec program is responsible for the job of
encoding and decoding the image video and audio data. When it
comes to video, it is worth mentioning H.263 , Xvid and H.264.

The encoded video and audio data are streamed in a multimedia
container format, such as MP4 (MPEG-4 Part 14) , 3GP or AVI
(Audio Video Interleave) .
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Mobile Client SoftwareData Compression

These requirements can be defined as
 Video quality and bandwidth;
 Complexity (number of computations carried by the
algorithm);
 Synchronization (support to other sources of information
such as speech), and
 Delay (time delay between the encoding of a frame and its
decoding at the receiver) .
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Server Description and Theory

The analysis of the scenario above described shows us two ways
to provide audio/video content over the Web:
◦ Using a common Web server;
◦ Streaming it from a Stream Media Server.

Let us analyze these two technologies considering three points
of view:
◦ Deploying
◦ Hosting;
◦ Delivering
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Server Description and Theory

Web Server
◦ 1.1 Progressive Download
◦ 1.2 Embedding “Player”

Streaming from a Streaming Media Server
◦ 2.1 Streaming Media Architecture
◦ 2.2 Video compression
◦ 2.3 QoS control
◦ 2.4 Streaming Server
◦ 2.5Media synchronization
◦ 2.6 Security and Privacy
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Web Server

The original audio/video is compressed (encoded) into a single
media file, often Flash Video (FLV) or MPEG-4,and uploaded to a
Web server just like a normal file.

Basically,there are two ways to deliver our media file: Progressive
Download and Embedding “Player”.
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Progressive Download

The client player receives this file piece by piece and starts to
buffer until have a piece large enough to be played.

Progressive download uses Hyper Text Transport Protocol on top
of the Transmission Control Protocol for communication between
server and client
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Embedding “Player”

This approach has its limitations, to know:
◦ If our video is changed, it is necessary to reopen the wrapped file, embed the
video again and republish everything;
◦ The entire file must be downloaded from the web server before video playback
can begin;
◦ Some larger videos have problems with synchronization and duration;
11
Streaming from a Streaming Media
Server

Flash Media Server (Adobe);

Windows Media Service (Microsoft);

Darwin Streaming Server (Apple – Open
Source);

QuickTime Streaming Server (Apple –
Commercial).

Helix Server (Real Networks).
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Streaming from a Streaming Media
Server

Capture audio/video, by a camera/microphones integrated in a mobile equipment;

Raw video and audio are pre-compressed by their own algorithms. This still happens in the mobile equipment;

The media file is uploaded to a Streaming Media Server, using any available wireless network:

When the client request a streaming media, through a Web Server hosting the application to show the video to
the audience, the Streaming Media Server retrieves compressed video/audio data;

Application layer QoS control adapts and adjusts media file bit-streams according to the network status and
QoS requirements;

Transports protocol creates the packets with compressed bit-streams to send them to Internet. As usually, some
packets can be lost or delayed

Packets successfully delivered to the receiver are decoded after transport layer and their audio/video are
synchronized, then.
13
Streaming Media Architecture
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Video compression

It can be classified in two approaches: scalable and non-scalable.

As the scenario will be set according to different demands of
stream (latency, andwidth, access points) the MPEG-4 is proposed,
as it uses a scalable mechanism called FGS (fine granularity
scalability) .
15
QoS control

Full: comparison between decoded video sequence a the
original, using an algorithm calculating the distortion;

Reduced: comparison between features calculated from the
original and decoded video sequence;

No reference: observations only on decoded video and
estimate the quality.
16
Streaming Server

Set up a streaming server consist basically in having three
components
◦ Communicator: involving two layers, Application and Transport. It is used to link
clients to the server;
◦ Operation System: it is mandatory that it satisfies the real-time requirements for
this kind of application;
◦ Storage system: a large enough storage system to support whole streaming to
be delivered.
17
Media synchronization

There are three levels of synchronization related to three semantic
layers of multimedia data:
◦ Intra-stream synchronization, to avoid interruptions by pauses or gaps;
◦ Inter-stream synchronization, which without this to skew between the streams
may become intolerable.
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Security and Privacy

Since this application can provide access to the user’s data in the
mobile, for example: file system to share photos, images, texts and
multimedia content, is mandatory for it to be safe.

Operating System - OS: our application is intended to run in
Symbian OS 9.x .

Application level privacy: photos and videos will only be displayed
to friends authorized by the user.
19
UI Concept

The key issues driving customer-centeredweb-design
20
Message Screen

HOME、Friends、Wall、
Video Screen

Video Screen with a user
transmission
21
SNS for Mobile Comparisons
22
Conclusion

The server storage capacity is another thing to worry about.

In the mobile client software, good progress has been made, with
streaming of a short video between peers, but we are still facing
errors when trying longer videos.

Our expectation is to continue the work and hopefully deliver a
more complete and stable prototype.
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