Ubiquitous environment can include heterogeneous terminals that haven't the same characteristics. Exchange multimedia data using heterogeneous terminals requires an adaptation of contents or other types of adaptation. In this paper we present a state of the art as: related work in term of approaches followed by a comparative study, comparative study of five existing adaptation architectures. On the second hand we present our architecture based on Client/Intermediary/Server model. So, we distinguish four main parts: multimedia client sender and multimedia client receiver, server with descriptors of environment, and proxy as a web services. This investigation aims to conceive an open system that integrates heterogeneous mobile phones. This open architecture aims to improve Qos between multimedia sender and multimedia receiver. Our proposed architecture allows multimedia clients to deliver multimedia content according to the mobile phone's specification receiver. As study case, we present a specification of some mobile phones: Nokia 2610, Samsung X640, Sony Ericsson K320, Siemens CX65 and Nokia N93i with four illustrative adaptation scenarios.
Currently, a lot of different end multimedia client’s devices (mobile phones in our case) are heterogeneous. So, hardware and software capacities are heterogeneous and some times limited. End user devices features have different capabilities in terms of memory size, display size, or supported formats. However, rendering multimedia content in such an environment remains challenging, because the content itself is heterogeneous in terms of encoding. For instance, a video can be encoded in different formats such as 3gpp, MPEG-4, or WMV, using different encoder settings such as spatial and temporal resolution, or bit rate. These limitations require an adaptation of contents or other type of adaptation. Therefore, a lot of research works where proposed in literature. Among the existing architectures, we find: ISIS [1] that follows the client/server model; NAC [2] is based in Client/Intermediary(s)/Server model. There are other architectures based on P2P model like PAAM [3]. DCAF [4] architecture is based on content adaptation services developed externally to make content transformations. The main objective of our research is to bring a solution for the multimedia client sender to deliver any multimedia document without getting an echo message due to the incapacity of the multimedia client receiver mobile phone to support the sent multimedia document. In other term, our proposed architecture aims to adapt multimedia document sent by a multimedia mobile phone before being delivered to the multimedia mobile phone receiver. Generally, the existing adaptation architectures treat multimedia data sent from a server machine to a client device but in our architecture the adaptation treatment is applied to the multimedia data sent from a multimedia client to other multimedia client and this is how our proposed architecture advances the state of the art. This paper is organized as follow, in section two we compare the existing adaptation multimedia approaches and we compare some existing multimedia adaptation architectures. Section three presents the proposed architecture, its aim and components. Section five presents studies cases using adaptation scenarios with mobile phone types.
We present in this section comparative study between adaptation approaches in Table.1 and a comparative study between five existing architectures in Table. 2. Table 1. Comparative study between the existing adaptation approaches.
Advantages +The author formulates advices or constrains in the adaptation. +Implementation of dynamic and static adaptation mechanisms. +For simple problematic. +Put results in hide. +The calculation charge is in the le proxy. +Disposes of a global view about the environment.
Disadvantages -The provider integrates adaptation mechanisms. -Calculation charge in the server. -Badly adapted to the situations when network constrains are difficult. -Not practice. -bad scalability -Security problem. -adaptation tools are brought to evaluate.
The Architecture proposed in this paper is illustrated in the figure 1. This architecture is based upon the Client/Intermediary/Server model. This open architecture aims to improve the flexibility and the adaptability of service (Qos) between multimedia sender and multimedia receiver. Our proposed architecture allows multimedia clients to deliver multimedia content according to the mobile phone’s specification receiver. It integrates heterogeneous mobile phones and provides an adaptation service for them in transparent manner.
Descriptors mobile/document
Original content Sender mobile phones
Server machine
Proxy
3.1 Components of the architecture
3.1.1 Multimedia client
There are two types of multimedia clients: multimedia client sender and multimedia
client receiver.
3.1.2 Server
The server has descriptors structured as data base. Each multimedia phone has
different characteristics (identifier, etc). The descriptor of the multimedia document
contains the original multimedia data received from the multimedia client sender. As
known, the server supports all kinds of multimedia data. Therefore, we suppose that
each sent message from the multimedia client sender will pass directly and
transparently to the server. Then, server selects from this message all environment’s
parameters: parameters of multimedia client receiver mobile phone characteristics
such as screen display, supported contents and multimedia content parameters like
format, size, image dimension etc. After collecting environment parameters, server
checks them in the descriptors. If these descriptors don’t exist, it stores them.
3.1.3 Proxy
Proxy constitutes the core of our architecture, it assists the server as a web services
with its two modules: decision module and adaptation module. Figure 2, presents the
behavior of the proxy. Because the success of the adaptation depends to the quality
and quantity of required knowledge about environment, the communication module in
the proxy receives environment’s parameters representing an adaptation request (
(
Decision module
Adaptation module
(
Communication module
(
OR
(
characteristics
capture image
of adaptation actions of every type. The optimal adaptation generator represents the minimum set of adaptation actions.
4.1 Mobiles Each multimedia mobile phone has a specification or a device context. For this reason, we are not able to specify all existing multimedia mobile phones in the market. As study case, we choose to specify dimensions, type, display size, ringtones type, memory card slot, GPRS, HSCSD, EDGE, WLAN, Bluetooth, Infrared port, USB, Supported image format, Supported video format, Supported audio format, Messaging, battery etc of some multimedia mobile phones [10]. These specifications are represented in table 3.
Table 3. Specification of four multimedia mobile phones
PNG, BMP BMP, GIF,
BMP, PNG, VND.WAP,
Nokia 2610 104 x 43 x 18 mm
SGH-X640 87.4 x 47 x 23 mm UFB,65K colors 128 x 160 pixels
No No mpeg4, mp4v-es
SMS, MMS,
750 mAh (BST-36) Yes real video 3pgg, aac, amr,amrwb, au, basic, mid, midi, mobile-xinf, mp3, mp4, mpeg, rmf, sp-midi, vn d.rm-real audio, wav, x-amr, x-au, xbeatnik-rmf, x-mid, x-midi, x-pn-real audio, x-pn-real audio plugin, x-rmf, x-wav
SMS,
MMS, WAP
Several adaptation techniques have been developed to deliver multimedia data to the multimedia client receiver in heterogeneous environment (heterogeneous mobile phones).Currently available techniques apply textual transformation, image transcoding, video and audio processing. A list of content adaptation technologies that can be applied to the basic media types: text, image, audio and video are presented in table 4.
In general sense, content adaptation techniques can be classified as semantic adaptation and physical adaptation. In our study, we are interested in physical adaptation (content level adaptation) techniques as illustrated in section 4.2. 4.2 Illustrative Scenarios for proposed architecture Scenario 1: Multimedia client sender is Nokia 93i mobile phone and has to transmit an image to another multimedia client receiver Nokia 2610 mobile phone. The image is stored in colored TIFF format. As specified in table 3, Nokia 2610 don’t use TIFF image format and in addition, dimension of the image is greater than the display screen Nokia 2610. So, two transformations are needed: adapt dimension adapt format.
Scenario 2: Multimedia client sender is Sony Ericsson K320 has to send a video to another multimedia client receiver Samsung X640. Multimedia client receiver can’t receive this video In this case, it is necessary to get image from the video sequence, convert audio to a text and changing dimension.
Scenario3: multimedia client sender Siemens CX65 can’t receive video stored in mpeg format sent from Sony Ericsson K320 mobile phone. Consequently, conversion of video format transformation is needed.
Scenario4: The audio stored in .wav format sent by a multimedia client sender Nokia N93i needs an audio conversion format to be received by the multimedia client receiver Samsung SGHX640 multimedia mobile phone. 5
In this article, we have presented the state of the art concerning approaches, multimedia adaptation architecture and a comparative study for each one. We have presented architecture to provide an open system for exchange multimedia data for multimedia mobile. The architecture is based upon the Client/Intermediary/server model, where proxy is as a web services. The aim of the open system is to improve the Qos in exchanging multimedia data over heterogeneous mobile type and to integrate several type of multimedia mobile phone. Our work is in progress, so we’ll model data bases essentially descriptors and adaptation type base with UML and implementation with Java language.