TRANSCODING CONTENT FOR TACTICAL MOBILE COMPUTING DEVICES

Bruce BennettDefense Information Systems Agency

Arlington, VA

ABSTRACT

Integration of mobile computing devices and high-speedwireless networks into the tactical domain provides theWarfighter with unprecedented access to information onthe battlefield. Challenges in information delivery forthese handheld computers can be solved by optimizingcontent through transcoding services. Employing com-mercial software, video and web content can be dynami-cally customized to meet the unique processing, storageand network requirements for mobile devices.

Transcoding can be applied to current operational systemsto provide content to the mobile Warfighter. A prototypetranscoding platform was built to demonstrate the integra-tion of Global Broadcast Service (GBS) streaming videoand wireless handheld devices. VLC Media Player wasused to transcode high quality 1.6 Mbps MPEG-2 videoreceived over GBS into low bitrate MPEG-4 for playbackon wireless handhelds. This prototype used commerciallyavailable tools to optimize operational resources for mo-bile devices and demonstrates how GIG net-centric ser-vices can be extended to tactical edge users.

INTRODUCTION

Developing tactical wireless transports will supply theWarfighter with network connectivity throughout the bat-tlefield, enabling the use of lightweight mobile computersfor C41 systems. Handheld devices like PDAs (PersonalDigital Assistant), smart phones and tablet computers andintegrated Objective Force Warrior systems will helpachieve unprecedented network connectivity and informa-tion superiority. The increase of net-centric services andtactical video available to the Warfighter necessitates theneed for content to be tailored to the unique specificationsof these mobile computing devices.

TRANSCODING TECHNOLOGY

The ability to receive, process, store and display informa-tion is dictated by hardware specifications like processingpower, network connection, storage space and screen size.Integrating mobile computing devices throughout the busi-ness, garrisoned and tactical domains will result in infor-mation sources and consumers with varying and mis-matched capabilities. Transcoding technology can bridge

andDillon BussertRebecca Pham

Booz Allen HamiltonMcLean, VA

this information gap by adapting content to match diversedevice capabilities, dynamically reformatting data to fitdifferent platforms.

Transcoding services act as interpreters by receiving con-tent in one format and translating it into another throughthe use of metadata or customized settings. Content prop-erties like bitrate, frame rate, resolution, screen size, fileformat, codec and language can be transformed dynami-cally. Content providers can deliver products with oneuniversal format that can be adapted as necessary insteadof creating multiple versions for different hardware speci-fications.

Transcoding technology plays a key role in extending theGlobal Information Grid (GIG) for end-to-end connec-tivity. Net-centric services in a service-oriented architec-ture aim to provide ubiquitous access to informationsources, however the Warfighter may be connectedthrough satellite and tactical networks, requiring specialoptimizations. Integration of transcoding products cansupply these end users with customized content from exist-ing operational sources.

COMMERCIAL DEVELOPMENTS

Platform interoperability is a major reason for growingcommercial transcoding developments. Open standardmultimedia codecs and XML derived languages have al-lowed data content to be separated from how that contentis presented. Users can access information across multi-ple platforms, devices and applications.

VLC Media Player is an open source multimedia playerimplementing popular audio and video codecs like MPEG-1, MPEG-2, MPEG-4, DivX, and mp3 on multiple plat-forms like Windows, Mac, Linux, BSD, PocketPC andothers. The integrated transcoding capabiltity can convertmultimedia of any supported type into another format.Using open standard media types, the player can transcodeaudio and video codecs and bitrates, video scale and audiochannels. This on-the-fly software processing can be ap-plied to files as well as streaming multimedia, enabling auser to capture a stream and rebroadcast the audio or videoin a different format and bitrate dynamically.

1 of 5

Transcoding can be applied to web content by middlewaregateways, like IBM Websphere Everyplace Mobile Portal.Mobile Portal optimizes and delivers web content to hand-held devices by determining end user capabilities, dynami-cally reformatting html through metadata tags. The mid-dleware uses hardware profiles of popular handhelddevices to determine screen size and display capabilities.HTML content with metadata is customized for each webserver request, serving the same content in different for-mats on-the-fly. Transcoding through Mobile Portal sup-ports dynamic and scalable network architectures of mo-bile devices where information can be "written once,rendered many."

The commercial need for transcoding technology is beingdriven by the cellular telecommunications industry to pro-vide content to mobile phones. One of the emerging mar-kets for cellular services is streaming live and recordedvideo to handsets. Services like SmartVideo are supplyingusers with video content transcoded specifically for mobilecomputing devices.

SmartVideo provides live streaming TV to cellular phonesand handheld PDAs. Content like MSNBC and theWeather Channel is transcoded from NTSC video into anIP stream. Available over 802.1 lb Wifi and high-speedcellular EV-DO (Evolution Data Only) networks, Smart-Video is optimizing existing television content specificallyfor the hardware and network capabilities of mobile de-vices.

Commercial transcoding can be applied to tactical net-works to save existing bandwidth by using more efficientaudio and video codecs. The bitrate of streaming mediacan also be reduced to match tactical wireless network ca-pabilities for disadvantaged users, and provide content thatcan be rendered by different devices.

TACTICAL DEVICES

The Global Broadcast Service (GBS) is currently used toinject Unmanned Aerial Vehicle (UAV) video and com-mercial television broadcasts into the tactical domain inthe CENTCOM Area of Responsibility (AOR). GBS Re-ceive Suite (RS) hardware supports end user disseminationof CNN and Fox News Network real-time feeds as well asencrypted Predator video. These IP multicast streams areMPEG-2 encoded at bitrates over 1.5 Mbps to providehigh resolution video playback using set top box MPEGhardware decoders as well as PC software decoders.

GBS satellite broadcasts received at the RS can be distrib-uted throughout tactical LANs, pushing data to the War-fighter. Edge users with mobile devices will be connectedto services like GBS as wireless extensions to tactical

LAN environments develop. These users however will notbenefit from news, surveillance and reconnaissance videobecause current playback requirements exceed mobile de-vice hardware and network capabilities.

The Tacter RPDA (Ruggedized PDA) from Talla-TechInc. is a MIL-STD 81 OF ruggedized mobile device cur-rently employed by units in Iraq. The device is convenientbecause it is small and easily stored and can be equippedwith a laser range finder and GPS system. Mobile deviceslike the RPDA are growing in the tactical domain and willbe connected to existing high speed networks as militaryand commercial wireless technologies mature. Connectingthese lightweight devices will support new capabilities forthe Warfighter and provide end-to-end connectivity forGIG net-centric services, but the tactical Warfighter willnot have access to unlimited bandwidth and processingpower.

Figure 1. Talla-Tech Ruggedized RPA

Transcoding content services can match the data from in-formation sources to the capabilities of the end user any-where throughout the enterprise, garrison and tactical do-mains. This pairing is fundamental for a scalable tacticalnetwork architecture reaching back to GIG. As tacticalnetworks continue to evolve, new and different deviceswill populate the network edge requiring content to be asdynamic as the mobile Warfighter.

Mobile devices like the RPDA can take advantage of cur-rent GIG services through transcoding. Handheld PDAhardware has unique characteristics that must be addressedto customize content for the platform. Although laptopand desktop computer screen sizes can range from 14" to19" and support display resolutions upwards of 1280 x 960pixels, most PDA screens are 3" with a resolution of 320 x240 pixels. GBS content is designed to be viewed on theReceive Broadcast Manager (RBM), a stationary Pana-sonic Toughbook computer, so it is not optimized for mo-bile computing.

2 of 5

Handheld devices also have limited battery power, andlighter processing, graphics, memory and hard drive speci-fications than fixed computers. Current commercial wire-less technologies like 802.1 lb for PDAs have limitedbandwidth because of battery power. Content must be op-timized for these requirements to provide the Warfighterwith a mobile computing solution to deliver informationproducts and services to the edge.

MOBILE COMPUTING PROTOTYPE

A tactical transcoding prototype was built by the DISAEagle Lab Technology Center (ELTC) to demonstrate atactical GBS video extension. GBS streaming video,VLC media player and handheld mobile computers wereintegrated into a prototype demonstration of operationalGBS capabilities for JUICE 2005 (Joint User Interopera-bility Communications Exercise). The lessons learnedprototyping and testing the hardware and software pro-vided a concept of how transcoding can be applied to ex-isting services.

Secnet 11 is a NSA approved Type 1 cryptographic devicethat implements the 802.1 lb wireless standard. Secnet 11PCMCIA cards can be loaded with Secret COMSEC keysto transmit classified data. The cards may be installed in alaptop or PocketPC PDA for simple point-to-point ad hocnetworking, or in a wireless access point in a hub-spokeinfrastructure network. For the JUICE 2005 exercise,Secnet 11 cards with unclassified test keys were installedinto the access point and mobile devices in infrastructuremode.

Initial testing used an iPaq 3850 PDA to receive and play-back the transcoded streaming video. The handheld iPaqis similar to the RPDA hardware and can use an externalPCMCIA jacket for the Secnet 11 wireless card. VLCMedia Player for PocketPC was installed on the handheld;however the software is still in beta development andproved to be too unstable to process the continuous stream.

Figure 3. HP Compaq TC 1100 Tablet PC

Figure 2. JUICE Receive Suite Hardware Configuration

Streaming IP video of the Pentagon Channel, broadcastfrom the Satellite Broadcast Manager (SBM) in Norfolk,VA was received at the Communications ElectronicsCommand (CECOM) Software Engineering Center (SEC)Annex in Ft Monmouth, NJ. A Receive Suite connected tothe GBS main carrier, a 23.5 Mbps downlink connectionfrom the Galaxy JOR satellite, was used to receive the 1.6Mbps multicast video stream. This content was transcodedand wirelessly transmitted to mobile devices to demon-strate extended GBS capabilities.

The IP multicast video streams disseminated over the sat-ellite are pushed to the laptop RBM through a managedLAN switch. These IP streams are also available to otherLAN users as the multicast traffic is forwarded throughoutthe network. A wireless extension to the GBS RS wasadded by connecting a Harris Secnet 11 wireless accesspoint (WAP) to the switch.

Instead a HP Compaq TC1100 tablet was used to receivethe streaming video in the JUICE exercise. Although lar-ger than a handheld PDA, the tablet is lightweight andhighly mobile. The tablet runs Windows XP Tablet Edi-tion 2005 and is compatible with all Windows software,including a stable release of the PC media player. Unlike atypical laptop, the tablet does not use a keyboard; instead itreceives user input through its 10 inch touch-sensitivescreen and a pen-like stylus.

The 1.6 Mbps MPEG-2 stream of the Pentagon Channelwas broadcast over the wireless access point and viewedon the mobile device. The video was received at full datarate over the wireless connection and showed some arti-facts, likely from lost UDP packets due to interference.VLC media player was installed on the RBM to receive,transcode and rebroadcast the GBS video to the wirelessmobile device. The video stream was transcoded intoMPEG-4 video and mp3 audio to optimize the availablewireless bandwidth. These codecs support higher com-pression rates and provide comparable quality of MPEG-2at much lower bitrates.

3 of 5

Transcoding is a processor intensive task that includesboth decoding and encoding audio and video streams on-the-fly. System utilization on the RBM was 60-70% CPUusage on a 1.6 Ghz PC with 1GB of RAM and Windows2000. The media player can be run on any PC connectedto the GBS RS switch, so processing could be offloadedonto a machine other than the RBM.

Figure 4. Video Codec and Bitrate Transcoding Options

For the wireless extension the initial video rate was set to512 Kbps and the audio to 64 Kbps because the mobiledevice lacks a high quality display or high fidelity speak-ers. The video was scaled to 75% of the original content,since the screen is smaller than a PC monitor. Additionalsettings like frame rate can also be changed to relieve theprocessing burden of full motion video playback. Thetranscoded video reduced the throughput on the wirelessextension from 1.6 Mbps to 725 Kbps while providingsimilar video quality on the mobile device.

Figure 5. Side by side comparison of 512 Kbps transcodedvideo (top, 1 second delay) and 1.6 Mbps source (bottom)

The mobile device was able to receive the transcodedvideo while using less network resources. The artifactsobserved in the 1.6 Mbps MPEG-2 stream were reduced asthe lower bitrate was less susceptible to errors from inter-ference. Additional testing was done with the bitrate op-tions to capture the full capabilities of transcoded video.Samples of output were recorded to characterize the effectof lowering bitrate and video scale. Although the GBSbroadcast is encoded at a constant 1.6 Mbps, thetranscoded video uses dynamic encoding to maximize re-sources. Only changes in-between frames are encodedreducing the bitrate of still scenes. Output was averagedover one minute of live video using MPEG-4 video andmp3 audio to approximate expected bandwidth.

Video Audio TotalBitrate (Kbps) Scale (%) Bitrate (Kbps) Output (Kbps)

512 1 64 780512 0.75 64 725512 0.5 64 660512 0.25 64 615384 1 64 580256 1 64 460128 1 64 400128 0.5 32 240

Figure 6. Transcoding Video Output

Video quality showed slight loss at bitrates as low as 256Kbps in a 1024x768 pixel screen size. Even 128 Kbpsvideo displays good picture quality in a 320x240 pixelscreen similar to the resolution used by PocketPC PDAs.Audio at 32 Kbps exceeds telephone quality and voicecommunication is clear.

Mobile device users rarely require high quality video oraudio so a transcoded stream can be save valuable band-width in a wireless environment. Transcoded video canprovide two or three times as much content in the samebandwidth as existing MPEG-2 GBS video, extendingmultiple video streams like Predator UAV to mobile users.

This prototype of GBS streaming video and mobile de-vices displayed how content from existing systems can bedelivered to an edge user over a secure wireless connec-tion. Software for mobile devices must continue to de-velop for rich multimedia interaction, but transcoding hasshown it is a powerful tool for content optimization.

FUTURE APPLICATIONS

Developing programs like Objective Force Warrior and theArmy 2010 and Beyond initiative will rely on wireless andmobile computing to be an integral resource to the tactical

4 of 5

Warfighter in the future. Supplying these users with opti-mized GIG content and services will ensure informationsuperiority with next generation wireless transports andhandheld devices.

Net-centric services for collaboration will connect theWarfighter, however transcoding audio and video will benecessary to provide quality of service guarantees overwired and wireless networks using devices with differenthardware capabilities. Video teleconferencing and Wire-less Voice Over IP (wVoIP) communication will optimizedata using transcoding services for real-time connectionsthroughout the GIG.

New wireless technologies in the tactical domain will im-prove the interactive capabilities of mobile computing de-vices. Two-way satellite transports and high speed wire-less extensions will provide bandwidth and servicesdirectly to the edge user. The Warfighter will have accessto content web portals through handheld devices, but staticcontent designed for desktop computers will need to bedynamically transcoded for access on new computing plat-forms.

Although wireless bandwidth and mobile computing willcontinue to improve, hardware and network requirementswill also continue to grow with rich multimedia and inter-active services. Transcoding is a scalable and dynamictool that can optimize content for Warfighter resourcestoday and in the future.

CONCLUSION

This paper has identified transcoding as a solution for pro-viding content optimization to mobile computing devicesin the tactical domain. A prototype integrating GBSstreaming video, Secnet 11 secure wireless and a tablet PCdemonstrated how content can be optimized for the uniquehardware and network characteristics of these wireless de-vices. An open source video player was used to transcodevideo properties like codec, video and audio bitrate andscreen size to improve the playback of wireless streamingvideo. Optimized content will continue to be an importantpart of providing the edge Warfighter with end-to-endconnectivity of GIG services and content.

5 of 5