multimedia in embedded linux guide

1FreeElectrons.Kernel,driversandembeddedLinuxdevelopment,consulting,trainingandsupport.http//freeelectrons.com

MultimediainembeddedLinuxsystems


FreeElectrons


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Copyright20042009,[email protected]

Documentsources,updatesandtranslations:http://freeelectrons.com/docs/multimedia

Corrections,suggestions,contributionsandtranslationsarewelcome!

Latestupdate:Sep15,2009


Scopeofthistraining

MultimediainembeddedLinuxsystemsThistrainingtargetsthedevelopmentofmultimediacapableembeddedLinuxsystems.ThoughitcanbeusefultoplayingorcreatingmultimediacontentonGNU/Linuxdesktops,itisnotmeanttocovereverythingaboutthistopic.

AudioinembeddedLinuxsystemsisalreadycoveredinadedicatedtraining:http://freeelectrons.com/training/audio

Linux2.6ThistrainingonlytargetsnewsystemsbasedontheLinux2.6kernel.Thisway,youleveragethemostadvancedtechnologyanddon'tlearnaboutsomethinggettingobsolete.


Contents

Introduction

Glossary

Multimedialibraries

SDL

DirectFB

Kernelsubsystems

Video4LinuxAPI

DVBAPI

FreeSoftwareVideo

Videocodecsandfileformats

Multimediadistributions


QuickGlossary(1)

Alphachannel:Aadditionalvalueinimagepixels,describingtheiropacity(1:opaque,0:transparent)

Blitting:fromBitBLT"BitBlockTransfer"Copyingimagedata(e.g.copyingasurfaceonanother),applyingimagecombinationoperations.

Keying:Whencompositing2imageframestogether,removingpartsofoneaccordingtoakey(likeitscolororbrightness),torevealthecorrespondingpartintheother.


QuickGlossary(2)

VBI:VerticalBlankingIntervalIntervalduringwhichthetransmissionofavideosignalissuspendedtolettheelectrongungobacktothefirstscreenline.Usedtotransmitextradata,suchasteletext.

Seehttp://wikipedia.orgfordetails!



MultimedialibrariesSDL


SDL

SimpleDirectMediaLayerhttp://libsdl.org/License:LGPL

Crossplatformmultimedialibrary

Originallycreatedforwritinggames,bySamLantinga,forLokiEntertainmentSoftware,specializinginportinggamestoGNU/Linux.

Provideslowlevelaccesstoaudio,keyboard,mouse,joystick,3DhardwareviaOpenGL,and2Dvideoframebuffer.

NativeCAPIBindingsavailableformostprogrammingandscriptinglanguages


SDLscreenshots

Pig:ademoarcadegame.7000lines.QEMU:aCPUandsystememulator


SDLsupportedoperatingsystems

Officiallysupports:Linux,Windows,WindowsCE,BeOS,MacOS,MacOSX,FreeBSD,NetBSD,OpenBSD,BSD/OS,Solaris,IRIX,andQNX.

Codewithnoofficialsupport:AmigaOS,Dreamcast,Atari,AIX,OSF/Tru64,RISCOS,SymbianOSandOS/2.

Makesitveryeasytocreateplatformindependentapplications!


SDLcapabilities(1)

Video

Videomodesettingatanydepth(8bpporgreater).Automaticdetectionoftheclosestavailablemode.Optionalconversionifthevideomodeisnotsupportedbythehardware.

Writingdirectlytoalineargraphicsframebuffer.

Creatingsurfaceswithcolorkeyoralphablendingattributes.

Hardwareacceleratedblitandfilloperationsareusedifsupportedbythehardware(usingMMXaccelerationinx86).

OpenGLsupport.

FacilitytoloadBMPimages.


SDLcapabilities(2)

Events

Applicationvisibilitychanges

Keyboardinput

Mouseinput

Userrequestedquit

EacheventcanbeenabledordisabledwithSDL_EventState().

Eventspassedthroughauserspecifiedfilterfunctionbeforebeingpostedtotheinternaleventqueue.

Threadsafeeventqueue.


SDLcapabilities(3)

Audio

Audioplaybackof8bitand16bitaudio,monoorstereo.Optionalconversioniftheformatisnotsupportedbythehardware.

Audiorunindependentlyinaseparatethread,filledviaausercallbackmechanism.

CDROMaudio

CompleteCDaudiocontrolAPI


SDLcapabilities(4)

Threads

SimplethreadcreationAPI.

Simplebinarysemaphoresforsynchronization.

Timers

Measureelapsedmilliseconds.

Waitfornmilliseconds.

Setasingleperiodictimerwith10msresolution.

Endianindependence

Detecttheendianismofthecurrentsystem.

Routinesforfastswappingofdatavalues.

Readandwritedataofaspecifiedendianism.


SDLimplementationonGNU/Linux

Videodisplay.Eitheruses

X11:takingadvantageofXFree86DGAextensionsandnewMTRRaccelerationforfullscreendisplay.

OrDirectFB(seethenextsection)

UsestheOSSAPIforsound.FineforLinuxsystemswithALSA,thankstoOSSemulation.

Threadsareimplementedusingeithertheclone()systemcallandSysVIPC,orglibc2.1pthreads.


SDLinembeddedsystems

ShouldworkonanyplatformsupportingLinux.

EvenrunsonlightweightdeviceswithoutX11.Aframebufferdriverissufficient(usingtheDirectFBAPI).

Usefultodevelopyourapplicationonthehostinparallelwithtargetsystemdevelopment.

Facilitiestosupportthetargetendianism.


AdditionalSDLlibraries

SDL_image:http://libsdl.org/projects/SDL_image/ImageloadinglibrarysupportingJPEG,PNG,GIF,BMP...

SDL_ttf:http://libsdl.org/projects/SDL_ttf/TrueTypefontsupportlibrary

SDL_mixer:http://libsdl.org/projects/SDL_mixer/Samplemultichannelaudiomixerlibrary.SupportsOgg,MP3,MIDI.

SDL_gfx:http://freshmeat.net/projects/sdl_gfx/SDLgraphicsdrawingprimitivesandothersupportfunctions.

SAgl:http://freshmeat.net/projects/sagl/SmallAntialiasedgraphicslibrary.


OtherfreeSDLlibraries

Listedonhttp://libsdl.org/libraries.php

Lotsoflibrariestoeasethedevelopmentofgames,inparticulargameengines!

Manygraphics,GUIandOpenGLlibraries.

GlyphKeeperTrueTypefontrenderinglibrary.

FastEventsAfastthreadbasedreplacementforSDLeventroutines.

KyraAsimpleandpowerfulSpriteenginewritteninC++.


FreeSDLapplications(1)

Alistisavailableonhttp://libsdl.org/applications.php

Veryactivedevelopment.

Lotsofgames,ofcourse!

Asignificantnumberofsystememulators.Example:QEMU(http://qemu.org).

Somemultimediavisualizationplugins(e.g.forxmms).

OpenPictureSpace2http://membres.lycos.fr/mavati/openpicturespace2/Showspicturesinadirectorythroughthumbnails.


FreeSDLapplications(2)

MPEGMenuSystemVersion2http://mms.sunsite.dk/

Menusystemforeasymovie,audioandimageplayback.ElectronicTVprogramguide.

SupportsMP3,OGG,DivX,XviD,VCD,SVCD,DVD,JPEG,PNG,andGIF

Controlledusingaremotecontrolorkeyboard


GettingstartedwithSDLHelloWorld

#include "SDL.h"

int main( int argc, char* argv[] ){

/* initialize SDL */SDL_Init(SDL_INIT_VIDEO);

/* set the title bar */SDL_WM_SetCaption("SDL Test", "SDL Test");

/* create window */SDL_Surface* screen = SDL_SetVideoMode(640, 480, 0, 0);

/* load bitmap to temp surface */SDL_Surface* temp = SDL_LoadBMP("hello.bmp");

/* convert bitmap to display format */SDL_Surface* bg = SDL_DisplayFormat(temp);

/* free the temp surface */SDL_FreeSurface(temp);

SDL_Event event;int gameover = 0;

/* message pump */while (!gameover){

/* look for an event */if (SDL_PollEvent(&event)) {

/* an event was found */switch (event.type) {

/* close button clicked */case SDL_QUIT:

gameover = 1;break;

/* handle the keyboard */case SDL_KEYDOWN:

switch (event.key.keysym.sym) {case SDLK_ESCAPE:case SDLK_q:

gameover = 1;break;

}break;

}}

/* draw the background */SDL_BlitSurface(bg, NULL, screen, NULL);

/* update the screen */SDL_UpdateRect(screen, 0, 0, 0, 0);

}

/* free the background surface */SDL_FreeSurface(bg);

/* cleanup SDL */SDL_Quit();

return 0;}

ThankstoTony(http://tonyandpaige.com)fortheexample!


GettingstartedwithSDL(2)

Compiling

Easytodowithsdlconfig:gcc`sdlconfigcflagslibs`\hello.cohello

Moreexamples

Plentyofcodeexamplesavailableonhttp://www.libsdl.org/demos.php(checkthelicenses).


UsefulreadingaboutSDL

2niceintroductionstothedifferentpartsoftheAPIthroughsimpleexamples.

SDLIntroduction,bySamLantingahttp://www.libsdl.org/intro.php

SDLLibraryDocumentationhttp://www.libsdl.org/cgi/docwiki.cgi/

3niceSDLtutorialswithsimpleexampleshttp://andrew.textux.com/Articles.html



MultimedialibrariesDirectFB


DirectFB

http://www.directfb.org/License:LGPL

Userspacelibrarydevelopedforthespecialrequirementsofembeddeddevices.Small,powerful,flexibleandeasytouse.

Hardwareacceleratedgraphicssupport.Softwarefallbacksforoperationnotsupportedbytheunderlyinghardware.

Inputdevicehandlingandabstraction.

AlsosupportsSDL(when/dev/fb0isnotavailable).

Windowingsystemwithsupportfortranslucentwindows.

Multiplelayersupport.


DirectFBscreenshot

DemoofthenewTextureTriangles()methodusingexistingwindowsastextures(updatedinrealtime)


DirectFBinembeddedsystems

Extravalueinembeddedsystems

NoneedtorunaXserverusingdiskspaceandCPU.

Lightweight:veryfewgraphicslibrariesneeded.

Yourinterfacescanbeverysimple.Theydon'thavetohavethelookandfeelofdesktopapplications.

Portability:youcandevelopyourapplicationonthePChostwhilethetargetisstillunderdevelopment.


DirectFBgraphicalcapabilities

Rectanglefilling/drawing.

Trianglefilling/drawing.

Linedrawing.

Flatshadedtriangles.

Simpleblitting.

Stretchedblitting.

Texturedtriangles(perspectivecorrect).

Blendingwithanalphachannel(perpixelalpha).

Blendingwithanalphafactor(alphamodulation).

Ninesourceanddestinationblendfunctions.

Porter/Duffimagecompositionrulessupport.

Premultipliedalphasupported.

Colorizedblitting(colormodulation).

Sourcecolorkeying.

Destinationcolorkeying.


DirectFBoperation

Framebuffer Timingandmoderegisters

Accelerator

Framebufferdriver

DirectFBlibrary

DirectFBapp.2DirectFBapp.1 DirectFBapp.3

Chipsetdriver

Userspace

Kernelspace

Hardware

DisabledwhenDirectFBisused

mmap mappingI/Oregisters


DirectFBimplementation

Writingtotheframebuffer:directlywritestothememorymappedgraphicsdevicevideoRAM.

Accessinghardwareaccelerationcontrols:directlywritestothememorymappedgraphicsdeviceI/Oports.


Inputdevicesupport

Standardkeyboards.

SerialandPS/2mice.

Joysticks.

DevicesusingtheLinuxinputlayer(many!).

Infraredremotecontrols(usinglirc).

Sometouchscreens.


DirectFBimageloading

Thelibraryincludesimageproviders,whichallowtoloadimagesdirectlyintoDirectFBsurfaces:

JPEG(usinglibjpeg).

PNG(usinglibpng2).

GIF(builtin).

Variousotherimageformats(usingimlib2).


DirectFBvideoplayback

Includesdifferentvideoproviders,forrenderinginDirectFBsurfaces:

V4L(Video4Linux)andV4L2(/dev/video).

mpeg1/2(usinglibmpeg3).

AVI(usingavifile).

MOV(usingOpenQuicktime).

Flash(usinglibflash).


DirectFBfontrendering

Supportsantialiasedtext,andsupportsfontloadingthrough2providers:

DirectFBbitmapfont.

TrueType(usingFreeType2).


DirectFBAPI(1)

NativeAPIavailableinC.

13interfacesorproviders:structureswithfunctionpointers.Example:

Methods of IDirectFBVideoProvider

Retrieving information GetCapabilities Retrieve information about the video provider's capabilities.

GetSurfaceDescription Get a surface description that best matches the videocontained in the file.

Playback PlayTo Play the video rendering it into the specified rectangle of thedestination surface.

Stop Stop rendering into the destination surface.

Media Control SeekTo Seeks to a position within the stream.

GetPos Gets current position within the stream.

GetLength Gets the length of the stream.

Color Adjustment GetColorAdjustment Gets the current video color settings.

SetColorAdjustment Adjusts the video colors.


DirectFBAPI(2)

Morethan120types:datastructures.Example:DFBTriangleint x1; Xcoordinateoffirstedgeint y1; Ycoordinateoffirstedgeint x2; Xcoordinateofsecondedgeint y2; Ycoordinateofsecondedgeint x3; Xcoordinateofthirdedgeint y3; Ycoordinateofthirdedge

DFBScreenEncoderTVStandardsDSETV_UNKNOWN UnknownstandardDSETV_PAL PALDSETV_NTSC NTSCDSETV_SECAM SECAM


DirectFBAPI(3)

9definitions:macrostosimplifycode.Examples:

DFB_COLOR_EQUAL(x,y)Macrotocomparetwocolors.

DFB_DISPLAYLAYER_IDS_MAXMaximumnumberoflayerids.

DFB_DISPLAYLAYER_IDS_ADD(ids,id)Addstheidtothebitmaskoflayerids.

FullAPIdocumentationavailableonhttp://directfb.org/docs/DirectFB_Reference/


DirectFBAPI(4)

Onlyafewglobalfunctions

DirectFBInit(argc,argv)

DirectFBCreate(IDirectFB**dfb);

Then,throughtheIDirectFBinterface,itispossibletoworkonsurfaces,inputdevices,displaylayers,screens,mediafiles,etc.

Forexample,thedfb>CreateSurface()methodwillreturnaIDirectFBSurfaceinterfacepointer

TheIdirectFBSurfacethencontainsmethodstomanipulatethesurface:flipping,blitting,drawing,etc.


DirectFBHelloWorld

DirectFBInit(&argc,&argv);DirectFBCreate(&dfb);

dfb>SetCooperativeLevel(dfb,DFSCL_FULLSCREEN);

memset(&dsc,0,sizeof(DFBSurfaceDescription));dsc.flags=DSDESC_CAPS;dsc.caps=DSCAPS_PRIMARY;dfb>CreateSurface(dfb,&dsc,&primary);

dfb>CreateImageProvider(dfb,"test.png",&provider);provider>RenderTo(provider,primary,NULL);provider>Release(provider);

sleep(5);

primary>Release(primary);dfb>Release(dfb);


CompilingaDirectFBprogram

That'sveryeasytodothankstopkgconfig:

gcc`pkgconfigcflagsdirectfb`otesttest.c`pkgconfiglibsdirectfb`

pkgconfigisusedtoqueryneededClibraryheadersandsharedobjects.


Fusion

MakesitpossibleformultipleDirectFBapplicationstorunsimultaneously.

LayerusedbyDirectFBapplicationstocommunicate.

Previouslyimplementedcompletelyinuserspaceusingsemaphoresandmessagequeues..

NowcriticalpartsofFusionareimplementedinkernelspace(FusionKernelDevice),whichprovidesbetterperformanceandstability.SupportsbothLinux2.4and2.6.

LinuxkernelpatchavailableintheCoredownloadspage(linuxfusionmodule).


AfewDirectFBapplications

ByzantineOS,GeexBoxHomeentertainment

DBFSeeImageviewerandvideoplayer

DFBTermTerminalapplication

XDirectFBRootlessXServerusingDirectFBwindows.UsefultorunanyXwindowsapp.

ApplicationswithDirectFBbackends

gdkdirectfbDirectFBGDKforGTK

MPlayerDirectFBbackendsince2001.

SDLAlsohasaDirectFBbackend!

Moreonhttp://directfb.org!


UsefulreadingaboutDirectFB

DirectFBoverviewhttp://www.directfb.org/docs/DirectFB_overview_V0.2.pdfAniceandsyntheticarticle!



KernelsubsystemsVideo4linux


V4L:video4linuxsubsystem

Providessupportforaudio/videocaptureandoverlaydevicesandFMradio

V4L:Originalvideocapture/overlayAPIoftheLinuxkernel.Appearedinthe2.1.xdevelopmentcycleoftheLinuxkernel.

V4L2:Secondgenerationofthevideo4linuxAPIfixinganumberofdesignbugs.Integratedintothestandardkernelin2.5.x.Notsupportedyetbyalldrivers.

Mainwebpages:

VideoforLinuxresources:http://www.exploits.org/v4l

video4linuxHQ:http://linux.bytesex.org/v4l2/


v4loriginalAPI

API:Documentation/video4linux/API.htmlinthekernelsources(eveninLinux2.6).

Devicefiles

/dev/video(minor063):VideoCaptureInterfaceOfcourse,canreadvideoinputfromseveralofthesedevices:/dev/video0,/dev/video1...

/dev/radio(minor64127):AM/FMRadioDevices

/dev/vtx(minor192223):TeletextInterfaceChips

/dev/vbi(minor224239):RawVBIData(Intercast/teletext)


v4l2newAPI

AlsoonDocumentation/video4linux/API.html

Linux2.4nolongersupportedbyV4L2.

Linux2.6shipsthelatestV4L2versionsDevelopmentCVSsnapshotsavailableonhttp://dl.bytesex.org/cvssnapshots/.

OffersbackwardcompatibilitywithV4L:trueforV4Lapplications,notforV4Ldrivers.


V4L2APIspecification

NewAPIspecification:http://v4l2spec.bytesex.org/spec/ByMichaelH.SchimekandBillDirks

Averyexhaustivedocument(Oct2007:280pages!)

Specifiesalldetailsabouttheinterfaceadrivershouldimplement.Lotsofcodeexamples.

Providesdetailsaboutapplicationprogrammingtoo.

Alotoftechnicalbackgroundprovidedtoo!

Readthislikeareferencebook!


AfewV4L2features

Devices:Usesthesamedevicefiles,butit'suptothesystemadministratortoassignminornumbers.

Multipleopens:maysupportconcurrentaccessto/dev/files,forexampletocontrolbrightnessorcolor(panelapplication)whileanotherapplicationisplayingthevideo.

Standardcontrols:theAPIdefineshardwareindependentdevicecontrols(brightness,colorsaturation,etc),andawaytoenumerateavailablecontrols.Applicationscanbedriverindependent.


Communicatingwithioctl(1)

Afewdetailsabouttheioctl()systemcallareneededtounderstandhowavideo4linuxclientapplicationcaninteractwithavideo4linuxdriver.

Prototype:

#includeintioctl(intfd,intrequest,void*argp);

fd:filedescriptor(theopenedfile)

request:anioctlnumber,supportedbythedriver

argp:argumentstringorpointertoavalueorstructurereturnedbythedriver.


Communicatingwithioctl(2)

ioctlisusedtointeractwiththedriverhandlingtheopeneddevicefile,withouthavingtoreadorwritedata.

ToaccessaparticularsettingofthedriverExample:gettingtheserialnumberoftheunderlyinghardware.

TosetaparticulardriversettingExample:settingthespeedandflowcontrolofaserialport.

TohavethedriverperformaspecialoperationExample:formattingafloppydisk.


AfewV4L2ioctlnumberexamples

VIDIOC_QUERYCAPQueryingdriverscapabilities

VIDIOC_ENUMINPUTQueryingthenumber,typesandnamesofvideoconnectors.

VIDIOC_G_FREQUENCYGettingthetunerfrequency

VIDIOC_S_FREQUENCYSettingthetunerfrequency

VIDIOC_ENUMSTDQuerysupportedvideostandards(PAL,NTSC...)

VIDIOC_QUERYCTRLQueryavailablecontrols

VIDIOC_S_FMTSettingtheimageformat(includingcolorspaceinfo)

VIDIOC_REQBUFSAskingthedrivertoallocateabufferformemorymappedI/O


Concurrentaccessto/dev/video0

/dev/video0Driver

Hardware

App1(fd1) App2(fd2)

ioctl() ioctl()

read()write()

IdentifyingApp1andApp2bydifferentfiledescriptors,thedrivercansendthemdifferentdata.


I/Omodes

SeveralI/Omodescanbeproposedbythedriver

read()andwrite()Standardwayofaccessingdata.Basicbutcanstillbeefficient(canuseDMAinternally).Butcan'tcarrymetainformationlikeframecountersortimestamps.

StreamingI/O(memorymapping)Sharingpointerstomemorymappedbuffers(mmap),allocatedbythedriver.Nodatacopying.Bufferscan'tbeswappedouttodisk.

StreamingI/O(userpointers)Sharingpointerstoapplicationallocatedmemorybuffers.Bufferscanresideinsharedorvirtualmemory(canbeswappedout).


video4linuxusertools

V4L

LotsoftoolsstillseemtosupportonlyV4L.Fortunately,theV4L2highleveldrivercomeswithabackwardcompatibilitylayerwhichtranslatesV4LioctlcommandstoV4L2ones

Listedonhttp://www.exploits.org/v4l

V4L2

MPlayer(plugin)

DirectFBSupportsV4L2devicesasvideoprovidersforthedisplay

Morelistedonhttp://www.thedirks.org/v4l2/peopleprojects.htm


xawtvtoolset(1)

X11applications

xawtvWatchingTV

motvMotifbasedTVGUI

mttTextorMotifteletextbrowser

piaSimplemovieplayer

Commandline/consoletools

fbtvFramebufferTVapplication

streamerRecordingmovies

v4lctlSettingV4L2parameters

AsetofV4L2compatibletoolsforwatchingTV,recordingvideo,browsingteletext...http://linux.bytesex.org/xawtv/


xawtvtoolset(2)

Console/commandlinetools

scantvChannelscanner

radioSimple,cursesbasedradioapplication.

webcamCapturesimagesanduploadsthemtoaWebServer

alevtdhttpserverforvideotextpages

Fontshttp://linux.bytesex.org/xawtv/tvfonts.html

ledfixedBigfontusedbyxawtvforonscreendisplay.

etsteletextTeletextfont.Blockgraphiccharacters.

etscaptionFontforclosedcaptions(audiosubtitlesandscenedescription).


Writingtoscreens

Videoisbestwhenyoucanwatchit!

Needtochooseanexistingapplicationdisplayingvideo

Orcreateyourownusingagivenmultimediacapablelibrary:DirectFB,SDL...

2waysofaccessingthegraphics:Xserverorframebufferbased(mainlyDirectFBorQtopiaCore)

Anyway,youmostprobablywon'thavetoaccessthedisplaybyyourself,butthroughthelowlevellibrary.

Supportingvideocodecsinacustomapplication.Besttorelyongstreamer:http://gstreamer.freedesktop.org/



KernelsubsystemsDigitalVideoBroadcasting


DigitalVideoBroadcasting

DVB:DigitalVideoBroadcasting

DVBProject:http://www.dvb.org/

Since1993,industryledconsortiumofbroadcasters,manufacturers,networkoperators,softwaredevelopers,regulatorybodiesandothersinterestedinstandardsforthedeliveryofanydigitaltelevisionanddataservices.

CommittedtoopenstandardsStandardspecificationssupposedtobeavailablefreeofcharge(registrationrequired)fromETSI(EuropeanTelecommunicationStandardsInstitute)athttp://www.etsi.org/.

BasedonMPEG2transportstreams.


LinuxTVproject

http://linuxtv.org/

LinuxTVisavendorindependent,nonprofitLinuxprojectthatworksonastandardizedLinuxDVBAPIsince2000.

Version3oftheLinuxDVBAPIisincludedinLinux2.6.

VerypopularonPCsystems,mostlyinEuropeandinAustralia.

UsedbylotsofFreeSoftwareprojectsandcommercialSetTopBoxesondifferenthardwareplatforms.



FreeSoftwareVideoVideocodecsandfileformats


RealVideo

FromRealNetworkshttp://realnetworks.com/

Proprietaryformat

Originallyusedforlowbitratestreaming

SupportsstreamingthroughtheRealtimeTransportProtocol(RTP)

http://en.wikipedia.org/wiki/RealVideo

FreeSoftwaredecodersavailable(mplayer)

Supportedbysomemobilephones.

Mainlyusedforstreaming,usedbyasignificantnumberofonlinemedia.

Onlyproprietaryencoders.RealNetworksencoderfreeofchargeonlyforpersonaluse.


WMV

WindowsMediaVideo

Proprietaryvideocodec:Microsoft'snonstandardMPEG4implementation.

OftencomeswithWMAforAudio.

PackedintoAVIorAdvancedStreamingFormat(ASF)container.

SupportsDRMencryption.

Nowmanyhardwareplayersavailable.

Notmanyfilesownedbyusers(preferDivXorXviD).

However,moreandmoreonlinestreamsavailableinthisformat.Customersarelikelytoexpectsupportforthisformatinahardwareplayer.

LackofFreeSoftwareplayers(exceptlibavcodec)andencoders.

Reliesonpatentedalgorithms.

Licensesmayapplytoencoding,decodingorevensongs,thoughMSisstillverytolerantsofar(toachievedomination).


QuickTime

FromAppleComputerhttp://apple.com/quicktime/

Multimediatechnologysupportingseveraldigitalvideoformats,sound,text,animation,music,andvirtualrealitypanoramicimages.

Openfileformat1998:ApprovedbyISOasthebasisfortheMPEG4standard

MPEG4compatibilitysince2002.

VideooftenencodedwiththeSorensonproprietarycodec.

FewusershaveQuickTimevideosandwillaskforQuickTimesupport.

NoFreeSoftwareencodersSorensonpatentlicensewouldbeneededanywayinsomecountries.

Just1FreeSoftwaredecoder(FFmpeg'slibavcodec).

Moreonhttp://en.wikipedia.org/wiki/Quicktime


DivX

FromDivXNetworkshttp://divxnetworks.com/

DivX3.11:hackedversionoftheMicrosoftMPEG4layer2codec,whichmadethecodecpopular.

Abletoshrinka56GBDVDvideotoafilefittinginaCDROM(700MB)withminimumqualityloss.

DivX4andlater:cleanroomimplementationfromDivXNetworks,toavoidissueswithMicrosoftcopyright.

DivX4:MPEG4layer2compliant

FreeSoftwareplayersavailable.

Supportedbymosthardwarevideoplayerstoo.

StillburdenedbyMPEG4patents.Insomecountries,licenseneededtoimplementoruseasoftwareorhardwareplayer.

Seehttp://en.wikipedia.org/wiki/DivX


XviD

FromXviD.orghttp://xvid.org/

FreeSoftwarecodec,MPEG4based,competingwithDivX.

StartedfromDivXNetworksOpenDivX,afteraccesstoitssourcesgotclosed.

License:GNUGPL.

Manyhardwareplayers.

ManyFreeSoftwareplayers.

StillburdenedbyMPEG4patents.Insomecountries,licenseneededtoimplementoruseasoftwareorhardwareplayer.

Seehttp://en.wikipedia.org/wiki/XviD


OggTheora

FromXiph.orghttp://theora.org/

Ogg:containerformultimediastreams.

Theora:videocodeccompetingwithMPEG4,RealVideoandWMV.

DerivedfromOn2TechnologiesVP3codec.On2irrevocablygrantedtoanyonearoyaltyfreelicensetouseallitsVP3patents.

VorbisorFlac:soundlayer

TheoralibraryavailableunderaBSDstylelicense.

Theoraalreadysupportedbyvarioussoftwareplayers.

Theoralibrarystillinbetastage,butgettingclosetoastablerelease.Anyway,thebitstreamformatisfrozenandwillbesupportedbyallfutureversions.

Veryrarehardwareplayers



Multimediadistributions


GeexBox

http://geexbox.org/

MPlayerbasedfullfeaturedhomemultimediasystem:Multimedia(DVD,DivX,CD,Ogg,MP3)andphotogallery.

AvailablethroughaliveCD:bootyourcomputerwithit,ejecttheCD,andloadwhatevermediayouwanttoread.

Size:6MB.GreatforlearningaboutaembeddedLinuxmediaplayer!

Graphics:DirectFB.

Supportedplatforms:i386andppc.Activelymaintained.


MythTV

http://mythtv.org/

SetofFreeSoftwareapplicationstoturnaPCintoadigitalvideorecorder/digitalmultimediahomeentertainmentsystem.BasedontheQTlibrary.

RequiresTVtunercardssupportedbythevideo4linux(2)kerneldrivers.

Lotsofgreatfeatures:commercialskipping,accesstofreeTVlistings,DVDburning,webbrowser,RSSnewsreader,IPtelephony...

CanbetriedthroughtheKnoppMythliveCD:http://en.wikipedia.org/wiki/Mythtv.

Seehttp://en.wikipedia.org/wiki/Mythtvfordetails.


FreeVo

http://freevo.sourceforge.net/

AnotherPCbaseddigitalmultimediahomeentertainmentsystem/personalvideorecorder.

Supposedtobeeasytoinstallfornewusers.

BasedontheSDLlibrary.

FreeElectrons.Kernel,driversandembeddedLinuxdevelopment,consulting,trainingandsupport.http//freeelectrons.com

Relateddocuments

Allourtechnicalpresentationsonhttp://freeelectrons.com/docs

LinuxkernelDevicedriversArchitecturespecificsEmbeddedLinuxsystemdevelopment

FreeElectrons.Kernel,driversandembeddedLinuxdevelopment,consulting,trainingandsupport.http//freeelectrons.com

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