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1、Face and 2-D Mesh Animation in MPEG-4 AbstractThispaperpresentsanoverviewofsomeofthesyntheticvisualobjectssupportedbyMPEG-4version-1,namelyanimatedfacesandanimatedarbitrary2DuniformandDelaunaymeshes.Wediscussbothspecificationandcompressionoffaceanimationand2D-meshanimationin
2、MPEG-4.Faceanimationallowstoanimateaproprietaryfacemodelorafacemodeldownloadedtothedecoder.Wealsoaddressintegrationofthefaceanimationtoolwiththetext-to-speechinterface(TTSI),sothatfaceanimationcanbedrivenbytextinput.Keywords·MPEG-4; ·Faceanimation; ·Computergraphics; ·Deform
3、ation; ·VRML; ·Speechsynthesizer;·Electroniccommerce1.IntroductionMPEG-4isanobject-basedmultimediacompressionstandard,whichallowsforencodingofdifferentaudio–visualobjects(AVO)inthesceneindependently.Thevisualobjectsmayhavenaturalorsyntheticcontent,includingarbitraryshape vid
4、eoobjects,specialsyntheticobjectssuchashumanfaceandbody,andgeneric2D/3Dobjectscomposedofprimitiveslikerectangles,spheres,orindexedfacesets,whichdefineanobjectsurfacebymeansofverticesandsurfacepatches.Thesyntheticvisualobjectsareanimatedbytransformsandspecial-purposeanimation
5、techniques,suchasface/bodyanimationand2D-meshanimation.MPEG-4alsoprovidessyntheticaudiotoolssuchasstructuredaudiotoolsandatext-to-speechinterface(TTSI).ThispaperpresentsadetailedoverviewofsyntheticvisualobjectssupportedbyMPEG-4version-1,namelyanimatedfacesandanimatedarbitrar
6、y2DuniformandDelaunaymeshes.WealsoaddressintegrationofthefaceanimationtoolwiththeTTSI,sothatfaceanimationcanbedrivenbytextinput.Bodyanimationand3DmeshcompressionandanimationwillbesupportedinMPEG-4version-2,andhencearenotcoveredinthisarticle.Therepresentationofsyntheticvisual
7、objectsinMPEG-4isbasedonthepriorVRMLstandard [11], [12] and [13] usingnodessuchas Transform,whichdefinesrotation,scaleortranslationofanobject,and IndexedFaceSet describing3Dshapeofanobjectbyanindexedfaceset.However,MPEG-4isthefirstinternationalstandardthatspecifiesacompresse
8、dbinaryrepresentationofanimatedsyntheticaudio-visualobjects.Itisimportantto
