Contents

PVRG-MPEGCODEC1.1

AndyC.Hung

June14,1993Copyrightc1990,1991,1993AndyC.Hung,Allrightsreserved.

ThisworkwasdoneatthePortableVideoResearchGroup(PRVG),StanfordUniversity.

Thisdocumentisprovidedforgeneralinformationaluse.Noresponsibilityisassumedbytheauthorswith

regardtotheaccuracyoftheinformationcontainedherein.

Thedocumentationdescribedhereinmaybeused,copied,ortranscribedwithoutfeeorprioragreement

providedthatacknowledgementorreferenceismadeofthesource.

SunisatrademarkofSunMicrosystems,Inc.UNIXisatrademarkofAT&T.DECstationisatrademark

ofDigitalEquipmentCorporation.

ThispackageisbasedontheUNIXoperatingsystem.Weappreciateanycommentsorcorrections-they

canbesenttoAndyC.Hungatachung@cs.stanford.edu.Wecannotguaranteethatanybugswillbecorrected

however.

FundedbytheDefenseAdvancedResearchProjectsAgency.

IamespeciallygratefultoHewlettPackardandStormTechnologyfortheirfinancialsupportduringthe

earlierstagesofcodecdevelopment.Anyerrorsinthecodeanddocumentationaremyown.Thefollowing

peopleareacknowledgedfortheiradviceandassistance.Weapologizeifwehavemissedanyonefromthislist.

Thanks,oneandall.

ThePortableVideoResearchGroupatStanford:TeresaMeng,PeterBlack,NavinChaddha,BenGordon,

SheilaHemami,Wee-ChiewTan,EliTsern.

AdriaanLigtenbergofStormTechnology.JeanneWiseman,AndrewFitzhugh,GregoryYovanof,and

ChuckRosenbergofHewlettPackard.EricHamiltonandJean-GeorgesFritschofC-CubeMicrosystems.

LawrenceRoweoftheBerkeleyPlateauResearchGroup.

TomLaneoftheIndependentJPEGGroup.

ThierryTurletti,Inria.

KatsumiTahara,Sony;CiaranMcGoldrick;KarlLillevold;MatsLofkvist;HiroshiSaitoh,Panasonic;

FrankGadegast;ChadFogg,Cascade;AndersKlemets;GrahamLogan;JellevanZeijl;GeorgeWarner,

AT&T;ChrisAdams,HewlettPackard.

Dedicatedtothestandardizationcommitteesandtheireffortsinbringingtheadvancementoftechnologyto

everyone.

iContents

Contentsii

1GettingStarted1

1.1CommonQuestionsandAnswers1

1.2FurtherInformation2

2UnderstandingImageCompression3

2.1Introduction3

2.2ColorSpace3

2.3MPEGModel4

2.4MotionCompensationandEstimation4

2.5TransformStage6

2.6Quantization8

2.7CodingModel9

2.8EntropyCoding10

2.9Layering11

2.10Detailsonencoding12

2.11MotionEstimation13

2.12RateControl14

2.13DCIntraframeMode14

3CallingParameters15

3.1Encoder15

3.1.1Whatarethefiles?18

3.1.2EncodingExamples18

3.2Decoder18

3.2.1DecodingExamples19

3.3ProgramTrace19

3.4ReturnValues22

4TheProgramInterpreter23

4.1Terminology23

4.2Tokens23

4.2.1SpecialCharacters24

4.3Comments25

4.4Aborting25

4.5StructureDefinition25

4.6Invalidcommands26

4.7Printing27

4.8ArithmeticCommands27

4.9StackCommands28

4.10MemoryAccessCommands28

4.11ProgramAccessCommands28

ii4.12LabelsandEquivalences29

4.13BranchCommands29

4.14ReservedMemoryLocations30

4.15ReservedProgramLocations31

4.16CommandList31

4.17Examples32

4.17.1IntraframeCoding32

4.17.2ReferenceBlockCoding33

4.17.3ReferenceRateControl34

4.18EnablingtheProgramInterpreter:Anexample34

5ProgramDocumentation36

5.1ProgramFlow36

5.2FunctionalDescription36

5.2.1mpeg.c37

5.2.2codec.c39

5.2.3huffman.c39

5.2.4io.c40

5.2.5chendct.c41

5.2.6lexer.c42

5.2.7marker.c43

5.2.8me.c44

5.2.9mem.c44

5.2.10stat.c45

5.2.11stream.c45

5.2.12transform.c46

Bibliography48

iiiChapter1

GettingStarted

ThisdocumentdescribesthePortableResearchVideoGroup’s(PVRG)PVRG-MPEGsoftwarecodec.Theinitial

versionofthiscodecwasdevelopedin1990,basedontheveryearlyMPEGsimulationmodelspecifications.

ThePVRG-MPEGsoftwarecodecthatisdescribedhereisbasedontheSantaClara1991draft.Since1991,very

littledevelopmentonthePVRG-MPEGsoftwarecodechasoccurred,untilrecentverificationbecamepossible.

Weshouldcautiontheuserthatbugsareprobablystilllurking.

1.1CommonQuestionsandAnswers

Let’sanswersomecommonquestionsabouttheMPEG-Iproposedstandard.Inthefollowingdiscussionwewill

useMPEGtorefertoMPEG-I.Anotheremergingstandardforhigherbit-ratesisMPEG-II(orMPEGphaseII).

WhatisMPEGMPEGstandsforMovingPictureExpertsGroupwhichisresponsibleforaudio,video,and

combinedsynchronizationofinformationindigitalimagesequencecoding.MPEGisajointinternational

committee(ISO-IEC/JTC1/SC2/WG8).

HowdoesMPEG-IdifferfromH.261?TheMPEG-Ialgorithmisdefinedforhigherbitrates–0.9Mbps

to1.5MbpsandconsequentlyforhigherqualitytheH.261.TheH.261specificationtargetsasomewhat

lowertelecommunicationrate,aslowas64kbps,andashortinteractivedelay.Thecombinedencoder-

decoderdelayinMPEGmaybehigherthanisacceptablefortruetelecommunication;thisdelaymaynot

beobjectionableinmultimedia.

HowdoesMPEGdifferfromJPEG?MPEGistargetedtowardimagesequencecompression.JPEGis

targetedtowardstill(single)imagecompression.

Whatdoesthisparticularpackagedo?ThispackageimplementstheMPEGCommitteeDraft(Santa

Clara’91)compressionspecificationswithsomeencodingalgorithmsbasedonMPEGsimulationmodels

1-3,thoughnotidentical.ItshouldbeabletoencodeanddecodestreamsformostMPEGplayers.