转:ffmpeg使用x264编码的配置+ ffmpeg与 x264编码器参数完整对照表

本文链接:http://www.php-oa.com/2009/03/09/ffmpeg_x264.html

转帖:http://rhingheart.blogspot.com/2009/03/ffmpegx264-ffmpeg-x264.html

使用ffmpeg进行.264编码的相关文章比较少，google了一下，特总结如下：

qscale的取值可以是0.01-255但实际使用超过50就很糟糕了

ffmpeg的cbr模式可以把码率控制的不错，但是vbr无法限制最高码率（虽然有max的设置，但是程序没有实现）

x264标准的封装是x264+aacinflv或者x264+aacinMP4

接下来说明下ffmpeg命令行的语法规则（本块内容来自2009-03-02官方文档）：

语法规则结构：

ffmpeg[[infileoptions][`-i'infile]]...{[outfileoptions]outfile}...

一个最简单的命令形式：

ffmpeg-iinput.avi-b64koutput.avi

这个命令把视频以64k的码率重编码。

显然，输入文件前面要加一个-i选项下面介绍一些有用的全局参数：

-formats参数。会显示你机器当前支持的封装、编码、解码器的信息

-y参数,会指示ffmpeg覆盖输出文件

-t指定视频流持续的时常,支持以秒为单位的数字或"时:分:秒[.毫秒]"

-fs指定输出文件大小的限制

-ss指定开始的时间,和-t的单位一样

-target直接设定你想要转成的目标格式,所有的相关设置都会采用内设值,当然也你也可以加上自己要修改的参数。可用的选择有:

"vcd","svcd","dvd","dv","dv50","pal-vcd","ntsc-svcd",…

这个例子把视频转换成vcd的格式

ffmpeg-imyfile.avi-targetvcd/tmp/vcd.mpg

接下来介绍视频选项：

-b指定码率注意单位是bit/s,所以我们一般要加k,比如-b1000k就是1000kb/s

-g设置组的大小

-vframes指定要编码的帧数,比如-vframes1就是编码1帧,截图的时候就这样写.

-r指定帧率,默认是25

-s指定图像分辨率,用wxh的格式,比如320×240

-aspect指定宽高比可以些16:9这种,也可以写小数比如1.3333

-croptop指定顶部裁减多少像素,类似的还有-cropleft-cropright-cropbuttom

-bt设置比特率容许的误差,默认4000k,在第一阶段时使用这个参数会告诉码率控制器能够偏移平均码率多远,这个选项和最大最小码率无关.设太小了不利于质量

-maxrate和-minrate指定允许的最大和最小码率,一般如果要用cbr模式编码的话会用这个:

ffmpeg-imyfile.avi-b4000k-minrate4000k-maxrate4000k-bufsize1835kout.m2v

否则用处不大

-vcodec强制使用某种编码器

-sameq使用和源文件相同的质量,这个选项是动态码率的

-pass指定编码阶段,这个只有1和2,第一阶段的时候应该不处理音频,并且把输出导向空,比如:

ffmpeg-ifoo.mov-vcodeclibxvid-pass1-an-frawvideo-yNULffmpeg-ifoo.mov-vcodeclibxvid-pass1-an-frawvideo-y/dev/null

-qscale使用固定量化因子来量化视频这个是在vbr模式的,前面有提到,越小质量越好,不要超过50,相关的参数还有-qmin–qmax用来设定最大最小可使用的量化值

-qdiff指定固定量化器因子允许的最大偏差

-qblur指定量化器模糊系数，可用范围是0.0-1.0越大使得码率在时间上分配的越平均

-qcomp指定视频量化器压缩系数，默认0.5

-me_method指定运动估计方法（motionestimationmethod），可用的选择从垃圾到好排列如下：

zero（0向量）

phods

log

x1

hex

umh

epzs（默认）

full（完全搜索，很慢又好不到哪里去）

-mbd设定宏模块决策，可用的值：

0使用mb_cmp，不知道是什么东西，所以这些参数我参考一下mencoder里面的

1选用需要比特最少的宏块模式

2选用码率失真最优的宏块模式

-4mv使用宏块的4个运动向量，只支持mpeg4

-part使用数据划分，只支持mpeg4

-ilme强制允许交错的编码，只支持mpeg2和mpeg4，你可以选择用-deinterlace来去交错

音频部分:

-ar设置采样频率,默认44100hz

-ab设置比特率,默认64k

-an禁用音频录制

-acodec指定音频编码器

下面举几个x264编码的例子：

我使用mencoder调用x264编码一个psp用的视频：

x264+aacinmp4(我修改过的，原作者的不能使用)

mencodertest_video.vob-oaclavc-lavcoptsacodec=libfaac:abitrate=94-ovcx264-x264encopts\

cabac=1:ref=1:deblock=1,0,0:analyse=0x1,0x111:me=hex:subme=6:psy_rd=1.0,0.0:mixed_refs=0:me_range=32:chroma_me=1:trellis=1:8x\

8dct=0:no-chroma-me=0:chroma_qp_offset=-\

2:nr=0:dct_decimate=1:bframes=3:b_pyramid=0:b_adapt=1:b_bias=0:direct=3:keyint=250:keyint_min=25:scenecut=40:qp=18:bitrate=80\

0-lavdoptser=2-oflavf-lavfoptsformat=mp4-vfscale=720:480-omen.mp4

对应的ffmpeg编码参数是：

ffmpeg

ffmpeg-iinputfile.avi-fpsp-acodeclibfaac-ab94k-vcodeclibx264-cqp28-coder1-refs3-deblockalpha1-deblockbeta-1-me_methodumh-subq9-me_range32-trellis2-chromaoffset-2-nr0-bf2-b_strategy1-bframebias0-directpred3-g250-i_qfactor1.3-b_qfactor1.4-flags2+bpyramid+wpred+mixed_refs+8x8dct-er2-s480x320

需要注意的是,flags2里面那块,似乎要按照一定顺序才能正常工作,其他地方都差不多,详细情况可以从下面两篇文章得出:

第一篇是这个在网上被传了很多,但有些问题的对照表格,我修改了有问题的部分:

FFmpegoptionx264option

-g<frames>–keyint

-b<bitspersecond>–bitrate

-bufsize<bits>–vbv-bufsize

-maxrate<bits>–vbv-maxrate

-pass<1,2,3>–pass

-crf<float>–crf

-cqp<int>–qp

-bf<int>–bframes

-coder<0,1>–no-cabac

-bframebias<int>–b-bias

-keyint_min<int>–min-keyint

-sc_threshold<int>–scenecut

-deblockalpha<int>-deblockbeta<int>–deblock

-qmin<int>–qpmin

-qmax<int>–qpmax

-qdiff<int>–qpstep

-qcomp<float>–qcomp

-qblur<float>–qblur

-complexityblur<float>–cplxblur

-refs<int>–ref

-directpred<int>–direct

-me_method<epzs,hex,umh,full>–me

-me_range<int>–merange

-subq<int>–subme

-bidir_refine<0,1>–bime

-trellis<0,1,2>–trellis

-nr<int>–nr

-level<int>–level

-bt<bits>–ratetol=-bt/-b

-rc_init_occupancy<bits>–vbv-init=-rc_init_occupancy/-bufsize

-i_qfactor<float>–ipratio=1/-i_qfactor

-b_qfactor<float>–pbratio

-chromaoffset<int>–chroma-qp-offset

-rc_eq<string>–rc_eq

-threads<int>–threads

-cmp<-chroma/+chroma>–no-chroma-me

-partitions–partitions

+parti8×8i8×8

+parti4×4i4×4

+partp8×8p8×8

+partp4×4p4×4

+partb8×8b8×8

-flags

-loop/+loop–no-deblock/–deblock

-psnr/+psnr–no-psnr/nothing

-flags2

+bpyramid–b-pyramid

+wpred–weightb

+brdo–b-rdo我这里的ffmpeg已经不能用这个了

+mixed_refs–mixed-refs

+dct8×8–8×8dct

-fastpskip/+fastpskip–no-fast-pskip

+aud–aud

下面是一篇关于这些参数详细解释的文章,转自:http://ffmpeg.x264.googlepages.com/mapping

一下是这篇文章在2008年11月19日更新的版本:

Frame-typeoptions:

–keyint<integer>(x264)

-g<integer>(FFmpeg)

Keyframeinterval,alsoknownasGOPlength.ThisdeterminesthemaximumdistancebetweenI-frames.VeryhighGOPlengthswillresultinslightlymoreefficientcompression,butwillmakeseekinginthevideosomewhatmoredifficult.Recommendeddefault:250

–min-keyint<integer>(x264)

-keyint_min<integer>(FFmpeg)

MinimumGOPlength,theminimumdistancebetweenI-frames.Recommendeddefault:25

–scenecut<integer>(x264)

-sc_threshold<integer>(FFmpeg)

Adjuststhesensitivityofx264′sscenecutdetection.Rarelyneedstobeadjusted.Recommendeddefault:40

–pre-scenecut(x264)

UNKNOWN(FFmpeg)

Slightlyfaster(butlessprecise)scenecutdetection.Normalscenecutdetectiondecideswhetheraframeisascenecutaftertheframeisencoded,andifsothenre-encodestheframeasanI-frame.Thisisnotcompatiblewiththreading,however,andso–pre-scenecutisautomaticallyactivatedwhenmultipleencodingthreadsareused.

–bframes<integer>(x264)

-bf<integer>(FFmpeg)

B-framesareacoreelementofH.264andaremoreefficientinH.264thananypreviousstandard.Somespecifictargets,suchasHD-DVDandBlu-Ray,havelimitationsonthenumberofconsecutiveB-frames.Most,however,donot;asaresult,thereisrarelyanynegativeeffecttosettingthistothemaximum(16)sincex264will,ifB-adaptisused,automaticallychoosethebestnumberofB-framesanyways.ThisparametersimplyservestolimitthemaxnumberofB-frames.NotethatBaselineProfile,suchasthatusedbyiPods,doesnotsupportB-frames.Recommendeddefault:16

–b-adapt<integer>(x264)

-b_strategy<integer>(FFmpeg)

x264,bydefault,adaptivelydecidesthroughalow-resolutionlookaheadthebestnumberofB-framestouse.Itispossibletodisablethisadaptivity;thisisnotrecommended.Recommendeddefault:1

0:Veryfast,butnotrecommended.Doesnotworkwithpre-scenecut(scenecutmustbeofftoforceoffb-adapt).

1:Fast,defaultmodeinx264.Agoodbalancebetweenspeedandquality.

2:AmuchslowerbutmoreaccurateB-framedecisionmodethatcorrectlydetectsfadesandgenerallygivesconsiderablybetterquality.Itsspeedgetsconsiderablyslowerathighbframesvalues,soitsrecommendedtokeepbframesrelativelylow(perhapsaround3)whenusingthisoption.Italsomayslowdownthefirstpassofx264wheninthreadedmode.

–b-bias0(x264)

-bframebias0(FFmpeg)

Makex264morelikelytochoosehighernumbersofB-framesduringtheadaptivelookahead.Notgenerallyrecommended.Recommendeddefault:0

–b-pyramid(x264)

-flags2+bpyramid(FFmpeg)

AllowsB-framestobekeptasreferences.Thenameistechnicallymisleading,asx264doesnotactuallyusepyramidcoding;itsimplyaddsB-referencestothenormalreferencelist.B-referencesgetaquantizerhalfwaybetweenthatofaB-frameandP-frame.Thissettingisgenerallybeneficial,butitincreasestheDPB(decodingpicturebuffer)sizerequiredforplayback,sowhenencodingforhardware,disablingitmayhelpcompatibility.

–no-cabac(x264)

-coder0,1(FFmpeg)

CABACisthedefaultentropyencoderusedbyx264.Thoughsomewhatsloweronboththedecodingandencodingend,itoffers10-15%improvedcompressiononlive-actionsourcesandconsiderablyhigherimprovementsonanimatedsources,especiallyatlowbitrates.Itisalsorequiredfortheuseoftrellisquantization.DisablingCABACmaysomewhatimprovedecodingperformance,especiallyathighbitrates.CABACisnotallowedinBaselineProfile.Recommendeddefault:-coder1(CABACenabled)

–ref<integer>(x264)

-refs<integer>(FFmpeg)

OneofH.264′smostusefulfeaturesistheabillitytoreferenceframesotherthantheoneimmediatelypriortothecurrentframe.Thisparameterletsonespecifyhowmanyreferencescanbeused,throughamaximumof16.IncreasingthenumberofrefsincreasestheDPB(DecodedPictureBuffer)requirement,whichmeanshardwareplaybackdeviceswilloftenhavestrictlimitstothenumberofrefstheycanhandle.Inlive-actionsources,morereferencehavelimitedusebeyond4-8,butincartoonsourcesuptothemaximumvalueof16isoftenuseful.Morereferenceframesrequiremoreprocessingpowerbecauseeveryframeissearchedbythemotionsearch(exceptwhenanearlyskipdecisionismade).Theslowdownisespeciallyapparentwithslowermotionestimationmethods.Recommendeddefault:-refs6

–no-deblock(x264)

-flags-loop(FFmpeg)

Disableloopfilter.Recommendeddefault:-flags+loop(Enabled)

–deblock(x264)

-deblockalpha<integer>(FFmpeg)

-deblockbeta<integer>(FFmpeg)

OneofH.264′smainfeaturesisthein-loopdeblocker,whichavoidstheproblemofblockingartifactsdisruptingmotionestimation.ThisrequiresasmallamountofdecodingCPU,butconsiderablyincreasesqualityinnearlyallcases.Itsstrengthmayberaisedorloweredinordertoavoidmoreartifactsorkeepmoredetail,respectively.Deblockhastwoparameters:alpha(strength)andbeta(threshold).Recommendeddefaults:-deblockalpha0-deblockbeta0(Musthave‘-flags+loop’)

–interlaced(x264)

UNKNOWN(FFmpeg)

Enablesinterlacedencoding.x264′sinterlacedencodingisnotasefficientasitsprogressiveencoding;considerdeinterlacingformaximumeffectiveness.

Ratecontrol:

–qp<integer>(x264)

-cqp<integer>(FFmpeg)

Constantquantizermode.Notexactlyconstantcompletely–B-framesandI-frameshavedifferentquantizersfromP-frames.Generallyshouldnotbeused,sinceCRFgivesbetterqualityatthesamebitrate.

–bitrate<integer>(x264)

-b<integer>(FFmpeg)

Enablestargetbitratemode.Attemptstoreachaspecificbitrate.Shouldbeusedin2-passmodewheneverpossible;1-passbitratemodeisgenerallytheworstratecontrolmodex264has.

–crf<float>(x264)

-crf<float>(FFmpeg)

Constantqualitymode(alsoknownasconstantratefactor).Bitratecorrespondsapproximatelytothatofconstantquantizer,butgivesbetterqualityoverallatlittlespeedcost.Thebestone-passoptioninx264.

–vbv-maxrate<integer>(x264)

-maxrate<integer>(FFmpeg)

Specifiesthemaximumbitrateatanypointinthevideo.RequirestheVBVbuffersizetobeset.Thisoptionisgenerallyusedwhenencodingforapieceofhardwarewithbitratelimitations.

–vbv-bufsize<integer>(x264)

-bufsize<integer>(FFmpeg)

Dependsontheprofilelevelofthevideobeingencoded.Setonlyifyou’reencodingforahardwaredevice.

–vbv-init<float>(x264)

-rc_init_occupancy<float>(FFmpeg)

InitialVBVbufferoccupancy.Note:Don’tmesswiththis.

–qpmin<integer>(x264)

-qmin<integer>(FFmpeg)

Minimumquantizer.Doesn’tneedtobechanged.Recommendeddefault:-qmin10

–qpmax<integer>(x264)

-qmax<integer>(FFmpeg)

Maximumquantizer.Doesn’tneedtobechanged.Recommendeddefault:-qmax51

–qpstep<integer>(x264)

-qdiff<integer>(FFmpeg)

SetmaxQPstep.Recommendeddefault:-qdiff4

–ratetol<float>(x264)

-bt<float>(FFmpeg)

Allowedvarianceofaveragebitrate

–ipratio<float>(x264)

-i_qfactor<float>(FFmpeg)

QscaledifferencebetweenI-framesandP-frames.

–pbratio<float>(x264)

-b_qfactor<float>(FFmpeg)

QscaledifferencebetweenP-framesandB-frames.

–chroma-qp-offset<integer>(x264)

-chromaoffset<integer>(FFmpeg)

QPdifferencebetweenchromaandluma.

–aq-strength<float>(x264)

UNKNOWN(FFmpeg)

Adjuststhestrengthofadaptivequantization.Highervaluestakemorebitsawayfromcomplexareasandedgesandmovethemtowardssimpler,flatterareastomaintainfinedetail.Default:1.0

–pass<1,2,3>(x264)

-pass<1,2,3>(FFmpeg)

Usedwith–bitrate.Pass1writesthestatsfile,pass2readsit,and3bothreadsandwritesit.Ifyouwanttousethreepass,thismeansyouwillhavetouse–pass1forthefirstpass,–pass3forthesecond,and–pass2or3forthethird.

–stats<string>(x264)

UNKNOWN(FFmpeg)

Allowssettingaspecificfilenameforthefirstpassstatsfile.

–rceq<string>(x264)

-rc_eq<string>(FFmpeg)

Ratecontrolequation.Recommendeddefault:-rc_eq‘blurCplx^(1-qComp)’

–qcomp<float>(x264)

-qcomp<float>(FFmpeg)

QPcurvecompression:0.0=>CBR,1.0=>CQP.Recommendeddefault:-qcomp0.60

–cplxblur<float>(x264)

-complexityblur<float>(FFmpeg)

ReducefluctuationsinQP(beforecurvecompression)[20.0]

–qblur<float>(x264)

-qblur<float>(FFmpeg)

ReducefluctuationsinQP(aftercurvecompression)[0.5]

–zones/(x264)

UNKNOWN(FFmpeg)

Allowssettingaspecificquantizerforaspecificregionofvideo.

–qpfile(x264)

UNKNOWN(FFmpeg)

Allowsonetoreadinasetofframetypesandquantizersfromafile.Usefulfortestingvariousencodingoptionswhileensuringtheexactsamequantizerdistribution.

Analysis:

–partitions<string>(x264)

-partitions<string>(FFmpeg)

p8x8(x264)/+partp8x8(FFmpeg)

p4x4(x264)/+partp4x4(FFmpeg)

b8x8(x264)/+partb8x8(FFmpeg)

i8x8(x264)/+parti8x8(FFmpeg)

i4x4(x264)/+parti4x4(FFmpeg)

OneofH.264′smostusefulfeaturesistheabilitytochooseamongmanycombinationsofinterandintrapartitions.P-macroblockscanbesubdividedinto16×8,8×16,8×8,4×8,8×4,and4×4partitions.B-macroblockscanbedividedinto16×8,8×16,and8×8partitions.I-macroblockscanbedividedinto4×4or8×8partitions.Analyzingmorepartitionoptionsimprovesqualityatthecostofspeed.Thedefaultistoanalyzeallpartitionsexceptp4x4(p8x8,i8x8,i4x4,b8x8),sincep4x4isnotparticularlyusefulexceptathighbitratesandlowerresolutions.Notethati8x8requires8x8dct,andisthereforeaHighProfile-onlypartition.p8x8isthemostcostly,speed-wise,ofthepartitions,butalsogivesthemostbenefit.Generally,wheneverpossible,allpartitiontypesexceptp4x4shouldbeused.

–direct<integer>(x264)

-directpred<integer>(FFmpeg)

B-framesinH.264canchoosebetweenspatialandtemporalpredictionmode.Autoallowsx264topickthebestofthese;theheuristicusediswhichevermodeallowsmoreskipmacroblocks.Autoshouldgenerallybeused.

–direct-8×8(x264)

UNKONWN(FFmpeg)

Thisshouldbeleftatthedefault(-1).

–weightb(x264)

-flags2+wpred(FFmpeg)

ThisallowsB-framestouseweightedpredictionoptionsotherthanthedefault.Thereisnorealspeedcostforthis,soitshouldalwaysbeenabled.

–me

–merange<integer>(x264)

-me_range<integer>(FFmpeg)

MErangecontrolsthemaxrangeofthemotionsearch.ForHEXandDIA,thisisclampedtobetween4and16,withadefaultof16.ForUMHandESA,itcanbeincreasedbeyondthedefault16toallowforawider-rangemotionsearch,whichisusefulonHDfootageandforhigh-motionfootage.NotethatforUMHandESA,increasingMErangewillsignificantlyslowdownencoding.

–mvrange(x264)

UNKNOWN(FFmpeg)

Limitsthemaximummotionvectorrange.Sincex264bydefaultlimitsthisto511.75forstandardscompliance,thisshouldnotbechanged.

–subme6(x264)

-subq6(FFmpeg)

1:Fastest,butextremelylowquality.Shouldbeavoidedexceptonfirstpassencoding.

2-5:Progressivelybetterandslower,5servesasagoodmediumforhigherspeedencoding.

6-7:6isthedefault.Activatesrate-distortionoptimizationforpartitiondecision.Thiscanconsiderablyimproveefficiency,thoughithasanotablespeedcost.6activatesitinI/Pframes,andsubme7activatesitinBframes.

8-9:Activatesrate-distortionrefinement,whichusesRDOtorefinebothmotionvectorsandintrapredictionmodes.Slowerthansubme6,butagain,moreefficient.

Anextremelyimportantencodingparameterwhichdetermineswhatalgorithmsareusedforbothsubpixelmotionsearchingandpartitiondecision.

–psy-rd<float>:<float>(x264)

UNKNOWN(FFmpeg)

Firstvaluerepresentstheamountthatx264biasesinfavorofdetailretentioninsteadofmaxPSNRinmodedecision.Requiressubme>=6.Secondvalueispsy-trellis,anexperimentalalgorithmthattriestoimprovesharpnessanddetailretentionattheexpenseofmoreartifacting.Recommendedstartingvaluesare0.1-0.2.Requirestrellis>=1.Recommendeddefault:1.0:0.0

–mixed-refs(x264)

-flags2+mixed_refs(FFmpeg)

H.264allowsp8x8blockstoselectdifferentreferencesforeachp8x8block.Thisoptionallowsthisanalysistobedone,andboostsqualitywithlittlespeedimpact.Itshouldgenerallybeused,thoughitobviouslyhasnoeffectwithonlyonereferenceframe.

–no-chroma-me(x264)

UNKNOWN(FFmpeg)

Chromaisusedinthelaststepsofthesubpixelrefinementbydefault.Foraslightspeedincrease,thiscanbedisabled(atthecostofquality).

–8x8dct(x264)

-flags2+dct8x8(FFmpeg)

Givesanotablequalityboostbyallowingx264tochoosebetween8×8and4×4frequencytransformsize.Requiredfori8x8partitions.Speedcostforthisoptionisnear-zerobothforencodinganddecoding;theonlyreasontodisableitiswhenoneneedssupportonadevicenotcompatiblewithHighProfile.

–trellis<0,1,2>(x264)

-trellis<0,1,2>(FFmpeg)

0:disabled

1:enabledonlyonthefinalencodeofaMB

2:enabledonallmodedecisions

Themaindecisionmadeinquantizationiswhichcoefficientstoroundupandwhichtorounddown.Trellischoosestheoptimalroundingchoicesforthemaximumrate-distortionscore,tomaximizePSNRrelativetobitrate.Thisgenerallyincreasesqualityrelativetobitratebyabout5%forasomewhatsmallspeedcost.Itshouldgenerallybeenabled.NotethattrellisrequiresCABAC.

–no-fast-pskip(x264)

-flags2-fastpskip(FFmpeg)

Bydefault,x264willskipmacroblocksinP-framesthatdon’tappeartohavechangedenoughbetweentwoframestojustifyencodingthedifference.Thisconsiderablyspeedsupencoding.However,foraslightqualityboost,P-skipcanbedisabled.Inthiscase,thefullanalysiswillbedoneonallP-blocks,andtheonlyskipsintheoutputstreamwillbetheblockswhosemotionvectorshappentomatchthatoftheskipvectorandmotionvectorshappentomatchthatoftheskipvectorandwhichhavenoresidual.Thespeedcostofenablingno-fast-pskipisrelativelyhigh,especiallywithmanyreferenceframes.ThereisasimilarB-skipinternaltox264,whichiswhyB-framesgenerallyencodemuchfasterthanP-frames,butitcannotbedisabledonthecommandline.

–no-dct-decimate(x264)

UNKNOWN(FFmpeg)

Bydefault,x264willdecimate(removeallcoefficientsfrom)P-blocksthatareextremelyclosetoemptyofcoefficents.Thiscanimproveoverallefficiencywithlittlevisualcost,butmayworkagainstanattempttoretaingrainorsimilar.DCTdecimationshouldbeleftonunlessthere’sagoodreasontodisableit.

–nr(x264)

UNKNOWN(FFmpeg)

afast,built-innoisereductionroutine.Notaseffectiveasexternalfilterssuchashqdn3d,butfaster.Sincex264alreadynaturallyreducesnoisethroughitsquantizationprocess,thisparameterisnotusuallynecessary.

–deadzone-inter(264)

–deadzone-intra(x264)

UNKNOWN(FFmpeg)

UNKNOWN(FFmpeg)

Whentrellisisn’tactivated,deadzoneparametersdeterminehowmanyDCTcoefficientsareroundedupordown.Roundingupresultsinhigherqualityandmoredetailretention,butcostsmorebits–soroundingisabalancebetweenqualityandbitcost.Loweringthesesettingswillresultinmorecoefficientsbeingroundedup,andraisingthesettingswillresultinmorecoefficientsbeingroundeddown.Recommended:keepthematthedefaults.

–cqm(264)

–cqpfile(x264)UNKNOWN(FFmpeg)

UNKNOWN(FFmpeg)

Allowstheuseofacustomquantizationmatrixtoweightfrequenciesdifferentlyinthequantizationprocess.Thepresetsquantmatricesare"jvt"and"flat".–cqpfilereadsacustomquantmatricesfromaJM-compatiblefile.Recommendedonlyifyouknowwhatyou’redoing.