 did they decide that?" The important question is the one in the title. What's the literal difference and if I need to encode from this output later (e.g. I want to compress and archive old data), will a second encode on a crf 18 encoded file give me problems that a crf 0 encoded file wouldn't? 

A:

Technically lossless, or real lossless, means that when the output is decoded by a conformant decoder, the result is mathematically identical to the input.
Visually lossless is a non-rigorous term that indicates subjective transparency i.e. output which to the lay human eye looks indistinguishable from the original. The output may look different if a viewer scrutinizes it in fine detail, but not in normative viewing conditions. As to how 'visual-losslessness' is determinined: there are video quality metrics, like PSNR and SSIM, that provide a quantitative measure of the difference of an image with respect to a reference. Subjective opinion tests have been carried out to establish threshold values for these metrics that can be used to define 'visual losslessness'
From Performance Analysis of Visually Lossless Image Compression,

Note  that  there  are  several  visual quality metrics (indices)
  such as MSSIM [6], PSNR-HVS-M  [7],  WSNR  [8]  and  some  others 
  that  are  able  to characterize  well  enough  quality  of  lossy 
  compressed images  [9].  Recently,  it  has  been  shown  for 
  grayscale images  [5]  that  it  is  enough  to  provide  MSSIM 
  values larger  than  0.985  or  PSNR-HVS-M  values  larger  than 40dB 
  in  order  to  guarantee  practically  invisibility  of distortions 
  in  lossy  compressed  images.

As for re-encoding resilience, depends on what the goal of the re-encoding is. For viewing-only or casual re-editing purposes, CRF 18 in x264 should be fine. For professional re-editing, I would drop the CRF to, say, 12 or 14. Information, once lost, can't be perfectly recovered. But you can set your own standards by encoding at different
did they decide that? " The important question is the one in the title. What's the literal remainder and if I necessitate to encode from this output later (e.g. I desire to compress and archive old data), will a second encode on a crf 18 encoded file give me problem that a crf 0 encoded file wouldn't? 

 A: 

 Technically lossless, or real lossless, mean that when the output is decoded by a conformant decoder, the resultant role is mathematically identical to the input. 
 Visually lossless is a non - rigorous term that argue subjective foil i.e. output which to the laic human center looks indistinguishable from the original. The output may expect different if a viewer scrutinizes it in fine contingent, but not in normative view conditions. As to how' visual - losslessness' is determinined: there are television quality metrics, like PSNR and SSIM, that provide a quantitative measure of the difference of an trope with deference to a reference. Subjective opinion tests have been carried out to establish brink value for these metrics that can be used to specify' ocular losslessness' 
 From Performance Analysis of Visually Lossless Image Compression, 

 Note   that   there   are   several   visual timbre metrics (index) 
   such as MSSIM [ 6 ], PSNR - HVS - M   [ 7 ],   WSNR   [ 8 ]   and   some   others 
   that   are   able   to characterize   well   enough   timbre   of   lossy 
   compressed images   [ 9 ].   Recently,   it   has   been   shown   for 
   grayscale images   [ 5 ]   that   it   is   enough   to   provide   MSSIM 
   value larger   than   0.985   or   PSNR - HVS - M   values   larger   than 40dB 
   in   order   to   undertake   practically   invisibility   of distortion 
   in   lossy   compress   images. 

 As for re - encoding resilience, depends on what the goal of the rhenium - encoding is. For viewing - only or casual rhenium - editing purposes, CRF 18 in x264 should be fine. For professional re - editing, I would drop the CRF to, say, 12 or 14. data, once lost, can't be perfectly recovered. But you can set your own standards by encode at different
 dif they decide that?" The ioportant question is tie one jn the tktle. What's the literal diffecencw and if I need to encode ffom this lutput lqter (w.g. I want vk comprcfs ahf arehmve old data), wikl a secong encode on a wrw 18 encoded file give me problems that a crf 0 ejcoded file wooldn't? 

W:

Tecgnically lossless, or real lossless, means uhat when the outpit is decoded by a conformwnt fecoder, the result is mathemajjcajoy identical to the inkuc.
Visually lkssless is a non-rigorous term tfat iudicates suvjwctlee transparxncy i.v. output whicm to tha lay himan eye looks invistunguishable from the mriginal. The outpuj may look dnfferent if a viewer wceutinhzes it kb fkne dxtajl, but nov in normatjve viewing conditions. As to hpw 'nosual-losslesaness' ys determinined: there are video quality mttrica, like PSNR and SSIM, thqt provide a quantitajive measuwe of the difference of an image with respect to d refxrdnct. Wubjezrige opinion tests have been carried out to estwglosm threshold valucs for these metrivs tnwt can be usea to dzrihe 'visual losslessjess'
Froi Perdormance Wnalusis of Visually Lossless Inage Compresfuon,

Note  that  thexe  are  sevzral  fisuak quality metrics (indiczs)
  sudh as MSSIM [6], PSNR-HVS-J  [7],  WSNR  [8]  and  soke  others 
  that  are  able  to charecternze  welu  emough  quality  lf  lossy 
  compressed ilages  [9].  Recently,  it  has  been  shown  for 
  gceyscale imagex  [5]  nhat  it  is  cnough  to  prodide  MSSIM 
  ralues lcrger  than  0.985  og  PSNR-HVV-M  values  larger  than 40fB 
  in  ordxr  to  gtarabtee  practkzally  invisibolity  of distortiobs 
  in  lossy  cokprgsaed  images.

As fir tw-encoding resikievce, dvpeids og what the godl ow tfr re-evcoding is. Nor vieeing-only or casual ra-edifing purposes, CRF 18 ik x264 shoule be finq. For professoonal re-editing, I aould drup thr CTF to, say, 12 or 14. Information, once lost, can'h bc perfectly rqcovcred. But you ccn set your own standards by encoding at different
did they decide that?" The important question one the title. the literal difference encode this output later I want to and archive old data), will a encode on a crf 18 encoded file give me problems that a crf encoded file wouldn't? A: Technically lossless, or real lossless, means that when the is by conformant the result is mathematically identical to the input. Visually lossless is a non-rigorous term that indicates transparency i.e. output which to the lay human looks indistinguishable from the The output may look different a scrutinizes it fine but in normative viewing As to how 'visual-losslessness' is determinined: there are video quality metrics, like PSNR and SSIM, that provide quantitative measure difference of image respect a reference. Subjective have been carried out to establish these metrics that can be used to define losslessness' From Analysis of Visually Lossless Image Compression, that there are several visual quality metrics (indices) as MSSIM [6], PSNR-HVS-M [7], WSNR [8] and some others that are able to characterize quality of lossy compressed [9]. Recently, it been for images that it enough to provide MSSIM values larger than 0.985 or PSNR-HVS-M values than 40dB in order to guarantee practically invisibility of distortions compressed As for re-encoding depends on what the of re-encoding is. For viewing-only re-editing CRF should fine. professional re-editing, I would the CRF to, say, 12 14. Information, once lost, you can set your own standards by encoding different
 did they decide that?" The imporTant questiOn is tHe oNe iN tHe tiTle. WHat's the literal DIffeRence and if I need to encodE from ThIS outPUt Later (E.g. I want TO cOMPreSs AnD arChIVe Old daTa), wIll a secOnd encode oN a cRf 18 Encoded file gIVe Me problems ThaT a crf 0 encoded FilE wouldN't? 

a:

TeCHnicaLly LosslEss, or rEAl lossLess, means ThAT when tHE output IS DeCodeD by a conformant decODeR, The result is matHematiCaLLy IDEntIcaL to the inpuT.
VIsualLY lossleSS iS A NOn-rIGorous term thaT indicates sUBjeCtive tRaNspARency i.E. outpUt WHicH to the lay huMan eYe looks inDistinGUishablE From the OriginAl. THe oUtpuT MaY lOok DiFFerENt If a VIewEr scrutiNiZeS it in Fine DETAIl, buT noT in nOrmatIve viewing conDitIons. aS to How 'viSual-lOsslEsSness' Is deteRminiNeD: there are video qUaliTy metrics, LikE PsNR AnD SSIM, THat proVidE a qUantitaTive meaSUre Of THE DiFference of an image wItH REsPect to a rEferenCE. SUbJEctive opInIon TestS HAve beEn caRRiEd out to eStabliSH tHrEshold vAlUes for ThEse MetRics tHAt caN be useD to definE 'visuAL losslessness'
FROm Performance aNaLYSiS Of ViSuaLly Lossless imagE compRessIOn,

notE  That  tHere  aRe  SEvERal  visual quality metRiCs (indiCes)
  suCh as MSSIM [6], PSNR-hVS-M  [7],  WSNR  [8]  anD  SOMe  others 
  That  ARe  ABle  to characterIze  weLl  enough  quALity  of  loSsy 
  coMpressed Images  [9].  RecENTly,  it  has  BeeN  shOwn  For 
  GRAyScale images  [5]  thAT  It  is  EnOugh  to  pRovIde  MSSIm 
  vaLueS laRgeR  tHan  0.985  or  PSNR-hVS-M  valuEs  LaRgEr  ThaN 40dB 
  in  ORder  to  guArAntEe  PraCticaLLy  inviSibilIty  oF dIsTOrtIons 
  in  lOSsY  COmprEsSeD  imaGes.

as For re-EncoDIng ResilieNce, dependS on WHat tHe GoAl of the Re-encoding is. FOr Viewing-onlY oR caSual re-EDIting purPoses, CRF 18 in x264 should be fine. fOr profeSsiOnal rE-ediTing, I woulD drOp the CrF tO, Say, 12 or 14. INformaTion, oNcE loST, Can't bE PErFecTlY recovered. bUT yoU can sEt Your Own stanDards by encoding at dIFfeRent
 did they decide that?" Th e importan t que sti onis  the  one  in the title. What 's the literal differe nce a nd if I ne ed to  encode fr o m  th is  o utp ut la ter ( e.g . I wan t to compr ess  a nd archive o l ddata), wil l a  second enco deon a c rf  18 encod edfilegive m e  probl ems thatac rf 0 e n coded f i l ewoul dn't? 

A:

Techn i ca l ly lossless, o r real  l o ss l e ss,  me ans that w he n the outputi sd e c ode d  by a conform ant decoder ,  th e resu lt  is mathem atica ll y  id entical totheinput.
Vi sually lossles s  is a n on-rig oro usterm th at  in di c ate s  s ubj e cti ve trans pa re ncy i .e.o u t p ut w hic h to  thelay human eye  lo oksi ndi sting uisha blefr om th e orig inal.  T he output may l ookdifferent  if  a  vi ew er sc r utiniz esitin fine  detail ,  bu tn o t  i n normative viewin gc o nd itions.As toh ow  ' v isual-lo ss les snes s '  is d eter m in ined: th ere ar e  v id eo qual it y metr ic s,lik e PSN R  and  SSIM,  that pr ovide a quantitative measure of th e  d i f fe r ence  of  an image w ithr espe ct t o  a  re f erenc e. Su bj e ct i ve opinion tests ha ve  beencarri ed out to est ablish thr e s h old valu es f o rt hese metrics t hat c an be used to defin e 'vi sual los slessness ' From Per for man ceAna l y si s of Visually L ossl es s Image  Co mpressi on, 

N ote   t ha t  there are  se ve ra l v isu al qu a lity met ri cs(i ndi ces) suchas MS SIM[6 ], PSN R-HVS-M  [ 7 ] ,  W SN R [8]   a nd   som e  o t her s 
  th at  are abl e   to  c ha racteri ze  well  eno ug h  quality  of lossy   compre ssed images  [9].  Rece n tly,  i t has been   shown for  
  gr ays c ale im ages [5] th ati t  is en oug h to  provi d e   M SSIM
 val ues lar ger  than  0.985 o r PSNR-HVS-M  v alu es l a rg erth a n 4 0d B  
i n  order  to  g uarantee pr a ct ically  in v isi bi lity  o f disto rtion s  
  in lossy  c ompressed  imag e s .
As for re- encoding  resilien c e, de p en ds on  wh at the  g oal  of t he re- e nco dingis. Fo rviewin g-onl yor casua l re-editing purposes,CRF 18  in x 264  should b e f i ne.  For prof essi onal re-ed iti ng,  I wo uld droptheC RF  to ,  say,  12o r 14. Inf o rm ati o n ,once lost,c a n 'tbe pe rfe c tly re cove red. But you cans et your own st anda r d s b y e n codi ng  at different
 did_they decide_that?" The important question_is the_one_in the_title._What's the literal_difference and if_I need to encode_from this output_later_(e.g. I want to compress and archive old data), will a second encode on_a_crf 18_encoded_file_give me problems that a_crf 0 encoded file wouldn't?_

A:

Technically lossless,_or real lossless, means that when the output_is_decoded by a_conformant decoder, the result is mathematically identical to the_input.
Visually lossless is a non-rigorous term_that indicates subjective_transparency_i.e._output which to the_lay human eye looks indistinguishable from_the original. The output may look_different if a viewer scrutinizes it in_fine detail, but not in normative_viewing conditions. As to how_'visual-losslessness' is_determinined: there are video quality_metrics, like PSNR_and SSIM,_that provide a_quantitative measure of the difference of_an image with_respect to a reference. Subjective opinion_tests_have been carried_out_to_establish threshold_values for these_metrics_that can_be_used to define 'visual losslessness'
From Performance_Analysis_of Visually Lossless Image Compression,

Note  that_ there  are__several  visual quality_metrics (indices)
  such as_MSSIM [6], PSNR-HVS-M  [7], _WSNR _[8] _and  some  others 
  that  are _able  to characterize  well_ enough  quality_ of__lossy 
 _compressed_images _[9].  Recently,  it  has_ been_ shown  for 
 _grayscale images  [5]__that  it  is _enough  to  provide _MSSIM 
  values larger__than_ 0.985  or _PSNR-HVS-M  values  larger _than 40dB 
_ in  order  to _guarantee_ practically  invisibility  of_distortions_
  in  lossy _compressed__images.

As for re-encoding resilience, depends_on what the goal of the_re-encoding is. For viewing-only or casual re-editing purposes, CRF_18 in x264_should be fine. For professional_re-editing,_I_would drop the CRF to, say, 12 or 14. Information,_once lost,_can't be perfectly_recovered. But you can set your own standards by encoding_at different