Prologue

• Only 30fps telecined from 24fps can be converted back to 24fps by IVTC.
  If every frame is interlaced (most TV news and shows), we must apply deinterlace instead of IVTC.

• Generally speaking, IVTC bases on field combination and deinterlace bases on interpolation.
  field combination reconstructs original frames <=> interpolation produces artificial frames

• Once you find the video is created as 24fps originally, it's better to perform IVTC.
  Deinterlace downgrades the quality and 30fps remains. More processing time with larger compression size!

• Telecined 30fps is simple to identify. It's usually 3 progressive frames followed with 2 interlaced frames.

• Original 24fps (Odd field + Even field = Frame)

  
  

  1O+1E

  2O+2E

  3O+3E

  4O+4E

• 24fps -> 30fps (60 fields/s) This sample shows an odd field first telecine. Every two fields appends one field.
  NTSC TV bases on interlaced scan and displays only one field simultaneously at 59.94Hz, odd/even by turns.

  
  

  1O

  1E

  2O

  2E

  2O

  
  
  

  3E

  3O

  4E

  4O

  4E

• Actually, phosphorus of cathode-ray tube doesn't darken immediately after excited.
  The dark field is compensated by human eyes perceptually (so-called photogene, persistence of vision)
  Since 2/4 is displayed somewhat longer than 1/3, it's not ideal to display FILM source on NTSC TV.

  
  

• Why we see interlaced frames on PC?
  Different from TV, PC monitor bases on progressive scan.
  Most video editors combines 2 fields to 1 frame for display.

  
  

  1O+1E	2O+2E	2O+3E	3O+4E	4O+4E
  Odd First Telecine

  
  
  

  1E+1O	2E+2O	2E+3O	3E+4O	4E+4O
  Even First Telecine

• It's very important to set field order correctly before IVTC by AviUtl or TMPGEnc.
  IVTC with wrong field order will result in useless result (lots of interlaced frames)
  We must find out the right field order of input video at first.

  [1o1e][2o2e][3o3e][4o4e] => Odd First Telecine => [1o1e][2o2e][2o3e][3o4e][4o4e]
  [1o1e][2o2e][2o3e][3o4e][4o4e] => Odd First IVTC => [1o1e][2o2e][3o3e][4o4e]
  [1o1e][2o2e][2o3e][3o4e][4o4e] => Even First IVTC => fail

  [1o1e][2o2e][3o3e][4o4e] -> Even First Telecine => [1e1o][2e2o][2e3o][3e4o][4e4o]
  [1e1o][2e2o][2e3o][3e4o][4e4o] => Even First IVTC => [1o1e][2o2e][3o3e][4o4e]
  [1e1o][2e2o][2e3o][3e4o][4e4o] => Odd First IVTC => fail

• There are lots of progressive TV monitor and line doubler nowaday.
  It's too complicated to introduce so many glossaries, so I skip here.

Pros & Cons of Automatic IVTC compared to manual IVTC

• timesaving, easy to learn and easy to use
  Only experienced users handle well in manual IVTC.

• Accuracy of automatic IVTC depends on the algorithm of software and the nature of video.
  There is no automatic IVTC with 100% accuracy. Misjudging (interlaced) frame is possible.
  You have no chance to correct these frames in automatic IVTC except TMPGEnc.

• deInt 495 automatic IVTC for MotionJPEG only
• AVITuner 0.26b manual IVTC, hard to cooperate with other video editors/encoders
• VirtualDub 1.4c automatic IVTC & manual IVTC, hard to cooperate with other video editors/encoders
  It's a pity automatic IVTC doesn't work with Frame Server.

• AviUtl 0.96g automatic IVTC & manual IVTC, support VFAPI
  AviUtl performs instant automatic IVTC which gets rid of pre-processing! But... much slower

• TMPGEnc B12b automatic IVTC & manual IVTC, support VFAPI
  Although TMPGEnc is time-consuming at pre-processing, it's capable of frame correction.
  It's also possible to perform instant automatic IVTC when encoding by TMPGEnc B12b (all processing inside)

• Video source: D2V, 720x480, 79s, 29.97fps, 2394 frames
• D2V => AviUtl / TMPGEnc => VirtualDub (crop, resize) => TMPGEnc => Video-CD
• VirtualDub resize method: precise bicubic
• TMPGEnc motion search precision: normal, GOP:1/4/2

  Software	Method	Time Consumption
  Encoded by TMPGEnc B12b
  TMPGEnc B12b	Automatic IVTC	129s + 259s
  AviUtl 0.96g	Automatic IVTC	645s
  Encoded by TMPGEnc B12a
  TMPGEnc B12a	Automatic IVTC	185s + 302s
  TMPGEnc B12b	Automatic IVTC	129s + 300s

• Time Consumption = IVTC + [ crop/resize + MPEG-I encoding ]

• TMPGEnc B12b is visibly faster than previous version, not only encoding but also automatic IVTC.
• Although TMPGEnc is time-consuming at pre-processing 129s, overall speed 388s is much faster than AviUtl 645s.
  It's worth waiting for this pre-processing. In addition, it's possible to correct misjudging frames after automatic IVTC.

Automatic IVTC by AviUtl

• Open VFAPI project file (D2V, TPR), VDR or Reference AVI.
  Check Read as 60fps at the same time.
  

• Play forward by right arrow key. If it plays smoothly, the field order is right.
  If not, File -> General Settings -> Open video with delayed odd field then check this menuitem.
  Open video and Read as 60fps again, it will be fine now.
  That's the right field order to perform IVTC.

• Open video again. Now don't check Read as 60fps. We just use it to recognize field order.
• Setting -> Framerate Conversion -> 24<-30fps (4/5) then check this menuitem.
• Setting -> Framerate Conversion -> 24<-30fps invoke inverse telecine then check this menuitem.
• Setting -> Deinterlace -> Automatic inverse telecine then check this menuitem.
• Play forward by right arrow key. You will see the result of IVTC.

• Save Project File then convert AUP to reference AVI for other video editor or encoder.

Automatic IVTC by TMPGEnc

• Open VFAPI project file (D2V, AUP), VDR or Reference AVI.

• MPEG Setting -> Advanced -> Field order, choose Top field first (field A)
• Enable Deinterlace filter and double-click to setup the detail.
  

• Choose Even-odd field (field) That's like what you see on TV.
  Play forward by right arrow key. If it plays smoothly, the field order is right.
  If not, choose Bottom field first (field B) and try again. It will be fine now.
  

• That's the correct field order to perform Inverse Telecine.
• Remember to disable Deinterlace filter. We just use it to recognize the field order.
• BTW, we can enable Deinterlace filter and check it smooth or not by File -> Preview also.

• Enable Inverse telecine filter and double-click to setup the detail.
• Push Auto-setting and then push Start, waiting for pre-processing...
  

• After pre-processing is finished, play forward by right arrow key.
  You will see most frames are converted back to original FILM without interlaced.
  Maybe some interlaced (misjudging) frames remain, maybe not. It depends on the nature of video source.

• File -> Save Project then convert TPR to reference AVI for other video editor or encoder.

• Automatic (flicker priority): for variable telecined source, field combination based on flicker level
• Automatic (motion priority): for variable telecined source, field combination based on motion level
• Fixed sequence 3:2 pulldown: for fixed telecined source (hard-coded telecine, ex. FILM Type + Preserve FILM OFF)

• Those options have no relation to 30->24fps conversion.
  Automatic (convert to 30fps): 30fps deinterlace based on field combination, useful for variable field order
  Automatic (simple 60fps): 30->60fps, [1O1E][2O2E][3O3E]... => [1O1E][2O1E][2O2E][3O2E][3O3E][4O3E]...
  Automatic (24/30fps to 60fps): hybird 24/30fps->60fps based on field combination

• Pre-processing calculates flicker/motion information for each frame before IVTC.
  TMPGEnc stores these information in Cache folder.
  It's possible to resume the calculation after pre-processing aborted.

• The most time-consuming is information calculation which performs only once.
  Switching IVTC algorithms takes only a little while.

• Accuracy of automatic IVTC depends on the nature of video source and IVTC algorithm.
  There is no IVTC algorithm which can cope with all video sources. Misjudging (interlaced) frame is possbile.

• Misjudging frame correction is very tricky, so I suggest you forgetting it :-p
  Actually, the accuracy of TMPGEnc/AviUtl IVTC is good enough.

• Progressive frames usually beside interlaced frames. No matter how you tune up these frames...
  Once | Estimated - Current | > 1, A/V will lose synchronization!
  Verify the synchronization status by Check button.
  Once it says that there is a time gap, the video will be async.
  Correct misdjuging frames based on this guideline.
  

• If you understand Chinese, please refer to this page.

Parthian Shot

• Anime (Japanese Animation) especially old ones is very difficult to perform IVTC.
  It may looks interlaced but actually it's progressive (hard to explain ^^;)
  There are lots of notorious Anime which are hard to cope with, such as Lodoss OVA OP, EVA OP, Yamamoto Yoko OP

• If you encounter such kind of video and still want to remain x480 progressive frame (ex. MPEG4)
  Extra deinterlace is necessary.
  If your final goal is VCD (x240) authoring, just resize after IVTC.
  Resizing will decrease the influence of interlaced frame.

• Another trouble of Anime is that they are not always pure 24fps. It may be...
  • pure 30fps: ToHeart OP, Lain ED, Sakura War OVA2
  • pure 60fps: Silent Mobius OP
  • hybrid 30/60fps: Dual OP, SolBianca
  • hybrid 24/30fps: Lain OP, Kurumi OP, Angel Links OP
  Identify the nature of video at first.