Quantcast KDVD: Convert 24 to 30fps - digitalFAQ.com Forums [Archives]
  #1  
12-13-2005, 09:53 PM
Shibblet Shibblet is offline
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All right. Now we process our video at 24fps, progressive.

However, our output video has to be 30fps for DVD.

How do I re-convert it to 30fps, and keep the new encode progressive?
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  #2  
12-13-2005, 09:59 PM
kwag kwag is offline
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You don't reconvert anything
You encode your progressive video at 24fps, with 3:2 "pulldown" enabled.
That makes it DVD compliant.

-kwag
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12-14-2005, 02:32 AM
Shibblet Shibblet is offline
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Alright, that's what I was thinking.

But doesn't 3:2 Pulldown convert 24fps to 30fps by interlacing two frames together?

That being the case, haven't I ruined my progressive image?
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12-14-2005, 04:47 AM
Dialhot Dialhot is offline
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Quote:
Originally Posted by Shibblet
That being the case, haven't I ruined my progressive image?
There is almost no progressive display nowaday. Except if you are using a progressive player, with a brand new progressive HDMI projector or a plasma screen, you have to interlace your picture before you can see it.
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12-14-2005, 02:27 PM
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So then, what you're telling me is that Progressive Scan is a farce? Some kind of marketing tool?
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12-14-2005, 05:01 PM
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For DVD ? Yes I do.
Progressive scan will be used fully with HD formats (HD-DVD or BluRay). It's just the begining then.
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12-14-2005, 08:19 PM
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Well then does the DVD Hardware eliminate those lines (or frames), or is it up to your television to get rid of the interlace lines on 2:3 pulldown?
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12-14-2005, 08:25 PM
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That's the part you miss : a television does not know how to display other thing than interlace. You never noticed it, but all what you are watching on your TV is interlaced

Don't be fooled by the artefact (combos) that you see on a PC monitor when watching such interlaced material : monitors are progressive, and that is why you see artifacts !
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12-14-2005, 08:27 PM
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Now when you say artifacts, are you talking about the imaging noise around edges (JPEG or MPEG Compression) or are you talking about jagged looking lines or edges?

Also, does an LCD Projection or DLP Projection do this same thing?
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12-14-2005, 08:35 PM
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Quote:
Originally Posted by Shibblet
Now when you say artifacts, are you talking about the imaging noise around edges (JPEG or MPEG Compression) or are you talking about jagged looking lines or edges?
I mean this :
http://www.100fps.com/distortion2.jpg

Quote:
Also, does an LCD Projection or DLP Projection do this same thing?
DLP I'm sure they are interlaced. LCD I don't know if they are progressive or not. I don't think the low cost ones are.
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12-14-2005, 08:47 PM
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Sorry about this, now I feel like I am just pushing. But I do have one more question.

I really want to understand all this. I feel like I encode better when I understand what is actually going on during the encoding.

Alright, with DVD2AVI when you decode with Forced Film on, it decodes to 24fps, and there are NO interlaced frames. Now, I am doing the math in my head, if you eliminated the 2 interlaced frames from 2:3 Pulldown in 30fps, you would come up with 18fps. So something isn't right mathematically, unless I am looking at it differently.

Does the DVD Hardware interlace the frames, or is it interlaced on the DVD?
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12-14-2005, 10:00 PM
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When you ivtc an mpeg from a capture or telecined DVD, you restore the 2 interlaced frames to 2 progressive frames, that is what happens when you use Telecide(). Now every fifth frame is an extra progressive frame and that is why we use Decimate(cycle=5) to elimnate it. The original 30 fps (29.97) is changed because if you remove every fifth frame out of 30 you end up with 24 fps, 30/5=6 and 30-6=24, thus the 24 fps, which is the original film framerate. Most DVD's on the other hand are in 24 fps with pulldown flags added to the mpeg header to tell the DVD player to telecine the mepg's for proper display on an interlaced display.
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  #13  
12-15-2005, 04:07 AM
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The main reason why a Pulldon is applied is cause the original movie mostly will be shot at almost 24fps for cinema purposes and a final TV playback will be done under 60Hz circumstancies (NTSC).

@ PAL we do have 50Hz in our Power systems, so a Television does use the 50Hz for displaying 50 fields per second and 50 fields per second do equal 25 frames per second. So we just apply a speedup to reach the 25fps playback.

@ NTSC its more difficult as 24fps are more far away to 29.97 where a simple speedup would cuause the characters acting and speaking like litte "roadrunners". So to playback faster by maintaining the total lenght, we have to ADD fields and NOT full frames as that would end up in jerky playbacks.
So a pulldown does separate the fields, does double some fields at given points and finally does weave the fields back into frames.

In Avisynth:
Code:
AVISource("24fpsFilm.avi")
SeparateFields()
SelectEvery(8,0,1,2,3,2,5,4,7,6,7)
Weave()
Code:
Filmframe     A   B   C  D   E   F   G  H   I    J  K
Videofield1   A  B  B  C  D  E  F  F  G  H  I  J  J  K
Pairs             |  |/  /  /|   |  |/  /  /|   |  |/  /
Videofield2    A  B  C  D  D  E  F  G  H  H  I  J  K  L
Time         --p--p--i--i--p--p--p--i--i--p--p--p--i--i->


Filmframe     A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z
Videofields   0  2  5  7 10 12 15 17 20 22 25 27 30 32 35 37 40 42 45 47 50 52 55 57 60 62
              1  3  6  8 11 13 16 18 21 23 26 28 31 33 36 38 41 43 46 48 51 53 56 58 61 63
                 4     9    14    19    24    29    34    39    44    49    54    59    64
Time        ------------------------------------------------------------------------------>
Reference:
http://home.arcor.de/scharfis_brain/...rlacing/#2.3.1

But a bistream at 29.97fps would end up in a much more bitrate needed encode, not even mention the plus of needed bitrate as its now interlaced!

So thats why NTSC encoders dont apply a Pulldown direktly, but a Puldown "flag"! This flag included in a 23.976 stream does tell the SAP that "he" (the SAP) should do the pulldown in the given manner as shown above before sending the signal to the NTSC 60Hz TV Set.
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12-15-2005, 01:18 PM
the viking the viking is offline
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This stuff have caused a lot of trouble to me lately

I have some retail DVD,"Hollywood" movies,that I demuxed and
remuxed.The DVD are R1,ordered from U.S.

Some of them is reported as 23.976 fps and others 29,97
when I preview the in DVD2AVI/DGIndex.

My question is,should I run the demuxed .m2v file that has
23,976 fps through DGPulldown to get 29,97 fps when playback,or should I leave it as it is?

And what about .AVI? if the avi is 23,976 fps ,I use to encode with
encode mode "3:2 Pulldown when playback" in TMPGenc.

If the avi is 29,97 fps I just encode it as it is.

Am I doing this stuff right,or should I change my methods?

And the main purpose with pulldown is to get films/movies
compatible with the NTSC standards,right?

Thanks
------------
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  #15  
12-15-2005, 01:21 PM
Dialhot Dialhot is offline
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Quote:
Originally Posted by the viking
My question is,should I run the demuxed .m2v file that has
23,976 fps through DGPulldown to get 29,97 fps when playback,or should I leave it as it is?
It depends about what you plan to do with this m2v ?

Quote:
And what about .AVI? if the avi is 23,976 fps ,I use to encode with
encode mode "3:2 Pulldown when playback" in TMPGenc.

If the avi is 29,97 fps I just encode it as it is.

Am I doing this stuff right,or should I change my methods?
You are doing right.

Quote:
And the main purpose with pulldown is to get films/movies
compatible with the NTSC standards,right?
Yes it is.
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  #16  
12-15-2005, 01:58 PM
the viking the viking is offline
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Dialhot wrote:
Quote:
It depends about what you plan to do with this m2v ?
Nothing directly to the m2v,I demux the DVD in order to add
subtitles in my own language.(No, nothing to do with piracy and filesharing if anyone thinks so ).

After adding subs,I mux everything back together again.
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  #17  
12-15-2005, 05:40 PM
Dialhot Dialhot is offline
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The pulldown flag is included in the mpeg stream. It is not removed by a demux operation. So you don"t have to put it back : it is still there.
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  #18  
12-15-2005, 06:33 PM
Shibblet Shibblet is offline
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So then, if I understand Phil correctly...

the pulldown flag is in the MPEG Stream. Then is the decoder what produces the interlaced frames on your television?
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  #19  
12-15-2005, 06:55 PM
kwag kwag is offline
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Quote:
Originally Posted by Shibblet
Then is the decoder what produces the interlaced frames on your television?
Exactly.

-kwag
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  #20  
12-16-2005, 06:53 AM
the viking the viking is offline
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Dialhot wrote:
Quote:
The pulldown flag is included in the mpeg stream. It is not removed by a demux operation. So you don"t have to put it back : it is still there.
Ok.But does the the pulldown flag only work with SAP?

Cause when I playback the remuxed DVD in MPC, the video renderer
filter shows a playback rate of app.23.976 fps.
And previewing the remuxed DVD in DGIndex shows also
23.976 fps.
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