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Old 25th September 2015, 11:12   #141  |  Link
TheSkiller
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Quote:
Originally Posted by kolak View Post
Yes and same for DVD and BD due to lack of 25p support in the spec.
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Originally Posted by huhn View Post
BD and DVD doesn't support 25p only 50i.
I disagree. BD does indeed not support 25p at all, but DVD does. I'm not talking about encoding 25p interlaced.
You can use Zig-Zag scan for the actual encoding, progressive chroma sampling and have both the "Frametype progressive" and "Progressive sequence" flag set to true, as well as the "Film" flag in the IFOs, and still have a compliant DVD. A hardware player will recognize this and won't even try to deinterlace anything, which it would if the video was encoded interlaced, because the player would expect interlaced video then.

I'm not talking theoretically here, I have authored dozens of 25p DVDs in exactly this manner over the years, they all playback fine in old and new players, cheap and expensive ones.


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Originally Posted by johnmeyer View Post
Does 25p encoded as 50i actually produce a different effect on the screen than would that same content encoded and played at 25p?
Yes, if encoded interlaced the player, of course, expects interlaced video and will try to deinterlace it. This will hurt the video quality more or less, how much depends on the deinterlacer and field matcher, as noted by huhn.
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Originally Posted by huhn View Post
in worst case scenario it is bob deinteralced and this is visible.

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Originally Posted by davidhorman View Post
Chroma is also encoded (not in the sense of video compression; what's the word I really mean?!) slightly differently for interlaced video
I think the term you were looking for is "sampling".

Speaking of it, this is a "gotcha": if you are encoding 25p interlaced but with progressive chroma sampling, you are risking the infamous CUE (chroma upsampling error), because the progressive sampled chroma may be upsampled by the player as if it were interlaced (also depends on how exactly the player handles the upsampling, so it may not happen).
If you're encoding 25p progressive this won't happen.

This means: if you are encoding 25p interlaced you must use interlaced chroma sampling to completely avoid the CUE on all players!

Last edited by TheSkiller; 25th September 2015 at 11:37.
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Old 25th September 2015, 11:57   #142  |  Link
kolak
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If I remember well Cinemacraft encoders don't set Progressive sequence (you can set Frame type progressive=1), because there is no real 25p support in DVD spec. Progressive sequence=1 means whole file is purely progressive.
Having just Frame type progressive=1 indicates file which may be progressive, but possibly there are also interlaced frames in the file, so overall whole file is treated as interlaced. This is how most "25p" retail DVDs are flagged, which I think is the correct way (per spec).

I've seen only 1 or 2 DVDs with Progressive sequence=1.

Words of Jim Taylor (DVD guru):

In MPEG-2 encoding, the decision between progressive and interlaced format can be made all
the way down at the macroblock level.The DVD-Video specification limits MPEG-2 video to nonprogressive
sequences, which can include both progressive and interlaced frames.
Progressive frames are still encoded for display as two fields, but they are identified as progressive.
Interlaced frames can further include both progressive and interlaced macroblocks. Since progressive
macroblocks are more efficient (using one motion vector instead of two), even interlaced source
is often encoded with more than 50 percent progressive macroblocks. However, each frame is represented
as two fields of 720 x 240 pixels each for NTSC or 720 x 288 pixels each for PAL/SECAM.

Different source:

https://books.google.co.uk/books?id=...%20dvd&f=false

by well known here Ben Waggoner

Which is in line with Cinemacraft encoders behaviour (they are probably the most DVD compliant on the planet).
I think you can still use Progressive sequence=1 ( I've also done it) and have proper playback on most players anyway, but it's against DVD spec.


There may be also possibility that this "subject" is not covered in DVD spec for 25p based sources, but mentioned resources say quite clearly that DVD is limited to nonprogressive sequences.

As I side note: there are many "bad" discs which for 23.976p+pulldown use GOP>12 (should be 12 or less) , which is out of DVD spec (GOP<0.606 sec) and this can cause real playback issues on some players.

Last edited by kolak; 25th September 2015 at 12:43.
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Old 25th September 2015, 12:31   #143  |  Link
Music Fan
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Quote:
Originally Posted by manono View Post
No it doesn't. It'll be output by the DVD player at 59.94 fields per second, just like any other NTSC DVD.
Does it mean Sharc was wrong ?

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Originally Posted by Sharc View Post
I should add that correct IVTC will include decimation, as mentioned by vivian. Means playback will be restored at the original rate, means no duplicated frames = no judder.

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I don't know why, though, you'd want to encode a 25fps source at 29.97fps when you can just as easily encode for 25fps
That's what the OP needs.
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Old 25th September 2015, 12:35   #144  |  Link
kolak
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I don't really want to encode 25p as 29.97p for DVD, as someone mentioned (but answer would be- for eg. USA market).
I need conversion on the master level. I never said in original post anything about DVD or other delivery method (until later).

We're very out of topic now

It's for broadcast, so it will be hard coded and probably never restored to original fps, just played as 60i.
As I mentioned- my last worry are potential flashes on scene changes when watched through proper interlaced chain on a TV.

Last edited by kolak; 25th September 2015 at 12:55.
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Old 25th September 2015, 13:13   #145  |  Link
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.... We're very out of topic now
Nice refresher and tutorial, though.
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Old 25th September 2015, 14:30   #146  |  Link
TheSkiller
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Originally Posted by kolak View Post
As I mentioned- my last worry are potential flashes on scene changes when watched through proper interlaced chain on a TV.
I don't understand what you mean by flashes.

When you pulldown 25p to 29.97i for broadcast, the TV will bob-deinterlace to 59.94p (unless maybe it detects the cadence, but 25p-in-29.97i is so uncommon it'll probably end up being bob-deinterlaced).
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Old 25th September 2015, 14:47   #147  |  Link
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When scene change happens on bottom field (which in case of 'normal' interlaced file never happens).
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Old 25th September 2015, 15:16   #148  |  Link
TheSkiller
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So basically you mean comb artefacts at the scene change, as if the frame is weaved (not deinterlaced at all)?
Shouldn't happen, and if it does it's the TV's deinterlacer failing.

If you connect any home made analog tape format to a TV there will be plenty of scene changes that occur within the same frame (about 50% actually). Plus, every field blended NTSC<->PAL normconversion (so LOADS) has plenty of scene changes at bottom fields (for a TFF video). I have never witnessed a problem with that, except maybe that it's harder for the encoder to detect it as a scene change.

Last edited by TheSkiller; 25th September 2015 at 15:23.
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Old 25th September 2015, 15:36   #149  |  Link
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if you need it for broadcast you need both 720p60 and 1080i60.

so for 720p 3:2:3:2:2 frame cadence should clearly win alternative is frame blending...
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Old 25th September 2015, 17:08   #150  |  Link
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Originally Posted by TheSkiller View Post
Speaking of it, this is a "gotcha": if you are encoding 25p interlaced but with progressive chroma sampling, you are risking the infamous CUE (chroma upsampling error), because the progressive sampled chroma may be upsampled by the player as if it were interlaced (also depends on how exactly the player handles the upsampling, so it may not happen).
If you're encoding 25p progressive this won't happen.
Using interlaced chroma sampling is exactly the same as not doing anything special to the chroma, unless we're talking about one of those formats with oddball interlaced chroma sampling. (DV is one of them, I think?) If potential chroma aliasing from bad deinterlacing is a concern, you could always low-pass the chroma vertically first.

(Also, I just did a search on CUE and the first few results were from like 2001. How is this still a concern in 2015?)
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Old 25th September 2015, 20:38   #151  |  Link
manono
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Does it mean Sharc was wrong ?
To tell you the truth, I was puzzled by that, too, and figured he was referencing something earlier in the thread and I didn't feel like going back through the whole thing to figure it out. I also figured he was speaking of something else and we're not contradicting each other. In any event, any 60 (59.94) Hz display will have to output the video at either 59.94 fields per second or 59.94 frames per second. That's what pulldown, either hard or soft, is all about.
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Old 25th September 2015, 21:55   #152  |  Link
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Thus it means players can't make IVTC with decimation with this kind of video.
But I still have doubts because, by comparison, 3:2 pulldown flag is supposed to create 29,97 fps, but some players can make IVTC and output 23.976 hz (when resolution is set on 1080p). So the flag is used but the reverse operation is done just after, inside the player, as if there was no flag.
Why wouldn't it be possible too with 25p flagged as 29,97 fps ?

Last edited by Music Fan; 25th September 2015 at 21:59.
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Old 25th September 2015, 22:15   #153  |  Link
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Thus it means players can't make IVTC with decimation with this kind of video.
But I still have doubts because, by comparison, 3:2 pulldown flag is supposed to create 29,97 fps, but some players can make IVTC and output 23.976 hz (when resolution is set on 1080p). So the flag is used but the reverse operation is done just after, inside the player, as if there was no flag.
Why wouldn't it be possible too with 25p flagged as 29,97 fps ?

Cadence reading setups that have 3:2:3:2:2 support can read it. 100% for sure.

When you look at hardware reviews, they test varous cadence tests. 3:2:3:2:2 is one of the (fairly) common patterns tested. Most newer players in the medium to more expensive range can. Cheapo models usually cannot. "FAIL" means they are deinterlaced (jaggies)

But you should understand that over here, 99.99% of the TV's run at 60Hz. Even a successfully IVTCed 3:2 "24p" will have judder because you 're seeing frame repeats. Even on a native 24p Blu-ray (no pulldown), you will see 3:2 repeats because the display is running at 60. Only those "24p" capable TV's that have a refesh rate of an integer multiple of 24 (e.g. 120hz, 240) can display them properly without any judder.

So you will see the same thing pattern wise. 3:2:3:2:2 on a 60Hz display, whether or not you have a smart IVTC or dumb deinterlacing setup. The difference is the picture quality
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Old 25th September 2015, 23:46   #154  |  Link
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....Why wouldn't it be possible too with 25p flagged as 29,97 fps ?
It's possible provided that the player can handle the 2:1:1:1:1 cadence. You would have to watch the "inverse telecined" stream on a PAL TV (50Hz) however to enjoy it judder-free.
Strictly, the 25<->30 (29.97) fps conversion with the 2:1:1:1:1 pattern is not Telecining or IVTC respectively. It's pure pulldown and decimation respectively. Telecining always involves fields and interlacing.

Last edited by Sharc; 26th September 2015 at 07:39.
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Old 26th September 2015, 06:18   #155  |  Link
manono
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...by comparison, 3:2 pulldown flag is supposed to create 29,97 fps, but some players can make IVTC and output 23.976 hz
Sort of. Flag readers (the vast majority of the NTSC DVD players out there) can make progressive 23.976fps for soft telecined material. Cadence readers can both do that as well as perform an IVTC on-the-fly, so to speak - return hard telecined DVDs to progressive 23.976fps. But, if it's a 60Hz progressive display (a nice 60" LED television, for example) that progressive 23.976fps video still has to be displayed in the 3232323232 sequence. As pdr says, it's not being deinterlaced so the picture quality is better, but it still has that 3-2 judder (is that the correct word?). The 120 and 240 Hz displays can play it smoothly, though,
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Old 26th September 2015, 08:18   #156  |  Link
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.... but it still has that 3-2 judder (is that the correct word?).
I think so. In the context of framerate conversion and pulldown it is the commonly used term for unequal display durations of individual frames on the screen ("pulldown-judder").
There are other sources of judder of course, e.g. due to motion and camera sweeps which are not synchronized with the TV playback framerate whatever this is. Modern TV's do a lot to mitigate these effects (e.g. by interpolating), more or less successfully.

Last edited by Sharc; 26th September 2015 at 09:18.
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Old 26th September 2015, 09:44   #157  |  Link
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It's possible provided that the player can handle the 2:1:1:1:1 cadence. You would have to watch the "inverse telecined" stream on a PAL TV (50Hz) however to enjoy it judder-free.
Of course, I'm not talking about 60hz only TV's. European TV's support 50 and 60hz, and also very often 24 hz (which is generally displayed in 96 hz, with or without motion compensation).
If a european player connected to a european TV (both supporting 50 and 60hz) can't make decimation with 25p flagged as 29.97, it's perhaps due to a choice (to stay in the Ntsc logic and display only 23.976 or 29.97 fps when the flag is 29.97), not a technical limit (admitting the player can make decimation).

@ poisondeathray and manono : I understand, but that does not really answer my question about the possibility to display in 50hz on a 50/60hz screen this kind of dvd (25p flagged as 29.97).

Last edited by Music Fan; 26th September 2015 at 09:47.
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Old 26th September 2015, 10:46   #158  |  Link
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.....
@ poisondeathray and manono : I understand, but that does not really answer my question about the possibility to display in 50hz on a 50/60hz screen this kind of dvd (25p flagged as 29.97).
Not sure whether I interpret your question correctly, but:
- by "25p source flagged as 29.97" you mean soft-pulldown i.e. every 5th frames is flagged to be pulled down (repeated) by the player at playback time. The original 25p stream is otherwise untouched, the pulldown is done at playback time by the player. Correct?
- A 50Hz (PAL) system will ignore the pulldown flag and play every 25p frame twice, or in a multiple of 50Hz depending on TV with/without "smart" motion interpolation.
- A 60Hz system will normally play it at 60 (59,94) Hz in a 4:2:2:2:2 pattern with judder. Smart systems may apply some interpolation to smoothen the playback
- A multi-norm system should recognize the pulldown flag and the 2:1:1:1:1 cadence, ignore it and display it in 50 Hz (or a multiple 100, 200 ....thereof).
I think these are the options, no?

Last edited by Sharc; 26th September 2015 at 11:27.
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Old 26th September 2015, 11:23   #159  |  Link
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Yes, but I wonder if a 50hz or multi-norm system can really ignore the flag (or use it then make the reverse operation because I believe the flag can't be ignored) and display this kind of dvd in 50hz.
But I'm not talking only about 29.97p but also 29.97i (what is usually called 60i). Thus whatever 3:2:3:2:2 or 2:1:1:1:1, if the video is in 25p and flagged with DGpulldown (to be displayed in 29.97 fps), the ideal framerate to display it is 50hz (50p). But that's maybe not possible with standalone players. I'm gonna try.
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Old 26th September 2015, 11:33   #160  |  Link
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Looking forward to your test results ....
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