Avisynth replacements for DVD players features

[bilu]

Now let's consider the case where the clip is mostly video. In this case, we want avoid decimating the video portions be smooth. For the film portions, we want to leave them at the video rate but change the duplicated frame into a frame blend so it is not so obvious.

Decimate(mode=1) is useful for hybrid clips having mostly video. It allows you to leave the frame rate at video rates (to get smooth video sequences) but also to ameliorate the effect of duplicate frames that are emitted by Telecide() for film sequences (frames that are normally removed with mode=0)


@neuron2

Is this the same logic applied by Progressive Scan on NTSC DVD Players?

At first I thought it was IVTC, but then again they need to keep the framerate at 29.97 fps.

If so, those who encode NTSC DVDs (at least those without Progressive Scan players) would greatly benefit from using Decimate(mode=1) on every CCE encode!

PS: I don't encode DVDs, only XVID.

Best regards,

Bilu

[Guest]

Originally posted by bilu
Is this the same logic applied by Progressive Scan on NTSC DVD Players? I'm sorry, but I don't understand your question. Perhaps you could clarify it for me.

[bilu]

Originally posted by neuron2
I'm sorry, but I don't understand your question. Perhaps you could clarify it for me.

Well, it seems I didn't understood it either. :rolleyes:

Two of the main features on today's top DVD players (I've been reading it now for the first time, and have no experience in this field) seem to be "Progressive Scan" and "3:2 inverse pulldown".


http://www.znews.com/video/dvd/progressive-scan-dvd.html

While a regular DVD player displays in what is called 480i -- this stands for 480 lines resolution, with interlaced frames (a technology whereby the TV flashes one-half of the picture information at any given moment), a progressive scan DVD player outputs a 480p signal, which means the whole picture is on the screen at the same time, much like most computer monitors.

Keep in mind that your HDTV may convert the 480i signal to 480p, so you may not even need a Progressive Scan DVD Player even if you have an HDTV.

http://timefordvd.com/hardware/DVDBuyingGuide.shtml

To reduce motion artifacts to an absolute minimum, look for a progressive scan DVD player with a 2:3 pulldown feature (also known as "3:2 pulldown" or "3:2 inverse pulldown"). The 2:3 pulldown feature works on film-based video sources (most movies) and compensates for film's 24 frames per second versus progressive scan video's 60 frames per second refresh rate. What you get is smooth images with minimal motion artifacts when watching film-based sources. So if you're planning to buy a digital TV, look for 480p component video inputs, consider buying a progressive scan DVD player, then connect them using component video cables. A progressive scan DVD player can output a conventional interlaced picture so you can use it today with your current analog TV and later upgrade to a digital TV with 480p input.



Nothing can be done about the Progressive Scan feature - it depends exclusively on hardware. But maybe Decimate(mode=1) could help as an alternative Telecine process for those who have no 2:3 pulldown feature on their players? :sly:


Best regards,
Bilu

[scmccarthy]

@biluSo if you're planning to buy a digital TV, look for 480p component video inputs, consider buying a progressive scan DVD player, then connect them using component video cables. A progressive scan DVD player can output a conventional interlaced picture so you can use it today with your current analog TV and later upgrade to a digital TV with 480p input. What you are reading about progressive scan DVD players is for people who plan to view their DVDs on a digital TV. Everything you view on a computer screen is progressive. When you view an interlaced frame in progressive mode, you get combing artifacts and that is why you must use Decomb.

At first I thought it was IVTC, but then again they need to keep the framerate at 29.97 fps It is not clear whether you mean Decimate(mode=1) or a Progressive Scan player by 'it'. mode=1 is what you use when IVTC should not be done.

IVTC stands for inverse telecine which you only should do if your source was telecined in the first place. The terms video and film might be confusing you. In this context film means it has been telecined and you can IVTC it and video means it has not been telecined and IVTC will not work.

In the initial quote by Donald Graft at the top of this thread, he is explaining what to do with hybrid material where there is some telecining, but the majority of the clip is not. In the telecine portion, every fifth frame will be a duplicate. Normally these frames should be decimated, but using mode=1 will cause them to be blended instead.

Stephen

[edit] Watching movies on a computer screen is like watching them on a digital television except that the picture is much smaller. A computer screen has a much sharper image compared to a regular TV and it is always progressive. The picture is so much smaller that it is not really an advantage, but part of the fun of AviSynth is it's supersharp resizing filters.

[Guest]

Now let's consider the case where the clip is mostly video. In this case, we want avoid decimating the video portions be smooth. Oh my Darwin, did I emit that sentence?

I will correct the help file immediately. :o

This is how it should have read:

Now let's consider the case where the clip is mostly video. In this case, we want to avoid decimating the video portions so they will be smooth. For the film portions, we want to leave them at the video rate but change the duplicated frame into a frame blend so it is not so obvious.

[bilu]

@scmccarthy

I made some confusion on my first post, and then I searched a bit more to clarify my question to neuron2. I was thinking mainly in those people who author DVDs with CCE frameserving with Avisynth.

The feature mentioned as "2:3 pulldown" seems to be Telecine, the opposite of IVTC, to adjust DVDs released at film rates to NTSC 30 fps.

The 2:3 pulldown feature works on film-based video sources (most movies) and compensates for film's 24 frames per second versus progressive scan video's 60 frames per second refresh rate.


That's why I remembered Decimate(mode=1). Because we would want 24 fps converted to 30 fps, and blending could in theory look better than a standard Telecine process. For cheaper DVD players with no "2:3 pulldown" (should be called pullup :rolleyes: ) feature, reencoding with Decimate(mode=1) could improve watching.

Still worst than leaving at the original film rate, but then again we have no choice, right? :confused:


Bilu

[scmccarthy]

Yeah, there is no choice because we are talking about hybrid material where there is a little telecining but mostly not.

2:3 pulldown lets you save space on the disk by not storing the duplicate frames in telecined material on the DVD.

It is perfectly OK to save the dup frames in telecined material to the DVD and avoid having to use 2:3 pulldown on playback if that makes mastering the DVD easier. The fact that telecined material can be saved alternately both ways on the same disk creates confusion at first. 2:3 pulldown is always used for telecined material, but telecined material does not always require 2:3 playback. And it is a player feature that every DVD player must implement to conform to spec. The mpeg2dec dlls also perform 2:3 pulldown before Decomb sees it.

Hopefully you won't be confused by the next statement, if so just ignore it. Therefore, DeComb is decimating frames that were not even stored on the DVD originally. The 2:3 pulldown supplies the duplicates before they are decimated.

Stephen

[bilu]

@scmccarthy

I found your last statement a bit hard to read :)

My idea is to take DVD stream encoded at 23.996 fps and reencode them at 29.97 fps, not using Telecine (opposite of IVTC, 2:3 and not 3:2 pulldown) but Decimate(mode=1) instead, getting progressive NSTC frames with blending instead of duplicates. It could be worth it for those DVD players, because every movie will need to be played at 29.97 fps, the NTSC framerate.

I know what IVTC is, I'm talking about an alternative to the opposite process. If it's worth :)

Bilu

[scmccarthy]

@bilu

After careful study, I confirmed that the terminology is messed up as usual. 2:3 pulldown is used by DVD players to show 27.97 fps without storing duplicate fields on the DVD when the source has been telecined. So for regular players, 2:3 pulldown is a way to display the telecine picture while saving disc space. Progressive scan players don't perform 2:3 pulldown. The proper term would be 2:3 pulldown detection. All this means is that regular NTSC DVD players output 29.97 fps telecine that a progressive player will perform IVTC on at 23.976 fps. 2:3 pulldown is not IVTC.

Another thing to keep in mind is that NTSC and PAL are both interlaced broadcast standards. DVDs are designed to output interlaced streams always. Putting it another way, outputting NTSC from an NTSC DVD and outputting PAL from a PAL DVD is straight forward, but deinterlacing output from a DVD is complex with multiple stratagies depending on how the DVD was encoded and whether it is video or telecine. There can be progressive frames stored on a DVD, but never progressive sequences, only interlaced.

Maybe this is too complex, so here is the bottom line: all progressive players deinterlace, all PC DVD players are progressive, and DeComb deinterlaces using all the different possible strategies.

1) There is no such thing as progressive NTSC frames, NTSC is an interlaced standard.

2) DVDs do not store streams at 23.976 fps.

3) Telecine is 29.97 fps interlaced, same as video.

4) Progressive players don't have to output at the 29.97 fps NTSC framerate.

Checkout the following sections in the DVDFAQ:

[1.19] Is DVD-Video a worldwide standard? Does it work with NTSC, PAL, and SECAM?

[1.40] What's a progressive DVD player?

[3.4] What are the video details?

[3.8] What is the difference between interlaced and progressive video?

This is the other site I found:

http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html

Stephen

[manono]

Hi-

Ack! You were doing so well for awhile.

2) DVDs do not store streams at 23.976 fps.

With a fully progressive DVD (admittedly there aren't that many, but the situation's improving), they're all stored at 24fps. From Robshot's Article (http://www.doom9.org/index.html?/synch.htm) here on the Doom9 site:
The benefit of this that the movie CAN be stored in its original 24 FRAME per second, and thus SAVE 20% of total filesize!.
And from the Home Theater HiFi Article (http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html) that you linked:
For every film frame that had three fields made from it, the third field is a duplicate of the first, and (if the MPEG-2 encoder is behaving properly) won't even be stored on the DVD
The link should answer all of bilu's questions.

Edit Later: I just remembered that bilu's original question hasn't been answered yet. No, you don't want to use Decomb's Mode=1 feature when encoding in CCE (unless, perhaps, you're dealing with hybrid material). You'll take a 25% quality hit for the same file size because of the increased number of frames. And you'll also be outputting a considerable number of blended frames. Just keep on using Force Film or IVTC to bring film material back to 23.976fps and let Pulldown set the flags to output 29.97fps.

[bilu]

Manono,

Thanks for your answer. What I initially though was that blended frames like in Decimate(mode=1) could look better that the duplicates of Telecine, maintaining the 29.97 fps NTSC framerate.

But a good answer comes from the Robshot's article you mentioned :)


A good thing about Mpeg-2 Video is that it can contain some FLAGS or PROGRAMMING, that would tell a SOFTWARE or HARDWARE to perform a TELECINE when playing the Video.
Since the INTERLACED FRAMES that made-up the 29.97fps is a REPEATED field(s), it is REDUNDANT, and TRASHABLE.
Just let the FLAGS tells the player to perform the TELECINE. Really, it CAN do that ;).
The benefit of this that the movie CAN be stored in its original 24 FRAME per second, and thus SAVE 20% of total filesize!.


This sure is a greater benefit. Plus, if Decimate(mode=1) blended fields indeed looked better than the duplicates of Telecine, those players could implement such a feature :)


Thanks again to you and scmccarthy for your patience :)

Best regards,
Bilu

[Guest]

@bilu

One thing you are perhaps confused about. Telecine doesn't duplicate a frame! That would not look good. What actually happens is that two fields get duplicated, like this (letters are fields and the lowercase ones are the "pulled down", i.e., duplicated, fields):

A A a B B C C c D D

The duplicate frame emitted by Telecide() when inverting this is a side effect of the field matching.

So, while mode=1 may look better than frame duplication, it does not look better than field duplication, as described above!

[bilu]

@neuron2

Thanks, I was confused indeed :)

Bilu