Is there a way to find Percent Film from d2v? [Archive]

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Alcacia

23rd February 2005, 00:26

I have been using Robot4rip to rip DVD's, and as you probably know, Robot4rip is not able to do Force Film when calling on DGIndex.

I would like to be able to analyze the d2v's of the rips, and for those d2v's which are 100 Percent Film, I would like to manually re-index with DGIndex using the Force Film option.

Is there an app that can use the d2v, and tell you the percent film?

Of course, I'm still not sure if this is worth the extra effort, since the excellent Decomb filter will always do a better job than Force Film...

KaiserS

23rd February 2005, 00:43

Originally posted by Alcacia
Is there an app that can use the d2v, and tell you the percent film?

DGIndex tells you this when its creating the d2v file, but you can always just open the .d2v in notepad scroll to the very bottom and it gives you the film percentage.

raymod2

23rd February 2005, 05:00

Originally posted by Alcacia
I would like to be able to analyze the d2v's of the rips, and for those d2v's which are 100 Percent Film, I would like to manually re-index with DGIndex using the Force Film option.

There's no need to reindex. All you have to do is open the .d2v file with a text editor and change two lines (the field operation and frame rate).

Of course, I'm still not sure if this is worth the extra effort, since the excellent Decomb filter will always do a better job than Force Film...

Theoretically it should be safer to avoid the telecine process altogether (Force Film) rather than telecine and then inverse telecine (Decomb). Force Film is definitely quicker.

KaiserS

23rd February 2005, 05:08

Originally posted by raymod2
Theoretically it should be safer to avoid the telecine process altogether (Force Film) rather than telecine and then inverse telecine (Decomb). Force Film is definitely quicker.

There is no telecine that goes on if you don't use force film. Even a progressive DVD is stored as 30fps on the disc but is soft telecined as opposed to interlaced content which is hard telecined. Force film or an IVTC with something like Decomb should in all cases give you the exact same results when working with progressive content, though like you mentioned Force Film is faster.

raymod2

24th February 2005, 04:49

Originally posted by KaiserS
There is no telecine that goes on if you don't use force film. Even a progressive DVD is stored as 30fps on the disc

If you don't use Force Film dgdecode will obey the tff and rff flags and perform the telecine process (convert the 24fps progressive content on the DVD to 30fps interlaced). Then it needs to be inverse telecined (IVTC) using Decomb to convert it back to 24fps. If you use Force Film dgdecode will ignore the flags and deliver the frames unmodified (24fps progressive). That is why Force Film is theoretically more reliable. In practice, there are often non-progressive sections (30fps) on the DVD mixed in with the progressive sections (24fps) which can complicate things and then it makes sense to telecine and inverse telecine.

KaiserS

24th February 2005, 07:18

Originally posted by raymod2
If you don't use Force Film dgdecode will obey the tff and rff flags and perform the telecine process (convert the 24fps progressive content on the DVD to 30fps interlaced).

The content of all DVD is stored as 30fps whether the content is progressive or not (which is why when you author a disc from a IVTCed source you need to run pulldown on it before authoring). Force film just uses the 3:2 pattern of the flags to remove the extraneous fields and reconstructs the original 24fps stream. If you choose it to do nothing there is no telecine process going on its just passing the stream as it is on the DVD which is at 30fps.

Originally posted by raymod2
Then it needs to be inverse telecined (IVTC) using Decomb to convert it back to 24fps. If you use Force Film dgdecode will ignore the flags and deliver the frames unmodified (24fps progressive). That is why Force Film is theoretically more reliable.

In my experience TIVTC is better then force film with content where its not exactly 100% progressive as some combing frames can go through with Force film which doesn't happen with what TIVTC passes out.

Originally posted by raymod2
In practice, there are often non-progressive sections (30fps) on the DVD mixed in with the progressive sections (24fps) which can complicate things and then it makes sense to telecine and inverse telecine.

Again, there is no extra telecine going on if you don't use force film as the content is stored as soft telecined 30fps on the disc. When played back with a DVD player it will do basically the same thing that Force film does and uses the 3:2 pattern in the flags to know which fields to drop and then just reconstructs the 24fps stream.

Alcacia

24th February 2005, 19:00

KaiserS,

In the case of pure film, what is "physically" stored on disc is 24 frames per second. In other words, if you have a 1-second clip, there are physically only 24 frames (48 fields) encoded in the stream. If you telecine the 1-second stream, then you are just changing a few bits in the headers of these fields. In particular, it is the reading of the RFF tags which create the additional "virtual" fields to create a 30 fps stream from a physically stored 24 fps stream. RFF stands for "repeat first field". If you use something like the DoPulldown GUI to strip all of the TFF and RFF flags out of a stream, then you are left with a 24 fps stream (in the case of perfect 100 percent film), and therein lies the proof of what is "physically" on the disc in the form of encoded frames.

Don't get upset if this is exactly what you meant, but I found your description misleading.

Raymod's description was more clear, when he said that FF ignores the flags and causes the encoded frames to be delivered "unmodified".

However, Raymod left out a big part of the story, namely what happens when there is not exactly 2 RFF flags for every 4 encoded frames. Remember that during pure interlace segments there will not be any RFF flags, and during long static scenes, you may have more than 2 RFF flags per 4 encoded frames. In this case, FF will result in "dumb" decimation or duplication, respectively. This is necessary to maintain a 24 fps output framerate.

(I'll admit that "pulldown" has never seemed a very intuitive term, and perhaps that is a source of some confusion)

Finally, I'll mention that TFF stands for "top field first". These flags are necessary to enable the appropriate field blending in the telecine, but they have no effect on framerate.

Cyberia

24th February 2005, 22:00

Originally posted by Alcacia
KaiserS,

In the case of pure film, what is "physically" stored on disc is 24 frames per second. ... In particular, it is the reading of the RFF tags which create the additional "virtual" fields to create a 30 fps stream from a physically stored 24 fps stream. ...

Raymod's description was more clear, when he said that FF ignores the flags and causes the encoded frames to be delivered "unmodified".

A DVD physically stores 30fps on the disk. DGIndex uses the RFF flags to restore 24fps progressive content when ForceFilm is enabled.

DGIndex/DGDecode does not telecine or create 'virtual' fields.

By not enabling FF, DGInex passes the frames as-is.

Alcacia

24th February 2005, 22:43

Very Interesting...

I guess I'll have to trust you on this one since you're a moderator.

It does make me wonder, however, who the "genius" was that decided it would be a good idea to waste disc space by physically storing the exact same field more than once.

He deserves a medal, I think.

Alcacia

24th February 2005, 23:11

Well, not believing that such an illogical idea was actually true, I took a look at the DVD DeMystified FAQ, Section 3.8.

http://www.dvddemystified.com/dvdfaq.html#3.8

This section describes telecining, and if you look down a few paragraphs, you can read the following:

"For MPEG-2 encoding, repeated fields (B1 and D2) are not actually stored twice. Instead, a flag is set to tell the decoder to repeat the field."

I'm not actually a newbie. I have over 350 posts over at Videohelp under a different nym.

Didn't you guys actually wonder about how you could take a 24fps MPEG, run it through DoPulldown to set the flags to change it to a 30fps MPEG, and the 30fps MPEG *is no bigger* than the 24fps MPEG! That is because telecining is just setting flags...what is "physically" stored on disk is 24fps! It just looks like 30fps to the decoder because of the RFF flags.

DGIndex does, in fact, do dumb decimation/duplication if you choose FF on a source that is not 100 percent film. I know because I actually tested this a few years ago when DGIndex was DVD2AVI.

If you want DGIndex to *not* do dumb decimation/duplication, then you should choose the field operation "raw encoded frames", but I wouldn't recommend this, because unless your source is 100 percent film, you will end up with a non-standard framerate, and audio synch issues no matter what you do...

Wilbert

24th February 2005, 23:29

I guess I'll have to trust you on this one since you're a moderator.
The mod is indeed not correct here. He should read http://www.doom9.org/index.html?/synch.htm once more.

It is indeed stored as 23.976 fps on your dvd. DoPulldown GUI, for example, will add tff/rff flags, so that your dvd player will know what fields to duplicate to perform a 23.976 -> 29.97 fps conversion during playback.

raymod2

25th February 2005, 01:41

Originally posted by Cyberia
A DVD physically stores 30fps on the disk. DGIndex uses the RFF flags to restore 24fps progressive content when ForceFilm is enabled.

DGIndex/DGDecode does not telecine or create 'virtual' fields.

By not enabling FF, DGInex passes the frames as-is.

I have recently spent some quality time looking at raw MPEG-2 streams on DVDs and I can assure you that the film sections are stored as 24fps and that dgdecode is in fact performing the telecine (3:2 pulldown) when you set Field_Operation to 0 (None). When you set Field_Operation to 2 (RawFrames) the frames will be delivered exactly as they are stored on the DVD (well, it does do some frame reordering because the coded order is not the same as the display order). When you set Field_Operation to 1 (ForcedFILM) you get the same results as RawFrames except dgdecode will also decimate non-progressive sections (drop some frames) in order to keep the frame rate constant.

Cyberia

25th February 2005, 01:50

Originally posted by Wilbert
The mod is indeed not correct here. He should read http://www.doom9.org/index.html?/synch.htm once more.

It is indeed stored as 23.976 fps on your dvd. DoPulldown GUI, for example, will add tff/rff flags, so that your dvd player will know what fields to duplicate to perform a 23.976 -> 29.97 fps conversion during playback.

Not the first time I have been in error, probably won't be the last.

EDIT: I actually know this, see the FAQ for proof. I cannot explain my loopy answer. Good thing we have such alert people here to catch temporary stupidity. :rolleyes:

Tomorrow we may have a pop-quiz. :devil:

ppera2

27th February 2005, 16:20