Advice needed on NTSC interlaced title.

[Mysta187]

I have an NTSC title that I'm authoring from DVD-9 to DVD-R. It is reported by DVD2AVI as being interlaced. Using DIF4U originally produced the following avs script:

LoadPlugin("C:\WINDOWS\System32\mpeg2dec3.dll")
LoadPlugin("C:\WINDOWS\System32\decomb.dll")
Mpeg2Source("VTS__01_P02_1.d2v")
Telecide(guide=1)
Decimate(cycle=5)
ResampleAudio(44100)

Initially I was concerned because I knew that the source was not telecined (after studying the frames in VirtualDub) and that it was indeed 100% interlaced. After reading the AVISynth docs, I learned that Telecide should not be used with interlaced material.

I then launched DIF4U a 2nd time this time selecting "FieldDeinterlace()" option. This resulted in the following script.

LoadPlugin("C:\WINDOWS\System32\mpeg2dec3.dll")
LoadPlugin("C:\WINDOWS\System32\decomb.dll")
Mpeg2Source("VTS__01_P01_1.d2v")
FieldDeinterlace()
ResampleAudio(44100)

My question is 2-fold. First, should I be checking "AutoDetect NTSC ForceFilm/Decomb" in DIF4U at all when the target will be viewed on a TV? Particularly a true interlaced title. If so, when using the first AVS script, what should my CCE settings be? Currently they are as follows:

Add Sequence End Code=1
Dvd Compliant=1
Progressive Frames=1
Linear Quantizer Scale=0
ZigZag Scanning order=1
Upper Field First=1

If not, do I "need" to check "FieldDeinterlace()" in DIF4U?
I would like to stay as close to the original source material as possible. Thanks in advance.

[Eyes`Only]

I too read that Telecide should not be used with interlaced material. However, I use it all the time with pure interlacing and the output is fine, so I don't know why that claim was made.

I always deinterlace NTSC material though. I don't really know anyone who chooses to keep their NTSC interlaced, or what advantage it would have. I see you want to keep your source as close to the original as possible. In my experience, keeping NTSC interlaced hasn't resulted in the best quality video. Just a thought.

I have played around a lot with Telecide vs. FieldDeinterlace and I didn't see a difference in the end product. As a matter of fact, the decomb guide says that Telecide is now built-in to the FieldDeinterlace function. Assuming this is true, why in the world would the claim that you are not supposed to use Telecide on interlaced material be true?

Anyway, bottom line: Try both telecide and FieldDeinterlace. See if you even see a difference. If so, pick the one you like best. Oh, and post your result/preference here please. I'm interested to know your final decision. Like I said though, I use telecide exclusively for all IVTC and interlaced material and have been extremely satisfied with my transcoding. Except for the reduction of speed of course, but I can't do anything about that.

As for your settings:

Never check DVD Compliant. That sets your max bitrate to 9800 and overrides your current settings. Can result in a video that exceeds max bitrate and will be rejected by Scenarist/Maestro.

Other than that, your CCE settings look fine. When deinterlacing, always use the progressive checkbox. If you use telecide/decimate, pulldown afterwards. If you use FieldDeinterlace, you don't need to, I believe (been a while since my testing).

[int 21h]

You're not supposed to use Telecide on truly interlaced material, because in such material you have 29 or 25 (depending on PAL or NTSC) unique frames (or 59/50 unique fields) per second, and telecide is intended to use field matching to recover a progressive stream... So running Telecide on a truly interlaced frame will not recover a progressive stream, and usually will unintentionally decimate that stream. (Producing sometimes jerky output, etc.)

Further, Telecide is not built into FieldDeinterlace... FieldDeinterlace is built into Telecide... the following is a quote from the latest Decomb readme:

Do not use FieldDeinterlace after Telecide because the same functionality is built into Telecide.


In the case of a truly interlaced stream, the most important thing to remember is not to reduce the framerate, because you'll be eliminating needed data! (Yielding jerky movement), You can do one of two things, process it as interlaced video (Using the interlaced flag in your MPEG encoder, and not using a zigzag scanning order, see note below) or you can deinterlace it. With a deinterlacer like FieldDeinterlace, you probably won't notice much quality difference...

My opinion is that since MPEG-2 supports interlaced video (one of its bigger advantages over MPEG-1), you should use it and only deinterlace when you're converting to a format that has no interlaced video flags. Because remember, these flags are there so that the decoder can decide the best process to handle the video, bypassing these flags effectively neutralizes this entire advantage. Using the interlaced flag and encoding in the interlaced mode is the closest you can remain to the source (because its the same as how the source was originally encoded). But YMMV.

**Notes Regarding 'interlaced' or non-progressive mode of MPEG-2 encoders**: When Mpeg-2 encoders are in the interlaced mode, they process streams by fields, changing the accuracy of Motion precision, and DCT. You can read more about the entire process here: http://www.ece.cmu.edu/~ece796/mpeg2.pdf.

[Eyes`Only]

Thanks for the clarification int21.

I understand that is how it is supposed to work, but how is it that my telecide/decimate(cycle=5) video doesn't appear jerky then? I use it all the time on pure interlaced material, and it seems something in decomb steps up to the challenge and corrects things, because my videos are perfectly smooth. Could that be it? Is there something in the telecide function that actually works to fix this?

I just grabbed a DVDr off my shelf i did months back that was pure interlaced. I used telecide/decimate on it and I'm watching it as we speak and can't see jerkiness or a flaw in it!

[int 21h]

YMMV ;)

Movies vary, but a very specific example that the process you mention does not work correctly is StarTrek:TNG. The DVDs are mixxed with truly interlaced and progressive, and if you handle the entire stream as a progressive stream (with telecide/fieldeinterlace) the messed up results are clearly visible.

Regards,
int 21h.

[Eyes`Only]

So how would you deinterlace it? FieldDeinterlace would deinterlace this hybrid correctly?

[Mysta187]

Thanks for the input Eyes`Only and int 21h. I performed a test encode using both methods..(Telecide(guide=1)/Decimate(cycle=5)and FieldDeinterlace()) and I must say I cannot distinguish a difference. Both look nice. I also did an encode without using any Telecide/Decimate or FieldDeinterlace parameters and the video appears to be sharper. The downside is the bitrate remained high and never seemed to vary :(. I might add that this is a stage show that was put on DVD and there is very little fast motion.
Again, Thanks for the input.

[int 21h]

Originally posted by Eyes`Only
So how would you deinterlace it? FieldDeinterlace would deinterlace this hybrid correctly?

If you for sure had to have a progressive stream (i.e. AVI [MPEG-4 variants] or a VCD) then the best solution is to just fielddeinterlace it and live with the repeated frames and their affect on your bitrate, if you're going to an interlaced-capable medium, you don't touch it, and flag it as interlaced.

[Eyes`Only]

int21: Flag the whole stream as interlaced? Doesn't that do something to the progressive parts of your hybrid video?

Mysta: glad you got something you're happy with :D

[int 21h]

It just encodes your entire stream in field mode instead of frames. And allows the player to deal with it (PC player = deinterlace, TV = just play it). It has no ill effects on the progressive parts, whereas, the opposite (flagging a stream progressive with interlaced frames) may not work correctly.

[Calypso]

Originally posted by Eyes`Only
Thanks for the clarification int21.

I understand that is how it is supposed to work, but how is it that my telecide/decimate(cycle=5) video doesn't appear jerky then? I use it all the time on pure interlaced material, and it seems something in decomb steps up to the challenge and corrects things, because my videos are perfectly smooth.If this was true interlaced material, any combination of telicide/decimate would always produce a 'jerky' video. What you may 'perceive' to be true interlaced material may have been originally film that was telicined and then encoded as interlaced on the DVD itself. Very early DVD players did not have 3:2 pulldown capabilities, and thus DVD authors at the time encoded interlaced DVDs with the telecine already done. This kind of interlaced material can be IVTD'd.

Some of today's DVD's contain 'extras' that were originally filmed with professional DV camera equipment, and thus are natively recorded at 29.97 (or 30) FPS. This material is subsequently interlaced and encoded as such on the DVD. Any attempt to do a telecide/decimate on this kind of material will result in jerky video. This is what some refer to as 'true' interlaced material. The reason it is jerky is because you are dropping a non-duplicate frame, and as a consequence the video will appear to accelerate momentarally. This behavior is most obvious during scenes that pan.

In addition, many television broadcasts (both Digital Satellite and Over the Air) can be IVTD'd, as the original source is film, which is subsequently telecined and interlaced for broadcast.