DvD Compliancy/Compatibility and Progressive Content.

[PuzZLeR]

Greetings,

I am currently archiving much of my video into DivX, AVC and good ol’ MPEG-2.

The only reason I even encode anything to the higher bitrate MPEG-2 is for that content which I may need onto a DvD someday. Sure I can convert the others to DvD too, but we all know that MPEG-2 at DvD compliant specs would be much quicker, easier and, of course, lossless if you use the right software.

And speaking of DvD compliancy, all my MPEG-2 clips in the final file are frame-based (deinterlaced and progressive). I prefer all my video this way, however, I notice almost all commercial DvD content is interlaced. I personally don’t understand this since it’s a 1930s tech and looks so awful on modern Tvs and monitors.

My question(s):
Is my video safe as progressive? Is there a reason why so much material is still interlaced today? My main concern is wide compatibility. Is it an easy/possible/painless process to "interlace it" again if I need to?

So far I haven't had a problem, but I'm still not sure I didn't miss anything. The reason I ask is that it would suck if I discover down the road, after the fact, that there’s a problem with my MPEG-2 content being progressive…

Thanks for all your feedback in advance!

[guns1inger]

a. Mpeg-2 is not lossless, no matter which way you cut it, and at DVD bitrates, there will be a lot of loss. The best you can hope for is minimal visual impact from the compression.

b. Most DVDs from cinma films are progressive with pulldown flags. The flags allow for correct interlaced playback on television sets that require it.

c. The bulk of the material that is interlaced on DVD is encoded this way because it was shot this way, and it is almost impossible to reverse footage shot as interlaced back to progressive with any level of quality.

d. If your source allows you to create progressive (23.976 or 25 fps) material then you lose nothing by doing so. Reversing true 29.97i footage back to 23.976 is foolish however.

[PuzZLeR]

Hello Guns1inger, thanks for your fast answer.

Yes, MPEG-2 is lossy of course. I was just stating that if you have .mpg video clips in the MPEG-2 format at DvD specs, then it's lossless to just convert it to a DvD playback disc with software like TMPGEnc Author. (Ok, conversion to VOBs, etc, may involve transcoding, etc, but it would be much less lossy than converting AVC or DivX to MPEG-2 to DvD....)

When I mean "progressive" maybe I'm not knowlegable to define it correctly. I was referring to a "frame based" format that my editing software (VideoStudio) renders, which removes the interlacing. It's one of the three choices between "upper", "lower" and "frame-based", so I assume the latter is progressive. And the frame rate is 29.97 that it encodes to (since I'm in NTSC-land).

Can I just ask? You mentioned "television sets that require it". So far, on all players and TVs, I haven't gotten any problem with this "frame-based" MPEG-2 content onto DvD. Is there something I should know about certain hardware or displays that NEED interlaced content? I'm just hoping that I can get away with it as is right now with all players...

I will, in the meantime, investigate the 23.976 fps option and see what that does.

Thanks again for your help.

[guns1inger]

DVDs encoded as 29.97 fps are interlaced. You may have created progressive frames, but during the encoding they will become interlaced. What you won't see is the motion blur normally associated with true interlaced footage. If you have deinterlaced your footage to get this then you have really created something of lower quality than the original as software de-interlacing creates artifacts and bluring not int he original. If you are de-interlacing footage that was originally shot in 24 fps then you have really produced lower quality, as often this can be returned back to it's original progressive format and encoded properly at 23.976 fps.

Of course this all depends a lot on what your source material is and where it's coming from. If it is coming from standard mini-DV that is shot at 29.97 fps and you are de-interlacing in videostudio then you are producing lower quality footage than leaving it interlaced and encoding at 29.97 fps.

[PuzZLeR]

Hi again Guns1inger. I appreciate your posts and I thank you for the feedback and understanding.

Just for the record, much of my current source is from a DvR which captures from television (and from VHS tapes I'm digitizing) of which I migrate to my PC and edit. It's never fluid pristine DvD quality, as you can imagine, since TV hookups and older tapes have their limitations. All the "source" my DvR creates, from wherever it records from, is interlaced at 29.97fps. The "frame based" encoding option in VideoStudio does make it play without that blurriness or raking, but I should look into what it's really doing. Thanks for the heads-up.

Didn't realize that I had more to learn than I bargained for. This "frame-based" option's got me thinking wrong probably. I do consider myself knowlegable in video, but this interlacing, teleclined, pulldown, etc. stuff’s got me stumped. Forgive me.

Just so I understand, this “frame based” at 29.97fps *IS*, in theory, interlaced content that only *appears* to look better by eliminating the motion-blur and “raking”, right? In other words, it may as well be only just a filter. To properly de-interlace, you need to go to a different frame rate, etc. depending on source, etc. So in fact, all I’m really doing is diminishing the quality for something that *appears* to look better…

To clear something that confused me in your post:

DVDs encoded as 29.97 fps are interlaced. You may have created progressive frames, but during the encoding they will become interlaced.

Did you mean “decoding” instead of “encoding”? I AM paying attention, just thinking…

So in fact, even if I am encoding the content as “frame-based”, at 29.97 fps, the decoders and playback apps/devices will assume “interlaced” content, and accept it as such (with, of course, the quality loss of this process)?

Thanks for sharing your valued knowledge.

[manono]

So in fact, even if I am encoding the content as “frame-based”, at 29.97 fps...

I'm not quite sure why you keep repeating that. Probably 99% of the DVDs I've seen, progressively encoded or interlaced encoded, are frame-based. Very few DVDs use field-based encoding.

Although almost all true 29.97fps video is encoded as interlaced for DVD, I've seen some, and created others myself, which had a progressive source and used progressive encoding. However, there's a difference between a progressive or interlaced source and progressive or interlaced encoding. A 29.97fps progressive source, such as comes out of some digital video cameras these days, is usually encoded as interlaced. And almost all PAL movies on DVD, from a progressive source originally, are encoded as interlaced.

All the "source" my DvR creates, from wherever it records from, is interlaced at 29.97fps. The "frame based" encoding option in VideoStudio does make it play without that blurriness or raking, but I should look into what it's really doing.

Yes you should look into it. If it was shot using film cameras, as all movies and the majority of TV shows these days are, by deinterlacing it, you've seriously degraded it. Much better would be to IVTC it. And if it's really shot with interlaced 30fps video cameras, keeping it interlaced for DVD is almost certainly preferred.

I notice almost all commercial DvD content is interlaced.

Well, yes and no. DVD is an interlaced medium. All NTSC DVDs output interlaced 29.97fps. But much DVD content - that which was shot on film such as movies and many TV shows these days - is encoded progressively and stored on the DVD as 23.976fps progressive (with pulldown applied to output interlaced 29.97fps).

[jagabo]

much DVD content - that which was shot on film such as movies and many TV shows these days - is encoded progressively and stored on the DVD as 23.976fps progressive (with pulldown applied to output interlaced 29.97fps).

Just a note for PuzZLeR: "pulldow applied" means the MPEG data includes instruction (a few bits per frame) that tell the DVD player how to produce 59.94 fields per second from the 23.976 progressive frames per second stored on the disc. Standard definition CRT TV is always 59.94 fields per second. You see one field at a time, never an entire frame.

[edDV]

PuzZLeR,

It you want to understand it, here is a bit of tutorial.

A DVD recorder such as yours always records an interlace input as interlace to the DVD. This is known as 480i source. All NTSC, all VHS and anything coming over analog TV, composite or S-Video connections is encoded interlace.

Since day one NTSC has handled 24fps film through a process known as telecine or "pull-down". The frames are split into fields and repeated in a reversible pattern to make 29.97 fps. The resulting video can be viewed directly or reversed (aka IVTC) back to 23.976 fps progressive frames for display. You need to understand this doc to understand DVD, progressive DVD players and progressive display.
http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm

DVD authoring can be done in two official formats and two "cheater" formats.
(refer to https://www.videohelp.com/dvd for more detail). You can ignore #4 below.

1. 29.97 fps, 480i interlace.

2. 23.976 fps, 480p progressive (This intended for film source)

3*cheat. 29.97 fps, progressive frames split into fields and recorded as 480i interlace.

4*advanced cheat. 23.976PA progressive frames split into fields recorded as 480i interlace with fields recorded in a special (unwatchable) sequence intended for advanced processing.
(ref http://en.wikipedia.org/wiki/24p )

One key point is regardless of frame rate, #1 above records 59.94 time slices of motion per second, #3 records 29.97 time slices and #2 and #4 only 23.976 slices. If you deinterlace #1 into #3 you halve the motion smoothness and force a blend of fields recorded 1/59.94th second apart. During video motion, this produces image distortion unless handled at the pixel level with special deinterlace processing (expensive).

So, the solution used by the "pros" for archive is to store the NTSC master as 480i 29.97 fps or film scans as 23.976p. From those you can process all the other formats as needed. 29.97p makes sense for archive only if the camera shot 29.97 fps progressive (some do).

Next generation digital storage (e.g. HD/BD DVD and advanced tape formats) will allow a wider range of recording options that advanced players will respect. Supported frame rates will be 23.976, 29.97 and 59.94 for NTSC and 24, 25 and 50 for PAL.

Until then, it is best to stick to #1 or #2 above for capture and archive. If you don't like the field separation on a progressive monitor, use a deinterlacing software player (e.g. VLC, PowerDVD or WinDVD), a deinterlacing display (e.g. LCD-TV) or a standard interlace TV monitor.

[PuzZLeR]

Thank you once more my friends for sharing your thoughts and concepts. I have a much better understanding of this subject now. Like I said, forgive my lack of knowledge on this issue. (That’s why I go to forums, right? ) I've also taken this subject to support with VideoStudio as well as their forums.

BTW – Great posts, and also a great link edDV. Thanks!

To be honest, when I decide to compress this MPEG-2 content to DivX or H.264/AVC I get much better results, with better quality and smaller files with quantizers, when I render it as “frame based” beforehand. But we all know that this is a different science entirely when using advanced compression and further lossiness.

HOWEVER…

From reading the posts here, I gather that if the “source” is MPEG-2 at 29.97 fps interlaced, and you wish to archive and keep any video as MPEG-2, to maintain the best quality possible and widest compatibility, it is best to retain the interlacing AS IS and detinterlace in the decoding/playback phase instead. (At least for now until future technologies dictate otherwise.)

This answers my question, which is what my initiating this thread was all about and I thank you all very much.