Authoring HD/720p to SD-DVD: Render to 24p or 60i?

[mltwitz]

I have a couple of HD video files (AVC H.264, 4:3, NTSC, 960x720, 23.976 fps, progressive) that I want to author to SD DVD. My tools available are Sony Vegas Pro 9.0d and DVD Architect Pro 5.0b. I was going to re-encode the files to DVD-compliant mpeg-2 using the NTSC DVD-Architect template (interlaced), but then I saw there is also a DVD-A 24p template (which uses 23.976 +2-3 pulldown), which I never used before because I never had HD source files before and until now I was not aware that SD DVD supports progressive. So I did a test, rendered to both 24p and standard 29.97 interlaced, then authored both files to SD DVD in DVD Architect and confirmed they are actually on the DVD one as interlaced and the other as progressive. I can't see any differences when playing it back on my TV, but my set-up may also not be representative.

What I really want to know is: What is the difference of either preset when playing the DVD? How will it affect the picture quality when watching on different types of TVs (tube, HD) and using different types of DVD Players (standard, progressive scan, Blu-Ray)?

Any help in deciding which way to go is appreciated.

[manono]

What is the difference of either preset when playing the DVD?

Quality. Encoding as interlaced 29.97fps encodes 25% more frames as compared to encoding as progressive 23.976fps. It results in 40% of the frames being interlaced which are much harder to encode than are progressive frames (require many more bits for the same quality). You'll get something like 40% better quality for the same file size when encoding as progressive 23.976fps with pulldown applied.

How will it affect the picture quality when watching on different types of TVs (tube, HD) and using different types of DVD Players (standard, progressive scan, Blu-Ray)?

They'll all play either. When playing to an HDTV, if your progressive scan player is a flag-reader (and the vast majority are), it'll deinterlace the hard telecined one (the one with the interlacing encoded into the picture) resulting in further degradation of the picture. If quality is a concern, there's really no choice here.

[mltwitz]

So considering the type of source files I have there is never any reason why I would want to render to interlaced, correct?

[poisondeathray]

So considering the type of source files I have there is never any reason why I would want to render to interlaced, correct?

correct

[mltwitz]

Thanks! New question related to that: if you get better quality for the same file size using progressive, why are all commercial SD DVDs interlaced?

[poisondeathray]

Thanks! New question related to that: if you get better quality for the same file size using progressive, why are all commercial SD DVDs interlaced?

Most modern theatrical Hollywood DVD releases are progressive (soft telecine) , not encoded as interlaced

I can't think of a film content DVD I bought in the last 4-5 years that is encoded as interlaced

The exception is video content, like sports DVD's - those are interlaced, because content is 60i, not 23.976 progressive

[edDV]

You are likely to encounter 6 frame rate variations in "NTSC land"

For DVD (or Blu-Ray)...

23.976 progressive -> encode 23.976 progressive w pulldown for DVD
29.97 (telecine) -> inverse telecine to 23.976 progressive or encode 29.97 interlace (let DVD player or TV do ivtc)
29.97 progressive -> encode as 29.97 interlace
29.97 interlace -> encode as 29.97 interlace

Then there is broadcast 720p/480p
59.94 (2:3 frame repeats) -> decimate to 23.976* then encode 23.976 with pulldown
59.94 progressive -> encode as 29.97 interlace


* this can be tricky because abc/fox often use variable frame repeat sequences.

[mltwitz]

Most modern theatrical Hollywood DVD releases are progressive (soft telecine) , not encoded as interlaced

I can't think of a film content DVD I bought in the last 4-5 years that is encoded as interlaced

The exception is video content, like sports DVD's - those are interlaced, because content is 60i, not 23.976 progressive

Oops, I just realized that I was always using Gspot to check my .vob files, which always showed them as I/L. I since then learned that Gspot hasn't been updated since 2007. When I check the files with MediaInfo, it indeed shows them as progressive (2-3 pulldown). Wow, I have been fooled for years!!

[poisondeathray]

Most modern theatrical Hollywood DVD releases are progressive (soft telecine) , not encoded as interlaced

I can't think of a film content DVD I bought in the last 4-5 years that is encoded as interlaced

The exception is video content, like sports DVD's - those are interlaced, because content is 60i, not 23.976 progressive

Oops, I just realized that I was always using Gspot to check my .vob files, which always showed them as I/L. I since then learned that Gspot hasn't been updated since 2007. When I check the files with MediaInfo, it indeed shows them as progressive (2-3 pulldown). Wow, I have been fooled for years!!

Gspot will indicate soft telecine correctly most of the time. It will say 23.976 pics/s , 29.97 frames/s, and 59.94 fields/s with the 3:2 box lit . For interlaced encoded, hard telecine, it will say 29.97 pics/s

In fact, mediainfo is less reliable for this, because it doesn't scan the file, it just reads the header

The only 100% sure accurate way, is to examine the fields with your eyes

[manono]

Oops, I just realized that I was always using Gspot to check my .vob files, which always showed them as I/L. ... Wow, I have been fooled for years!!

No, you just haven't understood it properly for years. As pdr says, GSpot also indicates what's going on with the pics/s, frames/s and fields/s boxes. All NTSC DVDs are interlaced since they all output interlaced 29.97fps (really 59.94 fields per second), even the ones encoded as progressive 23.976fps with 3:2 pulldown applied.

[mltwitz]

I'm confused, if it's encoded as progressive, why does Gspot identify it as I/L and not PROG?

[jagabo]

I'm confused, if it's encoded as progressive, why does Gspot identify it as I/L and not PROG?

Because the progressive frames are marked with 3:2 pulldown flags -- instructions that tell the player how to create 59.94 fields per second from those progressive frames. Many MPEG decoders will perform the pulldown and create interlaced frames when they decompress the video. In fact, that is the only way to get the frame rate correct. The underlying progressive frame rate can vary from 19.98 to 29.97 fps. It's the pulldown that creates the consistent 59.94 fields per second rate (29.97 frames per second when they are woven together) that's required for analog output.

[mltwitz]

The only 100% sure accurate way, is to examine the fields with your eyes

What tool do you use to do that?

By the way thank you all for your quick and helpful replies and your patience. I'm learning a lot here!

[poisondeathray]

Forget I said that last sentence; I was mixing up content (interlaced vs. progressive vs. hybrid/other) with method of encoding (interlaced vs. progressive)

We're talking about method of encoding, and gspot works fine

To identify the content definitively, you have to use your eyes

Sorry for the confusion

[jagabo]

The only 100% sure accurate way, is to examine the fields with your eyes

What tool do you use to do that?

Use a bob deinterlace or a field separator. In AviSynth:

WhateverSource()
AssumeTFF() # or AssumeBFF() depending on the field order of your source
Bob()

or

WhateverSource()
AssumeTFF() # or AssumeBFF() depending on the field order of your source
SeparateFields()

In VirtualDub add the Bob Doubler filter.

Step through the video field by field. If every field is different you have interlaced video. If you see a pattern of 3:2 repeats you have telecined film. If every pair of pictures is the same you have a progressive video. Other patterns are possible.

MPG files are a little different. The MPEG decoder may or may not perform the pulldown. VirtualDubMod's MPG decoder doesn't perform the pulldown. VirtualDub's MPG decoder performs the pulldown.

[edDV]

I'm confused, if it's encoded as progressive, why does Gspot identify it as I/L and not PROG?

When DVD was established in the mid 1990s there was minimal processing economically possible in the player. Two ingenious tricks were used to make cheap players possible.

The first was the 1 GB VOB limit which kept the basic player memory requirement contained.

The second was the decision to store all data as fields whether the source was interlace or progressive. Progressive frames would be pulldown flagged and split into fields for storage on disc. Why? So a cheap player can simply assemble a telecine field sequence to output 60i NTSC. The heavy processing load was left to future premium "progressive" players that were to weave fields into frames, apply inverse telecine (aka "cinema processing") or deinterlace 60i to 60p (then called line doubling) for 60p* output as analog or digital component.

This scheme allowed allowed interlace or "progressive" discs from day one that were playable on very cheap players to 60i analog NTSC. As time passed premium priced progressive players became possible, and in the next decade additional processing was added to allow 480p/720p/1080i/1080p upscale output to HDMI. Today, all but the cheapest players have all this processing reduced to generic chip sets.

The PAL difference was lack of the telecine requirement. PAL 25p progressive source was simply flagged and split into fields for storage, then played either as interlace or weaved into progressive and frame repeated to 50p or 100p for output.


* "NTSC" progressive players output 60p (59.94p actually) over analog component or HDMI from either interlace (line doubled) or film progressive (23.976 frame repeated in 2:3 sequence).