Telecine: 1080i vs. 720p --> DVD

[eswrite]

I am coming up with scripts for converting HD 1080i and 720p material to DVD compliant video. I think what I have for 1080i is correct (after following the Decomb.dll tutorial steps to determine field order, etc.):


LoadPlugin("C:\Program Files\VDM\DGMpgDec\DGDecode.dll")
#LoadPlugin("C:\Program Files\VDM\AviSynth 2.5\plugins\NicAudio.dll")

### Load 1080i video
MPEG2Source("movie_30sec.d2v")
Video=last

#-Test: shows threshold at 25; above it, interlaced frames show up
#return Video.Telecide(order=1, guide=1, post=3, vthresh=25, show=true)

### Use NicAC3Source
Audio=NicAC3Source("movie_30sec AC3 T01 3_2ch 384Kbps DELAY 66ms.ac3")
AudioDub(Video,Audio)

### For Source AR of 1.778:1 -- 16:9 Wide-Ssreen
#-Apply IVTC for interlaced (1080i) source
Telecide(order=1, guide=1, post=2, vthresh=25)
Decimate(cycle=5) # for 24fps

#-Resize to DVD resolution (use DGPullDown on result)
v_out = Lanczos4Resize(720,480)


I am uncertain as to whether the procedure is the same, or whether it requires an extra step, i.e., SelectEven() for a 720p source (when I leave it out I get slow-mo with no audio sync, so at least I'm getting warm):


### For Source AR of 1.778:1 -- 16:9 Wide-Ssreen
#-Apply IVTC for progressive (720p) source
Telecide(order=1, guide=1, post=2, vthresh=25)
SelectEven() # <== Select every other frame since input is progressive?
Decimate(cycle=5) # for 24fps


BTW, would there ever be a case where SelectOdd() would be more correct? Does it matter?

Finally, is there a way to test for 720p (I've read 720i is possible)? This would allow me to have a single script, but the approach I'm envisioning is probably insufficient:


#Test for 720p up front to avoid repeated calls during processing?
is720p = Video.height() < 800 ? true : false

### For Source AR of 1.778:1 -- 16:9 Wide-Ssreen
#-Apply IVTC for progressive (1080i/720p) source
vt=Telecide(order=1, guide=1, post=2, vthresh=25)
#-Select every other frame for 720p
vs=is720p ? vt.SelectEven() : vt
vs.Decimate(cycle=5) # for 24fps

[Boulder]

You definitely do not need SelectEven/SelectOdd for IVTC'ing anything. Where did you get that one from:confused:

I think you have mixed up something. Bobbing produces a double-rate output (even though you shouldn't use them even then as you would be simply throwing away the other field), using Telecide doesn't.

[eswrite]

@Boulder
You definitely do not need SelectEven/SelectOdd for IVTC'ing anything. Where did you get that one from

If you held a gun to my head right now, I couldn't tell you, but I saw it on some other thread in one of the doom9 forums. As for not needing it, please note my comment:

when I leave [SelectEven] out I get slow-mo with no audio sync

I am way out of my knowledge realm here, but I think you need to pick every other frame after applying Telecine because the original 720 progressive is coming at double the rate (59.94fps) as the 1080i (29.97fps) video. Since Telecine takes you to 24fps progressive, leaving out SelectEven when you started at 59.94fps gives you too many (twice as many???) frames.

This is probably the wrong explanation or not totally correct on technical grounds (maybe neuron2 can educate me a little here). I just know if I leave SelectEven out when Telecining 720p content, the output video is slow and out of sync with the audio; when I use SelectEven, the output is dead on! That's why I'm asking how to determine whether I indeed have 720p coming at me, because I think DTV some times comes in 720i. I think FOX used to put out this format, maybe still does.

[Guest]

Yes, 720p at 59.94 fps needs the extra decimation by two to return to 23.976 fps.

720i does not exist.

[Boulder]

Ah, something new to learn every day:) We don't have any of the HDTV stuff here so I'm a newbie as well..

[eswrite]

Yes, 720p at 59.94 fps needs the extra decimation by two to return to 23.976 fps.

Thanks. Looks like I finally got one right, even if I kinda backed into it. Does it matter whether you decimate by two with odd or even frames?

720i does not exist.
Hmm. Maybe you meant to say it's part of the standard but not implemented [often] (actually, I think FOX was doing 720x480p before they added HD at 720p, and that's where I got my 720, which is typical for me when trying to drink from a fire hydrant):

The specified HDTV resolutions that are used in United States and most notably in Japan, are called 1080i, 720p and 720i.
http://www.allformp3.com/glossary/hdtv.htm

ATI Wonder supports it:
Receives and Decodes OTA DTV Signals
- 1080i (North American HDTV - ATSC)
- 720p (North American HDTV - ATSC)
- 720i (North American HDTV - ATSC)
- 480p (EDTV North American)
- 480i (SDTV North American)
http://www.viperlair.com/reviews/multimedia/ati/tvwond/hdtv/index.shtml

[Guest]

ATSC does not allow for 720i. Please see ATSC specification Doc. A/53, Table 3 and associated note. Perhaps it exists in Japan; I don't know.

[Guest]

Here is some clarification I found on the web:

"On page 23 of the ATSC Digital Television Standard (Annex A) dated 16 Sept 95, there is a chart (5.1.2 Compression format constraints) which shows the now famous Table 3. This Table 3 lists the allowed compression formats. This is an ATSC standard and was never officially adopted by the FCC as a broadcast standard.

Table 3 shows as High Definition, 1080x1920 format with both progressive and interlace scan formats and 720 as progressively scanned. Please note that although not a part of table 3, there was some talk of 720 interlace in some circles in an effort to reduce bandwidth consumption, but really never got off the ground.

In Table 3, standard definition comes in two flavors also, but both are 480 lines long. One has 704 pixels across may be either 4x3 or 16x9 aspect ratio while the other is 640 pixels across and is in the 4x3 aspect ratio only. Both of these may be scanned either progressively or interlaced. There are six different frame rates specified, but not all rates apply to each of the scan rates and aspect ratios. These are 23.976, 24, 29.97, 30, 59.94 and 60 Hz or frames per second.

The networks have initially polarized into various high definition formats. CBS and NBC are opting for 1080i while ABC is subscribing to 720p. Fox has also decided on 720p but say they will not be doing any HD in the near future. Most of the networks have gone on record as saying they will broadcast only limited programming in HD with the anticipation that they will increase the number of HD programs as viewership numbers in HD improve. The networks do not appear to have learned how to manage their bandwidth as yet and opt for the narrowest of the HD forms. 1080i is basically 2 each 540 pictures scanned at 60 fields, interlaced together to form the 1080i picture at 30 frames per second (fps). The holy grail of HD is 1080p at 60 fps, but compression techniques have not been develop, as yet, that can compress this much data into the 6 MHz at 19.4 Mbts standard. The operative words here are, "as yet."

It is anticipated that the affiliates will probably follow the networks on their choice of formats. Just because a network sends one format is no guarantee the station will broadcast it. There is nothing preventing a station from receiving the network feed in one format and converting it over to another. Observations of this happening confirm this as fact."

[eswrite]

ATSC does not allow for 720i. Please see ATSC specification Doc. A/53, Table 3 and associated note. Perhaps it exists in Japan; I don't know.

Well, I think we best stop talking about it lest some studio executive get the bright idea to start pumping 720i at us to save bandwidth and double up on programming. ;)

[MarkGrigsby]

Eswrite,

Did you have much success with those scripts? They seem to work fine (and make sense) to me, but the resulting files in CCE are encoding at a pretty low bitrate using 1 pass VBR (about 3.5Mbps). Is this to be expected?