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post #1 of 23 Old 11-12-2008, 03:25 PM - Thread Starter
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Hi,

I'm interested to know what the HD resolution, bitrate and frame rate of programs on the SciFi channel are, such as Atlantis.

I'm not sure but is the original resolution of these programs 720p? Is the resolution changed to 1080i depending on which supplier send the signal (i.e. cable/satellite)?

I'm interested because in the UK we don't have the luxury of SciFi HD so have to make to with MKV files (I know we shouldn't, but what are you going to do). The odd thing is that the MKV rips are encoded to 720p but at 24fps. I'm pretty sure but in the States/Canada all broadcasts are 30fps, 60Hz.

Its weird that the MKV would be encoded to 24fps. I have the option of setting the Video Drivers on the PC to output 1080p/24 (to a Pioneer Kuro) but there is still quite a bit of judder especially in pans, but still a good quality image.

I'm interested to know how the originals would have been captured and if there is anything that can be done to get a smother image.
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post #2 of 23 Old 11-12-2008, 03:36 PM
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Quote:
Originally Posted by swin70 View Post

Hi,

I'm interested to know what the HD resolution, bitrate and frame rate of programs on the SciFi channel are, such as Atlantis.

I'm not sure but is the original resolution of these programs 720p? Is the resolution changed to 1080i depending on which supplier send the signal (i.e. cable/satellite)?

I'm interested because in the UK we don't have the luxury of SciFi HD so have to make to with MKV files (I know we shouldn't, but what are you going to do). The odd thing is that the MKV rips are encoded to 720p but at 24fps. I'm pretty sure but in the States/Canada all broadcasts are 30fps, 60Hz.

Its weird that the MKV would be encoded to 24fps. I have the option of setting the Video Drivers on the PC to output 1080p/24 (to a Pioneer Kuro) but there is still quite a bit of judder especially in pans, but still a good quality image.

I'm interested to know how the originals would have been captured and if there is anything that can be done to get a smother image.

They are broadcast in 1920x1080i @ 29.97 FPS. I'm sure the original was 24 FPS(or 23.976) and the encodes are using inverse telecine to remove the extra frames. I capture several shows and I really don't notice any judder, when I get them to 23.975 FPS, but one thing that is hard to fix are those logos and bugs that pop up, I think they are probably 30FPS and the inverse telecine gets confused as to which frames to drop, etc and it causes hesitations and jerkiness because it's difficult to determine how to proceed when it processes the frames during those spots in the show.
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post #3 of 23 Old 11-12-2008, 04:49 PM
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On FiOS, SciFi HD is 1920x1080i, 29.97fps, about 16.6Mb/s MPEG2. Audio is DD5.1 at 384kb/s. Other providers like Comcast use a lower video bitrate, while satellite providers like Dish and DirecTV provide a much lower bitrate MPEG4 stream. Shows like Atlantis are shot at 23.976 fps, and are telecined to 29.97 for broadcast. Anyone planning to reencode the video would reverse the telecine, regardless of whether they were doing it for personal archives or some less legal purpose.
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post #4 of 23 Old 11-13-2008, 02:33 AM - Thread Starter
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Thanks for this, some interesting points to note - I take it that these MKV files that are referenced as 720P are actually re-sampled then from 1080i broadcasts, which would mean de-interlacing the fields and reducing the resolutions, as well as inversed telecined to reduce the frame rate?

Here's the output from Mediainfo regarding the video stream

Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L3.1
Format settings, CABAC : Yes
Format settings, ReFrames : 3 frames
Muxing mode : Container profile=Unknown@3.1
Codec ID : V_MPEG4/ISO/AVC
Duration : 27mn 37s
Bit rate : 3 228 Kbps
Nominal bit rate : 3 383 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16/9
Frame rate : 23.976 fps
Resolution : 24 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.153
Writing library : x264 core 65 r998M 6768543
Encoding settings : cabac=1 / ref=3 / deblock=1:-1:0 / analyse=0x3:0x133 / me=hex / subme=6 / psy_rd=1.0:0.0 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / chroma_qp_offset=-2 / threads=4 / nr=0 / decimate=1 / mbaff=0 / bframes=3 / b_pyramid=1 / b_adapt=1 / b_bias=0 / direct=1 / wpredb=1 / keyint=250 / keyint_min=25 / scenecut=40(pre) / rc=2pass / bitrate=3383 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=1:1.00
Language : English
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post #5 of 23 Old 11-13-2008, 02:34 AM - Thread Starter
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I have edited a file to create a 30 second clip to show the issue. Notice the horizon during the pan.

Have a look at
Judder Problem

(sorry for the adds - only site I could find to share a largish file simply over HTTP)
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post #6 of 23 Old 11-13-2008, 02:55 AM
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In the US most scripted drama (apart from soaps) and many sitcoms are shot on film or 24p video at 23.98frames per second (from now on abbreviated to 24).

No US broadcaster broadcasts 24p natively and instead they have to broadcast at 60Hz (59.94Hz in reality) SD and 1080i HD broadcasters use interlaced 60Hz, 720p broadcasters use progressive 60Hz. Interlaced 60Hz is sometimes described as 30fps (29.97fps) BUT because of interlace each frame is made up of two entirely independent fields sent 1/60th second apart - and consisting of even and odd lines. They DON'T have to be two halves of the same source frame though - which is important.

24p stuff is thus shown at 60Hz using 3:2 pull-down (usually). This means that one 24p film frame is shown for 3/60 of a second (3x720/60p frames or 3x480/1080/60i fields) and the next 24p film frame is shown for 2/60 of a second (2x720/60p frames or 2x480/1080/60i fields)

This pull-down is added either during the telecine transfer (common in 480/60i SD production) OR the film is transferred at 24p and the 3:2 pulldown added on playout to a 60i or 60p VTR when the broadcast master is created. (Telecine is just the name of the piece of equipment that scans film frames to video in real-time. Non-real time transfer devices are more commonly known as film scanners. Telecine DOESN'T mean 3:2 in the broadcast world - in Europe 2:2 is the format used by telecines...)

This means that in 720p you are sending 3 frames more than you need to, and in 480/1080i 1 field more than you need to. (In fact many MPEG2 and H264 encoders detect this redundancy and don't waste bandwith sending redundant fields/frames BUT this isn't universal)

SO - when people record TV shows shot at 24fps but broadcast at 720/60p or 1080/60i (or 480/60i) they often try to reverse the 3:2 pulldown so that you end up with a file just containing the original 24p frames, rather than the entire broadcast stream (completed with redundant, repeated frames). Often 1080/24p stuff created from 1080/60i with 3:2 removed is then scaled to 720p AIUI.

HOWEVER this isn't always done perfectly AIUI (I'm not a downloader)

It can also create issues where :

1. The 3:2 cadence isn't consistent (which can happen when film content is edited in the 60Hz domain rather than in the 24Hz domain)
2. 60i or 60p motion is mixed with 24p content - such as rolling/crawling captions - or some special effects. (The latter was the case with Star Trek : TNG - which was shot 24p on film, but the effects were added in the 60i domain)

ALSO - if you are watching 24p content you really need to watch it on a TV with 24p connections - or at 60Hz if you can cope with 3:2 judder. You REALLY don't want to try watching it at 50Hz (*)

(*) XBox Media Center (a hack for the original Xbox) has a neat 4% speed-up option that will replay 24p content at 25p with 2:2 pulldown, outputting at 50Hz, which works really for 24p SD content I believe.

I'll have a look at that clip tonight or tomorrow on a 24p display and see how it looks. One downside of 24p capture is that it suffers from temporal aliasing, so motion has to be well controlled to not break up into separate images. Most camera operators are very skilled at this - but some special effects artists are less experienced (though most are fine)
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post #7 of 23 Old 11-13-2008, 03:24 AM - Thread Starter
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Quote:
Originally Posted by sneals2000 View Post

In the US most scripted drama (apart from soaps) and many sitcoms are shot on film or 24p video at 23.98frames per second (from now on abbreviated to 24).

No US broadcaster broadcasts 24p natively and instead they have to broadcast at 60Hz (59.94Hz in reality) SD and 1080i HD broadcasters use interlaced 60Hz, 720p broadcasters use progressive 60Hz. Interlaced 60Hz is sometimes described as 30fps (29.97fps) BUT because of interlace each frame is made up of two entirely independent fields sent 1/60th second apart - and consisting of even and odd lines. They DON'T have to be two halves of the same source frame though - which is important.

24p stuff is thus shown at 60Hz using 3:2 pull-down (usually). This means that one 24p film frame is shown for 3/60 of a second (3x720/60p frames or 3x480/1080/60i fields) and the next 24p film frame is shown for 2/60 of a second (2x720/60p frames or 2x480/1080/60i fields)

This pull-down is added either during the telecine transfer (common in 480/60i SD production) OR the film is transferred at 24p and the 3:2 pulldown added on playout to a 60i or 60p VTR when the broadcast master is created. (Telecine is just the name of the piece of equipment that scans film frames to video in real-time. Non-real time transfer devices are more commonly known as film scanners. Telecine DOESN'T mean 3:2 in the broadcast world - in Europe 2:2 is the format used by telecines...)

This means that in 720p you are sending 3 frames more than you need to, and in 480/1080i 1 field more than you need to. (In fact many MPEG2 and H264 encoders detect this redundancy and don't waste bandwith sending redundant fields/frames BUT this isn't universal)

SO - when people record TV shows shot at 24fps but broadcast at 720/60p or 1080/60i (or 480/60i) they often try to reverse the 3:2 pulldown so that you end up with a file just containing the original 24p frames, rather than the entire broadcast stream (completed with redundant, repeated frames). Often 1080/24p stuff created from 1080/60i with 3:2 removed is then scaled to 720p AIUI.

HOWEVER this isn't always done perfectly AIUI (I'm not a downloader)

It can also create issues where :

1. The 3:2 cadence isn't consistent (which can happen when film content is edited in the 60Hz domain rather than in the 24Hz domain)
2. 60i or 60p motion is mixed with 24p content - such as rolling/crawling captions - or some special effects. (The latter was the case with Star Trek : TNG - which was shot 24p on film, but the effects were added in the 60i domain)

ALSO - if you are watching 24p content you really need to watch it on a TV with 24p connections - or at 60Hz if you can cope with 3:2 judder. You REALLY don't want to try watching it at 50Hz (*)

(*) XBox Media Center (a hack for the original Xbox) has a neat 4% speed-up option that will replay 24p content at 25p with 2:2 pulldown, outputting at 50Hz, which works really for 24p SD content I believe.

I'll have a look at that clip tonight or tomorrow on a 24p display and see how it looks. One downside of 24p capture is that it suffers from temporal aliasing, so motion has to be well controlled to not break up into separate images. Most camera operators are very skilled at this - but some special effects artists are less experienced (though most are fine)

Great info. There's a lot I been learning in the last few days if anything just purely down to interest. I certainly may not have a production set up or anything close but My TV should be able to cope with 24/25/30/50 and 60Hz video. Its a Pioneer PDP-428XD - you don't have that exact model in the US but it is capable of displaying the following

Video signals supported
720 (1440) x 576i@50 Hz
720 x 576p@50 Hz
1280 x 720p@50 Hz
1920 x 1080i@50 Hz
720 (1440) x 480i@59.94 Hz/60 Hz
720 x 480p@59.94 Hz/60 Hz
1280 x 720p@59.94 Hz/60 Hz
1920 x 1080i@59.94 Hz/60 Hz
1920 x 1080p@24 Hz
1920 x 1080p@50 Hz
1920 x 1080p@60 Hz

The PC used to output the MKV via HDMI can use the following video resolutions

1) 1280x720 - 50 Hz (interlaced)
2) 1280x720 - 60 Hz

3) 1920x1080 - 24 Hz (interlaced)
4) 1920x1080 - 25 Hz (interlaced)
5) 1920x1080 - 30 Hz (interlaced)
6) 1920x1080 - 50 Hz (interlaced)
7) 1920x1080 - 60 Hz

Now, this list is what Windows tells me the mode are (Screen Properties --> Settings --> Advanced Button --> Adapter Tab -> List All Modes Button). However, the TV tells me that I has a 720p input on setting (1) and 1080p on settings (3) and (6),. I trust the TV rather than windows and to be honest it also make sense - i.e. Blue ray @24 fps is progressive and both 50 Hz setting would indicate progressive sources (at least, that what I think).

The most likely setting is (3) 1920x1080/24, but I still see judder.

The particular clip looks like a "virtual" pan - i.e. computer generated
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post #8 of 23 Old 11-13-2008, 08:21 AM - Thread Starter
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I've created another clip that might show the problem even better. This time watch the pan accross the girls. I think its even more obvious to see but no matter what setting I chose for the Video Driver or TV modes, I could not remove the judder. The content is a little easier on the eye as well

Judder Problem, clip 2
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post #9 of 23 Old 11-13-2008, 09:31 AM
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Just for info - very few TVs have 1080/25p inputs as there are no real sources that use this.

Currently the Full 1080 24p panel usually accept :

480/60i
576/50i
480/60p
576/50p
720/60p
720/50p
1080/60i
1080/50i
1080/60p
1080/50p
1080/24p

(1080 is often referred to as 1125, 720 as 750, 576 as 625, 480 as 525, and 50i / 60i sometimes as i25 / i30)
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post #10 of 23 Old 11-13-2008, 11:10 AM - Thread Starter
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Quote:
Originally Posted by sneals2000 View Post

(1080 is often referred to as 1125, 720 as 750, 576 as 625, 480 as 525, and 50i / 60i sometimes as i25 / i30)

I do like the clarity of standards they have in this industry!
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post #11 of 23 Old 11-13-2008, 11:39 AM
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Looking at that clip, it was processed by someone who doesn't have a clue how to correctly process video. It was blend deinterlaced (or resized, which will blend the fields together) then 1 in 5 frames were deleted. To correctly reverse telecine, the fields from different frames have to be matched, which will leave 1 duplicate frame in 5. This duplicate frame is then removed, leaving clean motion. Nothing you can to do the video on your end will make it correct.
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post #12 of 23 Old 11-13-2008, 02:10 PM - Thread Starter
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Tidy.

Coyoteaz, I've been on a mission of discovery for the last few days and I'd be interested to know what you used to analyse the clip.

I'm guessing this is common with the "who can post it first" brigade. I watched another MKV today that had almost no judder whatsoever, so I can see that it can be done correctly.

I'm not in a position to make these but I am interested in the technology behind it all.

Once again. Thanks
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post #13 of 23 Old 11-13-2008, 02:59 PM
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Quote:
Originally Posted by swin70 View Post

I do like the clarity of standards they have in this industry!

Yep - though they all make sense if you dig far enough.

The larger line-number figure is the total number, the smaller is the active number.

i25=50i because if you put i before the number it indicates frame rate, if you put it after it indicates field rate.
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post #14 of 23 Old 11-13-2008, 03:29 PM
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I just opened the video and went frame-by-frame. Any half-decent media player should be able to do that. As you go frame-by-frame, you'll see that many of them have ghosting (as a result of blending 2 fields that are from different frames together) and you'll also see duplicate frames. Neither of these should occur when the telecine is reversed correctly, except for possibly on the frames where snipes or other superimposed elements (like the rating bug) move. Both will cause judder when watching.
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post #15 of 23 Old 11-14-2008, 03:08 AM - Thread Starter
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Quote:
Originally Posted by coyoteaz View Post

I just opened the video and went frame-by-frame. Any half-decent media player should be able to do that. As you go frame-by-frame, you'll see that many of them have ghosting (as a result of blending 2 fields that are from different frames together) and you'll also see duplicate frames. Neither of these should occur when the telecine is reversed correctly, except for possibly on the frames where snipes or other superimposed elements (like the rating bug) move. Both will cause judder when watching.

Cheers man, all good.

Ok, you don't have to get too technical because you've both answered my questions, but my inquisitive mind is wandering.

When you perform the 3:2 telecine on 24fps film material to create 60i broadcast material, 2 video frames for every 5 created will contain fields from two separate original frames that have been "combed" together. The other 3 frames will contains fields directly from 1 original frame. The pattern then 'should' repeat. When you perform the inverse telecine you must need to somehow detect where these frames are in the sequence so you can start the procedure at the correct point, otherwise you will recombine interlaced element from the wrong frame.

How can you tell where to start the process? Are the frames/fields marked in any specific way, or is it simply down to the software to make a best guess. Of course I'm talking about products available to a casual user, not production equipment. As sneals2000 said, "The 3:2 cadence isn't consistent", which I guess means that this pattern may change if something is do to break the sequence (i.e. and ad break). I'm guessing all these problem (and I'm sure many more) lead to the issue in some off these off-air rips?

As an aside, surely it's going to come to a time where this kind of technology could be built directly into the TV. This then leads on to another point that relates back to standards. I can understand why different countries had different standards that have their roots in technologies 100 years old and differing electrical supplies, but surely with today's modern electronics and the invention of HDTV, we could have come up with a worldwide standard in terms of frames rate/refresh rate. If more and more TV companies are filming using "film" at 24fps, and more and more people want to re-create this look on their expensive HDTVs - why do we have to go through the agro of transferring one frame rate to another, only to have to perform more transformation to get back to where you where originally, but with the possibility of introducing error into the system?

Bit of a rant at the end there, but interested on thoughts.
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post #16 of 23 Old 11-14-2008, 08:21 AM
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Quote:
Originally Posted by swin70 View Post

When you perform the 3:2 telecine on 24fps film material to create 60i broadcast material,...

Just a minor point: Back in #6 Sneals2000 stressed the differences between telecining and 2-3 pulldown. Notice that some magazine reviews still mix the two concepts. But AIUI film telecines (optical scanning) usually result in 1080/24p master tapes or discs (U.S.), then separate later encoding converts to 1080i30 (1080/60i) etc. But for 24-fps non-film productions, telecines wouldn't be involved, only 2-3 (or 2-2) pulldown so the 24-fps rate matches the 60-Hz (U.S.) broadcast rate.

Not sure if this '06 post by dr1394 will help, but I may have filed it away as an illustration why the pulldown is 2-3 and not 3-2--although the distinction is minor and I've tried to avoid copying a long paragraph outlining 2-3 pulldown from C. Poynton's "Digital Video and HDTV" (2003, Elsevier Science).
Quote:


As an aside, surely it's going to come to a time where this kind of technology could be built directly into the TV. This then leads on to another point that relates back to standards. I can understand why different countries had different standards that have their roots in technologies 100 years old and differing electrical supplies, but surely with today's modern electronics and the invention of HDTV, we could have come up with a worldwide standard in terms of frames rate/refresh rate. If more and more TV companies are filming using "film" at 24fps, and more and more people want to re-create this look on their expensive HDTVs - why do we have to go through the agro of transferring one frame rate to another, only to have to perform more transformation to get back to where you where originally, but with the possibility of introducing error into the system?

Agree it's getting very complex, likely to become more so, I suspect. Depending on the display, lots of the tech is built in. Reviews covering displays often mention how effective various video processors are at switching between video deinterlacing and inverse (or reverse) pulldown. I'm still using, as many are worldwide, an interlaced CRT RPTV (Philips 64PH9905) that only displays HD at 1080/60i--displaying the pulldown rather than performing inverse pulldown (not inverse telecine). -- John
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post #17 of 23 Old 11-14-2008, 09:41 AM
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Quote:
Originally Posted by John Mason View Post

Just a minor point: Back in #6 Sneals2000 stressed the differences between telecining and 2-3 pulldown. Notice that some magazine reviews still mix the two concepts. But AIUI film telecines (optical scanning) usually result in 1080/24p master tapes or discs (U.S.), then separate later encoding converts to 1080i30 (1080/60i) etc. But for 24-fps non-film productions, telecines wouldn't be involved, only 2-3 (or 2-2) pulldown so the 24-fps rate matches the 60-Hz (U.S.) broadcast rate.

It isn't quite that simple I'm afraid John.

Telecine's are real-time film to video scanners. They take the film, and output a video signal in real-time to be recorded (or in days gone by played directly to air - when film inserts to TV shows and movies were played directly from Telecine to-air - with real time colour balance etc.)

The 3:2 pull-down can certainly be added in the telecine itself, and in days gone by was a mechanical process that HAD to be applied in the telecine. These days 3:2 can be added digitally, and can be done after transfer to 24p, but in earlier times it was a mechanical system that "pulled down" after 3 frames, and then "pulled down" after 2 frames. The "pull down" refers to the act of changing the film frame or "pulling it down". This used to have to occur during the vertical blanking period (fast pull-down) which meant the film had to accelerate and decelerate very quickly and caused a lot of stress on the film. The advent of digital storage and line-scan CCD telecines meant that a constant film motion could be used instead, which is far less damaging to movie film.

You are right John, that film can (and in the HD world usually is AIUI) scanned at 24p and recorded at 24p to video or disc, with any 3:2 conversion to 60i or 60p done off-line, or even "in VTR" as a separate process. However it doesn't have to be - and in the SD world seldom was. (There were 24p SD video systems for video post of film developed quite late in the day - mainly based on slowing down 576/50i to 576/48i and using 24psf representation. ISTR that some of The X Files may have been posted this way - allowing a 576/50i master with speed-up and a scale to 480/60i with 3:2 from a common 576/48i=24psf master)

"Telecine" as a word is massively misused in the PC video community - and is often equated with 3:2 pulldown. They aren't the same thing. Even worse the phrase "Reverse Telecine" has become equated with 3:2 pulldown removal. (Whereas a Reverse Telecine could really be described as a film recorder - taking a video signal and converting it back to film!)

European Telecines will be running with 2:2 pulldown usually (and a 4% speed-up from 24p to 25p) - so the use "Telecine" to mean "3:2 pulldown" is very inaccurate.
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post #18 of 23 Old 11-14-2008, 09:53 AM
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Originally Posted by swin70 View Post

As an aside, surely it's going to come to a time where this kind of technology could be built directly into the TV. This then leads on to another point that relates back to standards. I can understand why different countries had different standards that have their roots in technologies 100 years old and differing electrical supplies, but surely with today's modern electronics and the invention of HDTV, we could have come up with a worldwide standard in terms of frames rate/refresh rate. If more and more TV companies are filming using "film" at 24fps, and more and more people want to re-create this look on their expensive HDTVs - why do we have to go through the agro of transferring one frame rate to another, only to have to perform more transformation to get back to where you where originally, but with the possibility of introducing error into the system?

Bit of a rant at the end there, but interested on thoughts.

We do now at least have a common resolution - 1920x1080 (and 1280x720) across all HD regions and the only difference is the frame rates.

Also in many regions (but not the US) TVs are sold that accept all the worldwide refresh rates (though often 24p is optional) In Europe all "HD Ready" displays must accept 50Hz and 60Hz HD via Component and HDMI/DVI in both 1080i and 720p, with 1080p optional.

Linear transmissions really still need to run at a single frame rate - hence there are no 24p linear channels broadcasting in 1080/24p (only VOD and download services) The difficulty of changing frame rates on the fly - and the disturbance that TVs will suffer when changing frame rate (re-syncing usually requires a screen blank etc.) mean that fixed rate channels are still the norm - and likely to remain so.

So - why don't we all run 60Hz then? Well if you live in a 50Hz territory where your SD is 50Hz, and your mains lighting is 50Hz, there are all sorts of conversion issues - and avoiding lighting flicker in discharge lighting areas is still a non-trivial issue. If you had to frame rate convert all SD contributions to HD shows, and all HD shows shown on SD networks, you'd be paying for lots, and lots of very expensive and bulky frame rate converters AND end up with poorer picture quality at the same time. Not going to happen anytime soon.

Some have suggested considering running at much higher frame rates - shooting at up to 300p. That would allow both 50 and 60Hz video to be generated from the source content, and also allow for 100p display and broadcast at a later date? Not really expected anytime soon either...
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post #19 of 23 Old 11-14-2008, 11:04 AM - Thread Starter
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A succinct, and eloquent summary. Many thanks for the response.

When you refer to non-linear broadcasts, I wasn't exactly referring to such a technology, but the possibility that TVs would include technology to apply reverse telecine (er, inverse pulldown) to broadcast material so to not just de-interlace the fields, but also slow film material down to 24 fps automatically, showing the material as it was intended.

I must admit I hadn't accounted for lighting shimmer and different frequencies, and wouldn't have thought it would have created that much of an issue, but I guess it might be something you would pick up on sub-consciously. I also see now understand the issue of combining SD/HD media with differing frame rate, although this must happen to a certain degree already.

As with the computer industry, backwards compatibility can be a complete pain in the ass.
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post #20 of 23 Old 11-14-2008, 11:38 AM
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Originally Posted by sneals2000 View Post

It isn't quite that simple I'm afraid John.

Telecine's are real-time film to video scanners. They take the film, and output a video signal in real-time to be recorded (or in days gone by played directly to air - when film inserts to TV shows and movies were played directly from Telecine to-air - with real time colour balance etc.)

The 3:2 pull-down can certainly be added in the telecine itself, and in days gone by was a mechanical process that HAD to be applied in the telecine. These days 3:2 can be added digitally, and can be done after transfer to 24p, but in earlier times it was a mechanical system that "pulled down" after 3 frames, and then "pulled down" after 2 frames. The "pull down" refers to the act of changing the film frame or "pulling it down". This used to have to occur during the vertical blanking period (fast pull-down) which meant the film had to accelerate and decelerate very quickly and caused a lot of stress on the film. The advent of digital storage and line-scan CCD telecines meant that a constant film motion could be used instead, which is far less damaging to movie film.

You are right John, that film can (and in the HD world usually is AIUI) scanned at 24p and recorded at 24p to video or disc, with any 3:2 conversion to 60i or 60p done off-line, or even "in VTR" as a separate process. However it doesn't have to be - and in the SD world seldom was. (There were 24p SD video systems for video post of film developed quite late in the day - mainly based on slowing down 576/50i to 576/48i and using 24psf representation. ISTR that some of The X Files may have been posted this way - allowing a 576/50i master with speed-up and a scale to 480/60i with 3:2 from a common 576/48i=24psf master)

"Telecine" as a word is massively misused in the PC video community - and is often equated with 3:2 pulldown. They aren't the same thing. Even worse the phrase "Reverse Telecine" has become equated with 3:2 pulldown removal. (Whereas a Reverse Telecine could really be described as a film recorder - taking a video signal and converting it back to film!)

European Telecines will be running with 2:2 pulldown usually (and a 4% speed-up from 24p to 25p) - so the use "Telecine" to mean "3:2 pulldown" is very inaccurate.

Adding historical background and mixing in older SD production does add complexity, sneals2000, but I generally aim for what I understand usually takes place currently. That might appear simpler. Always nice to cover the historical aspects of a topic, although it seems preferable to set off the history or real minutia, as publications do with tinted sidebars, so readers don't get bogged down.

Clearly a telecine machine's (or data scanner's) output signal could be pulled down immediately to a 2-3 etc. format, but in most cases believe it first goes to 1080/24p by producers (here).

BTW, mentioned 2-2 pulldown earlier above because, AIUI, that's what 720/60p uses here rather than 2-3 pulldown.

But, speaking of TV history, here's a good opportunity to link something I'd filed away last year when I came across it: a camera system that simultaneously captured both 24p film and 480i video, the Electronicam used for Jackie Gleason's film and video productions (and others) here. Here's a brief WIkipedia description and a separate site with shots of the camera.

Not a fan of vintage production hardware, but much prefer the crispness and smoother motion of 60i-captured productions compared to 24p. So I outlined a while back--not all that seriously--the benefits of "Capturing both 24 fps and 60i" simultaneously. -- John
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post #21 of 23 Old 11-14-2008, 12:25 PM
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Originally Posted by swin70 View Post

Cheers man, all good.

Ok, you don't have to get too technical because you've both answered my questions, but my inquisitive mind is wandering.

When you perform the 3:2 telecine on 24fps film material to create 60i broadcast material, 2 video frames for every 5 created will contain fields from two separate original frames that have been "combed" together. The other 3 frames will contains fields directly from 1 original frame. The pattern then 'should' repeat. When you perform the inverse telecine you must need to somehow detect where these frames are in the sequence so you can start the procedure at the correct point, otherwise you will recombine interlaced element from the wrong frame.

How can you tell where to start the process? Are the frames/fields marked in any specific way, or is it simply down to the software to make a best guess. Of course I'm talking about products available to a casual user, not production equipment. As sneals2000 said, "The 3:2 cadence isn't consistent", which I guess means that this pattern may change if something is do to break the sequence (i.e. and ad break). I'm guessing all these problem (and I'm sure many more) lead to the issue in some off these off-air rips?

Some newer encoders used by broadcast stations and cable networks have a mode called film detection where they reverse the pulldown and encode only the 24 frames per second, and use a bit in the output stream to tell the decoder to repeat the field on playback. This is also present on many, but not all, DVDs. Some pulldown removal/inverse telecine/whatever you want to call it filters can utilize this information to get perfect results. Most of the time on broadcast TV, the encoder in use doesn't have or doesn't utilize this technology, and the processing filter on the user's computer handles it. Any interruption in the cadence will only cause odd behavior for about a third of a second before everything syncs back up with the new pattern, so it still wouldn't cause the bad behavior in your clips.

Quote:


As an aside, surely it's going to come to a time where this kind of technology could be built directly into the TV. This then leads on to another point that relates back to standards. I can understand why different countries had different standards that have their roots in technologies 100 years old and differing electrical supplies, but surely with today's modern electronics and the invention of HDTV, we could have come up with a worldwide standard in terms of frames rate/refresh rate. If more and more TV companies are filming using "film" at 24fps, and more and more people want to re-create this look on their expensive HDTVs - why do we have to go through the agro of transferring one frame rate to another, only to have to perform more transformation to get back to where you where originally, but with the possibility of introducing error into the system?

Bit of a rant at the end there, but interested on thoughts.

Pulldown removal technology already exists in TVs. The 2007 models were a bit sketchy, but the 2008 models by and large perform quite respectably. As for a single framerate, I see that other posters have already coverd that, so I'll defer to their explanations.
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post #22 of 23 Old 11-14-2008, 04:07 PM
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Quote:
Originally Posted by John Mason View Post

Adding historical background and mixing in older SD production does add complexity, sneals2000, but I generally aim for what I understand usually takes place currently. That might appear simpler. Always nice to cover the historical aspects of a topic, although it seems preferable to set off the history or real minutia, as publications do with tinted sidebars, so readers don't get bogged down.

Yep - though my point is that the processes can be separate, but don't have to be, and that assuming a telecine doesn't also add pull down can cause confusion, particularly when including discussions about DVDs and SD TV shows shot on film and edited on tape in 60i (where a 24p copy doesn't exist)

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Clearly a telecine machine's (or data scanner's) output signal could be pulled down immediately to a 2-3 etc. format, but in most cases believe it first goes to 1080/24p by producers (here).

Yep - my historical point was to put into context the reason why it is called "pull down"!

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BTW, mentioned 2-2 pulldown earlier above because, AIUI, that's what 720/60p uses here rather than 2-3 pulldown.

??? If 720p used 2:2 pulldown for 24p film you'd have 720/48p. 720/60p has to use 3:2 pull-down (with frame repetition and 3 redundant frames per source frame pair) in the same way that 1080/60i has to use 3:2 pull-down (with field repetition and 1 redundant field per source frame pair)

3:2 cadence is the common method used to get 60 images per second from 24 - whether you are generating 60 fields or 60 frames you need to do something to keep the frame (or field if interlaced) count to 60 per second. (Others cadences are used : 2:3:3:2 is one that is used in some 60i DV camcorders to record 24p as it allows you to discard a redundant - middle - frame made of two repeated fields not just a single field ISTR)

2:2 cadence is used with 25fps to 50i/p in Europe (no redundant fields with 50i) - and also with 24fps to 48i ("Slow PAL") transfers. Effectively film transferred 2:2 to 50i is 25psf and 48i is 24psf.

Quote:


But, speaking of TV history, here's a good opportunity to link something I'd filed away last year when I came across it: a camera system that simultaneously captured both 24p film and 480i video, the Electronicam used for Jackie Gleason's film and video productions (and others) here. Here's a brief WIkipedia description and a separate site with shots of the camera.

Same thing was used in the UK - called Gemini. It wasn't that widespread - but consisted of a film and tubed video camera in one unit. It was seen as a way of shooting colour film whilst shooting black and white video (and thus allowing UK TV shows to shoot for US colour audiences - and futureproof for a future UK colour audience AIUI. This was when the US was colour and the UK only just switching to colour and still using a lot of B&W. It was too klunky and limiting - the worst of both worlds - to ever really take off. It used to try and run up the film cameras as their video feeds were cut-up, and recorded tally tones to audio tape to create a very early edit decision list - each camera had a different tone, so you could replay the audio tape and know which camera's film needed to be used - rather than running all the cameras continuously. I bet the cameras didn't run up anywhere near quickly enough!)

http://www.tvstudiohistory.co.uk/riverside%20wis.htm

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Not a fan of vintage production hardware, but much prefer the crispness and smoother motion of 60i-captured productions compared to 24p. So I outlined a while back--not all that seriously--the benefits of "Capturing both 24 fps and 60i" simultaneously. -- John

Well if you like that you'll love "VidFire"! This is the process that the BBC use to remaster their old B&W film telerecordings of Doctor Who for DVD release. Because the BBC archived most of their 405/50i productions to 25p film (sometimes ditching one field) rather than converting them to 625/50i video, a lot of shows shot on video now only exist with a "film look". Vidfire is a pretty good film to video interpolation process - that interpolates the missing frames (a bit like the nasty stuff now appearing in consumer 100/120Hz TVs - but much better) They use this for the sequences that were shot in-studio, but those shot on location on film are left with the 25p look. It works really well - and makes old shows somehow feel "newer" than when they are on film.
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post #23 of 23 Old 11-15-2008, 05:21 AM
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Originally Posted by sneals2000 View Post

??? If 720p used 2:2 pulldown for 24p film you'd have 720/48p. 720/60p has to use 3:2 pull-down (with frame repetition and 3 redundant frames per source frame pair) in the same way that 1080/60i has to use 3:2 pull-down (with field repetition and 1 redundant field per source frame pair)

3:2 cadence is the common method used to get 60 images per second from 24 - whether you are generating 60 fields or 60 frames you need to do something to keep the frame count to 60 per second. (Others cadences are used : 2:3:3:2 is one that is used in some 60i DV camcorders to record 24p as it allows you to discard a redundant - middle - frame made of two repeated fields not just a single field ISTR)

2:2 cadence is used with 25fps to 50i/p in Europe (no redundant fields with 50i) - and also with FPs to 48i ("Slow PAL") transfers. Effectively 50i is 25psf and 48i is 24psf.

Okay. Recall seeing different 24p pulldown rates for 1080i30 and 720/60p here on AVS over the years but never crunched the numbers. A bit of Googling shows Tim Farrell's fx blog :
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When importing 24p material into a 720p project, the 3/2 pulldown needs to be created with frames instead of fields. This is easily accomplished by timewarping to 40% in progressive mode. To remove a 3/2 pulldown at 720p, interlace the clip and remove pulldown as one normally would.

Of course, we all know how to "timewarp to 40%." -- John
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