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Discussion Starter #1
I apologize if this is not the correct place to ask.


I am trying to find out what format is used to record various programs for HDTV broadcast in North America. As best as I can tell, a lot is either shot in 1080p24 via digital camera or shot in film and transferred to 1080p24. From there it is converted to 1080i30 (60 fields a second) or 720p for broadcast. I gather that some material is filmed in an interleaved format (again 1080i30?) or some other format, but I cannot find out more about this nor can I confirm that my basic sense above is correct. Can any one direct me to a moderately detailed source or provide a quick answer here.


Thanks in advance.


Jim
 

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There are only 2 broadcast standards: 720p (at 60 frames) and 1080i (at 60 fields). Videomaterial (American Idol or Jay Leno) is shot in 1080i60 directly and broadcasted this way. A videoprocessor (or LCD/Plasma TV) has to deinterlace it before it can be displayed. With videomaterial you usually loose half the vertical resolution with fast movements (e.g. 540 lines with fast pans, 1080 lines with still images).


Filmmaterial is 24p (23.97 actually) - like cinema movies or TV series (Prison Break e.g.) and is either converted to 1080i60 (telecine with 3:2 pulldown) or to 720p60 (also 3:2 pulldown) for broadcast. With this kind of material and a deinterlacer with a good filmmode you'll have your full vertical resolution (1080 or 720 lines), no matter if there's movement present or not.


There is no 1080i30 though.
 

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It is very simple ... ALL HTDV channels are broadcast in 1080i with the exception of ABC, FOX, ESPN and NatGeo which are broadcast in 720p.


"Most" broadcast cameras (Ikegami/Sony) are multi-format which enables native 1080/60i, 1080/24p, and 720/60p directly and simultaneously from the camera head
 

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Discussion Starter #4
Thank you both for your prompt responses. I am still not clear, however, on a few things.


I did understand that relatively few networks/stations broadcast in the 720p format. Those that do are not very problematic.


My biggest uncertainty had to do with the actual recording format used for various productions at (or for) the networks that broadcast in 1080i. I have seen widely contrasting accounts, some indicating that the bulk of production is done in 1080i60 field (what I termed 1080i30 frame earlier, as I thought that was more accurate) format with its inherent temporal dislocation. Others have suggested that almost all production work is done in 1080p24 film or digital camera format and then processed. The two accounts are at obvious variance and I just wanted to know which was correct.


I take it that the notation 1080i30 (to reflect 30 full frames and 60 fields) is not normally used?


Thanks again.
 

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Just about all scripted dramatic television excluding soap opreas is produced at 1080/24P either via film capture and transfer or direct video capture at 24p. The studio master which is maintained in the studio vault is 24P. An "air" master is made from this and has 3/2 added for 1080i or 60P. No broadcaster will accept 24P due to NTSC compatability issues. Also as the broadcast process today is highly automated, they don't want to deal with format conversions on their end. This was the impetus for 24P in 1999. The studios need to serve both distribution formats and building dual format facilities was not finnacially feasible.


Sports, live TV, concerts are generally 1080i or 720P depending on the network's chosen standard.


The actual format used is not strictly 24P but 24sF further refined to 23.98sF. sF is a trick to make P video compatable with I equipment. The image is captured as a progressive frame but is distributed within the production systems as odd/even lines in fields. It looks like an interlaced signal but there is no temporal differences between the fields as is with true interlaced. This allows it to be converted to 24P or 60P without any artifcats.
 

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1080i30 would mean 30x540 lines and that's just not correct, it's 60x 540 lines per second.


1080p24 (or actual 35mm film at 24 frames per second) is only used for film material or TV stuff which is intended to look like film (Lost, Prison Break and all the stuff). It's then converted to 1080i60 by using a 3:2 cadence on the frames splitted into two fields.


All the broadcast HD cams which are installed for sport events or in TV studios do 1080i60, so it can be live processed and broadcast live.
 

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Discussion Starter #7
Thank you for the further clarifications. I was aware of the use of 24PsF, but not clear on how common that was for TV production. I also suspected that a lot of live broadcasting was done natively at 1080i60 (fields) with the concomitant risk of temporal issues.


Am I to assume that soaps and most "reality TV" broadcasts are also done with 1080i60?
 

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Discussion Starter #8
Fudoh:


My use of the term 1080i30 has obviously caused a problem. I was under the impression that these various formats were typically distinguished in terms of "frames per second." That meant characterizing 60 fields per second as 30 frames per second. I have seen both terminologies used, but was unclear which was preferred and which might be seen as more "technically correct."
 

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I had heard, although I am not sure of the extent, of 1080i sources mastered as 1440 pixels wide instead of 1920. These sources would be simply scaled to 1920 pixels wide for broadcast.


I take it that a camera that can output 1080/60i (I hafve used the term [email protected]) and 1080/24p and 720/60p simultaneously has to be capturing at 1080/60p.
 

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Quote:
Originally Posted by jimmacintosh /forum/post/12993197


Thank you for the further clarifications. I was aware of the use of 24PsF, but not clear on how common that was for TV production. I also suspected that a lot of live broadcasting was done natively at 1080i60 (fields) with the concomitant risk of temporal issues.


Am I to assume that soaps and most "reality TV" broadcasts are also done with 1080i60?

Always enjoy recorded or live 1080/60i (30i) here because that means it's captured, delivered, and displayed (1080i CRT RPTV) in the same format. This often provides the wow-type 'window effect'. BTW, writing 1080i30 is accurate, although it fails to show that 60-field-per-second capture (non-24p material) may be involved. 1080/60i capture, often with widely used Sony HDCAMs, is frequently used for documentaries/travelogues, such as the "Over Italy" and similar series that used to run on PBS. (Sony HDCAMs do limit recordings to 1440X1080i, and that's usually upconverted to 1920X1080 during editing and before delivery. Newer Sony HDCAM SRs don't have this bandwidth limitation.)


While there are 'temporal issues' for 1/60-sec differences between TV fields, motion, such as a chopper overflight, is noticeably smoother than with 24p/24PsF capture. Deinterlacing, not required for most CRT display, can be a factor with fixed-pixel displays, as Greg Rogers' reviews of higher-end front projection video processing demonstrated last year. AIUI, the only soap still being captured at 1080/60i is CBS's "The Young and the Restless," although other soaps as well as many comedies are video taped. -- John
 

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Quote:
Originally Posted by John Mason /forum/post/13025894


BTW, writing 1080i30 is accurate, although it fails to show that 60-field-per-second capture (non-24p material) may be involved.

Video terminology can be very arcane. (Try explaining 4:2:2 vs 4:2:0 vs 4:1:1 encoding.) It's not a big deal, but SMPTE 274M, which defines all of the 1080i and 1080p standards that are in use (and is a reference for ATSC broadcast video) defines the System Nomenclature for 1080i (60 fields per second, 30 frames per second) as 1080/60/I. This is consistent with the common terminology usage 1080i60. The "i" indicates that the following number represents fields/sec, while a "p" indicates the following number represents frames/sec. But if someone writes 1080i30, we know what they mean since there is no SMPTE standard format with 30 fields/sec, 15 frames/sec, but 1080i60 is much more commonly used and consistent with the SMPTE System Nomenclature.
 

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OT: To add to the nomenclature confusion, sometimes 525 is written instead of 480 for analog video. Example: 525i. We just have to understand that 525i and 480i mean the same thing. Both 480i and 480p analog video have 525 scan lines for every full frame's worth of video (with approximately 480 of them containing picture information). But the total data for a frame's worth of 480i or 480p digital video does not equal 525 rows of pixels. There is no standard format with 525 active (picture containing) scan lines per frame.

Quote:
Originally Posted by gregr /forum/post/13027050


Video terminology can be very arcane. (Try explaining 4:2:2 vs 4:2:0 vs 4:1:1 encoding.)

More OT: 4:x:y encoding. For every 4 luminance pixels in a row, x color pixels are retained for odd scan lines and y color pixels are retained for even scan lines. For example 4:2:0 has two color pixels (Cb, Cr pairs) kept for every 4 pixel positions across on odd scan lines and no color pixels kept for even scan lines. The result in this case is every 2x2 block of luminance pixels sharing the same coloration. The coloration may or may not be the average of the source pixels in question. Generally for interlaced video odd and even here refer to scan lines within the same field.
 

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also, most of the broadcasts are at a bit rate of about ~45 mbps, unfortunately we only see about 1/3 of it.
 

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Quote:
Originally Posted by Allan Jayne /forum/post/13021084


I had heard, although I am not sure of the extent, of 1080i sources mastered as 1440 pixels wide instead of 1920. These sources would be simply scaled to 1920 pixels wide for broadcast.


I take it that a camera that can output 1080/60i (I hafve used the term [email protected]) and 1080/24p and 720/60p simultaneously has to be capturing at 1080/60p.

The 1440h comes from the HDCAM format which records 1440x1080 at 3:1:1 sampling. Yes this is a compromised format but was deemed adequate in the ealry days of HDTV. This tape format is basically the same as Digital Betacam with 143mbs to tape. Sony just compressed HD anyway the could to get it to fit into 143mbs tape bandwidth. The machine I/O is still SMPTE292 at 1920x1080i. The 1440 is upsampled internally. HDCAM was the format of choice for most eposidic television work until about 2005.


Panasonic HDD5 has always been 1920x1080 4:2:2. Therefore thios format was perferred for feature mastering. Very few eposodic programs used it. This has intra frame DCT compression


Around 2006 most studios - especially Sony - started using HDCAM-SR. This is an MPEG4 intra frame compression that puts 440mbs to tape. It can record 1920x1080 at 4:4:4. It has another option that allows two 1920x1080i 4:4:4 streams on tape or a single 1080p/60 4:4:4 stream at 880mbs. Of course they do this by doubling the tape speed so you eat twice as much tape. This is the highest quality VTR on the market today.
 

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Discussion Starter #15
Thank you all again for your helpful information.


One final clarification. As I understand it, live broadcasts (other than those done by the few networks using 720p) are typically captured in 1080i60 which will entail some temporal issues requiring processing at the HDTV owner's end. Anything recorded on film or intended to look like film (prime time dramas) is captured in 1080p24sF. It is then stored in the 24p format but also interlaced and telecined to become 1080i60 for broadcast, but not with any temporal issues (because it uses one real frame to create two component fields). Hope I got this straight.
 

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Quote:
Originally Posted by jimmacintosh /forum/post/13064252


Thank you all again for your helpful information.


One final clarification. As I understand it, live broadcasts (other than those done by the few networks using 720p) are typically captured in 1080i60 which will entail some temporal issues requiring processing at the HDTV owner's end. Anything recorded on film or intended to look like film (prime time dramas) is captured in 1080p24sF. It is then stored in the 24p format but also interlaced and telecined to become 1080i60 for broadcast, but not with any temporal issues (because it uses one real frame to create two component fields). Hope I got this straight.

Basically yes. The term "telecine" - at least in the industry generally means realtime transfer to tape at any frame rate.


A 24p production is done at 24p all the way to completion. The final master is at 24p and this is what is archived. The network gets a digital copy of the master with 3/2 added. All the HD VTRS can add 3/2 internally on the fly. In other words you can insert a 24p tape and play out 60i - or 50i. However the networks will not accept a 24p master as they lack the infrastructure to do the conversion - mainly they have no sync system to lock the machine at 24p. Also these days the networks are highly automated and [with no disrespect intended] a less technically trained operations staff. They don't want the responsibility of having to do the conversion in house.


And remember all TV is at 23.98sF not true 24p. Likewise digital intermediate projects are true 24p. However again the VTRs can cross play from one to the other seamlessly.
 

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Quote:
Originally Posted by Glimmie /forum/post/13065850


Basically yes. The term "telecine" - at least in the industry generally means realtime transfer to tape at any frame rate.

Often spot reviews referring to 'reverse telecine'--the video processing in home equipment to extract 24p from 2-3 pulldown (from 1080i). Seems that 'inverse pulldown' (or reverse) is more accurate, though, since many TV productions and some feature movies are taped or otherwise recorded at 24PsF without film being involved at all.

Quote:
And remember all TV is at 23.98sF not true 24p. Likewise digital intermediate projects are true 24p. However again the VTRs can cross play from one to the other seamlessly.

Really? Thought 24PsF (segmented frames) was only involved with certain recorders such as Sony's HDCAM, storing full 24p frames in separate segments that can be re-combined to emulate full 24p film frames. Everything's stored segmentally? -- John
 

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For info - the following nomenclature is used by various organisations to describe the same, identical video formats :


1080i30 - 1080/60i - 1125i30 - 1125/60i

1080p24 - 1080/24p - 1125p24 - 1125/24p

720p60 - 720/60p - 750p60 - 750/60p


(replacing 24 or 30 with 25 and 60 with 50 gives you the 50Hz variants)


480i30 - 480/60i - 525i30 - 525/60i

576i25 - 576/50i - 625i25 - 625/60i


The first pair of figures refers to the active lines per frame - 480, 576, 720, 1080, the second pair of figures refers to the total lines per frame (including blanking/syncs) - 525, 625, 750, 1125.


When describing a progressive standard, the frame rate is always used. However when describing an interlaced standard some organisations use the frame rate (the EBU does and thus uses i25 rather than /50i to describe European SD and HD interlaced formats) whilst others use the field rate.


Personally I prefer the field rate nomenclature as it emphasises the fact that an interlaced frame is made from two interlaced fields AND that these two interlaced fields are not always sampled at the same time. (i.e. an interlaced frame is not a single image split into two halves, it can be sourced from two separate images)
 

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Quote:
Originally Posted by Fudoh /forum/post/12991255


There are only 2 broadcast standards: 720p (at 60 frames) and 1080i (at 60 fields). Videomaterial (American Idol or Jay Leno) is shot in 1080i60 directly and broadcasted this way.

Not strictly true - some live shows are also shot in 720/60p - with many facilities able to switch their cameras and infrastructure between 1080/60i and 720/60p on a show-by-show basis (with cameras like the LDK6000 World Cam, LDK 8000 and the HDC-1500 either 1080/60i or 720/60p outputs are possible in full quality)


American Idol, being a Fox show, is shot in 720/60p as a result, not 1080/60i. Leno is 1080/60i though - as you say.

Quote:
A videoprocessor (or LCD/Plasma TV) has to deinterlace it before it can be displayed. With videomaterial you usually loose half the vertical resolution with fast movements (e.g. 540 lines with fast pans, 1080 lines with still images).

Yep - any interlaced format like 1080/60i drops to 540/60p quality on fast motion, but then it takes the same bandwith as a 540/60p system and delivers higher resolution on more static stuff.

Quote:
Filmmaterial is 24p (23.97 actually) - like cinema movies or TV series (Prison Break e.g.) and is either converted to 1080i60 (telecine with 3:2 pulldown) or to 720p60 (also 3:2 pulldown) for broadcast.

Film for TV is often shot at 23.97 - though other 24fps film may not be and is slowed down slightly for TV use. 23.97 stuff is converted to 59.94 for US TV broadcast - often 23.97 and 59.94 are subbed to 24 and 60 to keep things simple.


The difference between 24p to 60i and 24p to 60p conversion is that 3:2 pulldown in 60i causes de-interlacing issues, whereas 24p to 60p is a simple frame repetition and doesn't cause de-interlacing issues.

Quote:
With this kind of material and a deinterlacer with a good filmmode you'll have your full vertical resolution (1080 or 720 lines), no matter if there's movement present or not.

Yep - 24p motion can be fully carried in 60i signals, as can 30p motion. It is only motion above this that cannot be correctly de-interlaced.

Quote:
There is no 1080i30 though.

1080i30 is the same as 1080/60i - it is a nomenclature difference. i30=30 interlaced frames, /60i = 60 interlaced fields. Different ways of saying the same thing.


On this board i30 is seldom used - but it is a valid format description - and is used by the EBU I believe, as well as others.
 
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