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Old 31st May 2017, 07:42   #41  |  Link
Ghitulescu
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Good that you mentioned BBC.

BBC used a different approach.

The digital frame sizes are 788 and 1050 respectively (PAR=1), for they include also what BBC calls blanking. The extra pixels are usually painted black.

Resize then to 788/1050 then cut the black borders and you'll end with some strange number of pixels but quadratic.
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Old 31st May 2017, 08:09   #42  |  Link
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Originally Posted by Logan9778 View Post
I'm beginning to think some of the time, wider or thinner bars than 8 pixels wide might mean a custom PAR.
Caution! Don't take this as a rule. The video can be cropped and borders become then wider than 8 pixels. Cropping does however NOT change the PAR. Only resizing will affect the PAR.
Circle test, circle test, circle test .....
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I just can't believe how they did whatever they felt like in putting these videos to DVD. Even the old CRTs wouldn't have played some of them at correct AR.
Absolutely. One can find all kind of crap, especially with old transfers. The studio monkeys sometimes just didn't know what they were doing.
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Old 31st May 2017, 15:38   #43  |  Link
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Edit: I'm working on one of my Fawlty Towers DVDs and it has 16 pixel wide black bars on both sides. So I re-calculated PAR assuming 688 pixels width was the actual video, and came out with 48:43 PAR. 12:11 never did look exactly right. Circles are looking a lot better! I'm beginning to think some of the time, wider or thinner bars than 8 pixels wide might mean a custom PAR. I just can't believe how they did whatever they felt like in putting these videos to DVD. Even the old CRTs wouldn't have played some of them at correct AR.
I wouldn't say it means a custom PAR was used as such as there's no logical reason for doing so, but I'll have to drag my Fawlty Towers DVDs out for a look because now you've mentioned it I have a vague memory of the grandfather clock face (next to the stairs) never looking quite round, even when using an ITU PAR. Are those "remastered"? I can't remember off the top of my head, but if they were remastered in a square pixel format before resizing for DVD, maybe someone stuffed up.

They wouldn't be the first DVDs with a large amount of black down the sides though, and sometimes it changes from scene to scene. My Men Behaving Badly DVDs are all over the place. I remember a few sections with well over 30 pixels of black down one side, but the picture aspect ratio still looked normal.
In those situations I'd crop the extra black and some extra picture from the top and bottom until what's left is 4:3 again, as that way it can be resized to the same 4:3 square pixels dimensions as the rest of the video.... if you're resizing to square pixels.... which I do.

Quite a while ago I encoded the extras from a Bluray. They were mostly SD, but many of them contained scenes from episodes, so I thought I'd resize them and compare the aspect ratio to the HD versions. An mpeg4 PAR wasn't right. If I remember correctly generic 16:9 resizing was much closer to the HD versions, although not perfect. That's the only time I've compared them like that, but it made me wonder if the mpeg4 PARs for SD Blu-ray are being ignored the same way ITU is for DVD.

Last edited by hello_hello; 31st May 2017 at 15:41.
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Old 1st June 2017, 18:14   #44  |  Link
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Originally Posted by Ghitulescu View Post
Good that you mentioned BBC.

BBC used a different approach.

The digital frame sizes are 788 and 1050 respectively (PAR=1), for they include also what BBC calls blanking. The extra pixels are usually painted black.

Resize then to 788/1050 then cut the black borders and you'll end with some strange number of pixels but quadratic.
Thanks, I'll try that.

Looking back at the Doctor Who's I've been trying to do, and they are also Waayyyy past 12:11 PAR stretch. As you said Sharc, I think in the end it's just circle test, and try to calculate out the real PAR. The amount of black bars doesn't seem to matter on most, except maybe Fawlty Towers.
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Old 2nd June 2017, 04:39   #45  |  Link
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Thanks, I'll try that.
I don't know where that theory came from, but it wouldn't make any difference.

ITU and mpeg4 resizing both give you 786 x 576 (or 1048 x 576), with the aspect error for the mpeg4 PAR being slightly higher, but still only 0.07%. Resizing to 788 or 1050 instead obviously only increases the width by 2 pixels, or just under 0.2%.

I could understand the BBC using 788 instead of 786 as it's mod4, but 1050 is mod2, so that doesn't seem like it'd be the reason.

I doubt you'll ever find the "real" aspect ratio for those DVDs, especially for episodes that were reconstructed from different sources. The aspect ratio probably would have been fudged differently throughout.
I recall seeing something on how one of the old Jon Pertwee series was restored. Apparently the only colour copy in existence was an old home VCR recording, but there was a sharper black and white film print, so they overlayed the colour from the video onto the film version, except the film version had been made by pointing a film camera at a TV screen, and back then TV screens were far from flat, so the film version had to be warped a little to match it to the VCR recoding. That probably wouldn't have been enough to fudge the aspect ratio noticeably on it's own, but back in the very early days I wonder how the TVs would have been calibrated before they were used to record the film version. Probably by playing a video while a technician fiddled with the picture width until it looked about right.

Last edited by hello_hello; 2nd June 2017 at 05:04.
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Old 2nd June 2017, 07:44   #46  |  Link
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I could understand the BBC using 788 instead of 786 as it's mod4, but 1050 is mod2, so that doesn't seem like it'd be the reason.
The reason is the blanking, and these are the figures BBC herself provided to contractors.
BBC tried all her time to enforce some standards, but not always was successful. BBC has her own audio level, her own frame sizes, her own Teletext/Videotext codings etc... not too different from the others but enough different to make "perfectionists" cry.
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Old 2nd June 2017, 11:20   #47  |  Link
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I'm a bit confused by this. The ABC describes a 702 pixel width as a "legacy" format.
The info below adds up to the whole 720 pixel width containing picture, but what's the result of the "digital Betacam format" part of the spec. Is it the same as analogue where the aspect ratio is a little wider than 4:3 (only 704 width), or is it 4:3 in and 4:3 out when it's digital? If the latter is the case and the same process is used for DVDs, they'd have an exact 4:3 or 16:9 aspect ratio too, I assume.

From 2011 (pdf link): http://www.abc.net.au/tv/independent...s_Aug_2011.pdf

Introduction
The following specifications are based on current and commonly accepted standards. The ABC thanks the BBC, Free TV Australia (Federation of Australian Commercial Television Stations), SMPTE, EBU, ITU, Dolby Laboratories and the Sony Corporation.

STANDARD DEFINITION
2.2.1 The Supplier shall deliver the product as a Standard Definition Television (SDTV) videotape recording in the Digital Betacam Format. The video tape recording shall be 625 lines at 25 frames per second and interlaced 2:1 (576/50i). This shall be in agreement with the specifications of Recommendation ITU-R BT. 601-5, SMPTE 259M (as revised).
2.2.3 All SDTV programs produced using modern digital equipment shall have narrow horizontal blanking, ie. active vision shall be 720 horizontal pixels wide. Legacy programs with 702 pixel wide vision (wide horizontal blanking) will also be acceptable. A single program shall have consistent blanking throughout.
2.2.4 All SDTV widescreen programs shall have 720 pixels x 576 lines active picture area

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Old 2nd June 2017, 13:41   #48  |  Link
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2.2.4 All SDTV widescreen programs shall have 720 pixels x 576 lines active picture area
The whole line is, after proper 4:3/16:9 DAR, 788 pixels wide in 4:3 and 1050 in 16:9.
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Old 2nd June 2017, 15:41   #49  |  Link
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I don't understand how you get 788 pixels from that. I don't see any mention of aspect ratio, only that there's 720 pixels of active picture. I'm not saying after resizing to a "proper" 4:3 it wouldn't be 788 pixels wide, but there's nothing there to indicate that's how it should be resized, or it should be wider than 4:3 (ie 788x576) before it's resized for 720x576 PAL.

It probably is the way it should be done, but the question is, is that the way people are doing it, or is it common for an exact 16:9 image to be resized to a 720 width.

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Old 3rd June 2017, 18:42   #50  |  Link
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Lol, I pretty much gave up as well on finding the "real" aspect ratios. I'm pretty much just going by circles now, and trying to work out a decent PAR. BBC just seems to be HORRIBLE. They should hire one of you guys to teach them the meaning of the word "aspect ratio".
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Old 4th June 2017, 10:50   #51  |  Link
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People keep telling me BBC had shot on film.
However, all BBC movies and serials I have bought here in Germany, all look like they have been if not shot at least edited, and if not edited then at least one intermediary copy was on tape. Maybe UK-market is fed with better editions, who knows....?

That is, at least once IMHO they had to work with non-square pixels. And this has been done according to their own rules. However, BBC does not manufacture any equipment. So they rely on foreign manufacturers, Sony, JVC, Panasonic. The way they implement what BBC requires may vary.

This Babel thing happens everywhere in the world where such methods are used. I was therefore one of the most early supporters of the BD, from the consumer point of view, for it eradicated (in the sense of WHO ) the rectangular PARs - and reverted to the natural way, of identical units on each scale. Yes, for compatibility sake BD kept some very used PARs, but it provided the technical/formal provision for an undisturbed view.

The correct way of resizing an image is to find a circle or a square or anything that can give (disclose ) the real ratio.
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Old 4th June 2017, 18:52   #52  |  Link
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Yeah, agreed. Cricles and squares seem to be the only way with these old movies. A I can tell some of these were "filmed" off of a TV screen, because you can tell how circles seem to change near the edges. Some early WHO video looks like it was shot with a fish eye camera.
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Old 12th August 2017, 18:49   #53  |  Link
Logan9778
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Originally Posted by Ghitulescu View Post
Good that you mentioned BBC.

BBC used a different approach.

The digital frame sizes are 788 and 1050 respectively (PAR=1), for they include also what BBC calls blanking. The extra pixels are usually painted black.

Resize then to 788/1050 then cut the black borders and you'll end with some strange number of pixels but quadratic.
Thanks! After a 2 month break to clear my head of all this, I realize what you're talking about now. So I assume it looks like ITU, but 788 pixels wide with 10 pixel wide black ( or some say it could be white) columns on each side? And I assume the black or white columns would be overscan on an old 4:3 TV, same as ITU?

The DVDs I have (Old Doctor Who from the 60's) seem to just be the whole film frame ( you can actually see the slight rounded corner at the bottom left sometimes ), so I'm assuming non-ITU and 768 pixels, and the 3 or 4 pixels of black you sometimes see are just sloppy capture as they went beyond the frame itself on to the actual frame holder. I now understand that the digital width is what "fits" into 720x576 non-square pixels, and the "digital pixel size" varies according to different companies. i.e. BBC's digital "pixel width" is different from most other standard "digital pixel widths", so 788 "BBC pixels" fit into 720x576 the same as the "standard 768 pixels" fit into 720x576.

Found a good post on this here:

http://www.lafcpug.org/phorum/read.php?1,263245,263324

@mods - Sorry for the double post, but it's been two months since my last post.

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Old 13th August 2017, 19:40   #54  |  Link
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If you read some of what I quoted from the ABC pdf earlier (and as far as I know the ABC do everything the same as the BBC):

2.2.3 All SDTV programs produced using modern digital equipment shall have narrow horizontal blanking, ie. active vision shall be 720 horizontal pixels wide. Legacy programs with 702 pixel wide vision (wide horizontal blanking) will also be acceptable. A single program shall have consistent blanking throughout.

And combine it with the 788 square pixel width Ghitulescu's mentioned, to me it still adds up to an mpeg4/ITU pixel aspect ratio but there's very little to no black at the sides.

I did a little more searching and I'm still a bit confused, but some anecdotal (almost) evidence the picture is supposed to be 720 pixels wide, although wider than 4:3.

EBU Technical Recommendation R92-1999 (pdf)
Active picture area and picture centring in analogue and digital 625/50 television systems
The EBU is aware of a certain amount of confusion about the active picture area in the implementation and use of digital signals conforming to the ITU-R Recommendation BT.601 [1].
Recommendation BT.601 specifies a line length of 720 luminance pixels (13.5 MHz sampling). ITU-R Recommendation BT.470[2], specifies a line length of 52 Ás for 625 line analogue signals. This corresponds to 702 luminance pixels.
This apparent difference can lead to difficulties in conversion, especially if users wish to maintain the correct aspect ratio of the pictures.
Recommendation BT.601 accommodates modest variations in the position and length of analogue blanking which arise before a signal is digitised or when digital signals pass through any subsequent analogue process.
The EBU recommends that:
In 625-line television systems sampled to ITU-R Rec. BT.601 part A, only the central 702 luminance samples of the digital active line (samples 9-710 inclusive) and their associated chrominance samples should be used to carry the active picture. The remaining 18 luminance samples and their associated chrominance samples may be used to carry picture information only but for no other purpose. It cannot be guaranteed that picture information in these samples will be displayed in either 4:3 or 16:9 aspect ratio images.


BBC Technical Standards for Network Television Delivery
4.1.4 Video Signal Timings.
Digitally delivered pictures are considered to have a nominal active width of 702 pixels (52us) starting on the 10th pixel and ending on the 711th pixel in a standard REC 601(720 sample) width. A minimum width of 699 pixels (51.75us) within these limits must be achieved. Additional active pixels outside the above limits must be an extension of the main picture.

There's information in this ITU PDF explaining the relationship between digital and analogue.
Studio encoding parameters of digital television for standard 4:3 and wide-screen 16:9 aspect ratios
Encoding parameter values for the 4:2:2, 13.5 MHz member of the family
The specification (see Table 3) applies to the 4:2:2 member of the family, to be used for the standard digital interface between main digital studio equipment and for international programme exchange of 4:3 aspect ratio digital television or wide-screen 16:9 aspect ratio digital television when it is necessary to keep the same analogue signal bandwidth and digital rates.

It refers to a chart on page 7 that lists the total number of samples per line for PAL as 864, with the number of samples per digital active line being 720.
On page 10 there's a diagram showing how the "digital blanking" interval is from pixel 720 to pixel 864.

My take on all that, and hopefully someone will correct me if I'm wrong, is the original BT.470 analogue spec is equivalent to 702 pixels wide in digital-speak, which is exactly 4:3, and BT.601 doesn't change that, only adding some bonus picture on each side.
If that's correct, it makes sense that a 4:3 DVD containing a video capture would have lashings of black down the sides, while a digital source (and those old Doctor Who episodes have been digitally process every which way), would be 720 pixels wide, although I assume still only 704 of the width would be 4:3. I'm still reasonably sure most 4:3 DVDs I've come across have an ITU/mpeg4 pixel aspect ratio, be they of BBC origins or otherwise..

I haven't seen enough of them to be certain, but I strongly suspect the few 16:9 BBC DVDs I've seen are ITU, despite the 720 width being almost entirely picture, but as a rule the rest of the world seems to be sticking to the 720 width being part of the total 16:9 aspect ratio.... mostly. I still don't fully understand why.

Some interesting reading here. (pdf)
The origins of the 4:2:2 DTV standard

Last edited by hello_hello; 23rd August 2017 at 23:36.
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Old 23rd August 2017, 05:44   #55  |  Link
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Thanks Hello! Sorry to get back so late.

Well, I'm looking at Doctor Who stuff again, and it looks like most have the BBC blanking. About 12 to 13 pixel columns of black on each side. I still have a hard time finding a decent circle to look at though, and some just don't come out whether I use non-ITU, ITU, or BBC Blanking PARs. Finally found a good circle at the beginning of "The War Games" Disk 2, where they shoot some kind of force field out, and its a bunch of blurry circles. Looks like Ghitulescu may be right about the 788 stretch, as it only looks circular if you stretch it out to 788.

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Originally Posted by Ghitulescu View Post
The whole line is, after proper 4:3/16:9 DAR, 788 pixels wide in 4:3 and 1050 in 16:9.
EDIT: In the end, after a lot of circle testing, I decided on going with 720x788 for Doctor Who. PAR for 720 x 788 is 197:180. I cropped it to 704 x 572 (cropping doesn't affect PAR), then went with a PAR of 197:180, to get 704 x 770, which seemed to give the best circles. Doctor Who NTSC videos, 720x480, seem to be ITU, with a 10:11 PAR, which produced the best circles.

There do seem to be parts of Doctor Who sometimes that appear to be 720 x 864, but examination of the rest of video shows circles at this DAR to be wildly off. You should stick with 720x788.

Thanks for your help guys!

Last edited by Logan9778; 9th September 2017 at 21:21.
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