HalfD1 Mode seems to use Non ITU compliant resizing

[scharfis_brain]

When I use HalfD1 Mode DVDRB seems to use Non ITU compliant resizing on 720 pixels wide sources, because I found a plain bilinearresize to 352 pixel width in the AVS.

IMO a simple check for 704 or 720 pixels width should be included:


(last.width=720) ? last.crop(8,0,-8,0).horizontalreduceby2() : \
(last.width=704) ? last.horizontalreduceby2() : last

[jdobbs]

I don't agree. If the original source was 720 wide you want to do a straight conversion to 352. Here's a simple test I've done to prove it:

1. Play the original source back on the screen and pause at a particular frame (one that has some part of the picture that is easy to measure).

2. Physically measure it on the screen (with a ruler).

3. Convert to 352 using the two methods and then do then measurement again.

What you will find is that doing the conversion to 704 before downsizing to 352 will stretch the picture horizontally and it will be measurable.

I know others argue the the 8 pixels on either side are overscan -- and that is true... but they are still a part of the picture and have to be included in the conversion. I also know that there are documents that contradict this... but the proof is in the measurement -- and every single one I've done against a 720 original has resulted in the same horizontal stretching.

[dragongodz]

i seem to remember there was a thread about this a long time ago aswell. :)

[jdobbs]

Yeah. I was in that one too, I think.

[scharfis_brain]

Most Software DVD-Players do playback 720pixels wide DVDs with wrong AR.

720!=704

720 is more wide chan 704, but this is constantly (sadly) ignored by software DVD-players

[Sir Didymus]

Originally posted by jdobbs
...I know others argue the the 8 pixels on either side are overscan -- and that is true... but they are still a part of the picture and have to be included in the conversion. I also know that there are documents that contradict this... but the proof is in the measurement -- and every single one I've done against a 720 original has resulted in the same horizontal stretching.

One of the contradicting documents seems to be Dvd Demystified too (I am currently doing some self teaching :D , so forgive me if I tend to reference to it too much into my last posts...):

http://img232.echo.cx/img232/6973/image15nk.th.gif (http://img232.echo.cx/my.php?image=image15nk.gif)

Maybe the reason most of the sw players are non ITU compliant is that the 2% of the discrepancy is discernable only through a direct measure. Maybe also due to such a small difference the whole topic is not of the strongest relevance... Apart this I tend to second scharfis_brain post...

Just out of curiousity, Jdobbs, the measuring test you performed were carried out with a standalone or with some sw player ?

[jdobbs]

Originally posted by scharfis_brain
Most Software DVD-Players do playback 720pixels wide DVDs with wrong AR.

720!=704

720 is more wide chan 704, but this is constantly (sadly) ignored by software DVD-players Again I disagree. What you will find is that when a 720 wide picture is played, there is an 8 pixel region that is not shown on either side. It is especially noticable when you look at a 4:3 recording from a television. There are "black bars" on either side if you edit it on a computer that aren't there on the television screen. So, yes, it plays back as with only 704 visible pixels -- but the other 16 are still there to the right and left of the viewing area.

I don't want to argue this point. Because frankly I think there are contradictions between different sources and it's and argument no one can win. I've made it the way it is because that's what works correctly.

[jdobbs]

@Sir Didymus,

I do all my testing on standalone players with a standard television. Software players seem to be wrong as often as they are right.

[Sir Didymus]

@Jdobbs.

Thanks for explaining.

So your argument is based on direct measures, using proper measuring equipments.

I think this is one of the (rare ?) situation where theory and practice fight together...

Well, for the moment the evidence of your arguments leaves no space for discussions (at least from my side), I would say...

All the best
SD

[jdobbs]

So your argument is based on direct measures, using proper measuring equipments. Well, I'm not sure whether a ruler is proper. :)

[Kika]

Long time ago, in a Galaxy... oops, wrong text.

Long time ago, TheWef explaint realy good, what a correct AR means. He did this here at Doom9.

352x480/576 ist based on 704x480/576, not on 720x480/576.

To make it a bit more easy for me, let's stay at PAL-Resolutions.
720 is exaktly the same as 704 - with 16 Pixels overscan area. To get a correct AR after a resizing to 352, you have to know what your source is.

Is it 720 without borders left and right? If so, you may have a stretched Picture. You also may have a correct Picture with an overscan area.
If the picture is just stretched, the DVD hasn't a correct AR. In this case, you can resize directly. But if you have a correct authored DVD, you have an Overscan of 16 Pixel and Half-D1 is an overscan-free resolution. So you must crop the picture to get a proper result.

[onesoul]

Interesting, but I have one question, if there aren't black borders in a 720 stream, how can you know if the correct Aspect Ratio is being used or not?

[Kika]

That's simple: i pray for a round object in the video and try to find it (that's NOT simple... ;) ) If there is one, i take a Screenshot and resize it to 768x576 and 786x576.
If the object is realy round in the 768-version, the DVD has a wrong AR and should have been encoded to 704x576, not 720x576.
If the object is round in the 786-version, the AR is correct and the DVD has an overscan area. In this case, you have to crop to 704 first if your target is 352.
Consider: 352x480/576 is called HALF-D1, not Half+extra-pixels-D1. ;)

[SeeMoreDigital]

Can some of you confirm the accuracy of this 16:9 720x576 Circle Test File (http://82.2.167.237/Uploaded_Files/Doom9_Forum_files/PAL_16.9_720x576_Circle_Test_01.7z) in your stand-alone and software DVD players please?


Cheers

[onesoul]

@Kika

I could be getting this wrong but if cropping hasn't been done, don't you mean this instead?:

-If the object is really round in the 768-version, the AR is correct and the DVD has an overscan area. In this case, you have to crop to 704 first if your target is 352.
-If the object is round in the 752-version, the DVD has a wrong AR and should have been encoded to 704x576, not 720x576.

But anyway, I trust jdobbs measuring, and what I ask is, could it be possible that different stand alone players could be decoding in different ways depending on each stream's width.
What I ask here is in part related on what SeeMoreDigital said.

@SeeMoreDigital

Your question sounds funny :). I fully agree on what you are proposing though.


edit: What I would add is that this kind of error would be virtually impossible for DVD-RB or a common user to decipher, and these different widths and AR's are really a b*tch.

[scharfis_brain]

all MPEG decoder Filters, I have installed seem to produce a circle.

With one exception:
Enabling "Use accurate aspect ratios" (ITU compliant scaling!) in the DSCALER MPEG Decoder shows that the circle is no more a circle.
It is more wide than tall.

The same with my DVD-SAP which is connected to my analogue TV: the circle is more wide!

This leads to the conclusion: This VOB has been made using a genericPAR of 1.0666 * 1.3333

It is NOT ITU compliant!

[SeeMoreDigital]

Originally posted by onesoul
SeeMoreDigital

Your question sounds funny :). I fully agree on what you are proposing though.Then hopefully you wont mind confirming the accuracy of this 4:3 720x576 Circle Test File (http://82.2.167.237/Uploaded_Files/Doom9_Forum_files/PAL_4.3_720x576_Circle_Test_01.7z) too?


Cheers

[jdobbs]

Originally posted by scharfis_brain
all MPEG decoder Filters, I have installed seem to produce a circle.

With one exception:
Enabling "Use accurate aspect ratios" (ITU compliant scaling!) in the DSCALER MPEG Decoder shows that the circle is no more a circle.
It is more wide than tall.

The same with my DVD-SAP which is connected to my analogue TV: the circle is more wide!

This leads to the conclusion: This VOB has been made using a genericPAR of 1.0666 * 1.3333

It is NOT ITU compliant! So what is the conclusion?

[Kika]

If the object is round in the 752-version

752? I've never seen somethin like that.
Like i wrote: its 768 and 786.

@SeeMoreDigital
I've checked the first file (just a Modem at home) with VLC and my Sat-Receiver.
VLC shows the complete Picture, as expected, the circle isn't a circle.
But i have not my TV here. it's a replacement, my well adjusted TV is broken. So i'm not sure, if the playback is at a correct AR.

Please can you explain the way you created the Picture?

My way (4:3) is the create a square pixel image of 768x576 an include a circle of 500x500. I do a resize to 704x576
The second one is a resize to 704x576 and a letterbox to 720x576.
The third one is a direct resize to 720x576.

The result: The first and the second picture is correct, the third one isn't correct.

[scharfis_brain]

Originally posted by jdobbs
So what is the conclusion?

That SMDs VOB has a wrong PAR,
which isn't widely used on DVDs.

Also the conclusion is:
A 720 px wide source needs to be cropped by 8 px on each side before scaling to 352 px
to be displayed with the same AR as before.

For DVD the SAP & TV sets are the reference according AR.
Not the PC.

[jdobbs]

There's something wrong in what you are saying...
Originally posted by scharfis_brain
Enabling "Use accurate aspect ratios" (ITU compliant scaling!) in the DSCALER MPEG Decoder shows that the circle is no more a circle.
It is more wide than tall.

The same with my DVD-SAP which is connected to my analogue TV: the circle is more wide! That doesn't make sense. If you crop the two sides before you resize --> it would make the picture even wider after the resize. This seems to be backwards.

[scharfis_brain]

That doesn't make sense. If you crop the two sides before you resize --> it would make the picture even wider after the resize. This seems to be backwards.

Please re-think about it.
My statement is correct.

Make your own tests.

create a circle in a 768x576 frame

resize the 768x576 frame to 704x576 (file A)
take file A add 8px each side. You've got 720x576 (file B)
take file A again and scale it to 352x576 (File C)

burn them all on DVD.

The circle IS equal with all these resolutions.
If it is not a real circle, the goemetrics of your TV-Set are screwed.

resizing 768 to 720 without adding borders is wrong.
also it is wrong to resize 720 to 352.

there are two major groups of ITU/MPEG resulutions

the ones with added overscan (borders) left and right
(corresponds with 788px):
360 (1/2),
480 (2/3) SVCD & DVB,
544 (3/4) DVB,
720 (full) DVD & DVB

and the ones without the borders
(corresponds with 768 px):
352 (half) CVD & DVD & DVB,
470 (2/3) non existant. only for comparision,
528 (3/4) DVB,
704 (full) DVD & DVB

[jdobbs]

Exactly. But that has nothing to do with what I'm saying...

If I take a 720 x 576 source and scaled it to 352 x 576, and it should have been cropped to 704 x 576 --- if it were wrong it would be taller than it should have been when displayed back -- not wider.

I understand how aspect ratio works ---> but the sizing filter in AVISYNTH resizes from one size to another... it doesn't give a rat's behind what scaling will be used when it is displayed, it just does what it is told.

-----

[Huh?] It looks like your answer changed while I was typing...

[Kika]

It is exactly like i postet here earlier: There a different kinds of 720-Resolutions: generic PAR and "true" PAR.

On generic PAR, the Source has a wrong AR and is CORRECT after a direct resize to 352x576.
But some DVDs do have a correct PAR with a pixel overscan, in this case, a direct resize to 352 results in taller picture. The source have to be cropped first.

So what IS a correct encoded 4:3 PAL-DVD?
There are 2 different ways.

1. Picture size of 704x576, letterboxed to 720x576
2. Motion Area of 704x576, but a pixel overscan of 16 extra pixels
Both of them are correct, and both of them do need a cropping before resizing.

What is generic PAR? Something terrible...
It's a 4:3 Picture, stretched to 720x576. The ORIGINAL DVD does have a wrong AR/PAR, but after a direct resize to 352x576 or any 4:3 resolution withour cropping, AR/PAR are CORRECT. Sound's crazy, IS crazy, but it's the truth.

[scharfis_brain]

So jdobbs, can we calm down the AR-war?

I would like to request a feature:
an ITU-compliant resizing ON/OFF switch, which takes care about the width of the source in ON-position :)

[jdobbs]

Sure...

[Kika]

Gee, i feel a BIT ignored here ... ;) (or something like that)

[SeeMoreDigital]

Originally posted by scharfis_brain
That SMDs VOB has a wrong PAR,
which isn't widely used on DVDs. Well that's most odd... because when I burned the files onto a shiny disc and spun them in my Pioneer DV-575A stand-alone player and viewed then on my 32" 16:9 CRT TV and on my 42" 16:9 HD plasma TV, via an analogue component connection... the circle was indeed "a perfect circle"!


Cheers

[jdobbs]

Originally posted by Kika
Gee, i feel a BIT ignored here ... ;) (or something like that) I'm listening. Would the overscan area of a true PAR have black bars in the overscan area? I can't remember the last time I saw that on a commercial disc (but it's always there on my DV sources).

There must be a lot of non-true PAR sources... because in all the testing I've done, the cropping/resizing causes a horizontally stretched picture.

[Kika]

You haven't explained your creation methode as requested...

I don't trust any Plasma or TFT TV, who knows who programmed the scaler.

And there is only ONE way to create a test picture: The ITU way.

@jdobbs

Would the overscan area of a true PAR have black bars in the overscan area?

OK, i am ignored here...

Like i explained: tthere are two ways to create a DVD with a correct PAR/AR.

Picture size of 704x576, letterboxed to 720x576
Motion Area of 704x576 with extra Pixels. These extra pixels may be black (letterboxed), they may be part of the picture, this does not matter. Only the PAR matters in this case.
Most DVDs i've seen do have a generic PAR, and that's a 704 picture stretched to 720 - and that's why a direct resize to 352 will work corectly. Simply because in fact you do a real resize from 704 to 352.

[scharfis_brain]

@ SMD:then either the TV has a wrong geometry
or the timing of your DVD-Player is wrong

my DVD Player (a cheap Cyberhome CH-505) does it all correct like ITU requires.

And my TV-Set - a JVC 50 Hz 4:3 TV - displays it correct, too.

It did much tests with 720, 704 & 352.
With ITU conform resizing and cropping the circle is always the same.

But with your kind of resizing (generic PAR) it displays it too wide.

@jdobbs: if you don't see black bars left & right, this is no sign for generic PAR.
the black bars are just filled with ADDITIONAL image information.

Also: pleaso do NOT test 720 vs. on your PC.
It will fail unless you use the dscaler MPEG decoder with the accurate AR enabled.

[scharfis_brain]

@KiKa:Most DVDs i've seen do have a generic PAR, and that's a 704 picture stretched to 720

I can't confirm this!

I never had a genericPAR DVD.
Also the extras (which are usually converted from NTSC) ALWAYS have black bars left & right,
cause they are real video stuff.

And we are talking here for halfD1 for extras, don't we?
So crop away the blackness and then the resize is the correct way.

[Kika]

Sorry, but it's true: most of my DVDs do have generic PAR. Or, to be correct: Most of the DVDs i checked. And my Days as a Reencoder of DVDs are over since years. Maybe the newer DVDs are correct.

Whatever... this has nothing to do with the rules, we are talking about here.

And yes, the converted ones always do have the black borders - as they should have.

[onesoul]

@ Kika

My confusion derived from me thinking that the right resizing should be done from 720 (including black borders) to 768*576. Now I see it is supposed to be done from 704*576 to 768*576.

This guide (http://www.uwasa.fi/~f76998/video/conversion/) is good.

The Video Size Calculator (http://biphome.spray.se/gunnart/video/) uses the conversion parameters described in the above guide.

It is fun to find out that the actual active picture size on pal DVD is 702 and not 704.

[Kika]

This guide is good

Yes, it is. Not perfect, but good. :D

It is fun to find out that the actual active picture size on pal DVD is 702 and not 704

Yeah, and on NTSC it is 711. ;) 711x486(!) to be correct.
720x480/576 is a compromise to make things easier for the DVD and Hardware creators (and to not hurt the MOD16 rule of MPEG).
If you look at the signal timing, you will see, no PAL TV is able to show you 720 pixels - 702 is the limit. If a TV shows you all the Pixels of a 720 video, it is not correctly adjusted. 52 µs are the limit, 720 pixels do need 53.33 µs.

But do some mathematics by using the rules on the guide: You will find out, that a correct PAL DVD without black bars on the left and/or right side will have to be 786x576 if you convert it to square pixels. Sometimes it's fun. :D

[SeeMoreDigital]

Originally posted by scharfis_brain
@ SMD:then either the TV has a wrong geometry
or the timing of your DVD-Player is wrong

my DVD Player (a cheap Cyberhome CH-505) does it all correct like ITU requires.I don't think any of my home widescreen TV's or DVD players are wrong. Plus first thing this morning I visited a couple "box shifter stores" and checked both the 4:3 and 16:9 encodes on a several DVD players pumped to several TV's. Sufficed to say I looked a bit of a plonker checking all the circles with a long stip of paper... but the circles were round!

Have you actually played either of my encodes scharfis_brain?


Cheers

[onesoul]

Originally posted by Kika
But do some mathematics by using the rules on the guide: You will find out, that a correct PAL DVD without black bars on the left and/or right side will have to be 786x576 if you convert it to square pixels. Sometimes it's fun. :D [/B] I used the Video Size Calculator tool which does the math described in the guide and the result from correct 720 pal dvd without bars to square pixels is 788*576. And the result of a 702*576 is 768*576. 704*576 would be 770*576. It is based on mod1.

But I admit the values are adapted to standard, so it is not so relevant the difference.
Who cares for 2 more or less pixels anyway? ;)

[Kika]

quod erat demonstrandum ;)

[jdobbs]

e pluribus unam

Sorry, that pretty much encompasses the extent of my understanding of Latin.

[Kika]

e pluribus unum

Isn't it shown onto the 1 Dollar note? ;)

[jdobbs]

Hey, I had to read some Latin somewhere... what's wrong with money?

How about habeous corpus, nolo contendre, or Caveat emptor?

[buzzqw]

sorry but all you are

sine ulla spe ;)

(from someone that had studied latin for 5 years, but 10 years ago...)

so mutate mutandis that show must go on ;) ;)

BHH

[onesoul]

e pluribus unum The portuguese football team "Benfica S.L.B." has it written in it's insignia. Rockas surely know what I am talking about :)

Hey I got another:

"Requiescat In Pace" which mean R.I.P or Rest In Peace. Now you know where R.I.P comes from.

Hmm, that was morbid, sorry. :scared: ;)

[SeeMoreDigital]

Moving back, a bit nearer to topic again....

I'm quite surprised as to how many vertical image pixels are lost/not seen when viewing via an analogue video connection (not VGA)... Somewhere in the region of 15-17 pixels, top and bottom. 30-34 pixels over-all :eek:


Cheers

[Kika]

Yes, that's true. And that's the reason for the image and the action safe area option in all authoring programs.
But it is not the vertical resolution only which is cropped, the horizontal resolution also.
In the "early days" of SVCD- and DVD-Encoding some people (me too) used resolutions like 448x544 or 672x544 to get a smaller overscan.

[scharfis_brain]

SeeMoreDigital, would you do a test, please?

Measuring the height & width of the circle of following DVD:

http://home.arcor.de/scharfis_brain/samples/ITU-AR.rar download about 1 MB; extracts to 150 MB


Titleset 1: 720x576 generic PAR (wrong, Circle too wide)

Titleset 2: 720x576 ITU PAR (correct, Circle is round)

Titleset 3: 704x576 ITU PAR (correct, Circle is round)

Titleset 4: 352x576 some PAR; directly scaled titleset 2 from 720 to 352 (wrong, Circle too thin)

Titleset 5: 352x576 ITU PAR; Titleset 2 cropped to 704 afterwards scaled to 352.
would be the same like scaling titleset 3 diectly to 352.
(correct, Circle is round)

Only the comparision of 704 ITU to 720 ITU can show us, who is the bad guy in your signal chain.

if 704 (Titleset 3) and 352 (Titleset 5) are NOT round, then the TV is adjusted wrongly.

if 720 (1) and 704 (3) show the same AR, then the DVD-SAP scales 720 in a bad way!

Thanks


EDIT: forgot to say that the DSCALER-decoder with its accurate AR enabled it plays back the VOBs itself in a correct way, but if I use the VIDEO_TS.IFO & MPC it falls back to the old (and wrong) mode meaning, that VTS 1 & VTS 2 are getting displayed wrong

[SeeMoreDigital]

Hi scharfis_brain,

I quickly tested all five of your files using a Pioneer DV-575A DVD player connected via component video to a 42" Hitachi 42DP5000 plasma and...... none of them produced an exact circle!

I will try some more DVD players and TV's over the weekend and report back ;)


Cheers

[onesoul]

Originally posted by scharfis_brain
http://home.arcor.de/scharfis_brain/samples/ITU-AR.rar download about 1 MB; extracts to 150 MB I had to download it to believe it! How in a hell you compressed 150mb to 1mb? :confused:

[scharfis_brain]

@SMD: could you be so kind to report the measuring results?
(metric system preferred :p )

For each kind of Hardware setup and for each VTS?


@onesoul: the MPEGs are I-Frame only.
so all images are bit-identcal.

this also is the case for the audio frames since they are built upon a perfect sine tone.

I even could have squezzed 4 GB easily into 1 MB.

[SeeMoreDigital]

By the way... here's what the good ol' BBC has to say about the subject: -

http://www.bbc.co.uk/commissioning/branding/picturesize.shtml


Cheers