Experts on ITU-R BT.601, please read!

[Chibi Jasmin]

I am currently trying to explain the itu-standard aspect ratio stuff in the Inmatrix Forums (it is about ZoomPlayer). As I am no real expert on this, I could need someone who can explain correctly and understandable what this is about. If you think you're qualified, please go here:

http://forum.inmatrix.com/ikonboard/ikonboard.cgi?s=3cee3ad62f8cffff;act=ST;f=7;t=422

Thanx in advance for any help!

[Ookami]

No expert, but i have a few links:

http://www.itu.int/rec/recommendation.asp?type=folders&lang=e&parent=R-REC-BT.601
http://www.mtxindia.com/An1.htm
http://www.uwasa.fi/~f76998/video/conversion/

All directly or indirectly from:

http://ookami.iwebland.com/programmers.html

As I'm not registered at the Zoom player board, you could post this links there...

Cheers,

Mijo.

[TheWEF]

hi jasmin!

there is nothing i can add to your explanation.
if blight doesn't want to add it, well...
as i'm in the same situation quite often i definitely respect that. :p

wef

[Chibi Jasmin]

Originally posted by TheWEF
hi jasmin!

there is nothing i can add to your explanation.
if blight doesn't want to add it, well...
as i'm in the same situation quite often i definitely respect that. :p

wef

Thanx...

Well, he said, he 'believes' it is already done for VCD/SVCD. And will never be for DVD. Shouldn't he KNOW, if it's done for VCD/SVCD, if he understood, what it's about?

And why for SVCD and not for DVD, which both use MPEG-2 streams...!?

I can't help the feeling he didn't understand what it's about except 'some AR thing' and said, well, ZP can already do every AR possible...

[Chibi Jasmin]

Originally posted by Ookami
No expert, but i have a few links:

http://www.itu.int/rec/recommendation.asp?type=folders&lang=e&parent=R-REC-BT.601
http://www.mtxindia.com/An1.htm
http://www.uwasa.fi/~f76998/video/conversion/

All directly or indirectly from:

http://ookami.iwebland.com/programmers.html

As I'm not registered at the Zoom player board, you could post this links there...

Cheers,

Mijo.

Thanx :)

[Chibi Jasmin]

If anyone is interested in this, there is good stuff (great explanations by TheWEF) in the ZoomPlayer forum (thread in first post).

[TheWEF]

i finally got to read some of the excellent documents that ookami linked above.
well, Jukka Aho, the guy who maintains A Quick Guide to Digital Video Resolution and Aspect Ratio Conversions (http://www.uwasa.fi/~f76998/video/conversion/), prooves everything wrong that we thought was right.
so it turns out that the itu option implemented in gknot is slightly wrong as well...
true pelAR for
PAL DVD 128/117 (1.0940) instead of 59/54 (1.0925)
NTSC DVD 72/79 (0.9114) instead of 10/11 (0.9091).

recommended reading for AR freaks! :p
you even find the explanation where the wrong numbers come from.

wef.

[Selur]

Huha,.. found some time to read the article it really IS a excellent document, thx for posting the link,..

Cu Selur

[Chibi Jasmin]

I also just stumbled across it...the result is I had to correct my resizing table:

Quote from http://www.lurkertech.com/lg/pixelaspect.html:

"If you have a 525-line analog NTSC (ANSI/SMPTE 170M-1994) video signal which you want to sample square pixel, the industry standard is to sample at exactly 12 + 27/99 million pixels per second.
If you have a 625-line analog PAL (Rec. ITU-R BT.470-3) video signal which you want to sample square pixel, the industry standard is to sample at exactly 14.75 million pixels per second.
Therefore, we can derive from this that:
525-line Rec.601 pixel aspect ratio = 13.5 / (12 + 27/99) = exactly 11/10 (y/x) 625-line Rec.601 pixel aspect ratio = 13.5 / (14.75) = exactly 54/59 (y/x)"

This is not exactly true.

Above mentioned square pixel industry standard actually gives 768/767 pixels for PAL and 396/395 pixels for ntsc. Correct sampling rates for true computer square pixels are 14 + 10/13 (instead of 14.75) and 12 + 24/79 (instead of 12 + 27/99) for NTSC. These give real square pixels.

See: http://www.uwasa.fi/~f76998/video/conversion/ for reference!

Therefore the correct pixel aspect ratios are actually not 11/10 (NTSC) and 54/59 (PAL), but 79/72 (NTSC) and 117/128 (PAL):

525-line Rec.601 pixel aspect ratio = 13.5 / (12 + 24/79) = exactly 79/72 (y/x) 625-line Rec.601 pixel aspect ratio = 13.5 / (14 + 10/13) = exactly 117/128 (y/x)"

So I corrected my resizing table to use 79/72 and 117/128 instead of 11/10 and 54/59 (see above)


Resizing of MPEG-sources compliant to ITU-R BT.601 standard

PAR=pixel aspect ratio – DAR=display aspect ratio

According to ITU-R BT.601:

PAL PAR 117/128 (y/x), x/y=1.094 [128/117] PAR
NTSC PAR 79/72 (y/x), x/y=0.911 [ 72/ 79] PAR

All correct resizing is based on 79/72 and 117/128.

anamorphic -> reduce height 3/4

DVD (D1=720)

PAL-anamorphic: 1.459:1 [512/351] PAR 1.823:1 [ 640/ 351] DAR (720x1.094 PAR=788, /432 (3/4 height) -> 1.823 DAR, 576x1.823=1050, /720=1.459 PAR)
PAL-nonanam.: 1.094:1 [128/117] PAR 1.368:1 [ 160/ 117] DAR (720x1.094 PAR=788, /576 -> 1.368 DAR)
NTSC-anam.: 1.215:1 [ 96/ 79] PAR 1.823:1 [ 144/ 79] DAR (720x0.911 PAR=656, /360 (3/4 height) -> 1.823 DAR, 480x1.823= 875, /720=1.215 PAR)
NTSC-nonanam.: 0.911:1 [ 72/ 79] PAR 1.367:1 [ 108/ 79] DAR (720x0.911 PAR=656, /480 -> 1.367 DAR)

SVCD (2/3 D1=480)

PAL-anamorphic: 2.188:1 [256/117] PAR 1.823:1 [ 640/ 351] DAR (1050x576 (2/3 D1=D1), 1050/480 (width)=2.188 PAR)
PAL-nonanam.: 1.641:1 [ 64/ 39] PAR 1.368:1 [ 160/ 117] DAR ( 788x576 (2/3 D1=D1), 788/480 (width)=1.641 PAR)
NTSC-anam.: 1.823:1 [144/ 79] PAR 1.823:1 [ 144/ 79] DAR ( 875x480 (2/3 D1=D1), 875/480 (width)=1.823 PAR)
NTSC-nonanam.: 1.367:1 [108/ 79] PAR 1.367:1 [ 108/ 79] DAR ( 656x480 (2/3 D1=D1), 656/480 (width)=1.367 PAR)

VCD

PAL: 1.094:1 [128/117] PAR 1.337:1 [1408/1053] DAR (352x1.094 PAR=385, /288=1.337:1 DAR)
NTSC: 0.911:1 [ 72/ 79] PAR 1.337:1 [ 528/ 395] DAR (352x0.911 PAR=321, /240=1.337:1 DAR)

@TheWEF: I think, you're going to correct it in upcoming Gordian Knot versions?