PAL: 720x576 OR 720x540? HELP!

Grazie wrote on 4/24/2007, 11:18 PM
I have always produced SD 720x576 and thru to DVDA and used the 720x576 MPEG2 Vegas MC Video stream for DVDA template. Now I have a client who has been advised to produce 720x540. What could this be about?

I play my 720x576 fine on Home DVD player. What would happen IF I should go 720x540? What can I impress on the client as being important?

TIA - g

Comments

ritsmer wrote on 4/24/2007, 11:32 PM
Yes,. it is a strange world with many standards.

Maybe this can help to clarify:
http://www.strata.com/support/3dmanual/ch13/ch13_7.html

Grazie wrote on 4/24/2007, 11:40 PM
Thank you for the link. However, there is no mention of this PAL 720x540 So, I am none the wiser.

What I have done just to rpove what I thought it would be like is to do a quick 20 sec 720x540. I ended up with motion jaggies on movement - no surprised there - and generally it was ever so slightly "flattened".

So, none the wiser . . g
farss wrote on 4/24/2007, 11:41 PM
Just found the same page!

PAL is 625 lines of which 576 contain picture, so 720x576 is the usual PAL stardard. However it looks like the 720x540 is a 1.0 PAR standard from way back.

What are you supplying the client and what are they doing with it?
If it's a DVD it'll matter zip to them if you do it 720x576, that's more resolution if nothing else.
Conversely if it's an AVI file and their systems need 720x540 best to not argue and give them what they've speced.

Bob.
RBartlett wrote on 4/24/2007, 11:48 PM
Like Bob said.

So your video, with rectangular pixels would be 720x576 interlaced.
However any assets you have for your DVDA-destined menu or a Vegas-destined still could be brought in as 720x540 if they are from an app that doesn't understand how to make the AR representative for a file format you'll import.

I believe 787x576 is it's educated equivalent. Search on this forum for 787 and 786 (and indeed 768x576) for more on the topic. However, if you insist that all your materials are AR true, then they ought to be fairly happy.

I suppose they might have some alternative app to play the DVD-Video in. However you'll be stretching at some point as DVDA or their set top player won't leave 720x540 content/footage alone.

I think this is where they are coming from with their request. They are trying to avoid unnecessary shrinkage from computer formats (that flag 1.0 AR in the file format even if it isn't).
Grazie wrote on 4/24/2007, 11:59 PM
Bob & RB thanks.

I've been asked to make a DVD of our completed project project and produce this for being able to play on any "domestic dvd player"? Then why all this other stuff? I make DVDs at 720x576. I play them on domestic DVD players.

Do I do the square pixel thing in Vegas prior to DVDA?

RB? I'm interested in your " . or their set top player won't leave 720x540 content/footage alone. " - Please be specific as to what WOULD happen?

Thanks guys - g
farss wrote on 4/25/2007, 12:14 AM
Then why all this other stuff?

Cause they think they know what they're talking about.

The 'standard' for PAL is 540 tvl resolution, I guess back decades ago someone figured it made no sense having more res in the digital realm than the anaolgue, maybe. Today given the amount of interpolation involved it'd obviously be simpler to have a 1:1 mapping however with interlaced video anymore than 540 lines of res and you can hit problems of line twitter, not usually a problem as the camera will not record more anyway but graphics / stills can be a problem as you probably know.

Just for the record, 787x576 is the normal way to do PAL in 1.0 PAR, as you've seen interpolating lines with interlaced video needs care or nasties creep in.

What will happen if you do this 720x540 thing, the player will have to expand it anyway, it'll end up on the screen the same. Your challenge will be going from DV's 720x576 to 720x540 without doing any harm. Personally I'd just ignore the clients specs and give them what you've always done, I seriously doubt they'll ever know or check, all they really care about is if the DVDs play.

Bob.
Grazie wrote on 4/25/2007, 12:28 AM
Thanks Bob. I understand your explanation.

I have "tracked-down" the person responsible for the tech info. I shall attempt to make contact today and will have a truly enlightening conversation.

I shall also attempt to convince, said person, of the need for the formatting to be in 720x756!
Mahesh wrote on 4/25/2007, 3:44 AM
>I shall also attempt to convince, said person, of the need for the formatting to be in 720x756!<
You do mean 720 x 576.

In the old days when I was in broadcasting (PAL), the picture size was
768 x 576. Advent of DV brought about the reduction to 720x576 because of the unused data due to blanking.

The 4:3 picture was quoted as (768 x 3) / 4= 576.

What has happened is the guy has applied the 4:3 rule incorrectly.

( 720 x 3 ) / 4 = 540 is not correct aspect ratio.

Jay Gladwell wrote on 4/25/2007, 4:06 AM

Remember, "seek first to understand, then to be understood."

When I'm confronted with like requests, I always ask "Why?" That way, if I have the answer I can discuss alternatives then and there. If I don't have the answer, I can go do my research, then go back to the client with an explanation of why we shouldn't do it that way.

When the client insists on doing it their way, and I know it will cause problems, I get them to put it in writing that I will not be held responsible for any potential problems it may cause down the road.


Grazie wrote on 4/25/2007, 7:36 AM
Mahesh - yes . . typo! But you kinda knew that?

Jay - of course.

In any event, I have NOW resolved my part of the story and I have had my enquiry for 720x576 accepted. At some point in the future I shall post my and our collective thoughts on the subject to the person. I was informed that this "740" was a guideline - well, it kinda guided me OFF the tracks for a few hours there - yeah?

Again, thanks Guys! What a bunch you are! Team-Vegas

And as I said, 720x576 DOES work on set top DVD boxes.

Grazie wrote on 4/25/2007, 9:20 AM


ANOTHER typo by me! I was informed that this - of course that WAS meant to be 540!!
ritsmer wrote on 4/25/2007, 2:09 PM
None the wiser... :-)
According to the link I quoted there is no such thing as PAL 720x540 - and your customer might be persuaded to understand that PAL IS 720x576.
RBartlett wrote on 4/25/2007, 3:16 PM
>>RB? I'm interested in your " . or their set top player won't leave 720x540 content/footage alone. " - Please be specific as to what WOULD happen?

If you are lucky, the playback device will figure this is some odd kind of DVD-Video with SuperVideoCD type attributes. So it'd scale the 540 or crop it. I'd expect it to convey each pixel into oblong format too. Completely detracting from the original intention of the client to give you some useful guidance.

Analogue PAL is 625-lines, 575 of these are regarded as being visible (deducted by the overscan and perceptive measurement due to the subject usually being distant from the TV/display). The horizontal measurement for broadcast standard def isn't stepped so 704, 720, 768, 787 and other figures are derived from this. DVD-Video has more than one profile but most videographers aim for the highest figure that is in the book and that is 720. 768 was a popular digitiser horizontal sample frequency purely because in it's implementation it allowed for a crude maths decision on how to keep the screen aspect ratio and number of lines at the right level for square pixels. Since EGA and VGA screens, squareness has been assumed. That depends on how you have your CRT setup of course, but folks work to ideals and standards whatever the true goings on really are.

Computer generated imagery and square-pixel oriented/restricted paint apps are usually where these 787x576 and 720x540 figures crop up. Not often for moving imagery as most moving picture oriented programs soon realise that video pixels are not square in the digital world. In the analogue TV world the closest thing to a pixel is a long multicoloured stripe or VBI-data. Analogue TV is continuous in nature.

Perhaps the person just made a simple mistake. Grazie - Charge them twice and run out an invoice for the cloths and your new keyboard you've just spluttered coffee onto <@ :-)
Grazie wrote on 4/25/2007, 3:26 PM
RB! LOL . .. hysterical!
Stuart Robinson wrote on 4/25/2007, 8:05 PM
If your client wants DVDs, then I'd ask him whether he wants them to be compatible with most players. 720×540 isn't a valid picture size in either NTSC or PAL.

FYI:

NTSC MPEG-2 (525/60): 720x480, 704x480, 352x480, 352x240
PAL MPEG-2 (625/50): 720x576, 704x576, 352x576, 352x288

Anything else is out of spec. and who knows how it'll play back (if at all).
Grazie wrote on 4/25/2007, 11:42 PM
Thank you Stuart. At some point I will make this info readily available to those that need to hear it. Thanks again for laying it out so succinctly.

G