A Few Resolution Questions

[petar]

So, the reason people do [720 x 480] Mpeg2 is for compatability only; it has nothing to do with the difference between monitor & tv pixels' horizontal sizes...correct?

Actually it has to do with both. 720x480 with the pixel sizes DVD uses is 4:3 (though as it seems DVD cheats and uses the same pixels for 720 and 704 and it's actually 702x576 for PAL and 711x486 for NTSC that is really 4:3; in practise you may not notice the difference)
So you need to resize for DVD for compatibility and pixel sizes.

And the Dvd player is the device that changes the format of those horizontal pixels to match the tv's horizontal pixel sizes (all that .9116 garbage)...right?

No, they are fixed at ".9116 garbage". If the DVD player were capable of changing the pixel sizes or capable of resizing (like the software mpeg players) you could use any resolution you want. The reason why there are only few resolutions you can use is because DVD players can only have two type of pixel sizes - one for 352 and another for 704/720 (I actually thought it used one for 704 and another for 720 but I was wrong).

And so, you're just supposed to take the resolution of the source and look for the closest DVD, SVCD, or VCD compatable resolution if compatability is an issue (as it is most of the time); otherwise, keep it at the resolution of the source or go down to maximize quality...correct?

Sort of. You should aim at the closest resolution for quality concerns. As I mentioned before if the source has the correct aspect ratio, you don't need to worry about anything. If it doesn't, you need to sort out the aspect ratio of the source before resizing and encoding to mpeg. Say you have a bitmap image of 680x480. That's not 4:3 (680/480=1.42). You need to crop/pad to get to 4:3 (say crop 40 lines horizontally to get to 640:480). Once you're there, look for the closest DVD resolution (there are only two really) which is 704x480, resize to that and encode at 4:3. That's it. If DVD resolution is not important, you can encode the 640x480 to mpeg 4:3 without resizing. This will play OK on a player with square pixels and/or one that can resize on playback (like a PC).

And this is the reason why when I was encoding the [640 x 480] to [720 x 480] and selecting Full Screen (Keep Aspect Ratio), it was adding padding to the left and right because the AR's were not the same, though I thought they were...right?

Yes. If you select 704 instead of 720, it shouldn't pad it

If you capture something at [1024 x 768] and then encode down to [720 x 480] and select Full Screen (Keep Aspect Ratio), will the DVD Player show it full screen on the TV? If you select Full Screen only aren't you altering the AR from 1.333...(1024/768) to 1.5 (720/480)?

DVD players will always show the picture full screen. The resolution ratio (720/480=1.5) is not equal to the display aspect ratio (4/3=1.33) because the pixels are not square. But as I mentioned before, don't worry about it. Just think that mpeg/DVD resolution (no matter the frame size) is 4:3 or 16:9 aspect ratio when displayed. Don't look at it as if it was a bitmap image.

[aamir12345678]

Ok, got it. Thanks.

[sacajaweeda]

I've learned a lot since joining this site just by reading these guys' posts. Good stuff, always. Pillars of knowledge they are, they are.

[aamir12345678]

This is what I was confused about petar. I was thinking that the encoder wasn't encoding to a true [720 x 480] pixel resolution. I was thinking that it was accounting for all Mpeg aspect ratio, tv pixel size difference, etc.

Seems the encoder encodes to a true [704 x 480], or [352 x 480], or [480 x 480], or any other resolution but leaves the 4:3 or 16:9 tag for the dvd player to determine what width it's going to display the picture at using the height and the 4:3 or 16:9 tag.

[petar]

Seems the encoder encodes to a true [704 x 480], or [352 x 480], or [480 x 480], or any other resolution but leaves the 4:3 or 16:9 tag for the dvd player to determine what width it's going to display the picture at using the height and the 4:3 or 16:9 tag.

That's right. MPEG can be any resolution you want (well, sort of; there are limitations) and then the aspect ratio flag can be used to resize on playback. However normal DVD players cannot resize and are limited to few resolutions hence you must serve them with the correct ones.
It's important to remember that the encoders are normally generic MPEG encoders, not DVD specific, so they will follow the MPEG standard in full. It's up to the user to make sure that he limits the encoder to the DVD standard.

[monzie]

Trevlac.....every post i have read of yours is total bollox...you get yourself into a corner, by being 'clever' yet giving no answers, always quoting the same links, then try and wriggle out by one means or another.......tell the man what he wants know or shut the **** up...OK?

[lordsmurf]

A lot of these recent resolution conspiracy theories are pure crap. You know, most of the MPEG decoder chips inside can handle what the firmware of the unit allows! The MPEG format is finite, true, but not as much as some want you to think. As soon as you consider the 544x480, 480x480, and other resolutions many players can accomodate (including screwball stuff like 320x240 and 512x384, sizes not part of the CD or DVD based specs), these "720=704 because they can't change pixels" stuff is out the window. Doesn't add up in the end. The aspect ratio is maintained within the confines of the AR flags and the limitations of the chips (which is not so constrained that it botches up true DVD resolutions).

[trevlac]

Trevlac.....every post i have read of yours is total bollox...you get yourself into a corner, by being 'clever' yet giving no answers, always quoting the same links, then try and wriggle out by one means or another.......tell the man what he wants know or shut the **** up...OK?

I'm sorry monzie. I was a little peeved when i was reading your reasonable response in that other thread then it some how got into my grandmother or something like that.

If you pm or email me, I'd be happy to have a civil discussion of our different methods. I really did not follow you. Perhaps we were getting at the same thing.

I will keep quiet.

[aamir12345678]

Thanks again petar and lordsmurf. After reading that Determining Aspect Ratios article & reading your responses, I seem to have finally got it.

Oh, and monzie, calm down, man. I wasn't devastatingly confused by anything trevlac said. I could tell he didn't know everything about it so I just kept on replying until I got someone that did know or could explain it to me.

Seems that VCD, SVCD, & DVD resolutions can get confusing at times.

[Wilbert]

Oh, and monzie, calm down, man. I wasn't devastatingly confused by anything trevlac said. I could tell he didn't know everything about it

Trevlac knows very well what he's talking about. IF you think otherwise, why don't say which post you don't agree with and we can discuss about that.

About this resolution vs size stuff. There are several meanings of resolution. One of them is framesize, which is the way many people use it (Trev knows this, so I don't understand why he doesn't mention it.) There is also another meaning which Trev gave in one of his first posts in this thread. To have/use that definition is also important for us (where us means analogue capping folks). That's why Trev, I and other folks prefer to call the first meaning just "framesize". It's, just semantics

[sacajaweeda]

I generally use "frame size" instead of "resolution" as the latter is less direct and concise in it's meaning. There's no mistaking or misinterpreting the meaning of "frame size". I tend to regard "resolution" and it's affects more along the lines of the effect raising and lowering the bit rate has on a given sized frame. Or like the dots per inch capabilities of your printer.

[sacajaweeda]

Trevlac.....every post i have read of yours is total bollox...you get yourself into a corner, by being 'clever' yet giving no answers, always quoting the same links, then try and wriggle out by one means or another.......tell the man what he wants know or shut the **** up...OK?

STFU noob.

PS, you had your ass handed to you in a paper sack in this thread...

https://www.videohelp.com/forum/viewtopic.php?t=234102

You've got unfinished business there in that thread, fool. Perhaps you are just waiting for the stinging to stop, I don't know, but you don't need to go walking away from it and starting your bullshit in another thread, you clearly clueless fuckwit, you.

Go flap that **** hole on the front of your head somewhere else.

/rant

[jimmalenko]

<gets a bag of popcorn and a comfy chair>

righto boys, I'm ready !

[chobo321321]

I think resolutions and frame sizes should be explained in the FAQ. The same questions keep coming up over, and over about resolutions, frame size, aspect ratio. I wish there would be an end it all answer to all of the above. Each time someone posts about one of those topics you get a whole lot of theories, and different way/techniques, it's confusing... Even the guides all differ from each other when it comes to this subject. It's hard to figure out who's right, and who's not so right

Sorry for the rant, but this has to be one of the most frustrating aspects (I've had to deal with) for video encoding, and no one has a straight answer.

[trevlac]

Frame Size - A measure of the video frame, usually in pixels. IE 720x80.

Resolution

A measure of the finest detail that can be seen, or resolved, in a reproduced image. Whilst it is influenced by the number of pixels in the display (e.g. high definition 1920 x 1080, broadcast SDTV 720 x 576 or 720 x 487) note that the pixel numbers do not define the resolution but merely the resolution of that part of the equipment chain. The quality of lenses, display tubes, film processes, edit systems and film scanners, etc. in fact any element in the programme stream (from scene to screen), must be taken into account in assessing overall system resolution.

Frame size limits resolution ... but it is not resolution. Commenly resolution is used to mean frame size. Top DVD frame widths like 720 or 704 never are the limiting factor. The video source had something up the chain lower it's resolution.

Aspect Ratio

1. - of pictures. The ratio of length to height of pictures. Nearly all TV screens are currently 4:3, i.e. four units across to three units in height but there is a growing move towards widescreen 16:9. Pictures presented this way are believed to absorb more of our attention and have obvious advantages in certain productions, such as sport. In the change towards 16:9 some in-between ratios have been used, such as 14:9.

2. - of pixels. The aspect ratio of the area of a picture described by one pixel. The ITU-R BT.601 digital coding standard defines luminance pixels which are not square. In the 525/60 format there are 486 active lines each with 720 samples of which 711 may be viewable due to blanking. Therefore the pixel aspect ratio on a 4:3 screen is:
486/711 x 4/3 = 0.911
(ie the pixels are 10 percent taller than they are wide)

For the 625/50 format there are 576 active lines each with 720 samples of which 702 are viewable so the pixel aspect ratio is:
576/702 x 4/3 = 1.094
(ie the pixels are 9% wider than they are tall)

So ... Pixel aspect ratios are actually a wierd made up thing because you can not use pixels to directly measure a Picture(or image or display). If you have a standard NTSC or PAL pixel, you can get there. If you don't, you need more info.

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Summary

-- Frames measured in pixels don't tell you your Picture AR unless you know what kind of pixel you have. Even then, you don't get to do simple 4 divided by 3 = 1.3333 math because you may have more or less pixels in your frame.

-- Frames measured in pixels don't tell you your resolution because resolution is an underlying aspect of the video picture. Just like it's color.

My quotes came from:

http://www.quantel.com/domisphere/infopool.nsf/HTML/DFBIndexOfTermsA

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Hope it helps someone. Took me a while to get it.

[Capmaster]

Moved to DVD Authoring forum

[aamir12345678]

--Wilbert, I think it was the wording that confused me more with trevlac's post. Thank you also, trevlac.

--Concerning the ability to show [711 x 486], is this the tv's capability or the DVD player's. What exactly happens when I feed a standard [720 x 480] Mpeg2 into the DVD Player. If the player has a 4:3 AR tag, then it's going to play that [720 x 480] back as [640 x 480], right? Exactly where does this [711 x 486] stuff fit in?