A Few Resolution Questions

[aamir12345678]

Is encoding a [640 x 480] Mpeg2 (1:1 VGA) to a [720 x 480] Mpeg2 (4:3 NTSC) going up, or is it the same?

If I have a [640 x 480] Mpeg4 PAL (1:1 VGA), and I convert it to [720 x 576] Mpeg2 PAL (4:3), is that encoding up?

[yoda313]

Hello,
Yes you are upcoding it. It won't improve the quality of the video. It just makes it dvd compliant.

Kevin

[aamir12345678]

But what about the pixel difference between tv's & computers?

Isn't that 720 equal to 640? what am I missing here?

[yoda313]

Hello,
I think your mixing them up. As far as I know 640x480 is the resolution used on old graphics card for full screen color on a computer. 720x480 is STRICTLY dvd resolution. If you notice the next highest setting over 640x480 on a computer is 800x600 (which is more than 720x480).

Kevin

P.S. I may be slightly understating this but I do believe they are different (otherwise they would have the same value)

[petar]

1:1 VGA means that the aspect ratio is in proportion of the resolution. So 640x480 has 4:3 aspect ratio. Just encode it to mpeg with 4:3 aspect ratio and that's it.

However, whether you should use 720 or 704 as horizontal resolution, if you want a full D1, not sure yet. There's an open debate in the "editing" forum. Check it out. Seems like DVD treats 720 as just a padded 704. If that's true, you should use 704 (x480 or x576, NTSC/PAL).

704 or 720, there's only 2% difference anyway, so it doesn't really matter if you choose the other.

[aamir12345678]

so, petar, you're saying that going from [640 x 480] VGA to [720 (or 704) x 480] NTSC is not encoding up?

[sacajaweeda]

You can add black lines to the sides on 704 to pad it to 720 to make it a full D1 frame and you probably won't even see any of the black on most TV sets.....overscan & all that.

[petar]

so, petar, you're saying that going from [640 x 480] VGA to [720 (or 704) x 480] NTSC is not encoding up?

Not sure what you mean by encoding up. If you mean resize (or upsize), yes. But there's nothing you can do about it. You can't put 640x480 (1:1) on a DVD.

[yoda313]

Hello,

You can't put 640x480 (1:1) on a DVD.

Huh? You can put anything on a dvd!

Just kidding, you can put it on but no player would be able to read it!

Kevin

[trevlac]

Is encoding a [640 x 480] Mpeg2 (1:1 VGA) to a [720 x 480] Mpeg2 (4:3 NTSC) going up, or is it the same?

If I have a [640 x 480] Mpeg4 PAL (1:1 VGA), and I convert it to [720 x 576] Mpeg2 PAL (4:3), is that encoding up?

Resolution is a measure of how much detail is in a picture. Frame size is well ... the frame size.

Going from 640x480 to 720x480 is indeed changing the frame size. However, it is not improving the resolution.

Think of it this way. Does a big blurry picture have more detail than a small sharp one? So frame size and resolution are not the same.

PS: Changing the frame size and maintaining the proper aspect ratio is a whole different story ...

BTW: Depending on how you do it, changing the frame size (even up) may actually lower the resolution. Try to go up and then down again. If you don't see a difference, no problem.

[aamir12345678]

So, if I have a [640 x 480] Mpeg4 (1:1 VGA), if my player can handle any resolution, should I keep it at [640 x 480] Mpeg2 (4:3 NTSC), or should I encode it to [720 x 480] Mpeg2 (4:3 NTSC)?

[johns0]

So, if I have a [640 x 480] Mpeg4 (1:1 VGA), if my player can handle any resolution, should I keep it at [640 x 480] Mpeg2 (4:3 NTSC), or should I encode it to [720 x 480] Mpeg2 (4:3 NTSC)?

Encode it to [720 x 480] Mpeg2 4:3 NTSC,the picture will resize properly and you wont notice any real loss if the source file is high quality.

[petar]

So, if I have a [640 x 480] Mpeg4 (1:1 VGA), if my player can handle any resolution, should I keep it at [640 x 480] Mpeg2 (4:3 NTSC), or should I encode it to [720 x 480] Mpeg2 (4:3 NTSC)?

MPEG2 can handle 640x480 4:3, no problem, but it won't be DVD compliant (i.e. you won't be able to make a DVD-Video but you can play it as an mpeg video). If you're sure your player can handle this, then you don't need to resize.

[aamir12345678]

Forget DVD compliance just for a second. From my understanding, a computer's pixels are 1 x 1, but a television's pixels are 8 x 9. Therefore, a [640 x 480] (1:1 VGA) picture is equal to (i.e. no real resizing necessary, just format change) a [720 x 480] (4:3 NTSC) picture...Does the encoder have to create extra data to encode a [640 x 480] Mpeg4 (1:1 VGA) to a [720 x 480] Mpeg2 (4:3 NTSC), or is it more of a format change? In other words, when I select "4:3 Display" under TMPGEnc's Aspect Ratio setting, does the encoder know that the [640 x 480] (1:1 VGA) is equal to the [720 x 480] (4:3 NTSC), or am I completely wrong here?

trevlac, what you were saying about the resolution and frame size, is not the frame size the same since the computer resolution is equal to the tv resolution? You said the frame size is changing, but not the real resolution... Is it not the frame resolution that is changing and not the real frame size. What am I missing?

Also, this should also answer my question in another post about Video Arrange Method. When I choose Center (Keep Aspect Ratio) and encode the [640 x 480] Mpeg4 (1:1 VGA) to [720 x 480] Mpeg2 (4:3 NTSC), it cuts off a little from the left & right. Aren't the resolutions equal? Shouldn't it maintain the AR? Aren't the AR's the same?...?...?...?...?...?

[johns0]

When played play the video wont be stretched so the sides will stay the same,it will show proper ar when encoded to 720x480 full screen so chose full screen in video arrange method.

[aamir12345678]

I did, but I picked Full Screen (Keep Aspect Ratio), and it cut off some of the sides.

[johns0]

Dont choose keep aspect ratio,full screen only.

[trevlac]

does the encoder know that the [640 x 480] (1:1 VGA) is equal to the [720 x 480] (4:3 NTSC), or am I completely wrong here?

trevlac, what you were saying about the resolution and frame size, is not the frame size the same since the computer resolution is equal to the tv resolution? You said the frame size is changing, but not the real resolution... Is it not the frame resolution that is changing and not the real frame size. What am I missing?

I don't use TMPGEnc, so my comments may be more confusing than useful. Sorry about that.

I don't know what the encoder does. But I can tell you the short story of AR for NTSC. NTSC 4:3 is 711x486. AKA pixel width is .9116 of height. Getting 640x480 to NTSC 4:3 with a 720x480 frame requires a resize and then a pad/crop. TMPGEnc may do all of this. If you are doing it yourself, and you don't care about DVD compliance, 640/.9116 = 702. Since mpeg should be divisible by 16 add 2.


As far as resolution goes ... forget it. I thought you were asking if you were increasing the resolution by resizing. The answer to that is no because resolution is a measure of detail in the pic. You will not get more detail by resizing.

[FOO]

I might point out that encoding and resizing are completely separate
operations. You may think they are related because some of the
applications do both (TMPGenc).
You don't Encode to another resolution.
and yes, making 720 dots where there were 640 before , definitely
requires inventing data

is there a new word ? Upcoding ? WTF ?

[jimmalenko]

I thought resolution = frame size ???

i.e. if my video is 352 X 288, isn't this the resolution of it ???

[aamir12345678]

FOO, this is the part that I don't get. Why does it have to reinvent data? Of course there were 640 dots there before, but those 720 (or 704, whatever) dots are each about that much smaller (.9116). If you choose 4:3 Display, does it take the 640 dots and make them that much smaller (.9116) and then resize it to 720 (or 704, or whatever)?

[petar]

Forget DVD compliance just for a second. From my understanding, a computer's pixels are 1 x 1, but a television's pixels are 8 x 9. Therefore, a [640 x 480] (1:1 VGA) picture is equal to (i.e. no real resizing necessary, just format change) a [720 x 480] (4:3 NTSC) picture...Does the encoder have to create extra data to encode a [640 x 480] Mpeg4 (1:1 VGA) to a [720 x 480] Mpeg2 (4:3 NTSC), or is it more of a format change? In other words, when I select "4:3 Display" under TMPGEnc's Aspect Ratio setting, does the encoder know that the [640 x 480] (1:1 VGA) is equal to the [720 x 480] (4:3 NTSC), or am I completely wrong here?

trevlac, what you were saying about the resolution and frame size, is not the frame size the same since the computer resolution is equal to the tv resolution? You said the frame size is changing, but not the real resolution... Is it not the frame resolution that is changing and not the real frame size. What am I missing?

Also, this should also answer my question in another post about Video Arrange Method. When I choose Center (Keep Aspect Ratio) and encode the [640 x 480] Mpeg4 (1:1 VGA) to [720 x 480] Mpeg2 (4:3 NTSC), it cuts off a little from the left & right. Aren't the resolutions equal? Shouldn't it maintain the AR? Aren't the AR's the same?...?...?...?...?...?

If you want to forget DVD compliance then 640x480 (1:1) can convert to MPEG (pick your resolution) 4:3 just by setting the aspect ratio to 4:3. An mpeg player will resize the horizontal resolution to match the 4:3 aspect ratio. However, that's as far as your PC is concerned which can resize all you want (same applies if you watch the video on your TV via the TV output on your PC). However your standalone will unlikely have this capability and will probably have few set resolutions (a standard DVD player can do 352 and 704/720 as far as horizontal resolution is concerned and that's it; and will have pixel sizes to match 4:3 and 16:9 for those resolutions only).

I think people worry too much over pixel aspect ratios and this is not helped by the sometimes over-technical explanations. The thing is, someone has already worried about this when designing your player . So if your player supports resolution X:Y in 4:3 that's because the pixel sizes are such to match this. So if you have a video that's in 4:3 all you need to do is resize is to X:Y, encode to mpeg flagging it as 4:3 and will play just fine by your player.

The only thing to worry about is what your player supports. However what exactly standalone DVD players support, I'm not exactly clear yet. That's why I mentioned before to check the other topic in the "editing" forum.

As for TMPGEnc, the video arrange methods can be a bit confusing to understand but they are quite useful (once someone explains you what they do ):
Full screen - is just that, will stretch/shrink both horizontally and vertically to fill the screen
Full screen (keep aspect ratio) - will also stretch/shrink both horizontally and vertically but in proportion. If the whole screen cannot be filled, it will pad with black
Full screen (keep aspect ratio 2) - will only stretch horizontally or vertically until the aspect ratio is correct. Then will pad with black to fill the screen (may pad both horizontally and vertically if you're cropping)
No margin - same as Full screen (keep aspect ratio) but will chop rather than pad to fill the screen
Center - will cut the center of the video in size of the target resolution (if the target is larger than the source, will pad will black)
Center (keep aspect ratio) - same but will stretch/crop to keep the aspect ratio
Center (custom size) - will let you choose the resolution. Then will pad to get to the target resolution

[jimmalenko]

Good stuff petar.

Some very useful info there.

[aamir12345678]

So... petar, if I have a [640 x 480] Mpeg4 (1:1 VGA), and my player can play it, I should just keep it [640 x 480] Mpeg2 (4:3 NTSC)?

[petar]

Yes

1:1 as pixel size for a resolution of 640x480 equals 4:3 aspect ratio

(640*1) / (480*1) = 1.3333 = 4:3

For a player to be able to display this, it will either (1) need to have square pixels support or (2) capable of resizing on playback, if it uses other than square pixels.

[aamir12345678]

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?

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?

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?

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?

If I've got that right, then I just have one final question. 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)?

[Capmaster]

Some good information here:

https://www.videohelp.com/guides#1;54

[trevlac]

I thought resolution = frame size ???

i.e. if my video is 352 X 288, isn't this the resolution of it ???

Resolution != frame size.

http://www.quantel.com/domisphere/infopool.nsf/HTML/E64C5BB026A8870F80256CCC00537329

There is a good reference.

Once you get past this, the next thing to know is you never see pixels. They are not what you think they are. They are measures used to re-create the analog image you do see. The same analog image can more or less be re-created from differing sets of measurements (aka 640 or 720 pixels).

The references posted by cap master are ok, but most of those don't really know the real story, and probably smooth over quite a few things.

So ... you can figure it out, or trust the hardware and software to do the right thing. They probably do fine, and knowing more about the process may make no practical difference.


PS: Sorry for the preachyness ... but it's more fun for me that way.
I really made my 1st comments because I thought the original poster was wondering if you got more from up sizing.

[aamir12345678]

Not exactly, trevlac. I was confused because I thought that people encoded to those resolutions because of the tv's pixels' horizontal size. I still don't get the very last question I asked about the [1024 x 768] to [720 x 480] conversion.

[trevlac]

Not exactly, trevlac. I was confused because I thought that people encoded to those resolutions because of the tv's pixels' horizontal size. I still don't get the very last question I asked about the [1024 x 768] to [720 x 480] conversion.

I tried to back out because I did not get your question. I think the most important thing for you is to have TMPGEnc get you close enough so you can not really tell the difference.

BTW: I don't really worry about aspect too much. It's nice to know, but not often worth the effort.

As far as your last question .... You are caught in incorrectly thinking about pixels, brother. The AR is an aspect of the analog image that you see. 720x480 is not a 1.5 AR. In fact, I don't know what the AR of 720x480 is because I don't know anything about the analog picture that was measured by those pixels. I can make some assumptions that you got your image digitized by devices/software that were following standards. Let's do that ....

Assume when you capture at 640x480 your device captured the full analog scan line as stated in the 601 spec. 53.333 Microseconds. Then if you resize this to 720x480 and put it on a DVD you are set.

In practice, things are usually a little off. But they are not worth worrying about.

It is hard for me to comment on a 1024x768 size. It's not close to a standard, so I don't know how you got it. If it came from a PC screen , and you resized it to 720x480 for DVD. The aspect would then be off a tad. Should be 702x480 and then pad the sides.



I think I will post a thread about what pixels really are. I doubt many people will say much because it just seems like babble.