Is there a bug in TMPGEnc regarding aspect ratios in NTSC?

[DRP]

I'm almost convinced there is because I can get everything to work perfectly with PAL but not with NTSC using exactly the same procedure/process (though modified of course for the different resolutions and frame rates)

Here's what I find.

The source is an uncropped 4:3 ratio XviD wanted to display full-screen on PAL 4:3 TV using DVD player capable of playing both PAL & NTSC VCDs.

1) For PAL, I create a 720x576 sized 25fps MPEG and then letterbox inside that an image sized at 672x544 (to allow for the TV overscan) using the "Centre (custom size)" option under 'Video arrange Method' and tell TMPEGEnc it will be played on a 4:3 TV.

This works fine. The picture fills the screen, it is the right aspect ratio, nothing's stretched and the quality is excellent.

When I go to do the same thing with NTSC however it doesn't work.

2) For NTSC, I create a 720x480 sized 29.97fps MPEG and then letterbox inside that an image sized at 672x448 (to allow for the TV overscan) using the "Centre (custom size)" option under 'Video arrange Method' and tell TMPEGEnc it will be played on a 4:3 TV.

This results in a video which is stretched by a factor of 1.2 (I estimate) horizontally. Everyone looks fat-faced. I imagine that the edges of the picture at the sides are being cut off as well because of this though I can't actually see this happening of course on the TV screen.

Anyone know why this is happening?

It seems to me that the 'Centre (custom size)' option in TMPGEnc doesn't work properly under NTSC.

[yysie]

You need to use the "clip frame" option in tmpgenc... it allows you to crop. You need to crop 1 /12 above & 1/12 beneath

It is not really bad to resize NTSC2PAL but PAL2NTSC is asking for problems... It's less annoying to have eggheads then rather fat people!

[DRP]

You need to use the "clip frame" option in tmpgenc... it allows you to crop. You need to crop 1 /12 above & 1/12 beneath

It is not really bad to resize NTSC2PAL but PAL2NTSC is asking for problems... It's less annoying to have eggheads then rather fat people!

Thanks for your reply, but why? Where does the 1/12th come from? And why do I have to crop the image of a 4:3 ratio AVI when I want it displayed in NTSC?

I don't understand. Are standard NTSC televisions not 4:3 ratio or something? Please forgive my ignorance, I've never been to an NTSC market before, but I thought the only differences were the frame rate and the resolution size of the MPEG between PAL & NTSC.

I'm obviously missing something here that should be really obvious, so if anyone could please explain it to me like I'm an 8 year old, I'd really appreciate it because I can't figure out what I'm doing wrong.

[DRP]

Sorry to bump this, but there must be someone out there who knows the procedure for making an NTSC SVCD without having it distort on playback or is everyone converting to PAL first?

Pleeeeease help me. If I can't get this to work soon I'm gonna run out of HDD space because I'm not getting any NTSC videos onto CD-R at the moment.

Thanks.

[yysie]

Oke I'll explain: Pal 4:3 & NTSC 4:3 aren't 4:3 exactly...

So the format is NTSC and the virtual aspect ratio is 4:3...
The 'real' aspect ratio is 3:2 for NTSC and 5:4 for PAL...

You cannot see fat people if PAL 4:3 (real: 5:4) is resized to 4:3 (computer aspect ratio). Even though you cannot see difference from NTSC 4:3 (real: 3:2) resized to 4:3. Divx movies are usually resized to 4:3 to get fullscreen on a pc. So you need to check if the movie is PAL or NTSC...

I hope you understand... I try to explain it good & simple... I know my english is not very good at all so please tell me if you don 't understand something!

[DRP]

Sorry but no, I still don't understand. I know that there are two aspect ratios in the MPEG file format. There's the pixel aspect ratio and the display aspect ratio, where the pixel one is just the same as in an AVI - horizontal / vertical and the display aspect ratio is just a flag in the header which tells the software playing it by how much to stretch the horizontal to make it display correctly.

If the display aspect ratio is set to be 4:3 (as it is in my case) then it shouldn't matter what the pixel aspect ratio is (as long as it is a legal size the player can understand) because it will be stretched to fit a 4:3 display size. At least that's how I understood it to be.

My source is an XviD at 23.976fps and I want to play it in NTSC format on the TV at 29.97fps. I am capable of converting it to PAL, but would really prefer to not have to do this if at all possible as my DVD player is capable of playing NTSC and converting the output signal to PAL on the fly for my PAL-only TV set.

Unless someone can help me to find out why NTSC videos don't display properly when encoded by TMPGEnc, I think my only option is going to be to have to convert everything to PAL. This is annoying though because it requires huge amounts of free space on the HDD to do the required NTSC2PAL audio editing for conversion. I'd really prefer to not have to go through this NTSC2PAL audio conversion if at all possible.

[DRP]

Oke I'll explain: Pal 4:3 & NTSC 4:3 aren't 4:3 exactly...

So the format is NTSC and the virtual aspect ratio is 4:3...
The 'real' aspect ratio is 3:2 for NTSC and 5:4 for PAL...

You cannot see fat people if PAL 4:3 (real: 5:4) is resized to 4:3 (computer aspect ratio). Even though you cannot see difference from NTSC 4:3 (real: 3:2) resized to 4:3. Divx movies are usually resized to 4:3 to get fullscreen on a pc. So you need to check if the movie is PAL or NTSC...

I hope you understand... I try to explain it good & simple... I know my english is not very good at all so please tell me if you don 't understand something!

I'm trying really hard here to understand what you're telling me. If I accept what you say (and I will, since you're the only one here trying to help me and I appreciate this), then can you please tell me what is normal to do in TMPGEnc setting wise when wanting to do what I describe?

How do others convert a 4:3 full screen (no black bars required top/bottom or side/side) DivX/XviD for display in NTSC format?

As it is at the moment, when I do the encode in the same way as I do for PAL the output has very small visible black bars top and bottom and it is stretched horizontally off the screen left and right which makes the characters look fat. There must be something in what you say I admit because now that I think about it, I would have to say that it does look like it's being displayed at a 3:2 aspect ratio on a 4:3 TV. How do I stop this happening? How do I squeeze it back into 4:3 ratio again? Where's the setting in TMPGEnc to do this?

[yysie]

I would prefer "No Margin (keep aspect ratio)" I think your problem will be solved!

[sterno]

I create NTSC exclusively and I haven't seen any problems with aspect ratios. I didn't check your resizing, but it looks about right.

One possibility is that your player doesn't convert the NTSC to PAL quite right. Have you tried playing other known-good NTSC discs in it before? I've heard that a lot of the US players that play PAL discs on NTSC TVs tend to give you a slightly distorted picture, mine makes people on PAL discs look tall and thin.

[DRP]

I would prefer "No Margin (keep aspect ratio)" I think your problem will be solved!

I don't really want to do this. I'm trying to make allowance for the TV overscan and this will not allow that. My point is that I can get it to work perfectly with PAL, so why doesn't the same thing work with NTSC?

For reference I am following the advice in this guide http://mitglied.lycos.de/sabinelmar/svcd/SVCDTips.html with regard aspect ratios and allowing for TV overscan.

[DRP]

I create NTSC exclusively and I haven't seen any problems with aspect ratios. I didn't check your resizing, but it looks about right.

Can you have a look at the following screen caps of my settings for me and tell me if there's anything you see here that's violently wrong?

One possibility is that your player doesn't convert the NTSC to PAL quite right. Have you tried playing other known-good NTSC discs in it before?

No I haven't. I don't have any known good NTSC discs available to me to try so this is something I can't test. When this test encode I'm doing in the screen caps above finishes though, I'll play the resulting MPEG through PowerDVD on the computer and see if the distortion is still there. If it is, then I think that should confirm the innocence of the DVD player.

[DRP]

I think your theory about the DVD player being at fault with the NTSC2PAL conversion for the PAL-only TV is correct.

The test encode I did as per the screen caps above plays perfectly in both WMP 6.4 *and* PowerDVD but as soon as I get the Sony DVD player to have a go, it all turns to sh*t.

The picture itself is fine as far as jerkiness or picture quality is concerned. Even the sound is perfect with no sync problems at all typical of dodgy format conversion, but the image is stretched horizontally leaving slightly visible black bars top and bottom which shouldn't be there and making everyone have an unaturally round face.

Oh well. Looks like I'm back to converting everything to PAL.

Thanks for everyone's help on this.

[Gazorgan]

Computer screen pixels are square or 1:1 .

TV pixels are not square, they are ...ummm can't remember. 9:11 maybe? Anyway, this is where the fat people come from. What looks good on your computer will look fat/skinny on your TV and vice versa. Remember that it absolutely doesn't matter what the encode looks like on your computer, only on your TV.

[sterno]

Remember that it absolutely doesn't matter what the encode looks like on your computer, only on your TV.

This is true as a general rule, most PC media players (like Windows Media Player) ignore the aspect ratio flags. However, PowerDVD is actually intended to play things that are meant for a TV screen, so it should make the necessary correction itself.

[SaSi]

DRP,

I read the thread and especially your original posting.

What I suspect is that you use the original source to create both PAL and NTSC streams.

If your original source is PAL then the steps you make are the correct ones and the result you have is expected to be correct (as it is).

Now, if you take the same original material (720x576) and resize it from 576 down to 480 scan lines (the fact that you downscale a little bit more to cater for overscan doesn't matter), means that you cause the video frame to "fatten".

Whatever you do, you can't alter the aspect ratio of the stream.

If the original has a 720 x 576 size, then it cannot become 720 x 480 without keeping the aspect ratio.

I'm not saying that the 720 x 576 frame cannot become a 720 x 480 without destroying the aspect ratio. It's just that the step required is not resizing but resampling it.

You need a program to take the 576 vertical scan lines, resample them and keep the information in 480 lines only. Obviously, some lines have to go and some information will be lost.