Changing resolutions (or, Do my math homework!)

[Mercury]

I'm trying to convert a 720x320 AVI to SVCD (480x480). The aspect ratio should be 2.35:1. (I don't know what the person who captured it was thinking, 720x320 makes no sense.)

Anyway, I figured out that to get the proper aspect ratio I have to set video arrange method in TMPGEnc to Center(custom) and set it at 480x272. This will give me 2.35:1AR when on viewed on a TV.

I can also achieve a good effect by using 564x320; this will chop off the edges of the video and I will end up with a 2:1AR, and no distortion of the video.

Basically, what I'm asking is, is my math right? This is my first time making a SVCD and I want to make sure that I know what I'm doing.

[bugster]

If you want to make a standrds complian SVCD the resolution MUST be 480 * 480 (for NTSC). In TmpGenc set Video arrange method to full screen Keep aspect ratio and TmpGenc will add black bars top and bottom.

[Mercury]

That would be well and good if the aspect ratio was correct to begin with. Since it's not, I had to compensate for that.

The SVCD will be 480x480, the resolutions I gave are for how much the video itself (not including the black bars) will be. In the second one, the 564 will be cut down to 480 by TMPGEnc, so it will be 480x320 (a 2:1 AR, right?)

[snowmoon]

720x360, does it "Look ok" in media player.... if so then it's 1:1 aspect ratio. n TMPGenc set your source AR to 1:1 and destination AR to 4:3 for image placement center keep aspect ratio. Done, let TMPGenc do the rest.

If it's not correct in MP then you're out of luck and will just have to play with it till you get it right.

[snowmoon]

Ok I think I know what happened. They took an anamorphic 16:9 2.35:1 movie and just "cut off" the black bars. Easy enough to fix.

Open in Vdub, add a resize filter, resize to 720x360 nearest neighbor expand to letterbox 720x480. In TMPGenc Source AR = 16:9 destination AR = 4:3 image placement = center keep aspect ratio.

[snowmoon]

I just dont stop do I.... mabye it's all the sugar.

I think you can skip the VDub step. Try loading it in TMPGenc and setting the source AR as 16:9 and see if the SVCD when played back looks OK.

[Mercury]

Try loading it in TMPGenc and setting the source AR as 16:9 and see if the SVCD when played back looks OK.

Nope, it's horribly squished (I can estimate from the preview). The movie itself is also squished when played normally in MP, if I expand it to 720x360 it looks worse (Since it's always compressed horizontally, stretched vertically.)

It does look fine at 752x320, (2.35:1 ratio) and that's what I based my calcs on.

480x272 or 564x320 (with sides chopped off to 480x320) should look fine. Maybe I should just try it instead of bothering you people?

[Umen Pich]

I had a similar situation. The first method you mentioned is better I think. i.e. 480x272 centered.
At least it is very easy to check the calculations by coding just first seconds of the movie, and then view the result in MS media player, full screen. Before that you try the original movie in the media player and put two marks for the vertical limits (with non permanent marker on your monitor. Then compare whether the size of the coded mpeg is the same as what you marked on the monitor.

[vitualis]

Nope, it's horribly squished (I can estimate from the preview). The movie itself is also squished when played normally in MP, if I expand it to 720x360 it looks worse (Since it's always compressed horizontally, stretched vertically.)

It does look fine at 752x320, (2.35:1 ratio) and that's what I based my calcs on.

480x272 or 564x320 (with sides chopped off to 480x320) should look fine. Maybe I should just try it instead of bothering you people?

No, that is wrong.

Just think about it. The pixel resolution of SVCD is 480x480 and the DAR (display aspect ratio) is 4:3. That is, if you play the MPEG-2 for SVCD on a player that doesn't know about the 4:3 DAR (i.e., if you just view it as 1:1 aspect ratio), it is going to look vertically stretched. It is supposed to.

If you view this on the TMPGEnc preview (which ONLY shows things in a 1:1 aspect ratio -- i.e., square pixels), chances are, you are doing things correctly.

If it looks "okay" (i.e., not vertically stretched) in the TMPGEnc preview for a SVCD, you are doing something wrong and your end SVCD will not play properly on a stand-alone player.

I think that you are still at the stage where you haven't gotten a handle on the fact that the "pixel resolution" of a video clip is completely separate to the "display aspect ratio".

You should so as snowmoon has detailed above.

Your SOURCE ASPECT RATIO should be set as 1:1 as it seems apparent that your source video clip was made with a pixel aspect ratio (as opposed to display aspect ratio) of 1:1 (i.e., designed for PC monitor playback).

Your DESTINATION ASPECT RATIO (i.e., for SVCD) should be set as 4:3 and your framesize should be 480x480. Basically, it is irrelevant what the framesize is (except for SVCD compliance). The DVD player will look at the 4:3 DAR setting and stretch the video to fill the TV screen.

Regards.

[Anonymous65]

Digital video NTSC: rectangular pixels

720x480 Full D1 resolution, aspect ratio 4:3
704x480 cropped D1 resolution, aspect ratio 4:3
480x480 2/3 D1 resolution, aspect ratio 4:3
352x480 1/2 D1 resolution, aspect ratio 4:3
352x240 1/4 D1 resolution, aspect ratio 4:3

The mpeg decoder playing the files will force 4:3 aspect ratio by changing the horizontal dimention of the pixels. This does not always happen on the PC, like Windows Media Player which does NOT force 4:3 aspect ratio, however all DVD players will force 4:3 aspect ratio when playing.

[vitualis]

Thanks for the clarity skittelsen!

It is a difficult concept for beginners, but you will have to get used to the fact that other than on the PC, the display aspect ratio is separate from the pixel resolution.

In effect, you are dealing with rectangular pixels rather than square ones.

Regards.

[Mercury]

Nononono, I have that part figured out. It took only a glance to see that the standard NTSC resolution ratios are nowhere close to the aspect ratios. 480x480 will appear as 4:3 on a TV, I know that.

Here's what I did:

First, I changed the horizontal res from 720 to 752 to get a 2.35:1 AR on my VGA monitor.

Now I compensated for the different pixel sizes. I multiplied 752 by .75 to get 564. 564x320 will appear on a TV like 752x320 would on a VGA monitor, yes? .75 is the distortion factor between SVCD and VGA, since SVCD pixels appear 4/3 as wide as they are tall, therefore there's only 3/4 as many as there would be on VGA.

So, that's my first option, 564x320, but that would cut off the edges, since there's only 480 pixels to work with.

To see the full video, I need to reduce that to 480x272, which is my second option.

I'm a newbie to SVCDs, but I'm good at math (or so I like to think.) I also realize TMPGEnc's preview isn't supposed to look proportional.

[Umen Pich]

Nononono, I have that part figured out. It took only a glance to see that the standard NTSC resolution ratios are nowhere close to the aspect ratios. 480x480 will appear as 4:3 on a TV, I know that.

exactly ! Actually if you use a half DVD resolution (which I strongly recommend) 352x480, it will appear again 4:3 on TV

I'm a newbie to SVCDs, but I'm good at math (or so I like to think.) I also realize TMPGEnc's preview isn't supposed to look proportional.

I told you in my first post. Your calculations are correct. Go ahead. I am also not very good in the theory of SVCDs but better in mathematics.

From my short experience however, I think the advice given here to set 1:1 aspect ratio of the source will not work well. Second - they didn't understand that you were talking about the (320x240) tmpgenc preview during the encoding , not the preview menu.

[vitualis]

NO!!!!!!!

The end framesize for SVCD must must must must must be 480x480 (for NTSC) or you ARE NOT MAKING A SVCD.

720 x 320 (1:1 pixel aspect ratio)

--> 480 x 213 (still 1:1 pixel aspect ratio)

To adjust the vertical value for the SVCD distortion...
213 * [(final y / final x) / (DAR y / DAR x)]

213 * [(480 / 480) / (3 / 4)]
= 284.

That is, your end framesize with the original video in it will be 480x284.

However, this is not a valid framesize for SVCD.

So basically, you will have to add letterboxing above and below (well whatever you want but most people want the video in the centre) so that the number of vertical pixels = 480.

Thus, your end framesize must be 480x480.

However, you do not need to do this calculation every time.

USE TMPGENC.

Set the aspect ratio of the SOURCE as 1:1.

Set the aspect ratio of the DESTINATION as 4:3.

It will correctly do the necessary resizing PLUS to the relevant letterboxing.

Regards.

[Mercury]

NO!!!!!!!

The end framesize for SVCD must must must must must be 480x480 (for NTSC) or you ARE NOT MAKING A SVCD.

720 x 320 (1:1 pixel aspect ratio)

--> 480 x 213 (still 1:1 pixel aspect ratio)

To adjust the vertical value for the SVCD distortion...
213 * [(final y / final x) / (DAR y / DAR x)]

213 * [(480 / 480) / (3 / 4)]
= 284.

That is, your end framesize with the original video in it will be 480x284.

No, you're still not getting it! The original movie is not in a proper aspect ratio, either for VGA, VCD, DVD, or anything that I can see. The AR is 2.25:1 which is wrong!

To correct the aspect ratio first, I expand the movie to 752x320 (2.35:1).
I can use your calcs now, with slightly different numbers.

752x320
----->480x204

204 * [(480 / 480) / (3 / 4)]
=272 :P

Also, the frame size will always be 480x480. The resolutions 480x272 and 564x320 are for the viewable image i.e. the movie itself, not including the black bars. In the latter, part of the image will be cut off because the frame size is 480x480.

[Umen Pich]

NO!!!!!!!

The end framesize for SVCD must must must must must be 480x480 (for NTSC) or you ARE NOT MAKING A SVCD.

Calm down. From the begining Mercury is talking about the <<Video Arrange Method>> --> Center (custom size) setting in TMPGenc.
The frame size is not touched at all.
Is it clear now ?

[vitualis]

No, you're still not getting it! The original movie is not in a proper aspect ratio, either for VGA, VCD, DVD, or anything that I can see. The AR is 2.25:1 which is wrong!

Well you can do whatever you want...

However, you haven't made something clear...

Firstly, there is no such as thing as a 2.35:1 aspect ratio per se. There is 4:3 (display aspect ratio), 16:9 (display aspect ratio) or 1:1 (pixel aspect ratio). Almost ALL video will be one of those three and if someone was making a DivX movie, intended for PC playback, it will be 1:1 pixel aspect ratio (unless they stuffed it up of course). Movies in the 2.35:1 format on DVD are actually in the 16:9 (display aspect ratio) WITH letterboxing.

Now, when you view the source video on your PC monitor (e.g., with WMP), does it look okay? This is what isn't clear to me. If it looks "okay", the pixel aspect ratio is 1:1 and you should do as I highlighted before.

If it doesn't look "okay" (i.e., pixel aspect ratio is NOT 1:1) then the original personal who made the video stuffed up. Then, yes, you will have to do some adjusting. BTW, you don't need to adjust UP and then resize down. Just do the maths before hand and resize it just ONCE but taking into account the required stretching. You'll save time and get better quality.

Mind stimulating stuff, no?

Regards.

[Mercury]

Now, when you view the source video on your PC monitor (e.g., with WMP), does it look okay? This is what isn't clear to me. If it looks "okay", the pixel aspect ratio is 1:1 and you should do as I highlighted before.

It looks almost okay, but not quite. The good thing about this movie (Gattaca) is that there are a few scenes with some really nice circles so I can see what kind of distortion I'm dealing with.

If it doesn't look "okay" (i.e., pixel aspect ratio is NOT 1:1) then the original personal who made the video stuffed up.

Didn't I say that at the beginning?

The aspect ratio should be 2.35:1. (I don't know what the person who captured it was thinking, 720x320 makes no sense.)

BTW, you don't need to adjust UP and then resize down. Just do the maths before hand and resize it just ONCE but taking into account the required stretching. You'll save time and get better quality.

Why do I keep getting the feeling someone's underestimating my intelligence?

Mind stimulating stuff, no?

That it is. 8)

BTW, thanks to Umen Pitch, who gave me the idea to make a CVD instead. For the record, with a frame size 352x480, the correct res's should be 352x272 and 414x320.

[Umen Pich]

Now, when you view the source video on your PC monitor (e.g., with WMP), does it look okay? This is what isn't clear to me. If it looks "okay", the pixel aspect ratio is 1:1 and you should do as I highlighted before.

Hi Michael,
Does the above mean that 4:3 SVCDs and CVDs we make must look bad in WMP ?
Because in my player they look just normal.

[vitualis]

It must be your player then...

WMP6.4 recognised the 4:3 aspect ratio on MPEG-1 files.

WMP7+ (WinXP) do not.

BTW, MPEG-2 playback on WMP is a bit touch and go since it depends on what MPEG-2 codecs you have installed on your PC.

Regards.

[vancouverite]

I'm trying to convert a 720x320 AVI to SVCD (480x480). The aspect ratio should be 2.35:1. (I don't know what the person who captured it was thinking, 720x320 makes no sense.)

Anyway, I figured out that to get the proper aspect ratio I have to set video arrange method in TMPGEnc to Center(custom) and set it at 480x272. This will give me 2.35:1AR when on viewed on a TV.

I can also achieve a good effect by using 564x320; this will chop off the edges of the video and I will end up with a 2:1AR, and no distortion of the video.

I built a litle tools for such cases:
http://poco.topcities.com/download/poco.zip
So what it says. For converting 720x320 to 480x480 Center(custom) should be 480x284, if you do it to 480x576 then a new internal size is 480x341.
If you chop off the edge to 564x320 the new sizes are 480x363 for NTSC and 480x435 for PAL.

[Mercury]

Well, I did it, and it looks pretty damn good. 564x320 gives the best results.

BTW, for me SVCDs and CVDs look like squeezed crap in WMP8, but play perfectly in PowerDVD.

[hp_lovecraft]

I think I understand now....

Your setting the frame-size as 480x480, and use the Center(custom) function to convert from 720x320 -> 480x272 1:1 resolution on the fly because the aspect ration in the ORIGINAL is stretched/distorted?

However, if it looked fine on your PC, then a framesize of 480x480 with FullScreen(keep Aspect) would of looked perfect. Don't trust the 'preview' image from TMPG, or even WMP.

nick

[Mercury]

Your setting the frame-size as 480x480, and use the Center(custom) function to convert from 720x320 -> 480x272 1:1 resolution on the fly because the aspect ration in the ORIGINAL is stretched/distorted?

Exactly.

[Umen Pich]

BTW, for me SVCDs and CVDs look like squeezed crap in WMP8, but play perfectly in PowerDVD.

I know (the squeezed crap). It was the same in my previous PC. Now, MPEG-2 files, prepared for the CVDs look the same normal way in PowerDVD and in MS Player (ver.7.01, Windows 2000)
But I don't use the Power DVD, because it causes a weird effect - the movie looks very dark (regardless of MPEG-1, 2 or whatever). And after that, the efect appears in the MS player as well. To solve the problem I change the Windows resolution (to whatever) and then change it back to the original one.
MS Player on the other hand never triggers that (d)effect.

[vitualis]

But I don't use the Power DVD, because it causes a weird effect - the movie looks very dark (regardless of MPEG-1, 2 or whatever). And after that, the efect appears in the MS player as well.

PowerDVD seems to sometimes set the video gamma / brightness / contrast way too low...

It does this for my DVDs and VCDs but not when just opening up an MPEG.

Regards.

[Umen Pich]

I built a litle tools for such cases:
http://poco.topcities.com/download/poco.zip

Great Page !!!

BTW you say there that CQ mode was clever because it uses a very low bandwith for the black stripes around the real picture. Does it mean that in CBR mode a high bandwith is used even for the black stripes ?