How do I know the aspect ratio of my source AVI

[targus]

Hi Folks

I can't tell you how pleased I am that I found this site - brilliant. I've torn most of my hair out but finally have my AVI and I want to convert it to MPG using TPMGEnc express 3.0

I have follwed the instructions on this site but having loaded the AVI I do not know how to set the aspect ratio. Pixel 1:1 (square pixel) is currently selected but there are other options for various 4:3 and 16:9 in NTSC or PAL.

I live in the UK so PAL is our format.

I'm so close that any help would be really appreciated.

Cheers
Karl

[thecoalman]

Probably 4:3, 16:9 is widescreen.

The reason for the selections is that the aspect is determined by what you choose. It's not determined by the resolution of the video. What to choose depends on the source. The DVD player or software adjusts the vdieo to the correct aspect.... Hope that makes sense, it doesn't to me....

Unless you camcorded the footage in 16:9(widescreen) use 4:3.

[mats.hogberg]

AVI usually has square pixels, so the aspect ratio can be determined by examining the resolution. If you resize it properly, it doesn't matter if you choose 4:3 or 16:9 when encoding, but if it is a "wide screen" AVI, you're better off encoding as 16:9, to avoid huge black bars top and bottom. Did this make any sense?

/Mats

[thecoalman]

so the aspect ratio can be determined by examining the resolution.

The aspect is not determined by the resolution. 720x480 (or it's PAL counterpart) can be either 4:3 or 16:9. What it is will be determined by how it was recorded.

That at least is as far as video recorded on a camcorder is concerned, video ripped from a disc can also be flagged as 16:9 if that is the correct display aspect. If you display this video in it's raw 1:1 aspect then everthing will be elongated. The DVD player squishes it to it's correct aspect. The black bars top and bottom are not part of the video.**

If it was recorded from broadcast TV then the aspect will be 4:3, I don't think there's any exceptions to this rule.

If it's a video from the web then most likely the correct aspect is 1:1 since most web video is reencoded so the resolution matches the correct aspect.

** Some web video and some cams will appear as 16:9, the same for a broadcast that appeared as 16:9. In this case the black bars are part of the video and what you really have is 16:9 video on a 4:3 matte.

Now I bet your really confused correct?

[targus]

Yes - very confused.

Unfortunately I do not know how the avi was originally encoded - it is a rip from a dvd. I would like to end up with dvd that I can watch in the UK on a wide screen TV. What would be the best setting please.
Thanks

Karl

[mats.hogberg]

Best bet is 16:9, center keep aspect ratio. (But that's just guessing.) What's the res of the AVI? (Use GSpot!)

/Mats

[thecoalman]

If it was ripped from a DVD the correct aspect would be whatever the origianl was. If it displayed full screen on a regular TV then 4:3, if it played widescreen then 16:9. You can make it anything you want but choosing the incorrect aspect is going to skew it.

You can't have both. If the original is widescreen it will display fine as widescreen on widesceen TV, if the original is full screen on a 4:3 and you set it as 16:9 everthing is going to look squished vertically.

[junkmalle]

There is no simple way to determine an AVI file's aspect ratio.

First you have to understand that there are two aspect ratios you need to think about: PIXEL and PICTURE.

Pixel aspect ratio is the shape of individual pixels. Pixels don't have to be square. They can short and fat or tall and skinny too.

Picture aspect ratio (AKA Display aspect ratio) refers to the shape of the final displayed image, regardless of the number of pixels in each dimension.

Of course these two values are related to each other. The picture aspect ratio is equal to the image dimensions times the pixel aspect ratio.

Then you have to consider that there are aspect ratios for both the input and output in TMPGEnc.

On the Advanced tab of the MPEG Settings dialog you have the source aspect ratio setting. Here is where you specify the aspect ratio of your source. They mix pixel and picture aspect ratios here. "1:1 (VGA)" is a pixel aspect ratio. All the others are picture aspect ratios.

On the Video tab of the MPEG Settings dialog is the aspect ratio for the output MPEG file. Again, TMPGEnc mixes pixel and picture aspect ratios.

As far as AVI files are concerned:

Most XVID and DIVX AVI files use 1:1 pixel aspect ratio. This is because most people's monitors use square pixels (for example a 4:3 monitor at at 1024x768, one common exception is 1280x1024). Xvid, and I think Divx, support pixel and picture aspect ratio settings. But you can't count on any piece of software to use those settings. And you can't always assume 1:1 pixel aspect ratio because people do all kinds of crazy stuff.

If you see a 720x480 (or 720x576 PAL) Divx AVI file it is probably a pixel-for-pixel DVD rip. If everything looks very tall and skinny it is probably 16:9 picture aspect ratio. If things look close to normal it's 4:3 picture aspect ratio.

If you see a 640x480 Divx AVI file it is probably a 1:1 pixel aspect ratio file -- but since the image dimensions have a 4:3 ratio it's also a 4:3 picture aspect ratio.

Usually when you have a frame size that's very wide, say 640x288, you have a 1:1 pixel aspect ratio.

DV AVI files are usually 4:3 picture aspect ratio. Of course there are 16:9 anamorphic DV AVI files now too. If your source is your own camcorder you should know which AR it is.

Otherwise, you pretty much need to eyeball the video. Look for something you know should be square or circular. Judge the AR from that.

[mats.hogberg]

Yup, I've yet to see a DivX that doesn't have square pixels. (PAR=1:1). If I find a DivX that has a resolution of 512*288, it's safe to say it should be encoded as 16:9. But of course, taking a peek usually does the trick.

/Mats

[junkmalle]

Yup, I've yet to see a DivX that doesn't have square pixels.

I've seen lots. For example an SVCD MPEG that was converted straight to Divx AVI at 480x480.

[mats.hogberg]

Made by a fool who didn't know any better no doubt. Any player that catched up on the odd PAR and played it correctly?

/Mats

[junkmalle]

You can always use Media Player Classic's "stretch to window" option and size the window manually. I'm not sure, but I think my Liteon 2002 guessed the proper display aspect ratio too.

[thecoalman]

I would like to end up with dvd that I can watch in the UK on a wide screen TV. What would be the best setting please.
Thanks

One last thing, NTSC or PAL is irrelevant as far as selecting aspect. If it is originally 4:3 encode as 4:3 and use the zoom function on DVD player.