720 x 480 scaled to 640 x 480

Can anyone explain to me why most online video sites use 640x x 480 for video size.
The basic "rule of thumb" here is to export for the device and let the device handle the display.

For instance, computer monitors are "square pixel" devices so your 640x480 display provides the standard 4:3 or 1.33:1 display area. Analog TVs, on the other hand, are described as "rectangular pixel" devices. (This is actually a misnomer since we a dealing with "lines" rather than "pixels" but does provide a convenient way to compare the two.) Thus, an analog TV with "rectangular pixels" having a display area of 720x480 is the equivalent of your 640x480 "square pixel" display with both having a 4:3 aspect ratio. Since DV (traditionally used for TV broadcast) and MPEG-2 (traditionally used for encoding DVDs for TV playback) are historically viewed on analog TV devices, they are normally encoded to the NTSC standard using a 720x480 data matrix which, of course, provides a one-to-one correlation with their targeted viewing devices.

Now most multimedia applications (like QT) are smart enough to display the video at the proper aspect ratio. For instance, if you open your DV file in the QT Player and check the "Inspector" window, your will likely note two display entries on the "Format" line -- usually something like "720x480 (640x480)" (for 4:3) or "720x480 (853x480)" (for anamorphic video). However, problems can arise when users convert to non-NTSC standard compression formats using the NTSC data encode matrix rather than the intended aspect ratio intended for actual viewing.

From Quick time pro when I select Preserve aspect ratio and fit to size 640 x 480 it will save my file out as 640 x 426. This looks correct but its not matching 640 x 480. Another size I tried which fits into my online design was 540 x 405 but using Quicktime Pro with the above settings it exports as 540 x 360. When I save it to 540 x 405 from other programs it seems to be slightly narrow.
Sounds correct to me. If the source file is a 720x480, then it has an aspect ratio of 1.50:1. If you then tell it to convert the file to a 640x480 file but keep the original aspect ratio then the file will come out as a 640x426 file which also has the original 1.50:1 aspect ratio you demanded by your setting.
Basically, you have two options here. If the "Current Display" setting for your 4:3 source file is 720x480 (or anything other than 640x480 or equivalent 4:3 aspect ratio), then you can
1) Reset the source file "Current Display" to 640x480 and convert using the "Current" display option or
2) Target your output file for 640x480 but leave the "Preserve Aspect" setting turned off.

1) Reset the source file "Current Display" to 640x480 and convert using the "Current" display option or
Do you mean like what I originally did by exporting it as 640 x 480 which comes out to 640 x 426. If not then how would I reset to 640 x 480
2) Target your output file for 640x480 but leave the "Preserve Aspect" setting turned off.
Do you mean letting it squash up slightly by forcing it into 640 x 480? Example QT export output window :
Image Size : Custom
w : 640 x H : 480
Preserve Aspect Ratio : uncheck
Fit within Size : selected
I mean:

1) Open the Movie in QT Pro.
2) Open the "Properties" window.
3) Select the video track
4) Select the "Visual Settings" tab
5) Change the "Current Display" setting (possibly 720x480 here) to 640x480 with the "Preserve Aspect" switch off.
6) Now convert either using the converter option's "Current" display setting or you can enter 640x480 again. In either case, the the "Preserve Aspect" setting will now have no effect since manually changing the "Properties" window "Current Display" setting in the steps above has already changed the original "rectangular pixel" aspect ratio (probably 1.50:1) to the correct 4:3 "square pixel" aspect ratio just as converting from 640x480 to 640x480 would have no effect on the dimensions. (I.e., you should end up with a 640x480 movie at the correct aspect ratio assuming the original file was a 4:3 aspect movie no matter what encode data matrix was used to "hold" the data or what the original "Current Display" was to begin with.)

Yes indeed my QT says "720x480 (640x480)" When I export this out to 640 x 480 and view it in my quicktime it looks slightly squashed or narrow. You mentioned that some most multimedia applications (like QT) are smart enough to display the video at the proper aspect ratio. If this is the case why is it not showing the exported 640 x 480 correctly?
Okay, lets go over it one more time. You say you have a 720x480 movie. If we divide 720 by 480 we get a display aspect ratio of 1.5000:1 for the source file. You said you told it to create a 640x480 file but additionally told the application to "Preserve" the original aspect ratio. You further said you ended up with a "slightly squashed or narrow" file with display dimensions of 640x426. If we now divide 640 by 426, we get a display aspect ratio of 1.5023:1 which both fits in your 640x480 display setting AS YOU SPECIFIED and is the same aspect ratio as your source file AS YOU ALSO SPECIFIED. In short, QT Pro delivered exactly what you asked for.

So my understanding is people save to 640 x 480 and accept the fact that the video is slightly squashed. Almost every site I see has 640 x 480 or 540 x 405. This would mean all their videos are like mine and are accepted to be slightly squashed?
Let's assume these other sites are showing standard 4:3 aspect ratio movies. If we divide 4 by 3 we get an aspect ratio of 1.3333:1 here. If we do the same for a 640x480 file, we get an aspect ratio of 1.3333:1. And for 540x405, the aspect ratio is also 1.3333:1. So, while the physical dimensions of the files are different, their aspect ratio remains constant -- i.e., there is no distortion being introduced , no "squishing," no "tall and thin" people, and no "short and fat" ones either.
On the other hand if you have either a 4:3 (1.3333:1 aspect) or a 16:9 (1.7778:1) DV source file which is encoded to the same 720x420 (1.5000:1 aspect) data matrix, and you output a file "which preserves the 720x480 1.5000:1 aspect ratio, it will look "squished" side-to-side with tall and skinny people if the original file was a 16:9 widescreen file or "squashed" top-to-bottom with short and fat people if the original file was a 4:3 file. In both cases, the fix is to either "pre-correct" the source file to the proper "square pixel" aspect or to set the output to the proper "square pixel" dimensions and not try to preserve the original, incorrect aspect ratio. If you are using the "Movie to iPod" preset, for instance, then you must "pre-correct" the display before conversion since there are no options to do so as part of the conversion. On the other hand, if you are using the "Movie to MPEG-4" conversion pre-set, then you can enter the corrections to your aspect as a user conversion setting.
Here is also something that might help. To better see your problem, open your distorted file in QT Pro. Go to the "Properties" window and, with the "Preserver Aspect" switch turned off, adjust the "Current Display" setting to 640x480 and 640x360. Which looks correct and undistorted? Which ever it is, that is the aspect/dimensions to which you should be exporting your file(s). (This is a quick fix for correcting improperly exported files, but does not provide the maximum quality that could have been achieved by correctly encoding the file in the first place.)

So you should scale 4:3 NTSC 720x480 rectangular pixel sampling matrix to 656x480 square pixels to see the correct proportions on a computer monitor (many applications cheat and scale to 640x480 but luckily the error is so small that it goes unnoticed unless looked for).
I wouldn't. Once again you are adding a distortion. A 656x480 file has an aspect ratio of 1.3667:1 and not 1.3333:1. True, the amount of distortion is less that 1.5000:1 or 1.5023:1 but why deliberately add any distortion at all if you don't have to do so. The object in any conversion is to come out with a file having the same aspect ratio as the one with which you started. About the only reason to not use such exact settings is if you end up with a odd vertical pixel heigh (which can add a "green" line of pixels across the bottom row of your display) or to use block-16 encoding which increases the efficiency of the H.264 video codec (and both 640 and 480 are block-16 numbers).

But the problem is the webpage that video is been embedded into is set for 640 x 480 and not 640 x 426.
You neglected to mention you were viewing on a web page or that you were embedding settings which override the movie's own internal settings.

Find out what actual dimensions/aspect ratio your movie is supposed to display at. You can't do anything else until you do this. You say your web page is set for a 640x480 movie. Is this really a 640x464 display movie being play in a 640x480 control player or a 640x480 display movie being played in an 640x496 control player? (I.e., if your movie is playing in "controller", then you must embed the width x height of the movie display and add an extra 16 pixels to the height for the default player controller.)

When I check the preserve ratio box my video is exported correctly to 640 x 426. At this size my video looks correct and not squashed... The 640 x 360 looked better and not squashed.
Well, which is it? Which one looks correct?
A 640x426 movie movie could be a slide show made from 3:2 digital camera images with both having an corrent aspect ratio of 1.50:1. Or, it could simply be the encoded data matrix used to encoded either a 4:3 or 16:9 movie but does not represent the true playback aspect of either. On the other hand, a 640x360 movie could be from an anamorphic widescreen video camera, TV broadcast, or anamorphic DVD having a correct aspect ratio of 1.78:1. In addition, anamorphic sized displays can also be used to letterbox higher order orders of common widescreen video to include 1.85:1, 2.35:1 or 2.40:1. And all this is in addition to standard 4:3 or 1.33:1 aspect dimensions.
Therefore, I repeat, you must find out/know in which aspect ratio your original file was meant to be displayed. Only then can you scale your movie to specific dimensions which can be properly encoded/embedded in your web page with or without additional settings as may be required. (If all else fails, post the URL to the web page and let me examine the file firsthand which may save time here in the long run.)

Jon thanks for the help on this.
Not sure if this will help or not. Created a comparison matrix to demonstrate the various aspect problems. Row "1" is of a 4:3 (1.33:1) source file, row "2" a 3:2 (1.50:1) source file, and row "3" is a 16:9 (1.78:1) while column "a" depicts the 4:3, "b" the 3:2, and "c" the 16:9 aspect ratio. This means the image 1a, 2b, and 3c are all displaying at their original correct aspect ratios and all other images depict how the correct image looks when displayed improperly at incorrect aspect ratios. Hopefully, you can download and use this file to find your particular case among them and apply the proper adjustment settings.

ASPECT COMPARISON

From your Aspect Ratio chart it looks like I'm getting Row 2 a 3:2 ratio.
My analysis is somewhat different. Would something like this be what you are trying to achieve?



Having seen your sample images, my best guess is that the original source file was was most probably a 1.85:1 aspect ratio file encoded as anamorphic. (Would have helped to understand what was going on if you had mentioned the "letterboxing" of the display earlier.) Since you appear to be preparing your file for display on a web page, I would normally recommend a different work flow here.

I generally prefer to remove the "letterbox" and simply deal with the one-to-one correspondence between the actual display dimensions and the aspect ratio rather than that of the letterbox area and maintaing its aspect ratio. Normally I would crop the letterbox using MPEG Streamclip at the same time I "transcode" source content to a target web compression format at the dimensions I wish to display the final content. MPEG Streamclip allows you to crop either the source data (when you know the actual aspect ratio) and scale the results to a specific output or to crop the output data (when you don't know the source file aspect ratio) and let the dimensions "fall where they may." (In your case, if you want a 540 width display, I would use a 292 height to achieve a 1.85:1 aspect ratio as in the sample screen posted above.)

Alternately, you could "crop" your already encoded file in QT Pro (see TUTORIAL) and then scale the "de-letterboxed" display in QT Pro without having to re-compress any files. (I.e., this was what I was suggesting above but did not realize you were dealing with letterboxed content at the time.)

If you opt to continue with "letterboxed" content, then use the same aspect ratio used in the source file. This could be 1.85:1 content letterboxed in either an anamorphic dimensioned display (smaller bars) or in a 4:3 dimensioned display (bigger bars). By maintaining the same aspect between source letterboxing and output letterboxing you will avoid the current "Preserve Aspect"/"Don't Preserve Aspect" setting problem since the setting will have no effect in this case.

In any case, if your are embedding specific display dimensions for the player on your web page, don't forget to add the extra 16 pixels to the height entry no matter which display strategy you end up employing.

The problem is when I add letterbox to the original source the letterbox becomes even larger at top and bottom. I don't mind the original letter box height which was 36 px at the top and 36 px at the bottom. When I add letterbox and set my export to 540 x 405 and un-check Preserve aspect ratio I now get 56 px top and bottom black lines so its much more black space and less video.
You still don't seem to understand the strategy here...

If the original file was a 640x346 (1.85:1 aspect ratio movie) over an anamorphic (16:9) 640x360 letterbox, then you should be exporting to 540x304 anamorphic (16:9) letterbox which will then contain a 540x292 movie which retains its original 1.85:1 aspect ratio.

If the original file was a 640x346 (1.85:1 aspect ratio movie) over a standard (4:3) 640x480 letterbox, then you should be exporting to a 540x405 standard (4:3) letterbox which will then contain the same 540x292 movie as above but displayed in your 540x405 letterbox.

What you are describing sounds like a case of exporting an anamorphic (16;9) letterboxed file to a standard (4:3) letterboxed display setting just because you want to use a specific display setting. If you choose to "Preserve" the aspect and then Letterbox at the same time, then the 540x292 movie which would have exported to a 540x304 display using my "letterbox" strategy would now be placed in a 540x405 display area and thus increase the letterbox area by (405-304) or 101 pixels in height (about 50 pixels added above and below the movie area over and above what you otherwise would have had using my strategy). Basically, all you did was tell the application to increase the area dedicated to letterboxing and, once again, the application did what you told it to do.

BTW, what application are you using that allows you to both deselect the "Preserve Aspect" setting AND use the "letterbox" option at the same time as you stated above?

Jumping in late here...

The standard for NTSC DV video is 720x480 with rectangular pixels. If you display that on a square pixel device it will be distorted unless you squeeze it to 640x480 or stretch it to 720x540 (not recommended due to interlacing).

If 640x480 video displays from 720 x 480 DV sources looks squashed to you, let me ask you this: What is your display resolution and aspect ratio? In order to get a little more stuff on my CRT screen, I usually run at 1152x864, which is a 4:3 square pixel ratio, but because of screen adjustments sometimes that looks a little squashed. If you are looking at properly resized DV video and it looks squashed, make sure that your screen is square before you assume that you're squashing improperly. It may be that your pixel count is correct but your display is squashed.

I should also caution you that if you are looking at reference materials that are geared towards producing VCDs and SVCDs...those formats use pixel aspect ratios that are even weirder than the DVD ratio.

Personally, I am still wondering why digital NTSC video isn't 700x525. After all, "everybody" knows that NTSC video is 262.5 lines per field, and because it is analog, the horizontal resolution isn't actually defined except by the 15.734kHz horizontal refresh rate...


--Dave Althoff, Jr.

The original file reads from the Movie Inspector under the title format : DV, 720 x 480 (640 x 480)
Which as I have previously said means nothing since all aspect ratios will be encoded to an NTSC 720x480 matrix whether they 1.33:1, 1.50:1, 1.65:1, 1.78:1, 1.85:1, 2.35:1, or 2.40:1 aspect movies. Further the content will either be flagged as SD (4:3) or Widescreen (16:9) content in which the various aspects can be "fit" as "letterboxed" content. Since the content seems to have been provide by someone else, you do not know what the original aspect ratio was or whether or not the work flow used by the original provider has stripped an "anamorphic" flag from the file which may have been present.

What I'm trying to do is create a exported file of size 540 x 405. All I'm trying to do is create a file 540 x 405 again 540 x 405 with no letterbox or if not that then the original 30 pixels of letter box at the top and bottom. but the problem is the original aspect ratio is not allowing me do that.
A 540x405 display without any letterbox is possibly if and only if the source file aspect ratio of the movie is 4:3 (1.33:1). In all other cases a 540x405 display without letterboxing will be rendered with some amount of distortion which you can fix by adjusting the display dimensions (as previously explained). With letterboxing, your 540x405 may be rendered at the proper aspect ratio within the letterbox display in which case, you need only crop the letterbox area from the display so that the player display area is equal to the dimensions of the movie content when playing at the proper aspect ratio. (I.e., you won't have 540x405 display area any more.) Further, a 540x405 display is not a good choice for encoding a movie since many codecs will create a green line of pixels across the bottom of your re-compressed movie.

When I select "Preserve Aspect Ratio" in QT pro it forces the exported QT file to export to 540 x 360.
Once again QT Pro is doing exactly what you asked it to do. In this case it is preserving the original aspect ratio of the encoded file (i.e., the 720x480 data matrix). Unfortunately, you want it to preserve the aspect ratio of the display matrix which you admit you neither know nor know how to determine.
Example: 720:480::540:360::1.50:1
i.e., (720/480) = (540/360) = (1.50/1)

As I have said before The only way I can achieve a file of 540 x 405 is select letter box it seems. This will give me a file of 540 x 405 but now instead of the original 30 px top and bottom now I get over 50 px top and bottom letterbox.
And as I have previously implied, aspect ratios and display dimensions have a specific mathematical relationship to one another. If you are going to keep the dimensions constant (540x405) then varying the aspect ratio contained within those fixed dimensions will, in turn, vary the proportionality of the letterbox and display areas also contained in those fixed dimensions. Basically you are trying to fit a square peg in a round hole but refuse to change the dimensions of the square peg even though such changes would maintain a constant aspect ratio (i.e., 1:1) and eventually allow you to put that square peg in the round hole. It is the same problem you have with your movie -- just grossly simplified.

As I have said before The only way I can achieve a file of 540 x 405 is select letter box it seems. This will give me a file of 540 x 405 but now instead of the original 30 px top and bottom now I get over 50 px top and bottom letterbox.
And I repeat, letterboxing (or pillaring) is mandatory if you must use a 540x405 display area since the only aspect ratio that is compatible with these dimensions is 1.33:1 and your file does not appear to have this aspect. The obvious solution is to use other dimensions whose aspect ratio are equal to your source file's actual aspect ratio. Until such time as you may decide to do that, there is nothing anyone can do for you here. It's simply a case of wanting to have your cake and eat it too.