Anamorphic resizing

[525/60]

Actually this resolution (1.8194) is closer to the desired 1.8181 than 1.778.Yeah, but that's because I messed up. That would not look right. I just accidentally reversed two numbers. This is what I meant:
crop(0,8,-0,8)
LanczosResize(768,432)
It is helpful if you can double check my results, mainly by learning what this means:

704:480 · 40:33 = 16:9

Like everyone else (including very smart people who know that they are talking about), I thought that the following was true:

720:480 · 40:33 = 16:9

Meaning that for an anamorphic DVD, that is easiest way to resize to the whole frame to the television widescreen aspect ratio of 16:9. Of course the math doesn't work; they are not equal, but most people don't do the math:mad: But I did, because I wanted my resizes to be perfect:confused: Most people would say that is a waste of time, but in the long run, I learned something useful from it. So if you will indulge me, let me explain what I learned.

In the above equation, when you resize like this:
720x480 --> 16x9, there is an implied PAR that you are using whether you know what it is or not. You can find the PAR you are using by solving the equation. Then you can use the PAR to resize the same way even if you crop first. You see, we are starting with the assumption that that is the correct transformation, but we want to know the ratio of the resize we are using. We've come far enough along that we can see why this is an advantage, so you do already understand this. In order to find that ratio, I have to solve this equation (here we go with the math):

720:480 · ? = 16:9

? = (480 · 16) : (720 · 9)
? = (160 · 16) : (720 · 3)
? = (10 · 16) : (45 · 3)
? = (2 · 16) : (9 · 3) = 32:27 = 1.185

Meanwhile I am reading the DVDFAQ because I trust it completely. I still do. DVD Frequently Asked Questions (and Answers) (http://www.dvddemystified.com/dvdfaq.html) checkout this part: [0.3] Is this FAQ any good? Who wrote it? How do I know it's accurate? (http://www.dvddemystified.com/dvdfaq.html#0.3) So, I got to one of the good parts, a tricky part on a topic that confuses most of us: [3.5] What's widescreen? How do the aspect ratios work? (http://www.dvddemystified.com/dvdfaq.html#3.5)
At the bottom that that section is a table: 720x480 720x576
704x480 704x576 352x480 352x576
4:3 0.909 1.091 1.818 2.182
16:9 1.212 1.455 2.424 2.909Lookng at the table, the first thing I noticed was that there is no sign of the 1.185 which I calculated and was already using for my AVI files. I asked myself whether this 'pixel aspect ratio' as he calls it is the same thing I was calculating or not? And if so, why was I not getting the same result? The second thing I noticed was that, based on my assumptions, the table was doing something odd. Based on how I as calculating it, PAR would change depending on what the starting frame, as stored on the DVD, would be. All commercial DVDs store their frame information 720 pixels across, yet the legal DVD 704 pixel wide frames shared the same number in the table with the 720 pixel wide frames. In all other cases, each different frame size gets a different number. Is this PAR as I understood it, or not?

So what I did next was experiment with calculating PAR using the new 704x480 frame that this FAQ, which I trust, claims to be legal. This was very smart of me:rolleyes: Taking the time to make my own calculations led to an interesting discovery:

704:480 · ? = 16:9
? = (480 · 16) : (704 · 9)
? = (15 · 16) : (22 · 9)
? = (15 · 8) : (11 · 9)
? = (5 · 8) : (11 · 3) = 40:33 = 1.212

1.212 was in the table! This told me two things. That what I meant by PAR was the same thing that Jim was talking about in his FAQ. And that in all cases PAR was calculated using frames 704 pixels across or frames exactly half that size: 352 pixels across.

Why does this make sense? Because we know (some of us) that all you can view from the image on a DVD on an analog TV is the equivalent of a 702x486 pixel frame, which we round up and down for the DVD format to 704x480 to keep it all mod 16 (that is everything divides evenly into 16), so the extra width on the 720 pixel line will all be buried in the overscan and be invisible anyway. For the 704x480 frame, the DVD player must be padding both sides with blank overscan information to keep the picture in sync. Because the actual length of the line for both NTSC and PAL does need to be 720, but that includes about 9 pixels worth of overscan on each side which can't view on the TV screen whether the DVD has been encoded with picture information on those sides or not. Presumably the information can't be that important, since it can't be seen.

If the actual image viewable on a TV is closer to the equivalent of 702x486 pixels, wouldn't PAR be more accurately calculated like this?

702:486 · ? = 16:9
? = (486 · 16) : (702 · 9)
? = (2 · 16) : (26 · 1)
? = (1 · 16) : (13 · 1) = 16:13 = 1.231

Yes, it could well be more accurate, but according to the DVDFAQ and of course according to every other authority, it is not according to spec and presumably DVDs are encoded using the specifications so following the specifications to reverse the process should give you the most accurate result.

But notice the vast difference between 1.231 and 1.185. All these calculations have unearthed an important finding. 1.185 isn't just slightly inaccurate, but acceptable, it is so inaccurate as to be deemed wrong.:devil:

And if you want to stick with a method that is as easy as resizing to a 16x9 frame or a 4x3 frame depending of which type of DVD you have, then resize using the method I advocated at the beginning of this post:

crop(0,8,-0,8)
LanczosResize(768,432)crop(0,8,-0,8)
LanczosResize(640,480)

Also AP was another one of my mistakes, AP does not mean aspect ratio, it is AR. I just got into the habit of typing it wrong and I did not notice the error.

Stephen

PS

If this equation balances:

528:360 · 40:33 = 16:9

then this Avisynth Script would result in an image with a correct aspect ratio:

(Crop(96, 60, -96, -60)
Spline16Resize(640,360)

It would look the same as if you had enlarged a 2.35 movie on a widescreen TV enough to remove the black mattes.

Or try:

660:360 · 40:33 = 800:360 = 20:9 = 2.22

(Crop(30, 60, -30, -60)
Spline16Resize(800,360)

Stephen

[chipzoller]

Stephen, I haven't yet heard what you think of this post (http://forum.doom9.org/showthread.php?p=958093#post958093).

[525/60]

Stephen, I haven't yet heard what you think of this post.The reason I haven't responded is because we have already established that the presence of black mattes or no is completely irrelavant to the question of resizing. There are only two PAR for DVD and the mattes don't affect that PAR.

That leaves the question of terminology. If the film has a 2.35 AR and the DVD is anamorphic, then the black mattes will be 60 pixels in height approximately, but it varies slightly from film to film. The mattes are about 62 pixels high on the Matrix DVD.

Terminolgy:

There are two widecreen formats for film:

flat (1.85 AR) and scope (2.4 AR)

(As I pause to consider all the teminology, let me point out that I don't know what you want to know. Sometimes when you post a question on Doom9, no one will answer because they don't know what you're asking. You need to take responsibility to phrase your question in a way that makes it easy to answer the question you really want the answer to. If people don't respond to one of your posts, it can only be for one of three reasons: 1) no one knows the answer. 2) It is not clear what you really need to know (we don't know what you are asking) 3) It is so far off topic that no one is really interested (then you need to post to a different part of the forum or to a different forum entirely) For the last point, you are not supposed to double post, so you would need to ask the moderator whether he thinks his moving the thread to a different part the the forum would help.

OK, so we've got 'flat' and 'scope'. These aspect ratios are both called widescreen. Before widescreen talking movies were shot with an aspect ratio fo 1.375. Silent films had an aspect ratio of 1.33. Since the transition from silent film to talkies occured between the years 1928 - 1932, most movies not shot in widescreen were actually shot in an aspect ratio slightly larger than 4:3. So the apect ratios of 4:3 and 16:9 do not correspond to any films except silent picures from the 1920s. Instead, those are aspect ratios of television sets, standard and widescreen respectively. Notice that because 1.85 is not as wide as 2.35, some people people don't call it widescreen, but it is, its just that there are several different widescreen aspect ratios for film. 1.375 is the standard non-widescreen aspect ratio called Academy ratio (http://en.wikipedia.org/wiki/Academy_ratio) or "Academy Aperture".

So what is the difference between those two images?

I think the first is a film in 1.85 AR and the second is in 16:9 AR specifically produced for widescreen TV and not for film! Both images are clearly off a 16:9 AR anamorphic DVD.

16:9 is always for TV including the logo that the DVD plays before the logo that was part of the movie as it was originally shown in the movie theaters. You might not even get that first logo if you use DVDDecrypeter in IFO mode instead of FILE mode.

OK, maybe the whole movie is in 16:9 AR for Footloose, making what I am saying seem implausable. If that is the case, then the film was cropped to fit that AR. Read the Academy Ratio link, because it mentions briefly touches on every film AR. Although there are many of them, not one of them is exactly 1.78.

Stephen

Stephen

[chipzoller]

The reason I haven't responded is because we have already established that the presence of black mattes or no is completely irrelavant to the question of resizing.
Yes this is true, and I realize this. Maybe I should have been more precise in asking not the difference in handling/resizing the two, but the difference in the appearance of the two as shown in those raw frames.

You might not even get that first logo if you use DVDDecrypeter in IFO mode instead of FILE mode.
OK, maybe the whole movie is in 16:9 AR for Footloose, making what I am saying seem implausable.
Actually, at least with this movie the studio logo is part of the film and not in a separate PGC, but I know what you mean. Sometimes studio logos are separated on the DVD from the actual film feature. Footloose would then indeed be all 16:9, which as you say was cropped to fit that AR. In reading the Academy Ratio link you provided, I'm guessing Paramount matted the shot to a wider AR, then in the production of this DVD cropped away the matting in order to make it 'FOR' widescreen TV, unlike the first screenshot in which they took the whole film frame (with mattes) and made it "enhanced" for widescreen. In your estimation is this a correct or plausible observation?

[525/60]

I'm guessing Paramount matted the shot to a wider AR, then in the production of this DVD cropped away the matting in order to make it 'FOR' widescreen TV,Yes, that is exactly what I think too. I think they routinely do the same thing for 1.375 aspect ratio films too, cropping off the very little picture from the sides to make it conforn to 4:3 ratio or 1.36 ratio.

Stephen

[chipzoller]

Well I now think I have a pretty good understanding of how to correctly handle these materials, which has piqued my interest even further. Tell me more! Or maybe point me in the direction of how matted anamorphic DVDs actually get displayed on 'standard' TV vs. widescreen. I did some reading that indicated x number of lines were dropped but don't know any specifics.
Taking those 2 screenshots as source material I'd like to know how each one is displayed on each TV kind. I'd gladly see myself and take some measurements if only I had a stand-alone DVD player.

And although this doesn't relate to this thread, the idea of crop after resize and the cpu time involved interests me. I wonder if the cpu time hit is significant since the pixels are basically zero-complexity and even after going through the encoder it probably doesn't waste too many cycles on those stagnant mattes. Even despite this, I'd still crop then resize, but maybe it would be better if I were to do some tests on my own.

[525/60]

Tell me more! Be more specific than that. In fact, google, search for answers on this forum and when you hit an impass, ask a question.

Stephen

[525/60]

I did some reading that indicated x number of lines were dropped but don't know any specifics.Remember I said the ratio between 4:3 and 16:9 is 4:3. The inverse of 4:3 is 3:4. That is how many lines are left when a DVD player adapts a 16:9 DVD to play on a 4:3 TV, three out of four. Then black mattes are added to the top and bottom. Its called letterboxing (http://en.wikipedia.org/wiki/Letterbox).

Stephen

[mpucoder]

Couple random thoughts.

The reason the PAR is the same for 720 or 704 is that the pixel clock never changes, it is 13.5MHz.

Why does 720 exist? Easy, NTSC has a sligthly wider active area than PAL's 702, it works aout to about 711 pixels. The intent was to use 720x480 for NTSC and 704x576 for PAL.

Both 704 and 720 are multiples of 16, a very necessary requirement for mpeg with sub-sampled chrominance.

While overscan does exist in CRTs, modern displays do not need it (it exists to make picture shrinking caused by low power line voltage or poor voltage regulation on bright scenes less noticable) and can eliminate it, showing the entire picture.

[525/60]

One thing we know for sure is that if you watched the DR NO movie on your TV, you would never see that the picture does not go all the way to the sides.

I'm sure mpucoder did not mean to imply otherwise, but NTSC and PAL have the same length of lines. They start each line using the same clock speed of 13.5 MHz as he said. They get in 720 pixels at that speed, not all of which are visible. We get into a debate on how much is not visible, but not all. The fact that some DVDs don't bother to write all the way to the edge is one indication of that.

PAL and NTSC write the lines at the same rate, but PAL has more time to write lines before it has to start at the top again. They start at the top at the same rate the electrical current alternates. So in PAL countries it alternates at a rate of 50 Hz which is slower than the 60 Hz AC of NTSC countries.

Stephen

[mpucoder]

I'm sure mpucoder did not mean to imply otherwise, but NTSC and PAL have the same length of lines. They start each line using the same clock speed of 13.5 MHz as he said. They get in 720 pixels at that speed, not all of which are visible.That was my point, that the active area, ie the area unblanked in the analog signal, is different. For NTSC the line is 52.66.. microseconds (52.66 * 13.5 = 710.9), for PAL it is 52 microseconds (52 * 13.5 = 702). This is not, however, to accomodate overscan.

[525/60]

@mpucoder
That was my point,Yeah, I know it was your point, but what I said might'd *APPEARED* to be contradicting you, but I wasn't.

Stephen

[chipzoller]

EDIT: I asked before I did some independent reading. Topic clear.

[525/60]

@chipzoller
What exactly is overscanHonestly, it isn't important.

You should consider encoding back to mpeg, then you can click 16:9 aspect ratio or 4:3 aspect ratio, scene detection, GOP size 12, pulldown or 3:2 pulldown depending on whether you use QuEnc or HCenc. Some players will play vob files. IfoEdit will play the vob file through the Ifo file. Some players will adjust the aspect ratio for you when playing mpeg files. But some won't. Using this method, you don't need to change the aspect ratio in the first place. So we don't want to get too far into this before we pull back and look at other options.

What player do you use to play back the files made from your DVDs? How do you encode the files?

Also you might consider starting a new thread before starting on a new topic, other people might be interested who won't read a thread on anamorphic resizing.

To wrap up this thread, I'd like to go back to the first post and discuss what aspect ratio you chose. I have no way to know how well you understand this stuff unless you give me an example.

Stephen

[chipzoller]

What player do you use to play back the files made from your DVDs? How do you encode the files?
This whole thread was designed with PC archival and playback and the files encoded to x264 (MPEG-4 Part 10)

I'd like to go back to the first post and discuss what aspect ratio you chose. I have no way to know how well you understand this stuff unless you give me an example.

Ok, for example I'll take a true anamorphic (shot and stored as film) film. This is obviously flagged as 16:9 (with mattes encoded). I took the raw frame size (720x480) and determined crop values of:
crop( 8, 64, -8, -64)
Which then gives me a starting frame of 704x352. Since we know the PAR for converting to square pixels is 40:30 or ~1.2121, multiplying these two gives me a DAR of ~2.42. I then resize (after cropping) to a mod 16 size of 624x256 (~2.437) for which the aspect ratio error is less than 1%.
Do I pass the test?

[525/60]

Do I pass the test?Yes, however that seems just the tiniest bit too small. 640x264 is exactly 80:33~2.42. If I want it be be mod 16 badly enough I could either crop even more down to 640x256 for the 2.5 AR which I seem to come back to over and over again (what is left of the picture is that much more enlarged within a relatively small file, so there's the trade off; if probably looks pretty good) or allow a small amount of black matting above and below the picture increasin the height relative to the width to 640x272. You can crop the sides off to make it fit in a 640x272 frame also. I'll show you the AviSynth script for the three different ways above to make it more clear.

Crop(8,64,-8,64)
LanczosResize(640,264)
Crop(0,4,0,-4)

Crop(8,64,-8,64)
LanczosResize(640,264)
AddBorders(0,4,0,-4)

Crop(8,60,-8,60)
LanczosResize(640,272)

OK, so it turns out that cropping less off the top and bottom allowed a closer approximation to 40:17 than cropping more off the sides does. The first example only increases the size of the picture by a ratio of 640:624 ~ 1.025641...

Do you have a particuliar player you like to use to play back your mpeg4 files?

Stephen

[chipzoller]

es, however that seems just the tiniest bit too small. 640x264 is exactly 80:33~2.42. If I want it be be mod 16 badly enough I could either crop even more down to 640x256 for the 2.5 AR which I seem to come back to over and over again (what is left of the picture is that much more enlarged within a relatively small file, so there's the trade off; if probably looks pretty good) or allow a small amount of black matting above and below the picture increasin the height relative to the width to 640x272. You can crop the sides off to make it fit in a 640x272 frame also. I'll show you the AviSynth script for the three different ways above to make it more clear.
Well like I said, 624x256 was the 'best' resolution that introduces the smallest amount of AR error for being a mod 16 resolution.

Do you have a particuliar player you like to use to play back your mpeg4 files?

I don't have any hardware player that will play AVC files. And I really don't know of any on the market yet, so I've been creating files that are profile-unrestricted and muxing in MKV for computer archival and playback.

[r0lZ]

I then resize (after cropping) to a mod 16 size of 624x256 (~2.437) for which the aspect ratio error is less than 1%.
Do I pass the test?That's exactly the values given by my calculator.
Anyway, take in mind that an error smaller than around 3% is totally unnoticeable.

[chipzoller]

Probably so, but since these are for computer playback (I'm still shooting for around 710MB muxed), I downsize them to around that resolution anyway, so why not TRY to be as precise as possible? And I thought I might add that reducing to this frame size and compressing with x264 on unrestricted profile will all goodies activated yields astonishing results on a 2hr. 5min. encode (with Nero AAC q=0.36 stereo audio). Its with these sizes that you can really see how advanced something like x264 is. It continually amazes me with quality at lower bitrates.

[525/60]

I don't have any hardware player that will play AVC files. And I really don't know of any on the market yet, so I've been creating files that are profile-unrestricted and muxing in MKV for computer archival and playback.I meant "How do you play them on your computer?". I was refering to software players.

I point out that my third example has slightly less AR error and size does matter. The other two have zero AR error, It's not necessary to have zero AR error, but again they are also bigger. It's a trade off; if you try to compress a really big image too much, it acctually looks worse than a smaller image that is well encoded. Still, you are losing a lot of detail at that size. 640 width is a popular optimal compromise between size and compressability. I suspect that the resize ratio from 640 to standard computer screen resolutions are simpler and therefore more pleasing when viewing full screen. Also, if you stretched 640x480 --> 704x480, you could re-encode that back to 4:3 DVD.

The reason I didn't mention this before is that you seemed to want to maximize the sharpness and detail of the image, discounting filesize entirely. I was thinking that you may want to burn it to a DVD-ROM, making the filesize restriction 4.7 gig instead of 700 meg. The more details you give us concerning what you are actually doing, the more we can help you.

I realize you may not want what you are doing scrutinized too much, but you should realize that this forum works best when you mix theory with practical application. If you stay only on theory, the thread becomes boring for us. In general, you should not focus on what you need to know, you should focus on what you are doing and let the experts tell what you need to know. (Well, it works both ways; either the answer will be along the lines that you expect or might get a surprise. You want to stay open minded.) So we need to know the application in order to even understand the question. Worst case senario, we dance around the question getting cross with each other or no one answers the question because no one is sure whether they have the answer that might really help. Being specific is almost a requirement on this forum. You started well, but we got derailed into theory alone; I brought it back to the application.

Stephen

[525/60]

I'm still shooting for around 710MB muxedThat's the thing Chip, I don't remember you mentioning you wanted to encode to that filesize.

Looking back now I see that when r0lZ said: IMO, 720x306 is still a bit too large for a good compression. you seemed to agree.

But then a couple of posts later, you gave this example: crop( 0, 60, -0, -62)
BilinearResize(840,358)
Completely throwing me off track. I saw immediately that was the wrong AR and tried to help with that, but I missed entirely that you were not going for that size.

IMO, I don't reccomend going below 640 and suggest that it would not be a waste of your time to actually use the following script in an encode and get back to me whether it is not a slight improvement.
Crop(8,64,-8,64)
LanczosResize(640,264)
Crop(0,4,0,-4)
Stephen

[chipzoller]

I meant "How do you play them on your computer?"
I'll usually play them back with MPC+ffdshow or VLC

if you try to compress a really big image too much, it acctually looks worse than a smaller image that is well encoded.
Yes, this is why I'm downsizing, but there isn't too much quality difference between 624 and 640. I prefer a somewhat smaller frame size for better compression rather than a larger size since I'm trying to fit about 2hours on a typical 1CD encode.

But then a couple of posts later, you gave this example:

crop( 0, 60, -0, -62)
BilinearResize(840,358)

That was merely an example of a proper resize and not a practical resolution which I use.

As for my exact processes, I'm only doing the following:
Compressing selected DVD movies shooting for 710MB (muxed with above audio) encoded to x264 only for home theater viewing and storing. I normally encode a frame size of anywhere from 624 up to about 640, or somewhere thereabouts. These encodes are not produced with an eventual DVD storage in mind, only for PC playback.

I try your last example and see how it works.

[525/60]

I try your last example and see how it works.Thanks.

I'll usually play them back with MPC+ffdshow or VLCThose are my favorites. QuickVCD is my current favorite for mpeg1/mp2 files. A narrow niche, but it does a fantastic job within that niche. Making a VCD only makes sense if you want to radically reprocess the audio or video some way, but if you do, it is a great way to save a two hour movie on one CD. Since you are saving it back to mpeg1, the aspect ratio does not have to be changed. The following script will work as long as you check the proper aspect ratio in the encoder.

Crop(8,0,-8.0)
ReduceBy2

Stephen

[chipzoller]

Ah, I understand fully what you mean by your suggestion of
Crop(8,64,-8,64)
LanczosResize(640,264)
Crop(0,4,0,-4)
...and I think I like this better as it gives a dead-on DAR (by the first crop and resize) and then retains mod 16 by the last crop. I was trying to do it in just one crop and resize, which was very close to the correct DAR but because I was also shooting for mod 16 it wasn't as good as I could be. I'm running a test now with
crop( 0, 56, 0, -56)
BilinearResize(640,264)
crop(0,4,-0,-4)
and will report back how it looks.

One of your first statements by getting absolute accurate results by crop-resize-crop now makes perfect sense :)

[525/60]

One of your first statements by getting absolute accurate results by crop-resize-crop now makes perfect sense That makes me smile. Yes, I'm sticking around until all my points make perfect sense. Partly it's the math; it's factors.

Another crop-resize-crop could be:

crop(8,48,-8,-48)
Spline16Resize(640,288)
crop(0,8,-0,-8)

This leaves a little bit of the orginal black matting though. Whereas the other one is the same as if we cropped 8 more pixels from the top and bottom. An analogy with our earlier discussion of television will explain my position and tie everything up nicely. Earlier we suggested that there is something called 'overscan'. While a little overscan is necessary for an analog interlaced TV, that is not the only reason television manufacturers make TVs that crop off the sides of the picture. The other reason is that cropping off the sides makes the image that is left bigger for a given screen dimension. Well that's perfectly analogous to the constraint that we want to have the highest possible resolution of the image while keeping the filesize as small as possible. So cropping off the sides of the picture is just another way to compress the file. It works well for TV (you never even noticed it before) so it should work well for us. This is more true than you know, because the same compromise is actually make in movie theaters. The mind reels. So what I am saying is the script you are trying now really is better than the script above.

Both scripts share the property that they are equivalent to converting a 16:9 DVD to a 4:3 DVD and then converting that to the 1:1 aspect ratio of the computer screen. When viewing a 16:9 DVD on an standard TV, the DVD player reduces the height of the frame by 25%. This is the same as multiplying the height be a ratio of 0.75. Once you have done that, the image is in the same aspect ratio as a 4:3 DVD. So, resizing in two separate steps gives:

352 x 0.75 = 264
704 x 10:11 = 640, also

384 x 0.75 = 288

This yields a general way to resize all DVDs, since if it is not an anamorphic DVD just skip the first step. The width must be divisible by 22 and the height by 8.

Stephen

[chipzoller]

I've done some tests encoded to 640:x and they do look quite good. I didn't encode the same film twice at two different dimensions so I can't make specific observations, but 640 is still very good. I don't think I would want to go over 640, however since some of these encodes approach 2hrs 20min and that's a lot for a 710MB (muxed) filesize.

Your previous discussion about overscan and cropping off 8px on either side...I know much of this hearkens back to what happens when DVD is played on TV, but if I can avoid cropping 'active' pixels-even if it's only 8 per side-then I'd rather do that. Of course, if there are any hints of mattes on the left and right sides, I'll crop 8 to keep mod16.
One thing I have noticed just calculating proper frame size for our crop-resize-crop method is to leave enough matting (which is almost always the case in mine) so that the PAR is achieved exactly when resized to 640:x...after the PAR is establish the remainder can be cropped (to mod16), but since the amount of matting varies for each film this method obviously has to be tailored for each encode. This is fine. I'll just need to do more practicing so I get the processes and numbers right in my mind.

[525/60]

OOPS, I made a mistake. 704:352 = 720:360 = 2.

If this works: Crop(8,64,-8,-64)
LanczosResize(640,264)
Crop(0,4,0,-4)
then this does too: Crop(0,60,-0,-60)
LanczosResize(640,264)
Crop(0,4,0,-4)
I think the first one crops too much from the top and bottom. Fitting a 2.39 DAR movie into a 2.5 DAR means cropping a little of the picture so that the frame is 16 mod. Cropping off more than you would need to make it 16 mod is unaccaptable.

@chipzoller
Besides, this doubles for my example of using the entire width rather than cropping off the sides. It really makes more sense to use the entire line if your target DAR is wider than it should be. Somehow I got turned around in the discussion.

@all
I believe it is the prevailing wisdom that 1.85 is the best aspect ration for films. I really can't back up that statement. The eye is not meant to see the entire CinemaScope image as once. In the theater the sides should wrap around the audience beyond the seating on either side. Most of the action takes place in the middle. If any action takes place on the side, the viewer must turn his head to see it. It there is action on both sides at the same time, the eyes must ping pong between them. This is an almost gimmiky effect. The sides of 1.85 image are close enough to be viewed simuteaneously. Nowadays the screen never wraps around the audience beyond the seating, so the sides of a CinemaScope movie must be cropped dramatically down to at least 2.2 or 2.0 and sometimes to 1.85 in a small theater. People making CinemaScope movies know that this is going to happen and plan the shots accordingly. CinemaScope was meant to go beyond your field of vision to give you an immersive experience similiar to IMAX today.

@chipzoller
but since the amount of matting varies for each film this method obviously has to be tailored for each encode. Well, there are a limited amount of templates you could use; there is just a lot of them. Every 2.39 movie on a 16:9 DVD could use the same script for instance. A 2.39 movie encoded on a 4:3 DVD would need a different script. Movies are commonly 1.375 1.66 1.75 1.85 2.2 2.39. 16:9 DVDs are made only for movies with aspect ratios greater than 1.78 except for moves that are cropped to fit 1.78, but any movie can be encoded to a regular 4:3 DVD. 1.375 aspect ratio movies are never cropped to fit a 16:9 DVD, yet they are almost always cropped to fit a 4:3 DVD, since otherwise there would be a hint of black matting on the top and bottom.

Stephen