Originally Posted by gblack
Ah, so I think (and from your sig) you're trying to use an anamorphic lens on a projector but not have a sled that moves the lens out of the way for non-scope content.
I don't have the answer for you, but I'm pretty sure that this would require a custom scale out setting and not a crop setting. Crop removes part of the picture before output, scale just distorts it. And it's the latter you'd want to do with a 16:9 image.
You're correct I have an anamorphic setup. I've, perhaps making my life more difficult, been trying to phrase my questions in order to avoid that detail, because I've read the "no anamorphic modes" responses already. However, that is not necessarilly a deal breaker, my IN76 doesn't have any anamorphic-specific functions either, but I can use the "4:3" scaling mode to properly display 16:9, and the Letterbox mode to properly display 2.35:1. End result is with the IN76 + a source configured for 16:9 output everything is displayed in the correct AR, despite the IN76 not having "scope support".
Originally Posted by Bob Pariseau
OK let's try and start with the basics. First it helps to know that the Anthem converts all video input it is going to process to 1920x1080p, so when you see numbers in the custom crop info, that's what they refer to.
Second, a lot of this material is covered in probably confusing detail in the posts linked off the first post of this thread -- see the "Fun With Custom Cropping and Scaling section of those links.
Thanks Bob, that's about where I was, I could see a lot of those posts involved the concepts I was seeking info on, but they were so specific, that they left a lot of the details I'm looking for up to interpretation/guessing/assumption.
So what is all this stuff?
Crop Input extracts a subset of the input video. The crop can never be bigger than the actual input frame in either dimension, but it can be smaller. The 4:3 and 16:9 crops are simply pre-defined crops. Imagine an input video frame that is the shape of a rectangle. Suppose it is a 4:3 frame from an SDTV channel. If you apply the 4:3 crop to it the crop just fits both horizontally and vertically. But if you apply the 16:9 crop to it the shape doesn't match. If you make the crop match the height of the image then the sides of the crop would be off the image left and right. As I said, you can't do that. Both dimensions of the crop have to fit WITHIN the pixels of the actual input frame.
So, just so I ensure that I understand perfectly clearly, 4:3 and 16:9 input crops crop 1/4 of the image off the sides or top/bottom respectively?
So what to do? Well if you think about it, any given input frame is either going to be wider aspect ratio than the crop, narrower than the crop, or just right. In this case the 4:3 input frame is narrower than the 16:9 crop.
So instead of making the crop match the input in height, the Anthem makes it match in width. But wait! If it is going to match in width and still be a 16:9 crop that means the height must be made shorter. I.e., you have to discard some of the input image top and bottom.
It might help to draw a picture of a 4:3 rectangle and then put a 16:9 rectangle on it that just matches in width. See? The 16:9 crop is going to "crop out" a 16:9 wide subset of the 4:3 input image that just matches in width but discards some of the top and bottom of the 4:3 input image.
Why would you want to do this? Well suppose your SDTV channel was presenting a letter-boxed movie -- a 16:9 movie embedded in the 4:3 broadcast frame with black bars top and bottom to make up the difference in shape.
Applying a 16:9 crop to that input video extracts the 16:9 movie from the center of that 4:3 frame.
Now suppose you are watching an HDTV channel broadcasting at 1080i. It will be broadcasting a 16:9 frame. But sometimes what is shown in that broadcast is actually an SDTV program, scaled up to 1080i by the broadcast station and fleshed out with pillar box bars on the left and right to make up the 16:9 shape.
If you apply a 16:9 crop to that it just fits. The Anthem has no work to do. It will pass on to the scaler the incoming video just as broadcast -- i.e., a 4:3 image embedded in a 16:9 frame with pillar box bars on either side.
Suppose you want the Anthem to stretch that 4:3 image out to fill the screen left to right -- getting rid of the pillar box bars at the expense of distorting the image (circles now look like wide ovals). The problem is, the Anthem has no way of knowing which pixels are real image and which are the pillar box bars added by the studio.
But wait! You can tell the Anthem. Simply apply a 4:3 crop to that input.
Now if the 4:3 crop is as wide as the broadcast frame (including the embedded pillar box bar pixels which are part of the image the studio sends out -- remember the Anthem can't know which pixels are real and which are pillar bars) then the height of the crop must be too tall. Again you can never have a crop that is BIGGER than the input image in either dimension.
So instead the 4:3 crop is set to match the HEIGHT of the 16:9 frame. But that must mean that the width of the crop is narrower than the width of the input frame (draw a picture here, again, if you need to). Indeed! That's just what you want! A 4:3 crop applied to a 16:9 frame will extract the 4:3 subset from the middle of that frame -- which just happens to be the pixels that make up the embedded SDTV program content.
OK so let's pause here and make sure everybody's on board. Honestly, I think your illustrations are confusing me more than they're helping, but I believe I finally understand how these crops work:
First the Anthem makes an assumption that I have not seen stated thus far:
SD content is assumed to be 4:3 by the Anthem.
HD content is assumed to be 16:9 by the Anthem.
That is assuming the Auto HDMI setting is disabled?
As for the crops:
4:3 crop cuts the input frame down to 4:3 (no effect on a 4:3 source determined per above assumption)
16:9 crop cuts the input frame down to 16:9 (no effect on 16:9 source determined per above assumption)
Or, this is another option (but the result is not really different), with Auto HDMI disabled, does the Anthem just assume square pixels?
Finally, suppose you have an HDTV station broadcasting a 16:9 frame at 1080i, but at the moment what it is broadcasting is SDTV program content -- and that program content is an SDTV version of a letter boxed 16:9 movie.
What you will see is that the movie is surrounded by black on all 4 sides. The SDTV program content adds black bars top and bottom to pad the 16:9 movie to a 4:3 shape, and the HDTV broadcast station then pads that 4:3 shape with bars left and right to pad it out to a 16:9 shape again. The result is that the 16:9 movie "floats" in the middle of the larger 16:9 frame.
Well if you apply a 16:9 crop to that nothing will happen. The input frame is ALREADY 16:9. The Anthem doesn't know that a bunch of those pixels are just black bar pixels.
And if you apply a 4:3 crop to that what you will extract is the 4:3 subset of the 16:9 input frame (remember this happens automatically because the Anthem just has to compare the aspect ratio of the crop to the aspect ratio of the frame and figure out whether it is matching height or width according to the rule that neither dimension of the crop can be bigger than the actual input frame). That's part-way there. You have now thrown away the left and right pillar box bars applied by the HDTV broadcast station. But the top and bottom pillar box bars applied to make the 16:9 movie fit into the SDTV 4:3 shape are still there.
So what's to do?
Well as it turns out, you can specify a Custom Crop setting in the Anthem. Again, think of this with respect to the 1920x1080p internal video frame of the Anthem processor. If you make the Custom Crop smaller in BOTH dimensions then you will discard part of the image on the left and right AND part of the image on the top an bottom. With just the right pair of numbers you can extract precisely that 16:9 movie, embedded in the 4:3 SDTV frame, which is embedded in the HDTV broadcast.
The math is shown in one of those posts linked off the first post of this thread.
Custom Cropping gives you an additional feature which can sometimes be handy. If either dimension of the Custom Crop is smaller than the basic 1920x1080p input buffer, then you can ALSO specify the centering of the Crop on that buffer.
Suppose you have a "wider than wide screen" movie in a 16:9 HDTV frame. E.g., a 2.35:1 movie for example. And suppose you would prefer not to see the letter box bars top and bottom which are included in the broadcast to pad that move out the 16:9 shape of the HDTV frame. Well again you can specify a Custom Crop that is the full 1920 wide but is less than 1080 high. By default that will be centered vertically on the image. But sometimes you will get these broadcasts of foreign films where they put subtitles BELOW the image -- in what would otherwise be the empty letter-box bar below the image. Well if you crop down the the shape of the movie you will lose the subtitles. And if you widen the height of the crop to include the subtitles you will also retain a portion of the letter-box bar above the image as well.
But instead you can make a custom crop which is just big enough to stretch from the bottom of the subtitles up through to the top of the movie -- and SHIFT IT DOWN in the image buffer so that it is no longer centered but is positioned to show the subtitles.
OK that's the input side of things. But we aren't done yet.
So to sumarize Custom Crop, the parameters are Width, Height, and Horizontal/Vertical Offset?
The shape of the output video is defined by the video output resolution you have specified for your display. Usually that will be precisely 16:9, but sometimes not depending on your display.
The shape of the output is now a THIRD rectangle to consider -- along with the shape of the input frame and the shape of the crop applied to that input frame.
It is the job of the Anthem Scaler to adjust the shape of the CROPPED INPUT to match the shape of the desired output. Again you just have two rectangles at this point. The two of them either match in aspect ratio (resolution is not important here, just the shape) or one of the rectangles is wider than the other.
You remember that the key rule for Cropping is that the crop can not be bigger than the input frame in either dimension. Well the key rule for scaling is that every pixel included in the Crop must make it on screen. That means the Crop shape must fit INSIDE the screen shape.
So suppose you have a 4:3 Crop shape and 16:9 TV? Well since the Crop has to fit inside the TV, the height of the Crop must be scaled to match the height of the TV. But then the Crop isn't wide enough. What to do?
Well if you set Scale Out = Letter/Pillar Box what the Anthem does is pad out the short dimension with either a letter or pillar box bar -- whichever is appropriate. The image itself is left unchanged. So a 4:3 crop sent to a 16:9 TV with Scale Out = Letter/Pillar Box means that the Anthem will generate pillar box bars on either side an the 4:3 image will be embedded in the middle of the screen.
But if you set Scale Out = Anamorphic then the Anthem will STRETCH the short dimension of the Cropped image (uniformly across the length of that dimension) so that it just fits!
If you send a 4:3 cropped image to a 16:9 TV with Scale Out = Anamorphic, then the height of the image will just match the TV (no vertical distortion) and the width of the image will be stretched left to right uniformly to ALSO just match the width of the TV. Thus the image is distorted (uniformly). Circles look like wide ovals and the shape of that circle/oval is identical regardless of where it is in the image.
Another option, Scale Out = Panoramic, also stretches the Cropped input (as necessary), but concentrates the stretching more to the edges of the short dimension so that the center of the image is less distorted. Sending a 4:3 Cropped input to a 16:9 TV with Scale Out = Panoramic means the image will also just fit top to bottom and left to right (NOTE: In reality the Anthem MAY do a setting only CLOSE to an exact fit to make the stretching produce less distortion), and circles will, again, look like wide ovals, but circles near the center of the image will be closer to actually being circles and circles near the left and right sides of the image will be shown WIDER than would result from Anamorphic.
Suppose you have a 2.35:1 movie embedded in an HDTV 16:9 input frame, and you select a Custom Crop which crops down on it to just match the actual height of this "wider than wide screen" movie. If you send that Cropped input to a 16:9 TV with Scale Out = Letter/Pillar Box, the Anthem will pad out the top and bottom of the Cropped input to make it match the desired 16:9 output shape. Which means you have just put back in the very same letter box bars you just Cropped Out! (Well it is a little different as the color of the output bars will be determined by your setting in the Anthem).
But if you specify Scale Out = Anamorphic, then the Anthem will STRETCH (uniformly) the Cropped, 2.35:1, input shape to make it just fit into your 16:9 output shape. Watched on a 16:9 TV, that means the 2.35:1 movie now just fills the screen top to bottom and left to right -- at the expense of distorting the image vertically (circles look like TALL ovals this time).
You could also make the Custom Crop somewhat taller than the actual 2.35:1 of the movie, in which case Anamorphic scaling would now be a compromise -- still some letter box bars but the bars are narrower, and still some vertical distortion but the distortion is not as much since the image doesn't have to be stretched vertically as much.
Or you could feed your Custom Cropped 2.35:1 movie -- stretched Anamorphically to just fit a 16:9 output shape -- into a projector that has a Constant Image Height Anamorphic lens which optically stretches the image into a wider shape. The net result is that your 2.35:1 movie is extracted (by the Crop), stretched to just fit the 16:9 shape the projector takes as input (by Anamorphic scaling), and then optically widened by the lens so that what you see on your projection screen just fits a 2.35:1 screen. Which is a cool thing to do because it means you are not wasting output pixel resolution to the projector by simply putting black letter box pixels in there.
OK, but what happens if you've got a 4:3 source, that the provider has upconverted into 16:9 HD without pillarboxing (ie the source is stretched horizontally), how would you undo that? If I'm reading everything you've posted correctly, there's no way to fix that.
Thanks again for the response I really appreciate it.