Screen Mirroring with HDMI Question

I'm seeing the same problem and it's quite annoying. Obviously I don't want to distort the aspect ratio, but given that the iPad can scale the output for certain applications quite comfortably, it seems odd that it can't do the same for the home screen -- particukarly when outputting to a 720p screen.

In my casei have checked the tv settings, and while I can scale the image up a little by forcing some "overscan" in the display settings, the root problem is obviously that the iPad is outputting an image with black Borders on all sides.

iPads do not display video with black borders. It displays a 4x3 image. What's happening is the tv is displaying a 4x3 image in letterbox mode. Perfectly normal. Your TV may or may not have the ability to rescale the image size to fill the height. You wil not have the ability to fill the width wthout stretching. Check your TV settings and see what's available to change picture modes. If it's really important to you, you can always buy a outboard scaler to remap the picture size

Not exactly, Mark.

The problem is not that it's displaying a 4:3 image, it's that it's displaying a 4:3 image with black borders on all four sides which are added to the picture signal by the iPad. What I want it to do is to proportionally scale the image to the screen height, and pillarbox as necessary for the aspect ratio. What it's doing (I suspect) is outputting an image such that there should be 1:1 pixel mapping at 1080p and filling the remaining space with black -- hence the black borders appearing top and bottom, as well as left and right. It's particularly annoying for me, as I bought my tv a few years back and it's a 720p set, so the iPad effectively uses fewer pixels on the tv screen than it does on the ipad's own display.

The iPad hardware clearly *does* have the ability to scale content to fit the screen -- a number of apps (keynote, YouTube, the photos app) scale content proportionally when outputting via HDMI, but they aren't displaying the same content on both screens. It could be a hardware limitation, but if that's the case then Apple have, at the very least, been a little disengenious in their advertising of this feature.

Theanorak wrote:

Not exactly, Mark.

The problem is not that it's displaying a 4:3 image, it's that it's displaying a 4:3 image with black borders on all four sides which are added to the picture signal by the iPad. What I want it to do is to proportionally scale the image to the screen height, and pillarbox as necessary for the aspect ratio. What it's doing (I suspect) is outputting an image such that there should be 1:1 pixel mapping at 1080p and filling the remaining space with black -- hence the black borders appearing top and bottom, as well as left and right. It's particularly annoying for me, as I bought my tv a few years back and it's a 720p set, so the iPad effectively uses fewer pixels on the tv screen than it does on the ipad's own display.

The iPad hardware clearly *does* have the ability to scale content to fit the screen -- a number of apps (keynote, YouTube, the photos app) scale content proportionally when outputting via HDMI, but they aren't displaying the same content on both screens. It could be a hardware limitation, but if that's the case then Apple have, at the very least, been a little disengenious in their advertising of this feature.

Has this issue been solved yet??

I JUST bought the new iPad 3 yesterday with the AV Adapter, and this is exactly the problem I'm seeing still. There are black bars on all 4 sides, even though the signal is 1080p. The signal is not being scaled properly to fit coming from the iPad.

No, I will not ZOOM my tv settings, Apple... that just incurs quality loss. I am upset too, as the pictures on the iPad sales site CLEARLY show the mirrored image flush with top & bottom of screen, and small black bars on either side.

This is definitely a software issue... because as noted, some apps properly scale the output:
Netflix - borders on all four sides
Videos (built-in app) - scales appropriately to fill screen either top-to-bottom on 4:3 or left-to-right for 16:9.

I see no options anywhere in settings to scale to edge. What can be done?

It's unfortunate that the iPad doesn't fit your tv screen exactly pixel too pixel. As I look at my iPad I can see the iPad is not a true 16 x 9 panel like my TV. When thats the case "rescaling" is going to be necessary to eliminate black borders.

You seem to be happy with rescaling video sources like Netflix but object to "zooming" your Tv picture. Zooming is a form of rescaling. There is a loss of video resolution in zooming as the pixel data in the black bars gets tossed out and replaced with rescaled picture data. Rescaling none the less. You need to choose what type of scaling works best for you. Unless your sitting really close to the TV, I would choose the Zoom mode. In this mode there is a lot less video processing going on which usually makes for a sharper image. Consumer TV's normally have really cheap video processors and total pixel remapping required for streching never looks good, especially when there is a lot of motion in the video.

Mark6275 wrote:

It's unfortunate that the iPad doesn't fit your tv screen exactly pixel too pixel. As I look at my iPad I can see the iPad is not a true 16 x 9 panel like my TV. When thats the case "rescaling" is going to be necessary to eliminate black borders.

You seem to be happy with rescaling video sources like Netflix but object to "zooming" your Tv picture.

Hi Mark, thanks for the reply!

Unfortunately, I don't think you're understanding the issue. I'm not expecting anything near a pixel to pixel match. I understand the iPad is not a 16x9 panel, and therefore would expect some black bars on horizontal to fill the space. But the current rescaled image through the AV Digital Adapter (and HDMI cable) is not being processed to fill even the vertical dimension (hence black bars on all 4 sides).

I'm NOT happy with Netflix.. or slideshow, or many other apps. They do NOT fill the screen horizontally or vertically. All the apps that are simply "mirrored" seem to suffer from the same 4 black bar problem. (see attached photo)

However, I do not think this is an issue with the hardware setup because there are other apps on my iPad 3 which use the exact same cables and to the same TV - and scale properly. For example, the built-in "VIDEOS" app (which doesn't mirror, but sends a signal through the adapter) scales a 16:9 video properly to fill the entire screen... and the same app scales a 4:3 video to at least fill the vertical space (and naturally black bars appear on the sides).

Does that makes sense? It seems it's a problem with the way the "mirror" video output is setup on the iPad 3.

I have seen videos where people have captured the output of the iPad 2 over HDMI and it's properly scaling to fit the HDTV. I can only guess the new resolution on the iPad 3 has changed the output algorithms. I've also seen a number of other posts detailing this same issue with the iPad 3, and so far has not been answered with anything other than "user error".

If there is something I'm not doing right, I'll be happy to post the fix.

Thanks for the response, I do appreciate it.

Christian Arild Strømmen wrote:

I might be remembering wrong here, but I'm pretty sure that's how it looked like when we got our iPad 2s, but it certainly doesn't now.

I've seen some videos of the iPad 2's in action, and they seem to be scaling properly when mirror'ing. Seems to be a new issue with the iPad 3's....

Mark6275 wrote:

iPads do not display video with black borders. It displays a 4x3 image. What's happening is the tv is displaying a 4x3 image in letterbox mode. Perfectly normal. Your TV may or may not have the ability to rescale the image size to fill the height. You wil not have the ability to fill the width wthout stretching. Check your TV settings and see what's available to change picture modes. If it's really important to you, you can always buy a outboard scaler to remap the picture size

I don't think it is "normal" to letterbox a 4x3 image... and even if you can rescale the image with your TV, that seems like a workaround for something that should work better. And buy an outboard scaler? C'mon. The AV Adapter is $39 already... shouldn't we expect it to work as advertised:

http://www.apple.com/ipad/accessories/

Note in the picture how the top & bottom of the iPad screen is flush with the HDTV. Yeah! That's all we want... what was advertised we were buying.

One correction... I guess this is what the iPad 2 did as well.

A number of videos on YouTube show the same output issues...

and one guy who did have a screen flush with the edges said he had to expand the native image.

So the question is... why is it setup like this?

If HDMI is 1920x1080... why wouldn't the output resolution use at least 1080 vertical pixels instead of something like say 900?

Thanks.

Default output for the iPad2 is 720p at 4:3. Tv default zoom should be set to 4:3 on the tv.

iPad3 is output at 1080 but aspect is still same at 4:3.

A TV's default zoom setting should be set to match the input signal. - ie 4:3 unless it has auto-detect like most high end sets, from makers such as Sony, Hitachi, Samsung, Panasonic, and newer models of LG etc.

It should aslso be remembered that whilst a lot of digital tv's support HD - those over 42 inch should do so by default, there are many that do not, and instead use onboard electronics to double the input signals processed at 720 to true HD on the screen output. Most sets below 36 inch emply this technology, though the situation is improving.

Your input signal defines your display output, settings on the tv allow you to match.

Apple's products do exactly what they say on the tin.

If in doubt refer to the technical specifications accompanying the product.

I have a Samsung 52. Some apps are built to match the 16.9 and fill the screen. Mirroring always come thru as 4.3, and I use the tv control to fill the screen without changing the scaling. I end up with black on the sides. I can also just blow it up a little more, keeping the scalding to fill the screen, but lose a little bit of content top and bottom. That is just the way it works.

Coppertiger wrote:

Default output for the iPad2 is 720p at 4:3. Tv default zoom should be set to 4:3 on the tv.

iPad3 is output at 1080 but aspect is still same at 4:3.

Your input signal defines your display output, settings on the tv allow you to match.

Apple's products do exactly what they say on the tin.

I'm getting the 1080p feed just fine, 4:3 aspect ratio is just fine... and yes, Apple's products are technically doing what they say on the "tin". What I was surprised at was the amount of underscan that is being used. I don't know why Apple is still using underscan to fill a 1080p signal... there used to be a need to do underscanning to fit in the safe area of television screens, but that has by and large disappeared with a proper HDTV and HDMI cabling.

I guess that's the way it was setup, and now all we can ask for is some kind of software settings that we can use to adjust overscan / underscan to manually adjust the output to fill the 1080p signal. Something like they have on mac's and mac mini's, etc. Example below:

Does that make sense?

Do you know anywhere where similar settings can be found, or app downloaded for the iPad 3?

I have a Samsung 52. Some apps are built to match the 16.9 and fill the screen. Mirroring always come thru as 4.3, and I use the tv control to fill the screen without changing the scaling. I end up with black on the sides. I can also just blow it up a little more, keeping the scalding to fill the screen, but lose a little bit of content top and bottom. That is just the way it works.

Right... some apps (when they are not using the mirror function) can fill the 16:9 aspect ratio. When you have the 4:3 mirror, you have to use the TV's scaling to go edge-to-edge. Without scaling somewhere, the 4:3 mirror image is underscanned quite a bit... and hopefully we'll have some kind of adjustment we can make on the iPad to adjust this in the future.

Underscanning is just overscanning, its employed alot still mainly to accomodate hidden screen edges caused by edge bevels. Without trying to sound authorative on something I know little about, a quick trip to the Wiki is in order. then there's the issue of Closed Captioning which has to be allowed for, so when showing it does not overly compress the vertical.

As for Apps that can overcome or accomodate the different outputs automatically, to me it would make little difference based on the limitations of the receiver, ie the TV.

For some it will be a compromise, whilst for a select few - heaven.

I think one of the neatest ideas was that seen on some freeview boxes where the 4:3 output matched the input 4:3 and the screen area was then filled at the side with the receivers Menu - a bit like the kind of captioning technology in Sky Sports etc. the better receivers allowed for the blanking out of the text area whilst watching a film.

There are a multitude of scanning standards based around the old terrestial Tv formats - IE, NSTC, PAL, SECAM, where those areas whilst adopting a true 1080HD at 16:9 almost universally, have, for whatever reasons utilised many different formats at the lesser 720p end of the spectrum. since it is touches on and supports this discussion I have taken the liberty of including this link;

http://en.wikipedia.org/wiki/Digital_television

Confusion abounds, and Apple as ever, as with so many others, is caught trying to cater for diverse standards with a device that it hopes can be used universally. Maybe in time - but in the meantime, compromise - may well be the order of the day.

Evidently I signed up for email alerts on this thread, and the ipad3 launch has brought the same problem. Which is disappointing.

To reiterate: the problem is *not* pillarboxing (black bars left and right) of 4:3 content on a 16:9 screen. That's the desired outcome.

The problem is that, for the iPad 2 at least (don't have an iPad3) the image is both pillarboxed AND letterboxed. The iPad is adding black borders to the output display, then scaling to the output resolution. Underscanning (and overscanning) aren't relevant in this case, as there's no reason for the iPad to do either when sending a specific signal (either 720p or 1080p) over a digital link.

If there's a hardware limitation preventing the video mirror output being properly proportionally scaled to fit the screen (as full screen apps do successfully) then it wouldn't be too hard to say so. If it's not a hardware issue but a deliberate decision (perhaps to accommodate CRT-based HDTVs with HDMI inputs, if such things exist), then it might be nice to give us the option of turning it off.