[Bug] Streaming vertical dummy display to M2 iPad Pro results in letterboxing/black bars

[wangxiaomeng000]

Hi there,

I'm encountering a persistent issue when trying to use my M2 iPad Pro as a vertical external display. The stream works, but the image on the iPad is always letterboxed with black bars, as if it's receiving a horizontal signal.

My Environment:

Mac Model: [MacBook air 13.6-inch, M2]
macOS Version: [sequoia 15.5]
iPad Model: iPad Pro 12.9-inch (M2, 2022)
iPadOS Version: [iPadOS 26]
BetterDisplay Version: [3.5.6 Build 40870]
Problem Description:
When I create a vertical dummy display (204x2752) and stream it to my iPad, the iPad screen shows the content with large black bars at the top and bottom. It seems to be receiving a horizontal signal and fitting it into the vertical screen, instead of filling the screen vertically.

Troubleshooting Steps I've Already Taken:
I have tried all the common troubleshooting steps, including:

Creating a dummy display with a correct portrait aspect ratio (3:4) and resolution 》
Confirming that I am using the "Stream" function from within the BetterDisplay menu for the dummy display, and NOT the native macOS Screen Mirroring in Control Center.
Rebooting both the Mac and the iPad multiple times to clear any cached states.
Trying the advanced "Associate then Stream" method:
Connecting via native Sidecar first.
Associating the dummy display with the iPad in BetterDisplay settings.
Initiating the stream from the dummy display's menu.
The result was still the same (black bars).
The BetterDisplay menu correctly shows that the dummy display has a portrait resolution (width < height), but the physical output on the iPad is always incorrect.

Expected Behavior:
The iPad should display the streamed content in full screen, vertically, without any black bars.

Actual Behavior:
The iPad displays the content with significant black bars at the top and bottom, as if a landscape source is being letterboxed into a portrait screen.

I've attached screenshots showing my configuration. Thank you for your time and help!

[wangxiaomeng000]

你好呀，

我在尝试将 M2 iPad Pro 用作垂直外接显示器时遇到了一个持续存在的问题。流媒体播放正常，但 iPad 上的图像总是带有黑边，就像接收的是水平信号一样。

我的环境：

Mac 型号：[MacBook air 13.6 英寸，M2]macOS 版本：[sequoia 15.5]iPad 型号：iPad Pro 12.9 英寸 (M2, 2022)iPadOS 版本：[iPadOS 26]BetterDisplay 版本：[3.5.6 Build 40870]问题描述：当我创建一个垂直虚拟显示屏（204x2752）并将其传输到我的 iPad 时，iPad 屏幕会显示顶部和底部带有大黑条的内容。它似乎正在接收水平信号并将其放入垂直屏幕，而不是垂直填满屏幕。

我已经采取的故障排除步骤：我已尝试所有常见的故障排除步骤，包括：

创建具有正确纵向宽高比（3：4）和分辨率的虚拟显示器》确认我正在使用 BetterDisplay 菜单中的“流”功能进行虚拟显示，而不是控制中心中的原生 macOS 屏幕镜像。多次重启 Mac 和 iPad 以清除所有缓存状态。尝试高级的“关联然后流”方法：首先通过原生 Sidecar 连接。在 BetterDisplay 设置中将虚拟显示器与 iPad 关联。从虚拟显示器的菜单启动流。结果仍然相同（黑条）。BetterDisplay 菜单正确显示虚拟显示器具有纵向分辨率（宽度<高度），但 iPad 上的物理输出始终不正确。

预期行为：iPad 应该全屏、垂直显示流媒体内容，并且没有任何黑条。

实际行为：iPad 显示的内容顶部和底部有明显的黑条，就好像横向源被放在纵向屏幕上一样。

我已附上我的配置截图。感谢您的时间和帮助！

[wangxiaomeng000]

The official can contact my email for communication?

[email removed for privacy]

[waydabber]

Hi there - sadly I don't see the attached screenshots. Did you try following this tutorial?

https://github.com/waydabber/BetterDisplay/wiki/Rotated-Sidecar