USB Wired Screen Casting for iOS and Android on Windows

The article introduces a USB‑based wired screen‑casting solution that allows mobile devices (iOS or Android) to stream their screen, microphone, and audio to a PC running the "PC Live‑caster" software. Wired casting overcomes the instability and network‑segmentation issues of wireless Wi‑Fi casting.

Background : The original live‑caster only supported wireless casting via LAN. The article explains how to replace this with a USB data‑exchange method on Windows.

Prerequisite knowledge : Basic understanding of USB architecture, Vendor ID (VID) and Product ID (PID), and how Windows associates drivers with USB devices.

iOS wired casting – Windows side :

Uses the open‑source libimobiledevice library (LGPL‑2.1) and the Apple Mobile Device Service (AMDS) that ships with iTunes.

AMDS creates a Windows service that bridges communication between the PC and the iOS device.

Device enumeration is performed via idevice_get_device_list() , connection via idevice_connect() , and data transfer with idevice_connection_send() / idevice_connection_receive_timeout() .

The data packets follow a custom header defined as:

struct TransferFrame {
    uint32_t version;
    uint32_t type;
    uint32_t tag;
    uint32_t payload_size;
    uint32_t identifier;
};

After a handshake (a packet with the above header and no payload), the iOS side encodes video/audio into an FLV stream, prepends the header, and sends it to the Windows receiver, which demuxes and decodes the stream.

iOS wired casting – iOS side :

Uses ReplayKit to capture screen, microphone, and device audio.

Audio/VideoToolbox encodes video to H.264 and audio to AAC, then packages them into FLV.

Data is transmitted over the private usbmux protocol via a TCP‑like socket created by the Broadcast Upload Extension.

Android wired casting – Windows side :

Relies on libusb (LGPL‑2.1) and the libusbK driver.

Device enumeration is performed with Windows SetupAPI (SetupDiGetClassDevsW, SetupDiEnumDeviceInfo) to locate portable devices (WPD) and filter by VID/PID.

After selecting a device, a custom libusbK driver INF is generated (VID/PID substituted) and installed via dpinst64.exe .

The device is switched to Android Open Accessory (AOA) mode; its VID/PID change to Google’s reserved IDs (0x18D1/0x2D00 or 0x2D01 if USB debugging is enabled).

Communication then proceeds with libusb_bulk_transfer() , using the same TransferFrame header as the iOS path.

Android wired casting – Android side :

From Android 3.1 onward, devices support both host and accessory modes. In accessory mode, the PC acts as the USB host.

The app declares an <intent-filter> and <meta-data> for hardware.usb.action.USB_ACCESSORY_ATTACHED and provides an accessory_filter.xml matching the PC’s accessory description.

When the accessory connects, the system notifies the app, which obtains a UsbAccessory via UsbManager , opens a ParcelFileDescriptor , and reads/writes the FLV stream.

Screen capture uses MediaProjection , audio capture uses AudioRecord , and encoding uses MediaCodec (H.264 for video, AAC for audio) before FLV packaging.

Driver uninstall :

To restore original device functionality, the custom libusbK driver can be removed using SetupAPI calls (SetupDiCallClassInstaller with DIF_REMOVE ) and SetupUninstallOEMInfW to delete the INF.

Conclusion : Wired USB casting provides a stable, low‑latency alternative to wireless LAN casting, requiring only a decent USB cable. The implementation involves driver installation, USB enumeration, and media encoding on both iOS and Android, with similar data‑transfer protocols on the Windows side.