DisplayFlow/demo/windows_sender/README.md

Windows Sender Demo

This is a simplified demo of the Windows Host sender for DisplayFlow.

It demonstrates:

1. Screen Capture using Desktop Duplication API (DXGI).
2. Hardware/Software H.264 Encoding using FFmpeg (switched from Media Foundation for better compatibility).
3. Network Transmission using UDP.

Prerequisites

• Windows 10/11
• Visual Studio 2022 or later (with C++ Desktop Development)
• CMake 3.10+
• FFmpeg Development Libraries (Shared)
  • Ensure you have the include and lib directories.
  • Example path: D:\tools\ffmpeg-8.0.1-full_build-shared

Build

1. Open a terminal (Developer Command Prompt for VS or PowerShell).

2. Navigate to this directory:

   cd demo\windows_sender
   

3. Create a build directory:

   mkdir build
   cd build
   

4. Configure and Build (Replace path with your FFmpeg location):

   cmake .. -DFFMPEG_ROOT="D:/tools/ffmpeg-8.0.1-full_build-shared"
   cmake --build . --config Release
   

   Note: If your FFmpeg is installed elsewhere, change the path accordingly.

5. Important: Copy FFmpeg DLLs to the executable directory.

   • Copy avcodec-*.dll, avutil-*.dll, swscale-*.dll, avformat-*.dll from your FFmpeg bin directory to demo\windows_sender\build\Release.

Run

Run the executable with optional arguments: Target IP, Port, and Output File.

.\Release\WindowsSenderDemo.exe [TargetIP] [Port] [OutputFile]

Examples

1. Basic Streaming (Default: 127.0.0.1:8888):

   .\Release\WindowsSenderDemo.exe
   

2. Specify Target:

   .\Release\WindowsSenderDemo.exe 192.168.1.100 8888
   

3. Stream and Save to File (for debugging):

   .\Release\WindowsSenderDemo.exe 127.0.0.1 8888 debug.h264
   

   You can play the saved debug.h264 using VLC player to verify the encoding quality.

Implementation Details

• ScreenCapture: Uses IDXGIOutputDuplication to capture desktop frames.
• VideoEncoder:
  • Uses FFmpeg (libx264) for encoding.
  • Performs BGRA to YUV420P color conversion using libswscale.
  • Configured for low latency (zerolatency tune, ultrafast preset).
• NetworkSender: Fragments the H.264 stream into UDP packets (MTU ~1400 bytes) and sends them to the target.

Protocol

The demo uses a simple custom protocol for feasibility verification:

• Packet Header (Network Layer): FrameID (4B), FragID (2B), TotalFrags (2B).
• Frame Header (Application Layer, in first fragment/reassembled): Timestamp (8B), Width (4B), Height (4B), Type (4B), Size (4B).
• Payload: H.264 NAL units.