Custom Input Source

This guide explains how to create a custom input source by inheriting from the Source class in GPUPixel. We'll explore the implementation process through two demo: SourceRawData and SourceCamera.

Overview

To create a custom input source, you need to:

1. Inherit from the Source class
2. Initialize the input source
3. Handle data input
4. Manage framebuffer
5. Control data flow

Class Inheritance

class YourCustomInput : public Source {
 public:
  static std::shared_ptr<YourCustomInput> Create();
  // Your custom methods
 private:
  // Your private members
};

Key Implementation Steps

1. Initialization

Implement a static create method and constructor:

std::shared_ptr<YourCustomInput> YourCustomInput::Create() {
  auto input = std::shared_ptr<YourCustomInput>(new YourCustomInput());
  if (input->Init()) {
    return input;
  }
  return nullptr;
}

2. GPUPixelFramebuffer Management

Create and manage framebuffer for your input source:

if (!framebuffer_ || (framebuffer_->GetWidth() != width ||
                      framebuffer_->GetHeight() != height)) {
  framebuffer_ =
      GPUPixelContext::GetInstance()->GetFramebufferFactory()->CreateFramebuffer(
          width, height);
}
this->SetFramebuffer(framebuffer_, outputRotation);

3. Data Input Processing

Implement methods to handle your input data. For example, with raw data:

void YourCustomInput::setFrameData(const uint8_t* pixels,
                                   int width,
                                   int height,
                                   int stride) {
 
  
  // Update texture
  glBindTexture(GL_TEXTURE_2D, this->GetFramebuffer()->GetTexture());
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0,
               GL_RGBA, GL_UNSIGNED_BYTE, pixels);
}

4. Data Flow Control

Call DoRender() to process the frame through the filter chain:

Source::DoRender(true, timestamp);

Example: SourceRawData

SourceRawData demonstrates handling raw pixel data:

1. Supports multiple input formats (RGBA and I420)
2. Manages OpenGL textures
3. Implements shader programs for format conversion

Key features:

• ProcessData(): Handle RGBA and YUV data
• Texture management for different formats
• Shader program for YUV to RGB conversion

Example: SourceCamera

SourceCamera shows how to handle camera input:

1. Platform-specific camera initialization
2. Frame capture and processing
3. Camera control (start, stop, flip)
4. Rotation and mirror handling

Key features:

• Camera session management
• Frame capture delegation
• Output rotation handling
• Mirror mode support

Best Practices

1. Memory Management

   • Use smart pointers for resource management
   • Release OpenGL resources properly
   • Reuse framebuffers when possible

2. Thread Safety

   • Use GPUPixelContext::SyncRunWithContext for OpenGL operations
   • Handle frame capture in appropriate threads

3. Error Handling

   • Check resource initialization
   • Validate input parameters
   • Handle platform-specific errors

4. Performance

   • Reuse textures and framebuffers
   • Optimize data conversion
   • Minimize context switches

Integration

To use your custom input source:

auto input = YourCustomInput::Create();
if (input) {
  auto filter = BeautyFaceFilter::Create();
  input->AddSink(filter);
  // Setup more filters or outputs
}

This guide covers the basic implementation of a custom input source. For more specific requirements, refer to the provided demo and adapt them to your needs.