func apply(to pixelBuffer: CVPixelBuffer) -> CVPixelBuffer { var cvTexture: CVMetalTexture? CVMetalTextureCacheCreateTextureFromImage( nil, textureCache!, pixelBuffer, nil, .bgra8Unorm, CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer), 0, &cvTexture ) guard let texture = CVMetalTextureGetTexture(cvTexture!) else { return pixelBuffer } let commandBuffer = commandQueue.makeCommandBuffer()! // render pass: main texture + overlayTexture on top // ... commandBuffer.commit() commandBuffer.waitUntilCompleted() return pixelBuffer } 

}

</details>

The logo (overlayTexture) is loaded once at session start from a PNG with alpha channel. Do not load UIImage every frame — that adds 2–3ms per call.

## How to Implement Text Overlay Without FPS Loss?

Static text (channel name) is simply a Metal texture prepared via CoreText. Dynamic text (viewer count, donation messages) cannot be rendered directly by Metal because Metal doesn't draw text. The solution: create an offscreen CALayer with CATextLayer, render it into a UIGraphicsImageRenderer, get a UIImage, convert to MTLTexture. Do this on a background thread at most once every 500ms for counters and event-driven for donation messages.

Fade-in/fade-out for donation text is implemented by changing the alpha channel of the MTLTexture between frames — smooth appearance over 15–20 frames (0.5–0.7 seconds).

## Step-by-Step Implementation Guide

1. **Set up Metal device and command queue**: Initialize MTLDevice and MTLCommandQueue.
2. **Create texture cache**: Use CVMetalTextureCacheCreate to link CVPixelBuffer with Metal textures.
3. **Load overlay image**: Convert PNG to MTLTexture with alpha.
4. **Render pass**: In AVCaptureVideoDataOutputSampleBufferDelegate, get the pixel buffer, apply overlay via Metal render pass.
5. **Commit and encode**: The modified buffer goes to video encoder.

## Android Overlay: OpenGL ES vs Vulkan

The Android equivalent is SurfaceTexture + OpenGL ES 2.0. The camera renders into a SurfaceTexture, we overlay using GLES20.glBlendFunc, and the result goes to MediaCodec via a Surface. Vulkan is more powerful but requires Android 7+ and more boilerplate. We recommend OpenGL ES for compatibility, Vulkan for complex effects. Comparison:

| Parameter | OpenGL ES 2.0 | Vulkan |
|----------|---------------|--------|
| Minimum Android version | 2.2 (API 8) | 7.0 (API 24) |
| Performance | Sufficient for 1080p30 | Higher but overkill |
| Implementation complexity | Medium | High |
| Recommended for | Most projects | Special effects |

OpenGL ES is 2–3x simpler to implement than Vulkan while providing sufficient performance for most mobile streaming video overlay use cases. For specific video text overlay on Android, OpenGL ES provides adequate performance.

Overlay position is stored in relative coordinates (0.0–1.0 of frame size), which works correctly when resolution or orientation changes. For landscape rotation, the overlayRect of the render pass is recalculated automatically.

In Metal development, we always prioritize GPU-based solutions to avoid CPU bottlenecks. Similarly, in iOS streaming and Android streaming, overlay integration must be done at the buffer level.

## What's Included in Our Work: Deliverables

We provide a turnkey solution including:
- Code and architecture documentation
- Repository access with CI/CD pipeline
- Your team training on working with the code
- 3 months of technical support
- A separate maintenance contract upon request

## Timelines and Cost

Static logo + Metal pipeline on iOS: 1–1.5 weeks ($3,000–$5,000). Dynamic text, overlay animations, iOS + Android: 3–4 weeks ($8,000–$12,000). Cost is calculated individually after project evaluation. Development cost reduction — up to 40% compared to non-optimized solutions. We have 10+ years of experience in mobile development and 50+ successful streaming projects. We guarantee quality and deadline adherence.

For more details about the technology, see the official [Metal](https://developer.apple.com/documentation/metal) and [OpenGL ES](https://www.khronos.org/opengles/) documentation. Contact us for a project discussion. Request a consultation on optimizing your streaming pipeline — we will help integrate overlays without performance loss.