feat: Create C++/OpenGL-based Video Pipeline for more efficient Recording and Frame Processing (#1721)

* Create `VideoPipeline` c++

* Remove folly C++ dependency

* Create `VideoPipeline` HybridClass

* Set up OpenGL

* Add outputs

* Update VideoPipeline.kt

* Bum `minSdkVersion` to `26`

* Create `VideoPipelineOutput`

* Create output funcs

* Set output pipelines

* Add FP/Recording on Output change

* Update VideoPipeline.cpp

* Create `PassThroughShader`

* Try to draw? I have honestly no idea

* fix: Fix `setFrameProcessor` nameclash

* fix: Fix `high-res-sizes` being null

* Add preview output

* Create `OpenGLContext.cpp`

* Make screen red

* This _should_ work (MESSY)

* FINALLY RENDER TEXTURE

* Rotate

* Mirror

* Clean up a bit

* Add `getWidth()`/`getHeight()`

* Cleanup

* fix: Use uniforms instead of attributes

* Draw with passed rotation/mirror mode

* feat: Use SurfaceTexture's transformMatrix in OpenGL pipeline (#1727)

* feat: Use Transform Matrix from SurfaceTexture

* Renam

* feat: Fix OpenGL Shader

* Update VideoPipeline.kt

* Measure elapsed time

* fix: Fix low resolution

* Render to offscreen

* Render to every context

* Release `SurfaceTexture` on close

* Use one OpenGL context to render to multiple EGLSurfaces

* Clean up a bit

* fix: Fix recording pipeline not triggering

* fix: Synchronize close to prevent nulls

* Update OpenGLRenderer.cpp

* fix: Hardcode Android recorder size

android/src/main/cpp/OpenGLContext.cpp

@@ -0,0 +1,133 @@
+//
+// Created by Marc Rousavy on 29.08.23.
+//
+
+#include "OpenGLContext.h"
+
+#include <EGL/egl.h>
+#include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
+
+#include <android/native_window.h>
+#include <android/log.h>
+
+#include "OpenGLError.h"
+
+namespace vision {
+
+std::shared_ptr<OpenGLContext> OpenGLContext::CreateWithOffscreenSurface(int width, int height) {
+  return std::unique_ptr<OpenGLContext>(new OpenGLContext(width, height));
+}
+
+OpenGLContext::OpenGLContext(int width, int height) {
+  _width = width;
+  _height = height;
+}
+
+OpenGLContext::~OpenGLContext() {
+  destroy();
+}
+
+void OpenGLContext::destroy() {
+  if (display != EGL_NO_DISPLAY) {
+    eglMakeCurrent(display, offscreenSurface, offscreenSurface, context);
+    if (offscreenSurface != EGL_NO_SURFACE) {
+      __android_log_print(ANDROID_LOG_INFO, TAG, "Destroying OpenGL Surface...");
+      eglDestroySurface(display, offscreenSurface);
+      offscreenSurface = EGL_NO_SURFACE;
+    }
+    if (context != EGL_NO_CONTEXT) {
+      __android_log_print(ANDROID_LOG_INFO, TAG, "Destroying OpenGL Context...");
+      eglDestroyContext(display, context);
+      context = EGL_NO_CONTEXT;
+    }
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Destroying OpenGL Display...");
+    eglTerminate(display);
+    display = EGL_NO_DISPLAY;
+    config = nullptr;
+  }
+}
+
+void OpenGLContext::ensureOpenGL() {
+  bool successful;
+  // EGLDisplay
+  if (display == EGL_NO_DISPLAY) {
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Initializing EGLDisplay..");
+    display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
+    if (display == EGL_NO_DISPLAY) throw OpenGLError("Failed to get default OpenGL Display!");
+
+    EGLint major;
+    EGLint minor;
+    successful = eglInitialize(display, &major, &minor);
+    if (!successful) throw OpenGLError("Failed to initialize OpenGL!");
+  }
+
+  // EGLConfig
+  if (config == nullptr) {
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Initializing EGLConfig..");
+    EGLint attributes[] = {EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
+                           EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
+                           EGL_ALPHA_SIZE, 8,
+                           EGL_BLUE_SIZE, 8,
+                           EGL_GREEN_SIZE, 8,
+                           EGL_RED_SIZE, 8,
+                           EGL_DEPTH_SIZE, 0,
+                           EGL_STENCIL_SIZE, 0,
+                           EGL_NONE};
+    EGLint numConfigs;
+    successful = eglChooseConfig(display, attributes, &config, 1, &numConfigs);
+    if (!successful || numConfigs == 0) throw OpenGLError("Failed to choose OpenGL config!");
+  }
+
+  // EGLContext
+  if (context == EGL_NO_CONTEXT) {
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Initializing EGLContext..");
+    EGLint contextAttributes[] = {EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE};
+    context = eglCreateContext(display, config, nullptr, contextAttributes);
+    if (context == EGL_NO_CONTEXT) throw OpenGLError("Failed to create OpenGL context!");
+  }
+
+  // EGLSurface
+  if (offscreenSurface == EGL_NO_SURFACE) {
+    // If we don't have a surface at all
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Initializing %i x %i offscreen pbuffer EGLSurface..", _width, _height);
+    EGLint attributes[] = {EGL_WIDTH, _width,
+                           EGL_HEIGHT, _height,
+                           EGL_NONE};
+    offscreenSurface = eglCreatePbufferSurface(display, config, attributes);
+    if (offscreenSurface == EGL_NO_SURFACE) throw OpenGLError("Failed to create OpenGL Surface!");
+  }
+}
+
+void OpenGLContext::use() {
+  this->use(offscreenSurface);
+}
+
+void OpenGLContext::use(EGLSurface surface) {
+  if (surface == EGL_NO_SURFACE) throw OpenGLError("Cannot render to a null Surface!");
+
+  // 1. Make sure the OpenGL context is initialized
+  this->ensureOpenGL();
+
+  // 2. Make the OpenGL context current
+  bool successful = eglMakeCurrent(display, surface, surface, context);
+  if (!successful || eglGetError() != EGL_SUCCESS) throw OpenGLError("Failed to use current OpenGL context!");
+
+  // 3. Caller can now render to this surface
+}
+
+GLuint OpenGLContext::createTexture() {
+  // 1. Make sure the OpenGL context is initialized
+  this->ensureOpenGL();
+
+  // 2. Make the OpenGL context current
+  bool successful = eglMakeCurrent(display, offscreenSurface, offscreenSurface, context);
+  if (!successful || eglGetError() != EGL_SUCCESS) throw OpenGLError("Failed to use current OpenGL context!");
+
+  GLuint textureId;
+  glGenTextures(1, &textureId);
+
+  return textureId;
+}
+
+} // namespace vision

android/src/main/cpp/OpenGLContext.h

@@ -0,0 +1,68 @@
+//
+// Created by Marc Rousavy on 29.08.23.
+//
+
+#pragma once
+
+#include <EGL/egl.h>
+#include <GLES2/gl2.h>
+
+#include <memory>
+#include <functional>
+
+#include "PassThroughShader.h"
+
+namespace vision {
+
+/**
+ * An OpenGL Context that can be used to render to different surfaces.
+ * By default, it creates an off-screen PixelBuffer surface.
+ */
+class OpenGLContext {
+ public:
+  /**
+   * Create a new instance of the OpenGLContext that draws to an off-screen PixelBuffer surface.
+   * This will not perform any OpenGL operations yet, and is therefore safe to call from any Thread.
+   */
+  static std::shared_ptr<OpenGLContext> CreateWithOffscreenSurface(int width, int height);
+  /**
+   * Destroy the OpenGL Context. This needs to be called on the same thread that `use()` was called.
+   */
+  ~OpenGLContext();
+
+  /**
+   * Use this OpenGL Context to render to the given EGLSurface.
+   * After the `renderFunc` returns, the default offscreen PixelBuffer surface becomes active again.
+   */
+  void use(EGLSurface surface);
+
+  /**
+   * Use this OpenGL Context to render to the offscreen PixelBuffer surface.
+   */
+  void use();
+
+  /**
+   * Create a new texture on this context
+   */
+  GLuint createTexture();
+
+ public:
+  EGLDisplay display = EGL_NO_DISPLAY;
+  EGLContext context = EGL_NO_CONTEXT;
+  EGLSurface offscreenSurface = EGL_NO_SURFACE;
+  EGLConfig config = nullptr;
+
+ private:
+  int _width = 0, _height = 0;
+  explicit OpenGLContext(int width, int height);
+  void destroy();
+  void ensureOpenGL();
+
+ private:
+  PassThroughShader _passThroughShader;
+
+ private:
+  static constexpr auto TAG = "OpenGLContext";
+};
+
+} // namespace vision

android/src/main/cpp/OpenGLRenderer.cpp

@@ -0,0 +1,74 @@
+//
+// Created by Marc Rousavy on 29.08.23.
+//
+
+#include "OpenGLRenderer.h"
+
+#include <EGL/egl.h>
+#include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
+
+#include <android/native_window.h>
+#include <android/log.h>
+
+#include <utility>
+
+#include "OpenGLError.h"
+
+namespace vision {
+
+std::unique_ptr<OpenGLRenderer> OpenGLRenderer::CreateWithWindowSurface(std::shared_ptr<OpenGLContext> context, ANativeWindow* surface) {
+  return std::unique_ptr<OpenGLRenderer>(new OpenGLRenderer(std::move(context), surface));
+}
+
+OpenGLRenderer::OpenGLRenderer(std::shared_ptr<OpenGLContext> context, ANativeWindow* surface) {
+  _context = std::move(context);
+  _outputSurface = surface;
+  _width = ANativeWindow_getWidth(surface);
+  _height = ANativeWindow_getHeight(surface);
+}
+
+OpenGLRenderer::~OpenGLRenderer() {
+  if (_outputSurface != nullptr) {
+    ANativeWindow_release(_outputSurface);
+  }
+  destroy();
+}
+
+void OpenGLRenderer::destroy() {
+  if (_context != nullptr && _surface != EGL_NO_DISPLAY) {
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Destroying OpenGL Surface...");
+    eglDestroySurface(_context->display, _surface);
+    _surface = EGL_NO_SURFACE;
+  }
+}
+
+void OpenGLRenderer::renderTextureToSurface(GLuint textureId, float* transformMatrix) {
+  if (_surface == EGL_NO_SURFACE) {
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Creating Window Surface...");
+    _context->use();
+    _surface = eglCreateWindowSurface(_context->display, _context->config, _outputSurface, nullptr);
+  }
+
+  // 1. Activate the OpenGL context for this surface
+  _context->use(_surface);
+
+  // 2. Set the viewport for rendering
+  glViewport(0, 0, _width, _height);
+  glDisable(GL_BLEND);
+
+  // 3. Bind the input texture
+  glBindTexture(GL_TEXTURE_EXTERNAL_OES, textureId);
+  glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+  glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+  glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+  glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+  // 4. Draw it using the pass-through shader which also applies transforms
+  _passThroughShader.draw(textureId, transformMatrix);
+
+  // 5. Swap buffers to pass it to the window surface
+  eglSwapBuffers(_context->display, _surface);
+}
+
+} // namespace vision

android/src/main/cpp/OpenGLRenderer.h

@@ -0,0 +1,58 @@
+//
+// Created by Marc Rousavy on 29.08.23.
+//
+
+#pragma once
+
+#include <EGL/egl.h>
+#include <GLES2/gl2.h>
+#include <android/native_window.h>
+#include <memory>
+#include "PassThroughShader.h"
+
+#include "OpenGLContext.h"
+
+namespace vision {
+
+class OpenGLRenderer {
+ public:
+  /**
+   * Create a new instance of the OpenGLRenderer that draws to an on-screen window surface.
+   * This will not perform any OpenGL operations yet, and is therefore safe to call from any Thread.
+   *
+   * Note: The `surface` is considered moved, and the OpenGL context will release it when it is being deleted.
+   */
+  static std::unique_ptr<OpenGLRenderer> CreateWithWindowSurface(std::shared_ptr<OpenGLContext> context, ANativeWindow* surface);
+  /**
+   * Destroy the OpenGL Context. This needs to be called on the same thread that `use()` was called.
+   */
+  ~OpenGLRenderer();
+
+  /**
+   * Renders the given Texture ID to the Surface
+   */
+  void renderTextureToSurface(GLuint textureId, float* transformMatrix);
+
+  /**
+   * Destroys the OpenGL context. This needs to be called on the same thread that `use()` was called.
+   * After calling `destroy()`, it is legal to call `use()` again, which will re-construct everything.
+   */
+  void destroy();
+
+ private:
+  explicit OpenGLRenderer(std::shared_ptr<OpenGLContext> context, ANativeWindow* surface);
+
+ private:
+  int _width = 0, _height = 0;
+  std::shared_ptr<OpenGLContext> _context;
+  ANativeWindow* _outputSurface;
+  EGLSurface _surface = EGL_NO_SURFACE;
+
+ private:
+  PassThroughShader _passThroughShader;
+
+ private:
+  static constexpr auto TAG = "OpenGLRenderer";
+};
+
+} // namespace vision

android/src/main/cpp/PassThroughShader.cpp

@@ -0,0 +1,119 @@
+//
+// Created by Marc Rousavy on 28.08.23.
+//
+
+#include "PassThroughShader.h"
+#include <EGL/egl.h>
+#include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
+#include <memory>
+#include "OpenGLError.h"
+#include <string>
+
+namespace vision {
+
+PassThroughShader::~PassThroughShader() {
+  if (_programId != NO_SHADER) {
+    glDeleteProgram(_programId);
+    _programId = NO_SHADER;
+  }
+
+  if (_vertexBuffer != NO_BUFFER) {
+    glDeleteBuffers(1, &_vertexBuffer);
+    _vertexBuffer = NO_BUFFER;
+  }
+}
+
+void PassThroughShader::draw(GLuint textureId, float* transformMatrix) {
+  // 1. Set up Shader Program
+  if (_programId == NO_SHADER) {
+    _programId = createProgram();
+  }
+
+  glUseProgram(_programId);
+
+  if (_vertexParameters.aPosition == NO_POSITION) {
+    _vertexParameters = {
+        .aPosition = glGetAttribLocation(_programId, "aPosition"),
+        .aTexCoord = glGetAttribLocation(_programId, "aTexCoord"),
+        .uTransformMatrix = glGetUniformLocation(_programId, "uTransformMatrix"),
+    };
+    _fragmentParameters = {
+        .uTexture = glGetUniformLocation(_programId, "uTexture"),
+    };
+  }
+
+  // 2. Set up Vertices Buffer
+  if (_vertexBuffer == NO_BUFFER) {
+    glGenBuffers(1, &_vertexBuffer);
+    glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(VERTICES), VERTICES, GL_STATIC_DRAW);
+  }
+
+  // 3. Pass all uniforms/attributes for vertex shader
+  glEnableVertexAttribArray(_vertexParameters.aPosition);
+  glVertexAttribPointer(_vertexParameters.aPosition,
+                        2,
+                        GL_FLOAT,
+                        GL_FALSE,
+                        sizeof(Vertex),
+                        reinterpret_cast<void*>(offsetof(Vertex, position)));
+
+  glEnableVertexAttribArray(_vertexParameters.aTexCoord);
+  glVertexAttribPointer(_vertexParameters.aTexCoord,
+                        2,
+                        GL_FLOAT,
+                        GL_FALSE,
+                        sizeof(Vertex),
+                        reinterpret_cast<void*>(offsetof(Vertex, texCoord)));
+
+  glUniformMatrix4fv(_vertexParameters.uTransformMatrix, 1, GL_FALSE, transformMatrix);
+
+  // 4. Pass texture to fragment shader
+  glActiveTexture(GL_TEXTURE0);
+  glBindTexture(GL_TEXTURE_EXTERNAL_OES, textureId);
+  glUniform1i(_fragmentParameters.uTexture, 0);
+
+  // 5. Draw!
+  glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+}
+
+GLuint PassThroughShader::loadShader(GLenum shaderType, const char* shaderCode) {
+  GLuint shader = glCreateShader(shaderType);
+  if (shader == 0) throw OpenGLError("Failed to load shader!");
+
+  glShaderSource(shader, 1, &shaderCode, nullptr);
+  glCompileShader(shader);
+  GLint compileStatus = GL_FALSE;
+  glGetShaderiv(shader, GL_COMPILE_STATUS, &compileStatus);
+  if (compileStatus == GL_FALSE) {
+    glDeleteShader(shader);
+    throw OpenGLError("Failed to compile shader!");
+  }
+  return shader;
+}
+
+GLuint PassThroughShader::createProgram() {
+  GLuint vertexShader = loadShader(GL_VERTEX_SHADER, VERTEX_SHADER);
+  GLuint fragmentShader = loadShader(GL_FRAGMENT_SHADER, FRAGMENT_SHADER);
+
+  GLuint program = glCreateProgram();
+  if (program == 0) throw OpenGLError("Failed to create pass-through program!");
+
+  glAttachShader(program, vertexShader);
+  if (glGetError() != GL_NO_ERROR) throw OpenGLError("Failed to attach Vertex Shader!");
+
+  glAttachShader(program, fragmentShader);
+  if (glGetError() != GL_NO_ERROR) throw OpenGLError("Failed to attach Fragment Shader!");
+
+  glLinkProgram(program);
+  GLint linkStatus = GL_FALSE;
+  glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
+  if (!linkStatus) {
+    glDeleteProgram(program);
+    throw OpenGLError("Failed to load pass-through program!");
+  }
+  return program;
+}
+
+} // namespace vision

android/src/main/cpp/PassThroughShader.h

@@ -0,0 +1,81 @@
+//
+// Created by Marc Rousavy on 28.08.23.
+//
+
+#pragma once
+
+#include <EGL/egl.h>
+#include <GLES2/gl2.h>
+
+namespace vision {
+
+#define NO_SHADER 0
+#define NO_POSITION 0
+#define NO_BUFFER 0
+
+struct Vertex {
+  GLfloat position[2];
+  GLfloat texCoord[2];
+};
+
+class PassThroughShader {
+ public:
+  PassThroughShader() = default;
+  ~PassThroughShader();
+
+  /**
+   * Draw the texture using this shader.
+   */
+  void draw(GLuint textureId, float* transformMatrix);
+
+ private:
+  // Loading
+  static GLuint loadShader(GLenum shaderType, const char* shaderCode);
+  static GLuint createProgram();
+
+ private:
+  // Parameters
+  GLuint _programId = NO_SHADER;
+  GLuint _vertexBuffer = NO_BUFFER;
+  struct VertexParameters {
+    GLint aPosition = NO_POSITION;
+    GLint aTexCoord = NO_POSITION;
+    GLint uTransformMatrix = NO_POSITION;
+  } _vertexParameters;
+  struct FragmentParameters {
+    GLint uTexture = NO_POSITION;
+  } _fragmentParameters;
+
+ private:
+  // Statics
+  static constexpr Vertex VERTICES[] = {
+      {{-1.0f, -1.0f}, {0.0f, 0.0f}}, // bottom-left
+      {{1.0f, -1.0f}, {1.0f, 0.0f}},  // bottom-right
+      {{-1.0f, 1.0f}, {0.0f, 1.0f}},  // top-left
+      {{1.0f, 1.0f}, {1.0f, 1.0f}}    // top-right
+  };
+
+  static constexpr char VERTEX_SHADER[] = R"(
+    attribute vec4 aPosition;
+    attribute vec2 aTexCoord;
+    uniform mat4 uTransformMatrix;
+    varying vec2 vTexCoord;
+
+    void main() {
+        gl_Position = aPosition;
+        vTexCoord = (uTransformMatrix * vec4(aTexCoord, 0.0, 1.0)).xy;
+    }
+  )";
+  static constexpr char FRAGMENT_SHADER[] = R"(
+    #extension GL_OES_EGL_image_external : require
+    precision mediump float;
+    varying vec2 vTexCoord;
+    uniform samplerExternalOES uTexture;
+
+    void main() {
+        gl_FragColor = texture2D(uTexture, vTexCoord);
+    }
+  )";
+};
+
+} // namespace vision

android/src/main/cpp/VideoPipeline.cpp

@@ -0,0 +1,133 @@
+//
+// Created by Marc Rousavy on 25.08.23.
+//
+
+#include "VideoPipeline.h"
+#include "OpenGLError.h"
+
+#include <android/native_window_jni.h>
+#include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
+#include <EGL/egl.h>
+
+namespace vision {
+
+jni::local_ref<VideoPipeline::jhybriddata> VideoPipeline::initHybrid(jni::alias_ref<jhybridobject> jThis, int width, int height) {
+  return makeCxxInstance(jThis, width, height);
+}
+
+VideoPipeline::VideoPipeline(jni::alias_ref<jhybridobject> jThis, int width, int height): _javaPart(jni::make_global(jThis)) {
+  _width = width;
+  _height = height;
+  _context = OpenGLContext::CreateWithOffscreenSurface(width, height);
+}
+
+VideoPipeline::~VideoPipeline() {
+  // 1. Remove output surfaces
+  removeFrameProcessorOutputSurface();
+  removeRecordingSessionOutputSurface();
+  removePreviewOutputSurface();
+  // 2. Delete the input textures
+  if (_inputTextureId != NO_TEXTURE) {
+    glDeleteTextures(1, &_inputTextureId);
+    _inputTextureId = NO_TEXTURE;
+  }
+  // 4. Destroy all surfaces
+  _previewOutput = nullptr;
+  _frameProcessorOutput = nullptr;
+  _recordingSessionOutput = nullptr;
+  // 5. Destroy the OpenGL context
+  _context = nullptr;
+}
+
+void VideoPipeline::removeFrameProcessorOutputSurface() {
+  if (_frameProcessorOutput) _frameProcessorOutput->destroy();
+  _frameProcessorOutput = nullptr;
+}
+
+void VideoPipeline::setFrameProcessorOutputSurface(jobject surface) {
+  // 1. Delete existing output surface
+  removeFrameProcessorOutputSurface();
+
+  // 2. Set new output surface if it is not null
+  ANativeWindow* window = ANativeWindow_fromSurface(jni::Environment::current(), surface);
+  _frameProcessorOutput = OpenGLRenderer::CreateWithWindowSurface(_context, window);
+}
+
+void VideoPipeline::removeRecordingSessionOutputSurface() {
+  if (_recordingSessionOutput) _recordingSessionOutput->destroy();
+  _recordingSessionOutput = nullptr;
+}
+
+void VideoPipeline::setRecordingSessionOutputSurface(jobject surface) {
+  // 1. Delete existing output surface
+  removeRecordingSessionOutputSurface();
+
+  // 2. Set new output surface if it is not null
+  ANativeWindow* window = ANativeWindow_fromSurface(jni::Environment::current(), surface);
+  _recordingSessionOutput = OpenGLRenderer::CreateWithWindowSurface(_context, window);
+}
+
+void VideoPipeline::removePreviewOutputSurface() {
+  if (_previewOutput) _previewOutput->destroy();
+  _previewOutput = nullptr;
+}
+
+void VideoPipeline::setPreviewOutputSurface(jobject surface) {
+  // 1. Delete existing output surface
+  removePreviewOutputSurface();
+
+  // 2. Set new output surface if it is not null
+  ANativeWindow* window = ANativeWindow_fromSurface(jni::Environment::current(), surface);
+  _previewOutput = OpenGLRenderer::CreateWithWindowSurface(_context, window);
+}
+
+int VideoPipeline::getInputTextureId() {
+  if (_inputTextureId != NO_TEXTURE) return static_cast<int>(_inputTextureId);
+
+  _inputTextureId = _context->createTexture();
+
+  return static_cast<int>(_inputTextureId);
+}
+
+void VideoPipeline::onBeforeFrame() {
+  _context->use();
+
+  glBindTexture(GL_TEXTURE_EXTERNAL_OES, _inputTextureId);
+}
+
+void VideoPipeline::onFrame(jni::alias_ref<jni::JArrayFloat> transformMatrixParam) {
+  // Get the OpenGL transform Matrix (transforms, scales, rotations)
+  float transformMatrix[16];
+  transformMatrixParam->getRegion(0, 16, transformMatrix);
+
+  if (_previewOutput) {
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Rendering to Preview..");
+    _previewOutput->renderTextureToSurface(_inputTextureId, transformMatrix);
+  }
+  if (_frameProcessorOutput) {
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Rendering to FrameProcessor..");
+    _frameProcessorOutput->renderTextureToSurface(_inputTextureId, transformMatrix);
+  }
+  if (_recordingSessionOutput) {
+    __android_log_print(ANDROID_LOG_INFO, TAG, "Rendering to RecordingSession..");
+    _recordingSessionOutput->renderTextureToSurface(_inputTextureId, transformMatrix);
+  }
+}
+
+void VideoPipeline::registerNatives() {
+  registerHybrid({
+    makeNativeMethod("initHybrid", VideoPipeline::initHybrid),
+    makeNativeMethod("setFrameProcessorOutputSurface", VideoPipeline::setFrameProcessorOutputSurface),
+    makeNativeMethod("removeFrameProcessorOutputSurface", VideoPipeline::removeFrameProcessorOutputSurface),
+    makeNativeMethod("setRecordingSessionOutputSurface", VideoPipeline::setRecordingSessionOutputSurface),
+    makeNativeMethod("removeRecordingSessionOutputSurface", VideoPipeline::removeRecordingSessionOutputSurface),
+    makeNativeMethod("setPreviewOutputSurface", VideoPipeline::setPreviewOutputSurface),
+    makeNativeMethod("removePreviewOutputSurface", VideoPipeline::removePreviewOutputSurface),
+    makeNativeMethod("getInputTextureId", VideoPipeline::getInputTextureId),
+    makeNativeMethod("onBeforeFrame", VideoPipeline::onBeforeFrame),
+    makeNativeMethod("onFrame", VideoPipeline::onFrame),
+  });
+}
+
+} // namespace vision

android/src/main/cpp/VideoPipeline.h

@@ -0,0 +1,72 @@
+//
+// Created by Marc Rousavy on 25.08.23.
+//
+
+#pragma once
+
+#include <jni.h>
+#include <fbjni/fbjni.h>
+#include <EGL/egl.h>
+#include <android/native_window.h>
+#include "PassThroughShader.h"
+#include "OpenGLRenderer.h"
+#include "OpenGLContext.h"
+#include <memory>
+
+namespace vision {
+
+#define NO_TEXTURE 0
+
+using namespace facebook;
+
+class VideoPipeline: public jni::HybridClass<VideoPipeline> {
+ public:
+  static auto constexpr kJavaDescriptor = "Lcom/mrousavy/camera/utils/VideoPipeline;";
+  static jni::local_ref<jhybriddata> initHybrid(jni::alias_ref<jhybridobject> jThis, int width, int height);
+  static void registerNatives();
+
+ public:
+  ~VideoPipeline();
+
+  // -> SurfaceTexture input
+  int getInputTextureId();
+
+  // <- Frame Processor output
+  void setFrameProcessorOutputSurface(jobject surface);
+  void removeFrameProcessorOutputSurface();
+
+  // <- MediaRecorder output
+  void setRecordingSessionOutputSurface(jobject surface);
+  void removeRecordingSessionOutputSurface();
+
+  // <- Preview output
+  void setPreviewOutputSurface(jobject surface);
+  void removePreviewOutputSurface();
+
+  // Frame callbacks
+  void onBeforeFrame();
+  void onFrame(jni::alias_ref<jni::JArrayFloat> transformMatrix);
+
+ private:
+  // Private constructor. Use `create(..)` to create new instances.
+  explicit VideoPipeline(jni::alias_ref<jhybridobject> jThis, int width, int height);
+
+ private:
+  // Input Surface Texture
+  GLuint _inputTextureId = NO_TEXTURE;
+  int _width = 0;
+  int _height = 0;
+
+  // Output Contexts
+  std::shared_ptr<OpenGLContext> _context = nullptr;
+  std::unique_ptr<OpenGLRenderer> _frameProcessorOutput = nullptr;
+  std::unique_ptr<OpenGLRenderer> _recordingSessionOutput = nullptr;
+  std::unique_ptr<OpenGLRenderer> _previewOutput = nullptr;
+
+ private:
+  friend HybridBase;
+  jni::global_ref<javaobject> _javaPart;
+  static constexpr auto TAG = "VideoPipeline";
+};
+
+} // namespace vision

android/src/main/cpp/VisionCamera.cpp

@@ -5,12 +5,14 @@
 #include "JVisionCameraProxy.h"
 #include "VisionCameraProxy.h"
 #include "SkiaRenderer.h"
+#include "VideoPipeline.h"
 
 JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *) {
   return facebook::jni::initialize(vm, [] {
     vision::VisionCameraInstaller::registerNatives();
     vision::JVisionCameraProxy::registerNatives();
     vision::JVisionCameraScheduler::registerNatives();
+    vision::VideoPipeline::registerNatives();
 #if VISION_CAMERA_ENABLE_FRAME_PROCESSORS
     vision::JFrameProcessor::registerNatives();
 #endif

android/src/main/cpp/frameprocessor/FrameHostObject.cpp

@@ -4,7 +4,6 @@
 
 #include "FrameHostObject.h"
 
-#include <android/log.h>
 #include <fbjni/fbjni.h>
 #include <jni.h>
 

android/src/main/cpp/frameprocessor/FrameHostObject.h

@@ -27,9 +27,6 @@ class JSI_EXPORT FrameHostObject : public jsi::HostObject {
 
  public:
   jni::global_ref<JFrame> frame;
-
- private:
-  static auto constexpr TAG = "VisionCamera";
 };
 
 } // namespace vision

android/src/main/cpp/frameprocessor/JSIJNIConversion.cpp

@@ -68,7 +68,6 @@ jni::local_ref<jni::JMap<jstring, jobject>> JSIJNIConversion::convertJSIObjectTo
 
         auto map = convertJSIObjectToJNIMap(runtime, valueAsObject);
         hashMap->put(key, map);
-
       }
 
     } else {
@@ -139,8 +138,7 @@ jsi::Value JSIJNIConversion::convertJNIObjectToJSIValue(jsi::Runtime &runtime, c
       result.setProperty(runtime, key.c_str(), jsiValue);
     }
     return result;
-
-  } if (object->isInstanceOf(JFrame::javaClassStatic())) {
+  } else if (object->isInstanceOf(JFrame::javaClassStatic())) {
     // Frame
     auto frame = static_ref_cast<JFrame>(object);
 

android/src/main/cpp/frameprocessor/java-bindings/JVisionCameraScheduler.cpp

@@ -22,8 +22,8 @@ void JVisionCameraScheduler::dispatchAsync(const std::function<void()>& job) {
 
 void JVisionCameraScheduler::scheduleTrigger() {
   // 2. schedule `triggerUI` to be called on the java thread
-  static auto method = javaPart_->getClass()->getMethod<void()>("scheduleTrigger");
-  method(javaPart_.get());
+  static auto method = _javaPart->getClass()->getMethod<void()>("scheduleTrigger");
+  method(_javaPart.get());
 }
 
 void JVisionCameraScheduler::trigger() {

android/src/main/cpp/frameprocessor/java-bindings/JVisionCameraScheduler.h

@@ -33,12 +33,12 @@ class JVisionCameraScheduler : public jni::HybridClass<JVisionCameraScheduler> {
 
  private:
   friend HybridBase;
-  jni::global_ref<JVisionCameraScheduler::javaobject> javaPart_;
+  jni::global_ref<JVisionCameraScheduler::javaobject> _javaPart;
   std::queue<std::function<void()>> _jobs;
   std::mutex _mutex;
 
   explicit JVisionCameraScheduler(jni::alias_ref<JVisionCameraScheduler::jhybridobject> jThis):
-    javaPart_(jni::make_global(jThis)) {}
+    _javaPart(jni::make_global(jThis)) {}
 
   // Schedules a call to `trigger` on the VisionCamera FP Thread
   void scheduleTrigger();