Add metal view, shaders and renderer.

webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.mm

+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import "RTCMTLNV12Renderer.h"
+
+#import <Metal/Metal.h>
+#import <MetalKit/MetalKit.h>
+
+#import "WebRTC/RTCLogging.h"
+#import "WebRTC/RTCVideoFrame.h"
+
+#include "webrtc/api/video/video_rotation.h"
+
+#define MTL_STRINGIFY(s) @ #s
+
+// As defined in shaderSource.
+static NSString *const vertexFunctionName = @"vertexPassthrough";
+static NSString *const fragmentFunctionName = @"fragmentColorConversion";
+
+static NSString *const pipelineDescriptorLabel = @"RTCPipeline";
+static NSString *const commandBufferLabel = @"RTCCommandBuffer";
+static NSString *const renderEncoderLabel = @"RTCEncoder";
+static NSString *const renderEncoderDebugGroup = @"RTCDrawFrame";
+
+static const float cubeVertexData[64] = {
+    -1.0, -1.0, 0.0, 1.0, 1.0, -1.0, 1.0, 1.0, -1.0, 1.0, 0.0, 0.0, 1.0, 1.0, 1.0, 0.0,
+
+    // rotation = 90, offset = 16.
+    -1.0, -1.0, 1.0, 1.0, 1.0, -1.0, 1.0, 0.0, -1.0, 1.0, 0.0, 1.0, 1.0, 1.0, 0.0, 0.0,
+
+    // rotation = 180, offset = 32.
+    -1.0, -1.0, 1.0, 0.0, 1.0, -1.0, 0.0, 0.0, -1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 0.0, 1.0,
+
+    // rotation = 270, offset = 48.
+    -1.0, -1.0, 0.0, 0.0, 1.0, -1.0, 0.0, 1.0, -1.0, 1.0, 1.0, 0.0, 1.0, 1.0, 1.0, 1.0,
+};
+
+static inline int offsetForRotation(webrtc::VideoRotation rotation) {
+  switch (rotation) {
+    case webrtc::kVideoRotation_0:
+      return 0;
+    case webrtc::kVideoRotation_90:
+      return 16;
+    case webrtc::kVideoRotation_180:
+      return 32;
+    case webrtc::kVideoRotation_270:
+      return 48;
+  }
+  return 0;
+}
+
+static NSString *const shaderSource = MTL_STRINGIFY(
+    using namespace metal; typedef struct {
+      packed_float2 position;
+      packed_float2 texcoord;
+    } Vertex;
+
+    typedef struct {
+      float4 position[[position]];
+      float2 texcoord;
+    } Varyings;
+
+    vertex Varyings vertexPassthrough(device Vertex * verticies[[buffer(0)]],
+                                      unsigned int vid[[vertex_id]]) {
+      Varyings out;
+      device Vertex &v = verticies[vid];
+      out.position = float4(float2(v.position), 0.0, 1.0);
+      out.texcoord = v.texcoord;
+
+      return out;
+    }
+
+    // Receiving YCrCb textures.
+    fragment half4 fragmentColorConversion(
+        Varyings in[[stage_in]], texture2d<float, access::sample> textureY[[texture(0)]],
+        texture2d<float, access::sample> textureCbCr[[texture(1)]]) {
+      constexpr sampler s(address::clamp_to_edge, filter::linear);
+      float y;
+      float2 uv;
+      y = textureY.sample(s, in.texcoord).r;
+      uv = textureCbCr.sample(s, in.texcoord).rg - float2(0.5, 0.5);
+
+      // Conversion for YUV to rgb from http://www.fourcc.org/fccyvrgb.php
+      float4 out = float4(y + 1.403 * uv.y, y - 0.344 * uv.x - 0.714 * uv.y, y + 1.770 * uv.x, 1.0);
+
+      return half4(out);
+    });
+
+// The max number of command buffers in flight (submitted to GPU).
+// For now setting it up to 1.
+// In future we might use triple buffering method if it improves performance.
+static const NSInteger kMaxInflightBuffers = 1;
+
+@implementation RTCMTLNV12Renderer {
+  __kindof MTKView *_view;
+
+  // Controller.
+  dispatch_semaphore_t _inflight_semaphore;
+
+  // Renderer.
+  id<MTLDevice> _device;
+  id<MTLCommandQueue> _commandQueue;
+  id<MTLLibrary> _defaultLibrary;
+  id<MTLRenderPipelineState> _pipelineState;
+
+  // Textures.
+  CVMetalTextureCacheRef _textureCache;
+  id<MTLTexture> _yTexture;
+  id<MTLTexture> _CrCbTexture;
+
+  // Buffers.
+  id<MTLBuffer> _vertexBuffer;
+
+  // RTC Frame parameters.
+  int _offset;
+}
+
+- (instancetype)init {
+  if (self = [super init]) {
+    // _offset of 0 is equal to rotation of 0.
+    _offset = 0;
+    _inflight_semaphore = dispatch_semaphore_create(kMaxInflightBuffers);
+  }
+
+  return self;
+}
+
+- (BOOL)addRenderingDestination:(__kindof MTKView *)view {
+  return [self setupWithView:view];
+}
+
+#pragma mark - Private
+
+- (BOOL)setupWithView:(__kindof MTKView *)view {
+  BOOL success = NO;
+  if ([self setupMetal]) {
+    [self setupView:view];
+    [self loadAssets];
+    [self setupBuffers];
+    [self initializeTextureCache];
+    success = YES;
+  }
+  return success;
+}
+
+#pragma mark - GPU methods
+
+- (BOOL)setupMetal {
+  // Set the view to use the default device.
+  _device = MTLCreateSystemDefaultDevice();
+  if (!_device) {
+    return NO;
+  }
+
+  // Create a new command queue.
+  _commandQueue = [_device newCommandQueue];
+
+  // Load metal library from source.
+  NSError *libraryError = nil;
+
+  id<MTLLibrary> sourceLibrary =
+      [_device newLibraryWithSource:shaderSource options:NULL error:&libraryError];
+
+  if (libraryError) {
+    RTCLogError(@"Metal: Library with source failed\n%@", libraryError);
+    return NO;
+  }
+
+  if (!sourceLibrary) {
+    RTCLogError(@"Metal: Failed to load library. %@", libraryError);
+    return NO;
+  }
+  _defaultLibrary = sourceLibrary;
+
+  return YES;
+}
+
+- (void)setupView:(__kindof MTKView *)view {
+  view.device = _device;
+
+  view.preferredFramesPerSecond = 30;
+  view.autoResizeDrawable = NO;
+
+  // We need to keep reference to the view as it's needed down the rendering pipeline.
+  _view = view;
+}
+
+- (void)loadAssets {
+  id<MTLFunction> vertexFunction = [_defaultLibrary newFunctionWithName:vertexFunctionName];
+  id<MTLFunction> fragmentFunction =
+      [_defaultLibrary newFunctionWithName:fragmentFunctionName];
+
+  MTLRenderPipelineDescriptor *pipelineDescriptor = [[MTLRenderPipelineDescriptor alloc] init];
+  pipelineDescriptor.label = pipelineDescriptorLabel;
+  pipelineDescriptor.vertexFunction = vertexFunction;
+  pipelineDescriptor.fragmentFunction = fragmentFunction;
+  pipelineDescriptor.colorAttachments[0].pixelFormat = _view.colorPixelFormat;
+  pipelineDescriptor.depthAttachmentPixelFormat = MTLPixelFormatInvalid;
+  NSError *error = nil;
+  _pipelineState = [_device newRenderPipelineStateWithDescriptor:pipelineDescriptor error:&error];
+
+  if (!_pipelineState) {
+    RTCLogError(@"Metal: Failed to create pipeline state. %@", error);
+  }
+}
+
+- (void)setupBuffers {
+  _vertexBuffer = [_device newBufferWithBytes:cubeVertexData
+                                       length:sizeof(cubeVertexData)
+                                      options:MTLResourceOptionCPUCacheModeDefault];
+}
+
+- (void)initializeTextureCache {
+  CVReturn status =
+      CVMetalTextureCacheCreate(kCFAllocatorDefault, nil, _device, nil, &_textureCache);
+  if (status != kCVReturnSuccess) {
+    RTCLogError(@"Metal: Failed to initialize metal texture cache. Return status is %d", status);
+  }
+}
+
+- (void)render {
+  // Wait until the inflight (curently sent to GPU) command buffer
+  // has completed the GPU work.
+  dispatch_semaphore_wait(_inflight_semaphore, DISPATCH_TIME_FOREVER);
+
+  id<MTLCommandBuffer> commandBuffer = [_commandQueue commandBuffer];
+  commandBuffer.label = commandBufferLabel;
+
+  __block dispatch_semaphore_t block_semaphore = _inflight_semaphore;
+  [commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> _Nonnull) {
+    // GPU work completed.
+    dispatch_semaphore_signal(block_semaphore);
+  }];
+
+  MTLRenderPassDescriptor *_renderPassDescriptor = _view.currentRenderPassDescriptor;
+  if (_renderPassDescriptor) {  // Valid drawable.
+    id<MTLRenderCommandEncoder> renderEncoder =
+        [commandBuffer renderCommandEncoderWithDescriptor:_renderPassDescriptor];
+    renderEncoder.label = renderEncoderLabel;
+
+    // Set context state.
+    [renderEncoder pushDebugGroup:renderEncoderDebugGroup];
+    [renderEncoder setRenderPipelineState:_pipelineState];
+    [renderEncoder setVertexBuffer:_vertexBuffer offset:_offset * sizeof(float) atIndex:0];
+    [renderEncoder setFragmentTexture:_yTexture atIndex:0];
+    [renderEncoder setFragmentTexture:_CrCbTexture atIndex:1];
+
+    [renderEncoder drawPrimitives:MTLPrimitiveTypeTriangleStrip
+                      vertexStart:0
+                      vertexCount:4
+                    instanceCount:1];
+    [renderEncoder popDebugGroup];
+    [renderEncoder endEncoding];
+
+    [commandBuffer presentDrawable:_view.currentDrawable];
+  }
+
+  // CPU work is completed, GPU work can be started.
+  [commandBuffer commit];
+}
+
+#pragma mark - RTCMTLRenderer
+
+- (void)drawFrame:(RTCVideoFrame *)frame {
+  [self setupTexturesForFrame:frame];
+  @autoreleasepool {
+    [self render];
+  }
+}
+
+- (void)setupTexturesForFrame:(nonnull RTCVideoFrame *)frame {
+  CVPixelBufferRef pixelBuffer = frame.nativeHandle;
+
+  id<MTLTexture> lumaTexture = nil;
+  id<MTLTexture> chromaTexture = nil;
+  CVMetalTextureRef outTexture = nullptr;
+
+  // Luma (y) texture.
+  int lumaWidth = CVPixelBufferGetWidthOfPlane(pixelBuffer, 0);
+  int lumaHeight = CVPixelBufferGetHeightOfPlane(pixelBuffer, 0);
+
+  int indexPlane = 0;
+  CVReturn result = CVMetalTextureCacheCreateTextureFromImage(
+      kCFAllocatorDefault, _textureCache, pixelBuffer, nil, MTLPixelFormatR8Unorm, lumaWidth,
+      lumaHeight, indexPlane, &outTexture);
+
+  if (result == kCVReturnSuccess) {
+    lumaTexture = CVMetalTextureGetTexture(outTexture);
+  }
+
+  // Same as CFRelease except it can be passed NULL without crashing.
+  CVBufferRelease(outTexture);
+  outTexture = nullptr;
+
+  // Chroma (CrCb) texture.
+  indexPlane = 1;
+  result = CVMetalTextureCacheCreateTextureFromImage(
+      kCFAllocatorDefault, _textureCache, pixelBuffer, nil, MTLPixelFormatRG8Unorm, lumaWidth / 2,
+      lumaHeight / 2, indexPlane, &outTexture);
+  if (result == kCVReturnSuccess) {
+    chromaTexture = CVMetalTextureGetTexture(outTexture);
+  }
+  CVBufferRelease(outTexture);
+
+  if (lumaTexture != nil && chromaTexture != nil) {
+    _yTexture = lumaTexture;
+    _CrCbTexture = chromaTexture;
+    _offset = offsetForRotation((webrtc::VideoRotation)frame.rotation);
+  }
+}
+
+@end