Add metal view, shaders and renderer.

webrtc/sdk/objc/Framework/Classes/metal/RTCNV12Renderer.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 "RTCNV12Renderer.h"
+
+#import <Metal/Metal.h>
+#import <MetalKit/MetalKit.h>
+
+#import "WebRTC/RTCLogging.h"
+#import "WebRTC/RTCVideoFrame.h"
+
+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(int rotation) {

[tkchin_webrtc, 2017/02/10 23:32:10]

Would rotation be better as an enum? Otherwise defaults to 0 and won't know.

[daniela-webrtc, 2017/02/13 12:32:06]

Done.

+  switch (rotation) {
+    case 0:
+      return 0;
+    case 90:
+      return 16;
+    case 180:
+      return 32;
+    case 270:
+      return 48;
+    default:
+      return 0;
+  }
+}
+
+// The max number of command buffers in flight.
+// For now setting it up to 1.
+// In future we might use tripple buffering method if it improves performance.
+
+static const NSInteger kMaxInflightBuffers = 1;
+
+@interface RTCNV12Renderer ()<MTKViewDelegate>

[tkchin_webrtc, 2017/02/10 23:32:10]

space after ()
() <MTK

+@end
+
+@implementation RTCNV12Renderer {
+  __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)initWithView:(__kindof MTKView *)view {

[tkchin_webrtc, 2017/02/10 23:32:10]

I don't think renderer should have dependency on having a view

[daniela-webrtc, 2017/02/13 12:32:06]

Not sure how to avoid this dependency without exposing some internal
implementation to the outside world. The _view variable needs to be setup
properly in the _setupView method otherwise the render would not work properly.

+  if (self = [super init]) {
+    _view = view;
+
+    // Offset of 0 is equal to rotation of 0.
+    offset = 0;
+    _inflight_semaphore = dispatch_semaphore_create(kMaxInflightBuffers);
+  }
+
+  return self;
+}
+
+- (BOOL)setup {
+  BOOL success = NO;
+  if ([self _setupMetal] && _device) {
+    [self _setupView];

[tkchin_webrtc, 2017/02/10 23:32:10]

don't use _ in method names

If they are meant to be private, stuff them in a #pragma mark - Private section

[daniela-webrtc, 2017/02/13 12:32:06]

This is taken from some of the Apple examples where they use _method to denote
methods involving the GPU and I thought it made sense. Wdyt?

[tkchin_webrtc, 2017/02/14 00:23:55]

I would recommend against it. _ frequently is used to denote private methods in
other codebases, and this could be confusing.
Instead, just place GPU methods in a pragma section.

+    [self _loadAssets];
+    [self _setupBuffers];
+    [self initializeTextureCache];
+    success = YES;
+  }
+  return success;
+}
+
+- (BOOL)_setupMetal {
+  // Set the view to use the default device.
+  _device = MTLCreateSystemDefaultDevice();
+
+  // Create a new command queue.
+  _commandQueue = [_device newCommandQueue];
+
+  // Load all the shader files with a metal file extension in the project.
+  NSError *libraryError = nil;
+  NSBundle *frameworkBundle = [NSBundle bundleWithIdentifier:@"org.webrtc.WebRTC"];

[tkchin_webrtc, 2017/02/10 23:32:10]

This should be a predefined constant somewhere that's globally available

[daniela-webrtc, 2017/02/13 12:32:06]

I'll think a bit how to best implement this. Ideally it would be derived from
the build target in a form of build argument or environmental variable. Do you
perhaps know of some reliable way of doing this?

+  NSString *libraryFile = [frameworkBundle pathForResource:@"rtc_shaders" ofType:@"metallib"];
+  if (!libraryFile) {
+    RTCLog(
+        @"Metal Error: library not found in framework bundle with identifier org.webrtc.WebRTC.");
+    return NO;
+  }
+
+  _defaultLibrary = [_device newLibraryWithFile:libraryFile error:&libraryError];
+  if (!_defaultLibrary) {
+    RTCLog(@"Metal error: Failed to load library. %@", libraryError);
+    return NO;
+  }
+
+  return YES;
+}
+
+- (void)_setupView {
+  _view.device = _device;
+  _view.delegate = self;
+  // This is very important, should not be removed.
+  _view.contentMode = UIViewContentModeScaleAspectFit;
+
+  _view.preferredFramesPerSecond = 30;
+  _view.autoResizeDrawable = NO;
+}
+
+- (void)_loadAssets {
+  // As defined in Shaders.metal.
+  id<MTLFunction> vertexFunction = [_defaultLibrary newFunctionWithName:@"vertexPassthrough"];
+  id<MTLFunction> fragmentFunction =
+      [_defaultLibrary newFunctionWithName:@"fragmentColorConversion"];
+
+  MTLRenderPipelineDescriptor *pipelineDescriptor = [[MTLRenderPipelineDescriptor alloc] init];
+  pipelineDescriptor.label = @"Pipeline";
+  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) {
+    RTCLog(@"Metal error: 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) {
+    RTCLog(@"Metal error: Failed to initialize metal texture cache. Return status is %d", status);
+  }
+}
+
+- (void)_render {
+  dispatch_semaphore_wait(_inflight_semaphore, DISPATCH_TIME_FOREVER);
+
+  id<MTLCommandBuffer> commandBuffer = [_commandQueue commandBuffer];
+  commandBuffer.label = @"RTCCommandBuffer";
+
+  __block dispatch_semaphore_t block_semaphore = _inflight_semaphore;
+  [commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> _Nonnull) {
+    dispatch_semaphore_signal(block_semaphore);
+  }];
+
+  MTLRenderPassDescriptor *_renderPassDescriptor = _view.currentRenderPassDescriptor;
+  if (_renderPassDescriptor) {  // Valid drawable.
+
+    id<MTLRenderCommandEncoder> renderEncoder =
+        [commandBuffer renderCommandEncoderWithDescriptor:_renderPassDescriptor];
+    renderEncoder.label = @"RTCEncoder";
+
+    // Set context state.
+    [renderEncoder pushDebugGroup:@"DrawFrame"];
+    [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];
+  }
+
+  [commandBuffer commit];
+}
+
+#pragma mark - MTKViewDelegate
+
+- (void)drawInMTKView:(MTKView *)view {
+  if (!yTexture && !CrCbTexture) {
+    NSLog(@"No current frame. Aborting drawinFrame:");
+    return;
+  }
+  @autoreleasepool {
+    [self _render];
+  }
+}
+
+- (void)mtkView:(MTKView *)view drawableSizeWillChange:(CGSize)size {
+}
+
+#pragma mark - RTCVideoRenderer

[tkchin_webrtc, 2017/02/10 23:32:10]

nit: newline after pragma

[daniela-webrtc, 2017/02/13 12:32:06]

Done.

+- (void)setSize:(CGSize)size {
+  _view.drawableSize = size;
+  [_view draw];
+}
+
+- (void)renderFrame:(nullable RTCVideoFrame *)frame {
+  if (frame == NULL) {
+    return;
+  }
+  [self setupSyncVariablesForFrame:frame];
+}
+
+- (void)setupSyncVariablesForFrame:(nonnull RTCVideoFrame *)frame {
+  CVPixelBufferRef pixelBuffer = frame.nativeHandle;
+
+  id<MTLTexture> lumaTexture = nil;
+  id<MTLTexture> chromaTexture = nil;
+  CVMetalTextureRef outTexture;
+
+  // 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);
+  }
+
+  CVBufferRelease(outTexture);
+  outTexture = nil;
+
+  // 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) {
+    dispatch_async(dispatch_get_main_queue(), ^{
+      yTexture = lumaTexture;
+      CrCbTexture = chromaTexture;
+      offset = offsetForRotation(frame.rotation);
+    });
+  }
+}
+
+@end