Implement H264 codec in Objective-C classes.

webrtc/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoDecoderH264.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 "WebRTC/RTCVideoCodecH264.h"
+
+#import <VideoToolbox/VideoToolbox.h>
+
+#if defined(WEBRTC_IOS)
+#import "Common/RTCUIApplicationStatusObserver.h"
+#endif
+#import "WebRTC/RTCVideoFrame.h"
+#import "WebRTC/RTCVideoFrameBuffer.h"
+#import "helpers.h"
+
+#include "webrtc/modules/video_coding/include/video_error_codes.h"
+#include "webrtc/rtc_base/checks.h"
+#include "webrtc/rtc_base/logging.h"
+#include "webrtc/rtc_base/timeutils.h"
+#include "webrtc/sdk/objc/Framework/Classes/VideoToolbox/nalu_rewriter.h"
+
+// Struct that we pass to the decoder per frame to decode. We receive it again
+// in the decoder callback.
+struct RTCFrameDecodeParams {
+  RTCFrameDecodeParams(RTCVideoDecoderCallback cb, int64_t ts) : callback(cb), timestamp(ts) {}
+  RTCVideoDecoderCallback callback;
+  int64_t timestamp;
+};
+
+// This is the callback function that VideoToolbox calls when decode is
+// complete.
+void decompressionOutputCallback(void *decoder,
+                                 void *params,
+                                 OSStatus status,
+                                 VTDecodeInfoFlags infoFlags,
+                                 CVImageBufferRef imageBuffer,
+                                 CMTime timestamp,
+                                 CMTime duration) {
+  std::unique_ptr<RTCFrameDecodeParams> decodeParams(
+      reinterpret_cast<RTCFrameDecodeParams *>(params));
+  if (status != noErr) {
+    LOG(LS_ERROR) << "Failed to decode frame. Status: " << status;
+    return;
+  }
+  // TODO(tkchin): Handle CVO properly.
+  RTCCVPixelBuffer *frameBuffer = [[RTCCVPixelBuffer alloc] initWithPixelBuffer:imageBuffer];
+  RTCVideoFrame *decodedFrame =
+      [[RTCVideoFrame alloc] initWithBuffer:frameBuffer
+                                   rotation:RTCVideoRotation_0
+                                timeStampNs:CMTimeGetSeconds(timestamp) * rtc::kNumNanosecsPerSec];
+  decodedFrame.timeStamp = decodeParams->timestamp;
+  decodeParams->callback(decodedFrame);
+}
+
+// Decoder.
+@implementation RTCVideoDecoderH264 {
+  CMVideoFormatDescriptionRef _videoFormat;
+  VTDecompressionSessionRef _decompressionSession;
+  RTCVideoDecoderCallback _callback;
+}
+
+- (instancetype)init {
+  if (self = [super init]) {
+  }
+  return self;
+}
+
+- (int)initDecodeWithSettings:(RTCVideoEncoderSettings *)settings numberOfCores:(int)numberOfCores {
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+- (void)dealloc {
+  [self destroyDecompressionSession];
+  [self setVideoFormat:nullptr];
+}
+
+- (void)setCallback:(RTCVideoDecoderCallback)callback {
+  _callback = callback;
+}
+
+- (int32_t)releaseDecode {
+  // Need to invalidate the session so that callbacks no longer occur and it
+  // is safe to null out the callback.
+  [self destroyDecompressionSession];
+  [self setVideoFormat:nullptr];
+  _callback = nullptr;
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+- (int)decode:(RTCEncodedImage *)inputImage
+          missingFrames:(BOOL)missingFrames
+    fragmentationHeader:(RTCRtpFragmentationHeader *)fragmentationHeader
+      codecSpecificInfo:(__nullable id<RTCCodecSpecificInfo>)info
+           renderTimeMs:(int64_t)renderTimeMs {
+  RTC_DCHECK(inputImage.buffer);
+
+#if defined(WEBRTC_IOS)
+  if (![[RTCUIApplicationStatusObserver sharedInstance] isApplicationActive]) {
+    // Ignore all decode requests when app isn't active. In this state, the
+    // hardware decoder has been invalidated by the OS.
+    // Reset video format so that we won't process frames until the next
+    // keyframe.
+    [self setVideoFormat:nullptr];
+    return WEBRTC_VIDEO_CODEC_NO_OUTPUT;
+  }
+#endif
+  CMVideoFormatDescriptionRef inputFormat = nullptr;
+  if (webrtc::H264AnnexBBufferHasVideoFormatDescription((uint8_t *)inputImage.buffer.bytes,
+                                                        inputImage.buffer.length)) {
+    inputFormat = webrtc::CreateVideoFormatDescription((uint8_t *)inputImage.buffer.bytes,
+                                                       inputImage.buffer.length);
+    if (inputFormat) {
+      // Check if the video format has changed, and reinitialize decoder if
+      // needed.
+      if (!CMFormatDescriptionEqual(inputFormat, _videoFormat)) {
+        [self setVideoFormat:inputFormat];
+        [self resetDecompressionSession];
+      }
+      CFRelease(inputFormat);
+    }
+  }
+  if (!_videoFormat) {
+    // We received a frame but we don't have format information so we can't
+    // decode it.
+    // This can happen after backgrounding. We need to wait for the next
+    // sps/pps before we can resume so we request a keyframe by returning an
+    // error.
+    LOG(LS_WARNING) << "Missing video format. Frame with sps/pps required.";
+    return WEBRTC_VIDEO_CODEC_ERROR;
+  }
+  CMSampleBufferRef sampleBuffer = nullptr;
+  if (!webrtc::H264AnnexBBufferToCMSampleBuffer((uint8_t *)inputImage.buffer.bytes,
+                                                inputImage.buffer.length,
+                                                _videoFormat,
+                                                &sampleBuffer)) {
+    return WEBRTC_VIDEO_CODEC_ERROR;
+  }
+  RTC_DCHECK(sampleBuffer);
+  VTDecodeFrameFlags decodeFlags = kVTDecodeFrame_EnableAsynchronousDecompression;
+  std::unique_ptr<RTCFrameDecodeParams> frameDecodeParams;
+  frameDecodeParams.reset(new RTCFrameDecodeParams(_callback, inputImage.timeStamp));
+  OSStatus status = VTDecompressionSessionDecodeFrame(
+      _decompressionSession, sampleBuffer, decodeFlags, frameDecodeParams.release(), nullptr);
+#if defined(WEBRTC_IOS)
+  // Re-initialize the decoder if we have an invalid session while the app is
+  // active and retry the decode request.
+  if (status == kVTInvalidSessionErr && [self resetDecompressionSession] == WEBRTC_VIDEO_CODEC_OK) {
+    frameDecodeParams.reset(new RTCFrameDecodeParams(_callback, inputImage.timeStamp));
+    status = VTDecompressionSessionDecodeFrame(
+        _decompressionSession, sampleBuffer, decodeFlags, frameDecodeParams.release(), nullptr);
+  }
+#endif
+  CFRelease(sampleBuffer);
+  if (status != noErr) {
+    LOG(LS_ERROR) << "Failed to decode frame with code: " << status;
+    return WEBRTC_VIDEO_CODEC_ERROR;
+  }
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+#pragma mark - Private
+
+- (void)setVideoFormat:(CMVideoFormatDescriptionRef)videoFormat {
+  if (_videoFormat == videoFormat) {
+    return;
+  }
+  if (_videoFormat) {
+    CFRelease(_videoFormat);
+  }
+  _videoFormat = videoFormat;
+  if (_videoFormat) {
+    CFRetain(_videoFormat);
+  }
+}
+
+- (void)destroyDecompressionSession {
+  if (_decompressionSession) {
+    VTDecompressionSessionInvalidate(_decompressionSession);
+    CFRelease(_decompressionSession);
+    _decompressionSession = nullptr;
+  }
+}
+
+- (int)resetDecompressionSession {
+  [self destroyDecompressionSession];
+
+  // Need to wait for the first SPS to initialize decoder.
+  if (!_videoFormat) {
+    return WEBRTC_VIDEO_CODEC_OK;
+  }
+
+  // Set keys for OpenGL and IOSurface compatibilty, which makes the encoder
+  // create pixel buffers with GPU backed memory. The intent here is to pass
+  // the pixel buffers directly so we avoid a texture upload later during
+  // rendering. This currently is moot because we are converting back to an
+  // I420 frame after decode, but eventually we will be able to plumb
+  // CVPixelBuffers directly to the renderer.
+  // TODO(tkchin): Maybe only set OpenGL/IOSurface keys if we know that that
+  // we can pass CVPixelBuffers as native handles in decoder output.
+  static size_t const attributesSize = 3;
+  CFTypeRef keys[attributesSize] = {
+#if defined(WEBRTC_IOS)
+    kCVPixelBufferOpenGLESCompatibilityKey,
+#elif defined(WEBRTC_MAC)
+    kCVPixelBufferOpenGLCompatibilityKey,
+#endif
+    kCVPixelBufferIOSurfacePropertiesKey,
+    kCVPixelBufferPixelFormatTypeKey
+  };
+  CFDictionaryRef ioSurfaceValue = CreateCFTypeDictionary(nullptr, nullptr, 0);
+  int64_t nv12type = kCVPixelFormatType_420YpCbCr8BiPlanarFullRange;
+  CFNumberRef pixelFormat = CFNumberCreate(nullptr, kCFNumberLongType, &nv12type);
+  CFTypeRef values[attributesSize] = {kCFBooleanTrue, ioSurfaceValue, pixelFormat};
+  CFDictionaryRef attributes = CreateCFTypeDictionary(keys, values, attributesSize);
+  if (ioSurfaceValue) {
+    CFRelease(ioSurfaceValue);
+    ioSurfaceValue = nullptr;
+  }
+  if (pixelFormat) {
+    CFRelease(pixelFormat);
+    pixelFormat = nullptr;
+  }
+  VTDecompressionOutputCallbackRecord record = {
+      decompressionOutputCallback, nullptr,
+  };
+  OSStatus status = VTDecompressionSessionCreate(
+      nullptr, _videoFormat, nullptr, attributes, &record, &_decompressionSession);
+  CFRelease(attributes);
+  if (status != noErr) {
+    [self destroyDecompressionSession];
+    return WEBRTC_VIDEO_CODEC_ERROR;
+  }
+  [self configureDecompressionSession];
+
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+- (void)configureDecompressionSession {
+  RTC_DCHECK(_decompressionSession);
+#if defined(WEBRTC_IOS)
+  VTSessionSetProperty(_decompressionSession, kVTDecompressionPropertyKey_RealTime, kCFBooleanTrue);
+#endif
+}
+
+@end