host/frontend/webrtc/display_handler.cpp

/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "host/frontend/webrtc/display_handler.h"

#include <chrono>
#include <functional>
#include <memory>

#include <libyuv.h>

#include "host/frontend/webrtc/libdevice/streamer.h"

namespace cuttlefish {
DisplayHandler::DisplayHandler(webrtc_streaming::Streamer& streamer,
                               ScreenConnector& screen_connector)
    : streamer_(streamer), screen_connector_(screen_connector) {
  screen_connector_.SetCallback(std::move(GetScreenConnectorCallback()));
  screen_connector_.SetDisplayEventCallback([this](const DisplayEvent& event) {
    std::visit(
        [this](auto&& e) {
          using T = std::decay_t<decltype(e)>;
          if constexpr (std::is_same_v<DisplayCreatedEvent, T>) {
            LOG(VERBOSE) << "Display:" << e.display_number << " created "
                         << " w:" << e.display_width
                         << " h:" << e.display_height;

            const auto display_number = e.display_number;
            const std::string display_id =
                "display_" + std::to_string(e.display_number);
            auto display = streamer_.AddDisplay(display_id, e.display_width,
                                                e.display_height, 160, true);
            if (!display) {
              LOG(ERROR) << "Failed to create display.";
              return;
            }

            display_sinks_[display_number] = display;
          } else if constexpr (std::is_same_v<DisplayDestroyedEvent, T>) {
            LOG(VERBOSE) << "Display:" << e.display_number << " destroyed.";

            const auto display_number = e.display_number;
            const auto display_id =
                "display_" + std::to_string(e.display_number);
            streamer_.RemoveDisplay(display_id);
            display_sinks_.erase(display_number);
          } else {
            static_assert("Unhandled display event.");
          }
        },
        event);
  });
}

DisplayHandler::GenerateProcessedFrameCallback DisplayHandler::GetScreenConnectorCallback() {
    // only to tell the producer how to create a ProcessedFrame to cache into the queue
    DisplayHandler::GenerateProcessedFrameCallback callback =
        [](std::uint32_t display_number, std::uint32_t frame_width,
           std::uint32_t frame_height, std::uint32_t frame_stride_bytes,
           std::uint8_t* frame_pixels,
           WebRtcScProcessedFrame& processed_frame) {
          processed_frame.display_number_ = display_number;
          processed_frame.buf_ =
              std::make_unique<CvdVideoFrameBuffer>(frame_width, frame_height);
          libyuv::ABGRToI420(
              frame_pixels, frame_stride_bytes, processed_frame.buf_->DataY(),
              processed_frame.buf_->StrideY(), processed_frame.buf_->DataU(),
              processed_frame.buf_->StrideU(), processed_frame.buf_->DataV(),
              processed_frame.buf_->StrideV(), frame_width, frame_height);
          processed_frame.is_success_ = true;
        };
    return callback;
}

[[noreturn]] void DisplayHandler::Loop() {
  for (;;) {
    auto processed_frame = screen_connector_.OnNextFrame();

    std::shared_ptr<CvdVideoFrameBuffer> buffer =
        std::move(processed_frame.buf_);

    const uint32_t display_number = processed_frame.display_number_;
    {
      std::lock_guard<std::mutex> lock(last_buffer_mutex_);
      display_last_buffers_[display_number] =
          std::static_pointer_cast<webrtc_streaming::VideoFrameBuffer>(buffer);
    }
    if (processed_frame.is_success_) {
      SendLastFrame(display_number);
    }
  }
}

void DisplayHandler::SendLastFrame(std::optional<uint32_t> display_number) {
  std::map<uint32_t, std::shared_ptr<webrtc_streaming::VideoFrameBuffer>>
      buffers;
  {
    std::lock_guard<std::mutex> lock(last_buffer_mutex_);
    if (display_number) {
      // Resend the last buffer for a single display.
      auto last_buffer_it = display_last_buffers_.find(*display_number);
      if (last_buffer_it == display_last_buffers_.end()) {
        return;
      }
      auto& last_buffer = last_buffer_it->second;
      if (!last_buffer) {
        return;
      }
      buffers[*display_number] = last_buffer;
    } else {
      // Resend the last buffer for all displays.
      buffers = display_last_buffers_;
    }
  }
  if (buffers.empty()) {
    // If a connection request arrives before the first frame is available don't
    // send any frame.
    return;
  }
  {
    // SendLastFrame can be called from multiple threads simultaneously, locking
    // here avoids injecting frames with the timestamps in the wrong order.
    std::lock_guard<std::mutex> lock(next_frame_mutex_);
    int64_t time_stamp =
        std::chrono::duration_cast<std::chrono::microseconds>(
            std::chrono::system_clock::now().time_since_epoch())
            .count();

    for (const auto& [display_number, buffer] : buffers) {
      auto it = display_sinks_.find(display_number);
      if (it != display_sinks_.end()) {
        it->second->OnFrame(buffer, time_stamp);
      }
    }
  }
}

}  // namespace cuttlefish