remoting/codec/webrtc_video_encoder_vpx.cc

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "remoting/codec/webrtc_video_encoder_vpx.h"

#include <algorithm>
#include <utility>

#include "base/bind.h"
#include "base/callback.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/system/sys_info.h"
#include "build/build_config.h"
#include "build/chromeos_buildflags.h"
#include "remoting/base/util.h"
#include "remoting/proto/video.pb.h"
#include "third_party/libvpx/source/libvpx/vpx/vp8cx.h"
#include "third_party/libvpx/source/libvpx/vpx/vpx_encoder.h"
#include "third_party/libyuv/include/libyuv/convert_from_argb.h"
#include "third_party/webrtc/modules/desktop_capture/desktop_frame.h"
#include "third_party/webrtc/modules/desktop_capture/desktop_geometry.h"
#include "third_party/webrtc/modules/desktop_capture/desktop_region.h"

namespace remoting {

namespace {

// Number of bytes in an RGBx pixel.
const int kBytesPerRgbPixel = 4;

// Defines the dimension of a macro block. This is used to compute the active
// map for the encoder.
const int kMacroBlockSize = 16;

// Magic encoder profile numbers for I420 and I444 input formats.
const int kVp9I420ProfileNumber = 0;
const int kVp9I444ProfileNumber = 1;

// Magic encoder constants for adaptive quantization strategy.
const int kVp9AqModeNone = 0;
const int kVp9AqModeCyclicRefresh = 3;

const int kDefaultTargetBitrateKbps = 1000;

// Minimum target bitrate per megapixel. The value is chosen experimentally such
// that when screen is not changing the codec converges to the target quantizer
// above in less than 10 frames.
// TODO(zijiehe): This value is for VP8 only; reconsider the value for VP9.
const int kVp8MinimumTargetBitrateKbpsPerMegapixel = 2500;

void SetCommonCodecParameters(vpx_codec_enc_cfg_t* config,
                              const webrtc::DesktopSize& size) {
  // Use millisecond granularity time base.
  config->g_timebase.num = 1;
  config->g_timebase.den = base::Time::kMicrosecondsPerSecond;

  config->g_w = size.width();
  config->g_h = size.height();
  config->g_pass = VPX_RC_ONE_PASS;

  // Start emitting packets immediately.
  config->g_lag_in_frames = 0;

  // Since the transport layer is reliable, keyframes should not be necessary.
  // However, due to crbug.com/440223, decoding fails after 30,000 non-key
  // frames, so take the hit of an "unnecessary" key-frame every 10,000 frames.
  config->kf_min_dist = 10000;
  config->kf_max_dist = 10000;

  // Allow multiple cores on a system to be used for encoding for
  // performance while at the same time ensuring we do not saturate.
  config->g_threads = (base::SysInfo::NumberOfProcessors() + 1) / 2;

  // Do not drop any frames at encoder.
  config->rc_dropframe_thresh = 0;
  // We do not want variations in bandwidth.
  config->rc_end_usage = VPX_CBR;
  config->rc_undershoot_pct = 100;
  config->rc_overshoot_pct = 15;
}

void SetVp8CodecParameters(vpx_codec_enc_cfg_t* config,
                           const webrtc::DesktopSize& size) {
  SetCommonCodecParameters(config, size);

#if defined(OS_LINUX) && !BUILDFLAG(IS_CHROMEOS_LACROS)
  // On Linux, using too many threads for VP8 encoding has been linked to high
  // CPU usage on machines that are under stress. See http://crbug.com/1151148.
  config->g_threads = std::min(config->g_threads, 2U);
#endif  // defined(OS_LINUX) && !BUILDFLAG(IS_CHROMEOS_LACROS)

  // Value of 2 means using the real time profile. This is basically a
  // redundant option since we explicitly select real time mode when doing
  // encoding.
  config->g_profile = 2;
}

void SetVp9CodecParameters(vpx_codec_enc_cfg_t* config,
                           const webrtc::DesktopSize& size,
                           bool lossless_color,
                           bool lossless_encode) {
  SetCommonCodecParameters(config, size);

  // Configure VP9 for I420 or I444 source frames.
  config->g_profile =
      lossless_color ? kVp9I444ProfileNumber : kVp9I420ProfileNumber;

  if (lossless_encode) {
    // Disable quantization entirely, putting the encoder in "lossless" mode.
    config->rc_min_quantizer = 0;
    config->rc_max_quantizer = 0;
    config->rc_end_usage = VPX_VBR;
  } else {
    config->rc_end_usage = VPX_CBR;
    // In the absence of a good bandwidth estimator set the target bitrate to a
    // conservative default.
    config->rc_target_bitrate = 500;
  }
}

void SetVp8CodecOptions(vpx_codec_ctx_t* codec) {
  // CPUUSED of 16 will have the smallest CPU load. This turns off sub-pixel
  // motion search.
  vpx_codec_err_t ret = vpx_codec_control(codec, VP8E_SET_CPUUSED, 16);
  DCHECK_EQ(VPX_CODEC_OK, ret) << "Failed to set CPUUSED";

  // Use the lowest level of noise sensitivity so as to spend less time
  // on motion estimation and inter-prediction mode.
  ret = vpx_codec_control(codec, VP8E_SET_NOISE_SENSITIVITY, 0);
  DCHECK_EQ(VPX_CODEC_OK, ret) << "Failed to set noise sensitivity";
}

void SetVp9CodecOptions(vpx_codec_ctx_t* codec, bool lossless_encode) {
  // Request the lowest-CPU usage that VP9 supports, which depends on whether
  // we are encoding lossy or lossless.
  // Note that this is configured via the same parameter as for VP8.
  int cpu_used = lossless_encode ? 5 : 6;
  vpx_codec_err_t ret = vpx_codec_control(codec, VP8E_SET_CPUUSED, cpu_used);
  DCHECK_EQ(VPX_CODEC_OK, ret) << "Failed to set CPUUSED";

  // Use the lowest level of noise sensitivity so as to spend less time
  // on motion estimation and inter-prediction mode.
  ret = vpx_codec_control(codec, VP9E_SET_NOISE_SENSITIVITY, 0);
  DCHECK_EQ(VPX_CODEC_OK, ret) << "Failed to set noise sensitivity";

  // Configure the codec to tune it for screen media.
  ret = vpx_codec_control(codec, VP9E_SET_TUNE_CONTENT, VP9E_CONTENT_SCREEN);
  DCHECK_EQ(VPX_CODEC_OK, ret) << "Failed to set screen content mode";

  // Set cyclic refresh (aka "top-off") only for lossy encoding.
  int aq_mode = lossless_encode ? kVp9AqModeNone : kVp9AqModeCyclicRefresh;
  ret = vpx_codec_control(codec, VP9E_SET_AQ_MODE, aq_mode);
  DCHECK_EQ(VPX_CODEC_OK, ret) << "Failed to set aq mode";
}

void FreeImageIfMismatched(bool use_i444,
                           const webrtc::DesktopSize& size,
                           std::unique_ptr<vpx_image_t>* out_image,
                           std::unique_ptr<uint8_t[]>* out_image_buffer) {
  if (*out_image) {
    const vpx_img_fmt_t desired_fmt =
        use_i444 ? VPX_IMG_FMT_I444 : VPX_IMG_FMT_I420;
    if (!size.equals(webrtc::DesktopSize((*out_image)->w, (*out_image)->h)) ||
        (*out_image)->fmt != desired_fmt) {
      out_image_buffer->reset();
      out_image->reset();
    }
  }
}

void CreateImage(bool use_i444,
                 const webrtc::DesktopSize& size,
                 std::unique_ptr<vpx_image_t>* out_image,
                 std::unique_ptr<uint8_t[]>* out_image_buffer) {
  DCHECK(!size.is_empty());
  DCHECK(!*out_image_buffer);
  DCHECK(!*out_image);

  std::unique_ptr<vpx_image_t> image(new vpx_image_t());
  memset(image.get(), 0, sizeof(vpx_image_t));

  // libvpx seems to require both to be assigned.
  image->d_w = size.width();
  image->w = size.width();
  image->d_h = size.height();
  image->h = size.height();

  // libvpx should derive chroma shifts from|fmt| but currently has a bug:
  // https://code.google.com/p/webm/issues/detail?id=627
  if (use_i444) {
    image->fmt = VPX_IMG_FMT_I444;
    image->x_chroma_shift = 0;
    image->y_chroma_shift = 0;
  } else {  // I420
    image->fmt = VPX_IMG_FMT_YV12;
    image->x_chroma_shift = 1;
    image->y_chroma_shift = 1;
  }

  // libyuv's fast-path requires 16-byte aligned pointers and strides, so pad
  // the Y, U and V planes' strides to multiples of 16 bytes.
  const int y_stride = ((image->w - 1) & ~15) + 16;
  const int uv_unaligned_stride = y_stride >> image->x_chroma_shift;
  const int uv_stride = ((uv_unaligned_stride - 1) & ~15) + 16;

  // libvpx accesses the source image in macro blocks, and will over-read
  // if the image is not padded out to the next macroblock: crbug.com/119633.
  // Pad the Y, U and V planes' height out to compensate.
  // Assuming macroblocks are 16x16, aligning the planes' strides above also
  // macroblock aligned them.
  static_assert(kMacroBlockSize == 16, "macroblock_size_not_16");
  const int y_rows =
      ((image->h - 1) & ~(kMacroBlockSize - 1)) + kMacroBlockSize;
  const int uv_rows = y_rows >> image->y_chroma_shift;

  // Allocate a YUV buffer large enough for the aligned data & padding.
  const int buffer_size = y_stride * y_rows + 2 * uv_stride * uv_rows;
  std::unique_ptr<uint8_t[]> image_buffer(new uint8_t[buffer_size]);

  // Reset image value to 128 so we just need to fill in the y plane.
  memset(image_buffer.get(), 128, buffer_size);

  // Fill in the information for |image_|.
  unsigned char* uchar_buffer =
      reinterpret_cast<unsigned char*>(image_buffer.get());
  image->planes[0] = uchar_buffer;
  image->planes[1] = image->planes[0] + y_stride * y_rows;
  image->planes[2] = image->planes[1] + uv_stride * uv_rows;
  image->stride[0] = y_stride;
  image->stride[1] = uv_stride;
  image->stride[2] = uv_stride;

  *out_image = std::move(image);
  *out_image_buffer = std::move(image_buffer);
}

}  // namespace

// static
std::unique_ptr<WebrtcVideoEncoder> WebrtcVideoEncoderVpx::CreateForVP8() {
  LOG(WARNING) << "VP8 video encoder is created.";
  return base::WrapUnique(new WebrtcVideoEncoderVpx(false));
}

// static
std::unique_ptr<WebrtcVideoEncoder> WebrtcVideoEncoderVpx::CreateForVP9() {
  LOG(WARNING) << "VP9 video encoder is created.";
  return base::WrapUnique(new WebrtcVideoEncoderVpx(true));
}

// See
// https://www.webmproject.org/about/faq/#what-are-the-limits-of-vp8-and-vp9-in-terms-of-resolution-datarate-and-framerate
// for the limitations of VP8 / VP9 encoders.
// static
bool WebrtcVideoEncoderVpx::IsSupportedByVP8(
    const WebrtcVideoEncoderSelector::Profile& profile) {
  return profile.resolution.width() <= 16384 &&
         profile.resolution.height() <= 16384;
}

// static
bool WebrtcVideoEncoderVpx::IsSupportedByVP9(
    const WebrtcVideoEncoderSelector::Profile& profile) {
  return profile.resolution.width() <= 65536 &&
         profile.resolution.height() <= 65536;
}

WebrtcVideoEncoderVpx::~WebrtcVideoEncoderVpx() = default;

void WebrtcVideoEncoderVpx::SetTickClockForTests(
    const base::TickClock* tick_clock) {
  clock_ = tick_clock;
}

void WebrtcVideoEncoderVpx::SetLosslessEncode(bool want_lossless) {
  if (use_vp9_ && (want_lossless != lossless_encode_)) {
    lossless_encode_ = want_lossless;
    if (codec_)
      Configure(webrtc::DesktopSize(codec_->config.enc->g_w,
                                    codec_->config.enc->g_h));
  }
}

void WebrtcVideoEncoderVpx::SetLosslessColor(bool want_lossless) {
  if (use_vp9_ && (want_lossless != lossless_color_)) {
    lossless_color_ = want_lossless;
    // TODO(wez): Switch to ConfigureCodec() path once libvpx supports it.
    // See https://code.google.com/p/webm/issues/detail?id=913.
    // if (codec_)
    //  Configure(webrtc::DesktopSize(codec_->config.enc->g_w,
    //                                codec_->config.enc->g_h));
    codec_.reset();
  }
}

void WebrtcVideoEncoderVpx::Encode(std::unique_ptr<webrtc::DesktopFrame> frame,
                                   const FrameParams& params,
                                   EncodeCallback done) {
  // TODO(zijiehe): Replace "if (frame)" with "DCHECK(frame)".
  if (frame) {
    bitrate_filter_.SetFrameSize(frame->size().width(), frame->size().height());
  }

  webrtc::DesktopSize previous_frame_size =
      image_ ? webrtc::DesktopSize(image_->w, image_->h)
             : webrtc::DesktopSize();

  webrtc::DesktopSize frame_size = frame ? frame->size() : previous_frame_size;

  // Don't need to send anything until we get the first non-null frame.
  if (frame_size.is_empty()) {
    std::move(done).Run(EncodeResult::SUCCEEDED, nullptr);
    return;
  }

  DCHECK_GE(frame_size.width(), 32);
  DCHECK_GE(frame_size.height(), 32);

  // Create or reconfigure the codec to match the size of |frame|.
  if (!codec_ || !frame_size.equals(previous_frame_size)) {
    Configure(frame_size);
  }

  UpdateConfig(params);

  vpx_active_map_t act_map;
  act_map.rows = active_map_size_.height();
  act_map.cols = active_map_size_.width();
  act_map.active_map = active_map_.get();

  webrtc::DesktopRegion updated_region;
  // Convert the updated capture data ready for encode.
  PrepareImage(frame.get(), &updated_region);

  // Update active map based on updated region.
  if (params.clear_active_map)
    ClearActiveMap();

  if (params.key_frame)
    updated_region.SetRect(webrtc::DesktopRect::MakeSize(frame_size));

  SetActiveMapFromRegion(updated_region);

  // Apply active map to the encoder.
  if (vpx_codec_control(codec_.get(), VP8E_SET_ACTIVEMAP, &act_map)) {
    LOG(ERROR) << "Unable to apply active map";
  }

  vpx_codec_err_t ret = vpx_codec_encode(
      codec_.get(), image_.get(), 0, params.duration.InMicroseconds(),
      (params.key_frame) ? VPX_EFLAG_FORCE_KF : 0, VPX_DL_REALTIME);
  if (ret != VPX_CODEC_OK) {
      LOG(ERROR) << "Encoding error: " << vpx_codec_err_to_string(ret) << "\n"
                 << "Details: " << vpx_codec_error(codec_.get()) << "\n"
                 << vpx_codec_error_detail(codec_.get());
      // TODO(zijiehe): A more exact error type is preferred.
      std::move(done).Run(EncodeResult::UNKNOWN_ERROR, nullptr);
      return;
  }

  if (!lossless_encode_) {
    // VP8 doesn't return active map, so we assume it's the same on the output
    // as on the input.
    if (use_vp9_) {
      ret = vpx_codec_control(codec_.get(), VP9E_GET_ACTIVEMAP, &act_map);
      DCHECK_EQ(ret, VPX_CODEC_OK)
          << "Failed to fetch active map: " << vpx_codec_err_to_string(ret)
          << "\n";
    }

    UpdateRegionFromActiveMap(&updated_region);
  }

  // Read the encoded data.
  vpx_codec_iter_t iter = nullptr;
  bool got_data = false;

  std::unique_ptr<EncodedFrame> encoded_frame(new EncodedFrame());
  encoded_frame->size = frame_size;
  if (use_vp9_) {
    encoded_frame->codec = webrtc::kVideoCodecVP9;
  } else {
    encoded_frame->codec = webrtc::kVideoCodecVP8;
  }

  while (!got_data) {
    const vpx_codec_cx_pkt_t* vpx_packet =
        vpx_codec_get_cx_data(codec_.get(), &iter);
    if (!vpx_packet)
      continue;

    switch (vpx_packet->kind) {
      case VPX_CODEC_CX_FRAME_PKT: {
        got_data = true;
        // TODO(sergeyu): Avoid copying the data here..
        encoded_frame->data.assign(
            reinterpret_cast<const char*>(vpx_packet->data.frame.buf),
            vpx_packet->data.frame.sz);
        encoded_frame->key_frame =
            vpx_packet->data.frame.flags & VPX_FRAME_IS_KEY;
        CHECK_EQ(vpx_codec_control(codec_.get(), VP8E_GET_LAST_QUANTIZER_64,
                                   &(encoded_frame->quantizer)),
                 VPX_CODEC_OK);
        break;
      }
      default:
        break;
    }
  }

  std::move(done).Run(EncodeResult::SUCCEEDED, std::move(encoded_frame));
}

WebrtcVideoEncoderVpx::WebrtcVideoEncoderVpx(bool use_vp9)
    : use_vp9_(use_vp9),
      clock_(base::DefaultTickClock::GetInstance()),
      bitrate_filter_(kVp8MinimumTargetBitrateKbpsPerMegapixel) {
  // Indicates config is still uninitialized.
  config_.g_timebase.den = 0;
}

void WebrtcVideoEncoderVpx::Configure(const webrtc::DesktopSize& size) {
  DCHECK(use_vp9_ || !lossless_color_);
  DCHECK(use_vp9_ || !lossless_encode_);

  if (use_vp9_) {
    VLOG(0) << "Configuring VP9 encoder with lossless-color="
            << (lossless_color_ ? "true" : "false")
            << ", lossless-encode=" << (lossless_encode_ ? "true" : "false")
            << ".";
  }

  // Tear down |image_| if it no longer matches the size and color settings.
  // PrepareImage() will then create a new buffer of the required dimensions if
  // |image_| is not allocated.
  FreeImageIfMismatched(lossless_color_, size, &image_, &image_buffer_);

  // Initialize active map.
  active_map_size_ = webrtc::DesktopSize(
      (size.width() + kMacroBlockSize - 1) / kMacroBlockSize,
      (size.height() + kMacroBlockSize - 1) / kMacroBlockSize);
  active_map_.reset(
      new uint8_t[active_map_size_.width() * active_map_size_.height()]);
  ClearActiveMap();

  // TODO(wez): Remove this hack once VPX can handle frame size reconfiguration.
  // See https://code.google.com/p/webm/issues/detail?id=912.
  if (codec_) {
    // If the frame size has changed then force re-creation of the codec.
    if (codec_->config.enc->g_w != static_cast<unsigned int>(size.width()) ||
        codec_->config.enc->g_h != static_cast<unsigned int>(size.height())) {
      codec_.reset();
    }
  }

  // Fetch a default configuration for the desired codec.
  const vpx_codec_iface_t* interface =
      use_vp9_ ? vpx_codec_vp9_cx() : vpx_codec_vp8_cx();
  vpx_codec_err_t ret = vpx_codec_enc_config_default(interface, &config_, 0);
  DCHECK_EQ(VPX_CODEC_OK, ret) << "Failed to fetch default configuration";

  // Customize the default configuration to our needs.
  if (use_vp9_) {
    SetVp9CodecParameters(&config_, size, lossless_color_, lossless_encode_);
  } else {
    SetVp8CodecParameters(&config_, size);
  }

  config_.rc_target_bitrate = kDefaultTargetBitrateKbps;

  // Initialize or re-configure the codec with the custom configuration.
  if (!codec_) {
    codec_.reset(new vpx_codec_ctx_t);
    ret = vpx_codec_enc_init(codec_.get(), interface, &config_, 0);
    CHECK_EQ(VPX_CODEC_OK, ret) << "Failed to initialize codec";
  } else {
    ret = vpx_codec_enc_config_set(codec_.get(), &config_);
    CHECK_EQ(VPX_CODEC_OK, ret) << "Failed to reconfigure codec";
  }

  // Apply further customizations to the codec now it's initialized.
  if (use_vp9_) {
    SetVp9CodecOptions(codec_.get(), lossless_encode_);
  } else {
    SetVp8CodecOptions(codec_.get());
  }
}

void WebrtcVideoEncoderVpx::UpdateConfig(const FrameParams& params) {
  // Configuration not initialized.
  if (config_.g_timebase.den == 0)
    return;

  bool changed = false;

  if (params.bitrate_kbps >= 0) {
    bitrate_filter_.SetBandwidthEstimateKbps(params.bitrate_kbps);
    if (config_.rc_target_bitrate !=
        static_cast<unsigned int>(bitrate_filter_.GetTargetBitrateKbps())) {
      config_.rc_target_bitrate = bitrate_filter_.GetTargetBitrateKbps();
      changed = true;
    }
  }

  if (params.vpx_min_quantizer >= 0 &&
      config_.rc_min_quantizer !=
          static_cast<unsigned int>(params.vpx_min_quantizer)) {
    config_.rc_min_quantizer = params.vpx_min_quantizer;
    changed = true;
  }

  if (params.vpx_max_quantizer >= 0 &&
      config_.rc_max_quantizer !=
          static_cast<unsigned int>(params.vpx_max_quantizer)) {
    config_.rc_max_quantizer = params.vpx_max_quantizer;
    changed = true;
  }

  if (!changed)
    return;

  // Update encoder context.
  if (vpx_codec_enc_config_set(codec_.get(), &config_))
    NOTREACHED() << "Unable to set encoder config";

}

void WebrtcVideoEncoderVpx::PrepareImage(
    const webrtc::DesktopFrame* frame,
    webrtc::DesktopRegion* updated_region) {
  updated_region->Clear();

  if (!frame) {
    return;
  }

  if (image_) {
    // Pad each rectangle to avoid the block-artifact filters in libvpx from
    // introducing artifacts; VP9 includes up to 8px either side, and VP8 up to
    // 3px, so unchanged pixels up to that far out may still be affected by the
    // changes in the updated region, and so must be listed in the active map.
    // After padding we align each rectangle to 16x16 active-map macroblocks.
    // This implicitly ensures all rects have even top-left coords, which is
    // is required by ConvertRGBToYUVWithRect().
    // TODO(wez): Do we still need 16x16 align, or is even alignment sufficient?
    int padding = use_vp9_ ? 8 : 3;
    for (webrtc::DesktopRegion::Iterator r(frame->updated_region());
         !r.IsAtEnd(); r.Advance()) {
      const webrtc::DesktopRect& rect = r.rect();
      updated_region->AddRect(AlignRect(webrtc::DesktopRect::MakeLTRB(
          rect.left() - padding, rect.top() - padding, rect.right() + padding,
          rect.bottom() + padding)));
    }

    // Clip back to the screen dimensions, in case they're not macroblock
    // aligned. The conversion routines don't require even width & height,
    // so this is safe even if the source dimensions are not even.
    updated_region->IntersectWith(
        webrtc::DesktopRect::MakeWH(image_->w, image_->h));
  } else {
    CreateImage(lossless_color_, frame->size(), &image_, &image_buffer_);
    updated_region->AddRect(webrtc::DesktopRect::MakeWH(image_->w, image_->h));
  }

  // Convert the updated region to YUV ready for encoding.
  const uint8_t* rgb_data = frame->data();
  const int rgb_stride = frame->stride();
  const int y_stride = image_->stride[0];
  DCHECK_EQ(image_->stride[1], image_->stride[2]);
  const int uv_stride = image_->stride[1];
  uint8_t* y_data = image_->planes[0];
  uint8_t* u_data = image_->planes[1];
  uint8_t* v_data = image_->planes[2];

  switch (image_->fmt) {
    case VPX_IMG_FMT_I444:
      for (webrtc::DesktopRegion::Iterator r(*updated_region); !r.IsAtEnd();
           r.Advance()) {
        const webrtc::DesktopRect& rect = r.rect();
        int rgb_offset =
            rgb_stride * rect.top() + rect.left() * kBytesPerRgbPixel;
        int yuv_offset = uv_stride * rect.top() + rect.left();
        libyuv::ARGBToI444(rgb_data + rgb_offset, rgb_stride,
                           y_data + yuv_offset, y_stride, u_data + yuv_offset,
                           uv_stride, v_data + yuv_offset, uv_stride,
                           rect.width(), rect.height());
      }
      break;
    case VPX_IMG_FMT_YV12:
      for (webrtc::DesktopRegion::Iterator r(*updated_region); !r.IsAtEnd();
           r.Advance()) {
        const webrtc::DesktopRect& rect = r.rect();
        int rgb_offset =
            rgb_stride * rect.top() + rect.left() * kBytesPerRgbPixel;
        int y_offset = y_stride * rect.top() + rect.left();
        int uv_offset = uv_stride * rect.top() / 2 + rect.left() / 2;
        libyuv::ARGBToI420(rgb_data + rgb_offset, rgb_stride, y_data + y_offset,
                           y_stride, u_data + uv_offset, uv_stride,
                           v_data + uv_offset, uv_stride, rect.width(),
                           rect.height());
      }
      break;
    default:
      NOTREACHED();
      break;
  }
}

void WebrtcVideoEncoderVpx::ClearActiveMap() {
  DCHECK(active_map_);
  // Clear active map first.
  memset(active_map_.get(), 0,
         active_map_size_.width() * active_map_size_.height());
}

void WebrtcVideoEncoderVpx::SetActiveMapFromRegion(
    const webrtc::DesktopRegion& updated_region) {
  // Mark updated areas active.
  for (webrtc::DesktopRegion::Iterator r(updated_region); !r.IsAtEnd();
       r.Advance()) {
    const webrtc::DesktopRect& rect = r.rect();
    int left = rect.left() / kMacroBlockSize;
    int right = (rect.right() - 1) / kMacroBlockSize;
    int top = rect.top() / kMacroBlockSize;
    int bottom = (rect.bottom() - 1) / kMacroBlockSize;
    DCHECK_LT(right, active_map_size_.width());
    DCHECK_LT(bottom, active_map_size_.height());

    uint8_t* map = active_map_.get() + top * active_map_size_.width();
    for (int y = top; y <= bottom; ++y) {
      for (int x = left; x <= right; ++x)
        map[x] = 1;
      map += active_map_size_.width();
    }
  }
}

void WebrtcVideoEncoderVpx::UpdateRegionFromActiveMap(
    webrtc::DesktopRegion* updated_region) {
  const uint8_t* map = active_map_.get();
  for (int y = 0; y < active_map_size_.height(); ++y) {
    for (int x0 = 0; x0 < active_map_size_.width();) {
      int x1 = x0;
      for (; x1 < active_map_size_.width(); ++x1) {
        if (map[y * active_map_size_.width() + x1] == 0)
          break;
      }
      if (x1 > x0) {
        updated_region->AddRect(webrtc::DesktopRect::MakeLTRB(
            kMacroBlockSize * x0, kMacroBlockSize * y, kMacroBlockSize * x1,
            kMacroBlockSize * (y + 1)));
      }
      x0 = x1 + 1;
    }
  }
  updated_region->IntersectWith(
      webrtc::DesktopRect::MakeWH(image_->w, image_->h));
}

}  // namespace remoting