modules/video_coding/codecs/vp9/svc_config.cc - src - Git at Google

 /*
  *  Copyright (c) 2018 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.
  */

 #include "modules/video_coding/codecs/vp9/svc_config.h"

 #include <algorithm>
 #include <cmath>
 #include <memory>
 #include <vector>

 #include "media/base/video_common.h"
 #include "modules/video_coding/codecs/vp9/include/vp9_globals.h"
 #include "modules/video_coding/svc/create_scalability_structure.h"
 #include "modules/video_coding/svc/scalability_mode_util.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"

 namespace webrtc {

 namespace {
 const size_t kMinVp9SvcBitrateKbps = 30;

 const size_t kMaxNumLayersForScreenSharing = 3;
 const float kMaxScreenSharingLayerFramerateFps[] = {5.0, 10.0, 30.0};
 const size_t kMinScreenSharingLayerBitrateKbps[] = {30, 200, 500};
 const size_t kTargetScreenSharingLayerBitrateKbps[] = {150, 350, 950};
 const size_t kMaxScreenSharingLayerBitrateKbps[] = {250, 500, 950};

 // Gets limited number of layers for given resolution.
 size_t GetLimitedNumSpatialLayers(size_t width, size_t height) {
   const bool is_landscape = width >= height;
   const size_t min_width = is_landscape ? kMinVp9SpatialLayerLongSideLength
                                         : kMinVp9SpatialLayerShortSideLength;
   const size_t min_height = is_landscape ? kMinVp9SpatialLayerShortSideLength
                                          : kMinVp9SpatialLayerLongSideLength;
   const size_t num_layers_fit_horz = static_cast<size_t>(
       std::floor(1 + std::max(0.0f, std::log2(1.0f * width / min_width))));
   const size_t num_layers_fit_vert = static_cast<size_t>(
       std::floor(1 + std::max(0.0f, std::log2(1.0f * height / min_height))));
   return std::min(num_layers_fit_horz, num_layers_fit_vert);
 }
 }  // namespace

 std::vector<SpatialLayer> ConfigureSvcScreenSharing(size_t input_width,
                                                     size_t input_height,
                                                     float max_framerate_fps,
                                                     size_t num_spatial_layers) {
   num_spatial_layers =
       std::min(num_spatial_layers, kMaxNumLayersForScreenSharing);
   std::vector<SpatialLayer> spatial_layers;

   for (size_t sl_idx = 0; sl_idx < num_spatial_layers; ++sl_idx) {
     SpatialLayer spatial_layer = {0};
     spatial_layer.width = input_width;
     spatial_layer.height = input_height;
     spatial_layer.maxFramerate =
         std::min(kMaxScreenSharingLayerFramerateFps[sl_idx], max_framerate_fps);
     spatial_layer.numberOfTemporalLayers = 1;
     spatial_layer.minBitrate =
         static_cast<int>(kMinScreenSharingLayerBitrateKbps[sl_idx]);
     spatial_layer.maxBitrate =
         static_cast<int>(kMaxScreenSharingLayerBitrateKbps[sl_idx]);
     spatial_layer.targetBitrate =
         static_cast<int>(kTargetScreenSharingLayerBitrateKbps[sl_idx]);
     spatial_layer.active = true;
     spatial_layers.push_back(spatial_layer);
   }

   return spatial_layers;
 }

 std::vector<SpatialLayer> ConfigureSvcNormalVideo(
     size_t input_width,
     size_t input_height,
     float max_framerate_fps,
     size_t first_active_layer,
     size_t num_spatial_layers,
     size_t num_temporal_layers,
     absl::optional<ScalableVideoController::StreamLayersConfig> config) {
   RTC_DCHECK_LT(first_active_layer, num_spatial_layers);

   // Limit number of layers for given resolution.
   size_t limited_num_spatial_layers =
       GetLimitedNumSpatialLayers(input_width, input_height);
   if (limited_num_spatial_layers < num_spatial_layers) {
     RTC_LOG(LS_WARNING) << "Reducing number of spatial layers from "
                         << num_spatial_layers << " to "
                         << limited_num_spatial_layers
                         << " due to low input resolution.";
     num_spatial_layers = limited_num_spatial_layers;
   }

   // First active layer must be configured.
   num_spatial_layers = std::max(num_spatial_layers, first_active_layer + 1);

   // Ensure top layer is even enough.
   int required_divisiblity = 1 << (num_spatial_layers - first_active_layer - 1);
   if (config) {
     required_divisiblity = 1;
     for (size_t sl_idx = 0; sl_idx < num_spatial_layers; ++sl_idx) {
       required_divisiblity = cricket::LeastCommonMultiple(
           required_divisiblity, config->scaling_factor_den[sl_idx]);
     }
   }
   input_width = input_width - input_width % required_divisiblity;
   input_height = input_height - input_height % required_divisiblity;

   std::vector<SpatialLayer> spatial_layers;
   for (size_t sl_idx = first_active_layer; sl_idx < num_spatial_layers;
        ++sl_idx) {
     SpatialLayer spatial_layer = {0};
     spatial_layer.width = input_width >> (num_spatial_layers - sl_idx - 1);
     spatial_layer.height = input_height >> (num_spatial_layers - sl_idx - 1);
     spatial_layer.maxFramerate = max_framerate_fps;
     spatial_layer.numberOfTemporalLayers = num_temporal_layers;
     spatial_layer.active = true;

     if (config) {
       spatial_layer.width = input_width * config->scaling_factor_num[sl_idx] /
                             config->scaling_factor_den[sl_idx];
       spatial_layer.height = input_height * config->scaling_factor_num[sl_idx] /
                              config->scaling_factor_den[sl_idx];
     }

     // minBitrate and maxBitrate formulas were derived from
     // subjective-quality data to determing bit rates below which video
     // quality is unacceptable and above which additional bits do not provide
     // benefit. The formulas express rate in units of kbps.

     // TODO(ssilkin): Add to the comment PSNR/SSIM we get at encoding certain
     // video to min/max bitrate specified by those formulas.
     const size_t num_pixels = spatial_layer.width * spatial_layer.height;
     int min_bitrate =
         static_cast<int>((600. * std::sqrt(num_pixels) - 95000.) / 1000.);
     min_bitrate = std::max(min_bitrate, 0);
     spatial_layer.minBitrate =
         std::max(static_cast<size_t>(min_bitrate), kMinVp9SvcBitrateKbps);
     spatial_layer.maxBitrate =
         static_cast<int>((1.6 * num_pixels + 50 * 1000) / 1000);
     spatial_layer.targetBitrate =
         (spatial_layer.minBitrate + spatial_layer.maxBitrate) / 2;
     spatial_layers.push_back(spatial_layer);
   }

   // A workaround for situation when single HD layer is left with minBitrate
   // about 500kbps. This would mean that there will always be at least 500kbps
   // allocated to video regardless of how low is the actual BWE.
   // Also, boost maxBitrate for the first layer to account for lost ability to
   // predict from previous layers.
   if (first_active_layer > 0) {
     spatial_layers[0].minBitrate = kMinVp9SvcBitrateKbps;
     // TODO(ilnik): tune this value or come up with a different formula to
     // ensure that all singlecast configurations look good and not too much
     // bitrate is added.
     spatial_layers[0].maxBitrate *= 1.1;
   }

   return spatial_layers;
 }

 // Uses scalability mode to configure spatial layers.
 std::vector<SpatialLayer> GetVp9SvcConfig(VideoCodec& codec) {
   RTC_DCHECK_EQ(codec.codecType, kVideoCodecVP9);

   absl::optional<ScalabilityMode> scalability_mode = codec.GetScalabilityMode();
   RTC_DCHECK(scalability_mode.has_value());

   // Limit number of spatial layers for given resolution.
   int limited_num_spatial_layers =
       GetLimitedNumSpatialLayers(codec.width, codec.height);
   if (limited_num_spatial_layers <
       ScalabilityModeToNumSpatialLayers(*scalability_mode)) {
     ScalabilityMode limited_scalability_mode =
         LimitNumSpatialLayers(*scalability_mode, limited_num_spatial_layers);
     RTC_LOG(LS_WARNING)
         << "Reducing number of spatial layers due to low input resolution: "
         << ScalabilityModeToString(*scalability_mode) << " to "
         << ScalabilityModeToString(limited_scalability_mode);
     scalability_mode = limited_scalability_mode;
     codec.SetScalabilityMode(limited_scalability_mode);
   }

   absl::optional<ScalableVideoController::StreamLayersConfig> info =
       ScalabilityStructureConfig(*scalability_mode);
   if (!info.has_value()) {
     RTC_LOG(LS_WARNING) << "Failed to create structure "
                         << ScalabilityModeToString(*scalability_mode);
     return {};
   }

   // TODO(bugs.webrtc.org/11607): Add support for screensharing.
   std::vector<SpatialLayer> spatial_layers =
       GetSvcConfig(codec.width, codec.height, codec.maxFramerate,
                    /*first_active_layer=*/0, info->num_spatial_layers,
                    info->num_temporal_layers, /*is_screen_sharing=*/false,
                    codec.GetScalabilityMode() ? info : absl::nullopt);
   RTC_DCHECK(!spatial_layers.empty());

   // Use codec bitrate limits if spatial layering is not requested.
   if (info->num_spatial_layers == 1) {
     spatial_layers.back().minBitrate = codec.minBitrate;
     spatial_layers.back().targetBitrate = codec.maxBitrate;
     spatial_layers.back().maxBitrate = codec.maxBitrate;
   }

   return spatial_layers;
 }

 std::vector<SpatialLayer> GetSvcConfig(
     size_t input_width,
     size_t input_height,
     float max_framerate_fps,
     size_t first_active_layer,
     size_t num_spatial_layers,
     size_t num_temporal_layers,
     bool is_screen_sharing,
     absl::optional<ScalableVideoController::StreamLayersConfig> config) {
   RTC_DCHECK_GT(input_width, 0);
   RTC_DCHECK_GT(input_height, 0);
   RTC_DCHECK_GT(num_spatial_layers, 0);
   RTC_DCHECK_GT(num_temporal_layers, 0);

   if (is_screen_sharing) {
     return ConfigureSvcScreenSharing(input_width, input_height,
                                      max_framerate_fps, num_spatial_layers);
   } else {
     return ConfigureSvcNormalVideo(input_width, input_height, max_framerate_fps,
                                    first_active_layer, num_spatial_layers,
                                    num_temporal_layers, config);
   }
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2018 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.
	*/

	#include "modules/video_coding/codecs/vp9/svc_config.h"

	#include <algorithm>
	#include <cmath>
	#include <memory>
	#include <vector>

	#include "media/base/video_common.h"
	#include "modules/video_coding/codecs/vp9/include/vp9_globals.h"
	#include "modules/video_coding/svc/create_scalability_structure.h"
	#include "modules/video_coding/svc/scalability_mode_util.h"
	#include "rtc_base/checks.h"
	#include "rtc_base/logging.h"

	namespace webrtc {

	namespace {
	const size_t kMinVp9SvcBitrateKbps = 30;

	const size_t kMaxNumLayersForScreenSharing = 3;
	const float kMaxScreenSharingLayerFramerateFps[] = {5.0, 10.0, 30.0};
	const size_t kMinScreenSharingLayerBitrateKbps[] = {30, 200, 500};
	const size_t kTargetScreenSharingLayerBitrateKbps[] = {150, 350, 950};
	const size_t kMaxScreenSharingLayerBitrateKbps[] = {250, 500, 950};

	// Gets limited number of layers for given resolution.
	size_t GetLimitedNumSpatialLayers(size_t width, size_t height) {
	const bool is_landscape = width >= height;
	const size_t min_width = is_landscape ? kMinVp9SpatialLayerLongSideLength
	: kMinVp9SpatialLayerShortSideLength;
	const size_t min_height = is_landscape ? kMinVp9SpatialLayerShortSideLength
	: kMinVp9SpatialLayerLongSideLength;
	const size_t num_layers_fit_horz = static_cast<size_t>(
	std::floor(1 + std::max(0.0f, std::log2(1.0f * width / min_width))));
	const size_t num_layers_fit_vert = static_cast<size_t>(
	std::floor(1 + std::max(0.0f, std::log2(1.0f * height / min_height))));
	return std::min(num_layers_fit_horz, num_layers_fit_vert);
	}
	} // namespace

	std::vector<SpatialLayer> ConfigureSvcScreenSharing(size_t input_width,
	size_t input_height,
	float max_framerate_fps,
	size_t num_spatial_layers) {
	num_spatial_layers =
	std::min(num_spatial_layers, kMaxNumLayersForScreenSharing);
	std::vector<SpatialLayer> spatial_layers;

	for (size_t sl_idx = 0; sl_idx < num_spatial_layers; ++sl_idx) {
	SpatialLayer spatial_layer = {0};
	spatial_layer.width = input_width;
	spatial_layer.height = input_height;
	spatial_layer.maxFramerate =
	std::min(kMaxScreenSharingLayerFramerateFps[sl_idx], max_framerate_fps);
	spatial_layer.numberOfTemporalLayers = 1;
	spatial_layer.minBitrate =
	static_cast<int>(kMinScreenSharingLayerBitrateKbps[sl_idx]);
	spatial_layer.maxBitrate =
	static_cast<int>(kMaxScreenSharingLayerBitrateKbps[sl_idx]);
	spatial_layer.targetBitrate =
	static_cast<int>(kTargetScreenSharingLayerBitrateKbps[sl_idx]);
	spatial_layer.active = true;
	spatial_layers.push_back(spatial_layer);
	}

	return spatial_layers;
	}

	std::vector<SpatialLayer> ConfigureSvcNormalVideo(
	size_t input_width,
	size_t input_height,
	float max_framerate_fps,
	size_t first_active_layer,
	size_t num_spatial_layers,
	size_t num_temporal_layers,
	absl::optional<ScalableVideoController::StreamLayersConfig> config) {
	RTC_DCHECK_LT(first_active_layer, num_spatial_layers);

	// Limit number of layers for given resolution.
	size_t limited_num_spatial_layers =
	GetLimitedNumSpatialLayers(input_width, input_height);
	if (limited_num_spatial_layers < num_spatial_layers) {
	RTC_LOG(LS_WARNING) << "Reducing number of spatial layers from "
	<< num_spatial_layers << " to "
	<< limited_num_spatial_layers
	<< " due to low input resolution.";
	num_spatial_layers = limited_num_spatial_layers;
	}

	// First active layer must be configured.
	num_spatial_layers = std::max(num_spatial_layers, first_active_layer + 1);

	// Ensure top layer is even enough.
	int required_divisiblity = 1 << (num_spatial_layers - first_active_layer - 1);
	if (config) {
	required_divisiblity = 1;
	for (size_t sl_idx = 0; sl_idx < num_spatial_layers; ++sl_idx) {
	required_divisiblity = cricket::LeastCommonMultiple(
	required_divisiblity, config->scaling_factor_den[sl_idx]);
	}
	}
	input_width = input_width - input_width % required_divisiblity;
	input_height = input_height - input_height % required_divisiblity;

	std::vector<SpatialLayer> spatial_layers;
	for (size_t sl_idx = first_active_layer; sl_idx < num_spatial_layers;
	++sl_idx) {
	SpatialLayer spatial_layer = {0};
	spatial_layer.width = input_width >> (num_spatial_layers - sl_idx - 1);
	spatial_layer.height = input_height >> (num_spatial_layers - sl_idx - 1);
	spatial_layer.maxFramerate = max_framerate_fps;
	spatial_layer.numberOfTemporalLayers = num_temporal_layers;
	spatial_layer.active = true;

	if (config) {
	spatial_layer.width = input_width * config->scaling_factor_num[sl_idx] /
	config->scaling_factor_den[sl_idx];
	spatial_layer.height = input_height * config->scaling_factor_num[sl_idx] /
	config->scaling_factor_den[sl_idx];
	}

	// minBitrate and maxBitrate formulas were derived from
	// subjective-quality data to determing bit rates below which video
	// quality is unacceptable and above which additional bits do not provide
	// benefit. The formulas express rate in units of kbps.

	// TODO(ssilkin): Add to the comment PSNR/SSIM we get at encoding certain
	// video to min/max bitrate specified by those formulas.
	const size_t num_pixels = spatial_layer.width * spatial_layer.height;
	int min_bitrate =
	static_cast<int>((600. * std::sqrt(num_pixels) - 95000.) / 1000.);
	min_bitrate = std::max(min_bitrate, 0);
	spatial_layer.minBitrate =
	std::max(static_cast<size_t>(min_bitrate), kMinVp9SvcBitrateKbps);
	spatial_layer.maxBitrate =
	static_cast<int>((1.6 * num_pixels + 50 * 1000) / 1000);
	spatial_layer.targetBitrate =
	(spatial_layer.minBitrate + spatial_layer.maxBitrate) / 2;
	spatial_layers.push_back(spatial_layer);
	}

	// A workaround for situation when single HD layer is left with minBitrate
	// about 500kbps. This would mean that there will always be at least 500kbps
	// allocated to video regardless of how low is the actual BWE.
	// Also, boost maxBitrate for the first layer to account for lost ability to
	// predict from previous layers.
	if (first_active_layer > 0) {
	spatial_layers[0].minBitrate = kMinVp9SvcBitrateKbps;
	// TODO(ilnik): tune this value or come up with a different formula to
	// ensure that all singlecast configurations look good and not too much
	// bitrate is added.
	spatial_layers[0].maxBitrate *= 1.1;
	}

	return spatial_layers;
	}

	// Uses scalability mode to configure spatial layers.
	std::vector<SpatialLayer> GetVp9SvcConfig(VideoCodec& codec) {
	RTC_DCHECK_EQ(codec.codecType, kVideoCodecVP9);

	absl::optional<ScalabilityMode> scalability_mode = codec.GetScalabilityMode();
	RTC_DCHECK(scalability_mode.has_value());

	// Limit number of spatial layers for given resolution.
	int limited_num_spatial_layers =
	GetLimitedNumSpatialLayers(codec.width, codec.height);
	if (limited_num_spatial_layers <
	ScalabilityModeToNumSpatialLayers(*scalability_mode)) {
	ScalabilityMode limited_scalability_mode =
	LimitNumSpatialLayers(*scalability_mode, limited_num_spatial_layers);
	RTC_LOG(LS_WARNING)
	<< "Reducing number of spatial layers due to low input resolution: "
	<< ScalabilityModeToString(*scalability_mode) << " to "
	<< ScalabilityModeToString(limited_scalability_mode);
	scalability_mode = limited_scalability_mode;
	codec.SetScalabilityMode(limited_scalability_mode);
	}

	absl::optional<ScalableVideoController::StreamLayersConfig> info =
	ScalabilityStructureConfig(*scalability_mode);
	if (!info.has_value()) {
	RTC_LOG(LS_WARNING) << "Failed to create structure "
	<< ScalabilityModeToString(*scalability_mode);
	return {};
	}

	// TODO(bugs.webrtc.org/11607): Add support for screensharing.
	std::vector<SpatialLayer> spatial_layers =
	GetSvcConfig(codec.width, codec.height, codec.maxFramerate,
	/first_active_layer=/0, info->num_spatial_layers,
	info->num_temporal_layers, /is_screen_sharing=/false,
	codec.GetScalabilityMode() ? info : absl::nullopt);
	RTC_DCHECK(!spatial_layers.empty());

	// Use codec bitrate limits if spatial layering is not requested.
	if (info->num_spatial_layers == 1) {
	spatial_layers.back().minBitrate = codec.minBitrate;
	spatial_layers.back().targetBitrate = codec.maxBitrate;
	spatial_layers.back().maxBitrate = codec.maxBitrate;
	}

	return spatial_layers;
	}

	std::vector<SpatialLayer> GetSvcConfig(
	size_t input_width,
	size_t input_height,
	float max_framerate_fps,
	size_t first_active_layer,
	size_t num_spatial_layers,
	size_t num_temporal_layers,
	bool is_screen_sharing,
	absl::optional<ScalableVideoController::StreamLayersConfig> config) {
	RTC_DCHECK_GT(input_width, 0);
	RTC_DCHECK_GT(input_height, 0);
	RTC_DCHECK_GT(num_spatial_layers, 0);
	RTC_DCHECK_GT(num_temporal_layers, 0);

	if (is_screen_sharing) {
	return ConfigureSvcScreenSharing(input_width, input_height,
	max_framerate_fps, num_spatial_layers);
	} else {
	return ConfigureSvcNormalVideo(input_width, input_height, max_framerate_fps,
	first_active_layer, num_spatial_layers,
	num_temporal_layers, config);
	}
	}

	} // namespace webrtc