| /* |
| * 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 <vector> |
| |
| #include "modules/video_coding/include/video_codec_interface.h" |
| |
| namespace webrtc { |
| |
| std::vector<SpatialLayer> GetSvcConfig(size_t input_width, |
| size_t input_height, |
| size_t num_spatial_layers, |
| size_t num_temporal_layers) { |
| 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); |
| |
| std::vector<SpatialLayer> spatial_layers; |
| |
| // Limit number of layers for given resolution. |
| const size_t num_layers_fit_horz = static_cast<size_t>(std::floor( |
| 1 + std::max(0.0f, |
| std::log2(1.0f * input_width / kMinVp9SpatialLayerWidth)))); |
| const size_t num_layers_fit_vert = static_cast<size_t>( |
| std::floor(1 + std::max(0.0f, std::log2(1.0f * input_height / |
| kMinVp9SpatialLayerHeight)))); |
| num_spatial_layers = |
| std::min({num_spatial_layers, num_layers_fit_horz, num_layers_fit_vert}); |
| |
| for (size_t sl_idx = 0; 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.numberOfTemporalLayers = num_temporal_layers; |
| |
| // minBitrate and maxBitrate formulas were derived to fit VP9 |
| // subjective-quality data for bit rate below which video quality is |
| // unacceptable and above which additional bits do not provide benefit. |
| // 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; |
| spatial_layer.minBitrate = |
| static_cast<int>(360 * std::sqrt(num_pixels) / 1000); |
| spatial_layer.maxBitrate = |
| static_cast<int>((1.5 * num_pixels + 75 * 1000) / 1000); |
| spatial_layer.targetBitrate = |
| (spatial_layer.maxBitrate + spatial_layer.minBitrate) / 2; |
| |
| spatial_layers.push_back(spatial_layer); |
| } |
| |
| return spatial_layers; |
| } |
| |
| } // namespace webrtc |