| /* Copyright (c) 2013 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 "webrtc/modules/video_coding/codecs/vp8/screenshare_layers.h" |
| |
| #include <stdlib.h> |
| |
| #include <algorithm> |
| |
| #include "webrtc/base/checks.h" |
| #include "vpx/vpx_encoder.h" |
| #include "vpx/vp8cx.h" |
| #include "webrtc/modules/video_coding/include/video_codec_interface.h" |
| #include "webrtc/system_wrappers/include/clock.h" |
| #include "webrtc/system_wrappers/include/metrics.h" |
| |
| namespace webrtc { |
| |
| static const int kOneSecond90Khz = 90000; |
| static const int kMinTimeBetweenSyncs = kOneSecond90Khz * 5; |
| static const int kMaxTimeBetweenSyncs = kOneSecond90Khz * 10; |
| static const int kQpDeltaThresholdForSync = 8; |
| |
| const double ScreenshareLayers::kMaxTL0FpsReduction = 2.5; |
| const double ScreenshareLayers::kAcceptableTargetOvershoot = 2.0; |
| |
| // Since this is TL0 we only allow updating and predicting from the LAST |
| // reference frame. |
| const int ScreenshareLayers::kTl0Flags = |
| VP8_EFLAG_NO_UPD_GF | VP8_EFLAG_NO_UPD_ARF | VP8_EFLAG_NO_REF_GF | |
| VP8_EFLAG_NO_REF_ARF; |
| |
| // Allow predicting from both TL0 and TL1. |
| const int ScreenshareLayers::kTl1Flags = |
| VP8_EFLAG_NO_REF_ARF | VP8_EFLAG_NO_UPD_ARF | VP8_EFLAG_NO_UPD_LAST; |
| |
| // Allow predicting from only TL0 to allow participants to switch to the high |
| // bitrate stream. This means predicting only from the LAST reference frame, but |
| // only updating GF to not corrupt TL0. |
| const int ScreenshareLayers::kTl1SyncFlags = |
| VP8_EFLAG_NO_REF_ARF | VP8_EFLAG_NO_REF_GF | VP8_EFLAG_NO_UPD_ARF | |
| VP8_EFLAG_NO_UPD_LAST; |
| |
| // Always emit a frame with certain interval, even if bitrate targets have |
| // been exceeded. |
| const int ScreenshareLayers::kMaxFrameIntervalMs = 2000; |
| |
| ScreenshareLayers::ScreenshareLayers(int num_temporal_layers, |
| uint8_t initial_tl0_pic_idx, |
| Clock* clock) |
| : clock_(clock), |
| number_of_temporal_layers_(num_temporal_layers), |
| last_base_layer_sync_(false), |
| tl0_pic_idx_(initial_tl0_pic_idx), |
| active_layer_(-1), |
| last_timestamp_(-1), |
| last_sync_timestamp_(-1), |
| last_emitted_tl0_timestamp_(-1), |
| min_qp_(-1), |
| max_qp_(-1), |
| max_debt_bytes_(0), |
| frame_rate_(-1) { |
| RTC_CHECK_GT(num_temporal_layers, 0); |
| RTC_CHECK_LE(num_temporal_layers, 2); |
| } |
| |
| ScreenshareLayers::~ScreenshareLayers() { |
| UpdateHistograms(); |
| } |
| |
| int ScreenshareLayers::CurrentLayerId() const { |
| // Codec does not use temporal layers for screenshare. |
| return 0; |
| } |
| |
| int ScreenshareLayers::EncodeFlags(uint32_t timestamp) { |
| if (number_of_temporal_layers_ <= 1) { |
| // No flags needed for 1 layer screenshare. |
| return 0; |
| } |
| |
| if (stats_.first_frame_time_ms_ == -1) |
| stats_.first_frame_time_ms_ = clock_->TimeInMilliseconds(); |
| |
| int64_t unwrapped_timestamp = time_wrap_handler_.Unwrap(timestamp); |
| int flags = 0; |
| if (active_layer_ == -1 || |
| layers_[active_layer_].state != TemporalLayer::State::kDropped) { |
| if (last_emitted_tl0_timestamp_ != -1 && |
| (unwrapped_timestamp - last_emitted_tl0_timestamp_) / 90 > |
| kMaxFrameIntervalMs) { |
| // Too long time has passed since the last frame was emitted, cancel |
| // enough debt to allow a single frame. |
| layers_[0].debt_bytes_ = max_debt_bytes_ - 1; |
| } |
| if (layers_[0].debt_bytes_ > max_debt_bytes_) { |
| // Must drop TL0, encode TL1 instead. |
| if (layers_[1].debt_bytes_ > max_debt_bytes_) { |
| // Must drop both TL0 and TL1. |
| active_layer_ = -1; |
| } else { |
| active_layer_ = 1; |
| } |
| } else { |
| active_layer_ = 0; |
| } |
| } |
| |
| switch (active_layer_) { |
| case 0: |
| flags = kTl0Flags; |
| last_emitted_tl0_timestamp_ = unwrapped_timestamp; |
| break; |
| case 1: |
| if (TimeToSync(unwrapped_timestamp)) { |
| last_sync_timestamp_ = unwrapped_timestamp; |
| flags = kTl1SyncFlags; |
| } else { |
| flags = kTl1Flags; |
| } |
| break; |
| case -1: |
| flags = -1; |
| ++stats_.num_dropped_frames_; |
| break; |
| default: |
| flags = -1; |
| RTC_NOTREACHED(); |
| } |
| |
| int64_t ts_diff; |
| if (last_timestamp_ == -1) { |
| ts_diff = kOneSecond90Khz / (frame_rate_ <= 0 ? 5 : frame_rate_); |
| } else { |
| ts_diff = unwrapped_timestamp - last_timestamp_; |
| } |
| // Make sure both frame droppers leak out bits. |
| layers_[0].UpdateDebt(ts_diff / 90); |
| layers_[1].UpdateDebt(ts_diff / 90); |
| last_timestamp_ = timestamp; |
| return flags; |
| } |
| |
| bool ScreenshareLayers::ConfigureBitrates(int bitrate_kbps, |
| int max_bitrate_kbps, |
| int framerate, |
| vpx_codec_enc_cfg_t* cfg) { |
| layers_[0].target_rate_kbps_ = bitrate_kbps; |
| layers_[1].target_rate_kbps_ = max_bitrate_kbps; |
| |
| int target_bitrate_kbps = bitrate_kbps; |
| |
| if (cfg != nullptr) { |
| if (number_of_temporal_layers_ > 1) { |
| // Calculate a codec target bitrate. This may be higher than TL0, gaining |
| // quality at the expense of frame rate at TL0. Constraints: |
| // - TL0 frame rate no less than framerate / kMaxTL0FpsReduction. |
| // - Target rate * kAcceptableTargetOvershoot should not exceed TL1 rate. |
| target_bitrate_kbps = |
| std::min(bitrate_kbps * kMaxTL0FpsReduction, |
| max_bitrate_kbps / kAcceptableTargetOvershoot); |
| |
| cfg->rc_target_bitrate = std::max(bitrate_kbps, target_bitrate_kbps); |
| } |
| |
| // Don't reconfigure qp limits during quality boost frames. |
| if (active_layer_ == -1 || |
| layers_[active_layer_].state != TemporalLayer::State::kQualityBoost) { |
| min_qp_ = cfg->rc_min_quantizer; |
| max_qp_ = cfg->rc_max_quantizer; |
| // After a dropped frame, a frame with max qp will be encoded and the |
| // quality will then ramp up from there. To boost the speed of recovery, |
| // encode the next frame with lower max qp. TL0 is the most important to |
| // improve since the errors in this layer will propagate to TL1. |
| // Currently, reduce max qp by 20% for TL0 and 15% for TL1. |
| layers_[0].enhanced_max_qp = min_qp_ + (((max_qp_ - min_qp_) * 80) / 100); |
| layers_[1].enhanced_max_qp = min_qp_ + (((max_qp_ - min_qp_) * 85) / 100); |
| } |
| } |
| |
| int avg_frame_size = (target_bitrate_kbps * 1000) / (8 * framerate); |
| max_debt_bytes_ = 4 * avg_frame_size; |
| |
| return true; |
| } |
| |
| void ScreenshareLayers::FrameEncoded(unsigned int size, |
| uint32_t timestamp, |
| int qp) { |
| if (number_of_temporal_layers_ == 1) |
| return; |
| |
| RTC_DCHECK_NE(-1, active_layer_); |
| if (size == 0) { |
| layers_[active_layer_].state = TemporalLayer::State::kDropped; |
| ++stats_.num_overshoots_; |
| return; |
| } |
| |
| if (layers_[active_layer_].state == TemporalLayer::State::kDropped) { |
| layers_[active_layer_].state = TemporalLayer::State::kQualityBoost; |
| } |
| |
| if (qp != -1) |
| layers_[active_layer_].last_qp = qp; |
| |
| if (active_layer_ == 0) { |
| layers_[0].debt_bytes_ += size; |
| layers_[1].debt_bytes_ += size; |
| ++stats_.num_tl0_frames_; |
| stats_.tl0_target_bitrate_sum_ += layers_[0].target_rate_kbps_; |
| stats_.tl0_qp_sum_ += qp; |
| } else if (active_layer_ == 1) { |
| layers_[1].debt_bytes_ += size; |
| ++stats_.num_tl1_frames_; |
| stats_.tl1_target_bitrate_sum_ += layers_[1].target_rate_kbps_; |
| stats_.tl1_qp_sum_ += qp; |
| } |
| } |
| |
| void ScreenshareLayers::PopulateCodecSpecific(bool base_layer_sync, |
| CodecSpecificInfoVP8* vp8_info, |
| uint32_t timestamp) { |
| int64_t unwrapped_timestamp = time_wrap_handler_.Unwrap(timestamp); |
| if (number_of_temporal_layers_ == 1) { |
| vp8_info->temporalIdx = kNoTemporalIdx; |
| vp8_info->layerSync = false; |
| vp8_info->tl0PicIdx = kNoTl0PicIdx; |
| } else { |
| RTC_DCHECK_NE(-1, active_layer_); |
| vp8_info->temporalIdx = active_layer_; |
| if (base_layer_sync) { |
| vp8_info->temporalIdx = 0; |
| last_sync_timestamp_ = unwrapped_timestamp; |
| } else if (last_base_layer_sync_ && vp8_info->temporalIdx != 0) { |
| // Regardless of pattern the frame after a base layer sync will always |
| // be a layer sync. |
| last_sync_timestamp_ = unwrapped_timestamp; |
| } |
| vp8_info->layerSync = last_sync_timestamp_ != -1 && |
| last_sync_timestamp_ == unwrapped_timestamp; |
| if (vp8_info->temporalIdx == 0) { |
| tl0_pic_idx_++; |
| } |
| last_base_layer_sync_ = base_layer_sync; |
| vp8_info->tl0PicIdx = tl0_pic_idx_; |
| } |
| } |
| |
| bool ScreenshareLayers::TimeToSync(int64_t timestamp) const { |
| RTC_DCHECK_EQ(1, active_layer_); |
| RTC_DCHECK_NE(-1, layers_[0].last_qp); |
| if (layers_[1].last_qp == -1) { |
| // First frame in TL1 should only depend on TL0 since there are no |
| // previous frames in TL1. |
| return true; |
| } |
| |
| RTC_DCHECK_NE(-1, last_sync_timestamp_); |
| int64_t timestamp_diff = timestamp - last_sync_timestamp_; |
| if (timestamp_diff > kMaxTimeBetweenSyncs) { |
| // After a certain time, force a sync frame. |
| return true; |
| } else if (timestamp_diff < kMinTimeBetweenSyncs) { |
| // If too soon from previous sync frame, don't issue a new one. |
| return false; |
| } |
| // Issue a sync frame if difference in quality between TL0 and TL1 isn't too |
| // large. |
| if (layers_[0].last_qp - layers_[1].last_qp < kQpDeltaThresholdForSync) |
| return true; |
| return false; |
| } |
| |
| bool ScreenshareLayers::UpdateConfiguration(vpx_codec_enc_cfg_t* cfg) { |
| if (max_qp_ == -1 || number_of_temporal_layers_ <= 1) |
| return false; |
| RTC_DCHECK_NE(-1, active_layer_); |
| |
| // If layer is in the quality boost state (following a dropped frame), update |
| // the configuration with the adjusted (lower) qp and set the state back to |
| // normal. |
| unsigned int adjusted_max_qp; |
| if (layers_[active_layer_].state == TemporalLayer::State::kQualityBoost && |
| layers_[active_layer_].enhanced_max_qp != -1) { |
| adjusted_max_qp = layers_[active_layer_].enhanced_max_qp; |
| layers_[active_layer_].state = TemporalLayer::State::kNormal; |
| } else { |
| if (max_qp_ == -1) |
| return false; |
| adjusted_max_qp = max_qp_; // Set the normal max qp. |
| } |
| |
| if (adjusted_max_qp == cfg->rc_max_quantizer) |
| return false; |
| |
| cfg->rc_max_quantizer = adjusted_max_qp; |
| return true; |
| } |
| |
| void ScreenshareLayers::TemporalLayer::UpdateDebt(int64_t delta_ms) { |
| uint32_t debt_reduction_bytes = target_rate_kbps_ * delta_ms / 8; |
| if (debt_reduction_bytes >= debt_bytes_) { |
| debt_bytes_ = 0; |
| } else { |
| debt_bytes_ -= debt_reduction_bytes; |
| } |
| } |
| |
| void ScreenshareLayers::UpdateHistograms() { |
| if (stats_.first_frame_time_ms_ == -1) |
| return; |
| int64_t duration_sec = |
| (clock_->TimeInMilliseconds() - stats_.first_frame_time_ms_ + 500) / 1000; |
| if (duration_sec >= metrics::kMinRunTimeInSeconds) { |
| RTC_HISTOGRAM_COUNTS_10000( |
| "WebRTC.Video.Screenshare.Layer0.FrameRate", |
| (stats_.num_tl0_frames_ + (duration_sec / 2)) / duration_sec); |
| RTC_HISTOGRAM_COUNTS_10000( |
| "WebRTC.Video.Screenshare.Layer1.FrameRate", |
| (stats_.num_tl1_frames_ + (duration_sec / 2)) / duration_sec); |
| int total_frames = stats_.num_tl0_frames_ + stats_.num_tl1_frames_; |
| RTC_HISTOGRAM_COUNTS_10000( |
| "WebRTC.Video.Screenshare.FramesPerDrop", |
| (stats_.num_dropped_frames_ == 0 ? 0 : total_frames / |
| stats_.num_dropped_frames_)); |
| RTC_HISTOGRAM_COUNTS_10000( |
| "WebRTC.Video.Screenshare.FramesPerOvershoot", |
| (stats_.num_overshoots_ == 0 ? 0 |
| : total_frames / stats_.num_overshoots_)); |
| if (stats_.num_tl0_frames_ > 0) { |
| RTC_HISTOGRAM_COUNTS_10000("WebRTC.Video.Screenshare.Layer0.Qp", |
| stats_.tl0_qp_sum_ / stats_.num_tl0_frames_); |
| RTC_HISTOGRAM_COUNTS_10000( |
| "WebRTC.Video.Screenshare.Layer0.TargetBitrate", |
| stats_.tl0_target_bitrate_sum_ / stats_.num_tl0_frames_); |
| } |
| if (stats_.num_tl1_frames_ > 0) { |
| RTC_HISTOGRAM_COUNTS_10000("WebRTC.Video.Screenshare.Layer1.Qp", |
| stats_.tl1_qp_sum_ / stats_.num_tl1_frames_); |
| RTC_HISTOGRAM_COUNTS_10000( |
| "WebRTC.Video.Screenshare.Layer1.TargetBitrate", |
| stats_.tl1_target_bitrate_sum_ / stats_.num_tl1_frames_); |
| } |
| } |
| } |
| |
| } // namespace webrtc |
