modules/video_coding/codecs/vp8/temporal_layers_checker.cc

/*
 *  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/vp8/include/temporal_layers_checker.h"

#include <cstdint>
#include <memory>

#include "api/video_codecs/vp8_frame_config.h"
#include "api/video_codecs/vp8_temporal_layers.h"
#include "modules/video_coding/codecs/interface/common_constants.h"
#include "modules/video_coding/codecs/vp8/default_temporal_layers.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"

namespace webrtc {

std::unique_ptr<TemporalLayersChecker>
TemporalLayersChecker::CreateTemporalLayersChecker(Vp8TemporalLayersType type,
                                                   int num_temporal_layers) {
  switch (type) {
    case Vp8TemporalLayersType::kFixedPattern:
      return std::make_unique<DefaultTemporalLayersChecker>(
          num_temporal_layers);
    case Vp8TemporalLayersType::kBitrateDynamic:
      // Conference mode temporal layering for screen content in base stream.
      return std::make_unique<TemporalLayersChecker>(num_temporal_layers);
  }
  RTC_CHECK_NOTREACHED();
}

TemporalLayersChecker::TemporalLayersChecker(int num_temporal_layers)
    : num_temporal_layers_(num_temporal_layers),
      sequence_number_(0),
      last_sync_sequence_number_(0),
      last_tl0_sequence_number_(0) {}

bool TemporalLayersChecker::CheckAndUpdateBufferState(
    BufferState* state,
    bool* need_sync,
    bool frame_is_keyframe,
    uint8_t temporal_layer,
    Vp8FrameConfig::BufferFlags flags,
    uint32_t sequence_number,
    uint32_t* lowest_sequence_referenced) {
  if (flags & Vp8FrameConfig::BufferFlags::kReference) {
    if (state->temporal_layer > 0 && !state->is_keyframe) {
      *need_sync = false;
    }
    if (!state->is_keyframe && !frame_is_keyframe &&
        state->sequence_number < *lowest_sequence_referenced) {
      *lowest_sequence_referenced = state->sequence_number;
    }
    if (!frame_is_keyframe && !state->is_keyframe &&
        state->temporal_layer > temporal_layer) {
      RTC_LOG(LS_ERROR) << "Frame is referencing higher temporal layer.";
      return false;
    }
  }
  if ((flags & Vp8FrameConfig::BufferFlags::kUpdate)) {
    state->temporal_layer = temporal_layer;
    state->sequence_number = sequence_number;
    state->is_keyframe = frame_is_keyframe;
  }
  if (frame_is_keyframe)
    state->is_keyframe = true;
  return true;
}

bool TemporalLayersChecker::CheckTemporalConfig(
    bool frame_is_keyframe,
    const Vp8FrameConfig& frame_config) {
  if (frame_config.drop_frame ||
      frame_config.packetizer_temporal_idx == kNoTemporalIdx) {
    return true;
  }
  ++sequence_number_;
  if (frame_config.packetizer_temporal_idx >= num_temporal_layers_ ||
      (frame_config.packetizer_temporal_idx == kNoTemporalIdx &&
       num_temporal_layers_ > 1)) {
    RTC_LOG(LS_ERROR) << "Incorrect temporal layer set for frame: "
                      << frame_config.packetizer_temporal_idx
                      << " num_temporal_layers: " << num_temporal_layers_;
    return false;
  }

  uint32_t lowest_sequence_referenced = sequence_number_;
  bool need_sync = frame_config.packetizer_temporal_idx > 0 &&
                   frame_config.packetizer_temporal_idx != kNoTemporalIdx;

  if (!CheckAndUpdateBufferState(
          &last_, &need_sync, frame_is_keyframe,
          frame_config.packetizer_temporal_idx, frame_config.last_buffer_flags,
          sequence_number_, &lowest_sequence_referenced)) {
    RTC_LOG(LS_ERROR) << "Error in the Last buffer";
    return false;
  }
  if (!CheckAndUpdateBufferState(&golden_, &need_sync, frame_is_keyframe,
                                 frame_config.packetizer_temporal_idx,
                                 frame_config.golden_buffer_flags,
                                 sequence_number_,
                                 &lowest_sequence_referenced)) {
    RTC_LOG(LS_ERROR) << "Error in the Golden buffer";
    return false;
  }
  if (!CheckAndUpdateBufferState(
          &arf_, &need_sync, frame_is_keyframe,
          frame_config.packetizer_temporal_idx, frame_config.arf_buffer_flags,
          sequence_number_, &lowest_sequence_referenced)) {
    RTC_LOG(LS_ERROR) << "Error in the Arf buffer";
    return false;
  }

  if (lowest_sequence_referenced < last_sync_sequence_number_ &&
      !frame_is_keyframe) {
    RTC_LOG(LS_ERROR) << "Reference past the last sync frame. Referenced "
                      << lowest_sequence_referenced << ", but sync was at "
                      << last_sync_sequence_number_;
    return false;
  }

  if (frame_config.packetizer_temporal_idx == 0) {
    last_tl0_sequence_number_ = sequence_number_;
  }

  if (frame_is_keyframe) {
    last_sync_sequence_number_ = sequence_number_;
  }

  if (need_sync) {
    last_sync_sequence_number_ = last_tl0_sequence_number_;
  }

  // Ignore sync flag on key-frames as it really doesn't matter.
  if (need_sync != frame_config.layer_sync && !frame_is_keyframe) {
    RTC_LOG(LS_ERROR) << "Sync bit is set incorrectly on a frame. Expected: "
                      << need_sync << " Actual: " << frame_config.layer_sync;
    return false;
  }
  return true;
}

}  // namespace webrtc