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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "remoting/codec/audio_decoder_opus.h"
#include <cstddef>
#include <cstdint>
#include "base/containers/span.h"
#include "base/logging.h"
#include "base/numerics/safe_conversions.h"
#include "base/time/time.h"
#include "remoting/proto/audio.pb.h"
#include "third_party/opus/src/include/opus.h"
namespace remoting {
namespace {
// Maximum size of an Opus frame in milliseconds.
const int kMaxFrameSizeMs = 120;
// Hosts will never generate more than 100 frames in a single packet.
const int kMaxFramesPerPacket = 100;
const AudioPacket::SamplingRate kSamplingRate =
AudioPacket::SAMPLING_RATE_48000;
} // namespace
AudioDecoderOpus::AudioDecoderOpus()
: sampling_rate_(0), channels_(0), decoder_(nullptr) {}
AudioDecoderOpus::~AudioDecoderOpus() {
DestroyDecoder();
}
void AudioDecoderOpus::InitDecoder() {
DCHECK(!decoder_);
int error;
decoder_ = opus_decoder_create(kSamplingRate, channels_, &error);
if (!decoder_) {
LOG(ERROR) << "Failed to create OPUS decoder; Error code: " << error;
}
}
void AudioDecoderOpus::DestroyDecoder() {
if (decoder_) {
opus_decoder_destroy(decoder_);
decoder_ = nullptr;
}
}
bool AudioDecoderOpus::ResetForPacket(AudioPacket* packet) {
if (packet->channels() != channels_ ||
packet->sampling_rate() != sampling_rate_) {
DestroyDecoder();
channels_ = packet->channels();
sampling_rate_ = packet->sampling_rate();
if (channels_ <= 0 || channels_ > 2 || sampling_rate_ != kSamplingRate) {
LOG(WARNING) << "Unsupported OPUS parameters: " << channels_
<< " channels with " << sampling_rate_
<< " samples per second.";
return false;
}
}
if (!decoder_) {
InitDecoder();
}
return decoder_ != nullptr;
}
std::unique_ptr<AudioPacket> AudioDecoderOpus::Decode(
std::unique_ptr<AudioPacket> packet) {
if (packet->encoding() != AudioPacket::ENCODING_OPUS) {
LOG(WARNING) << "Received an audio packet with encoding "
<< packet->encoding() << " when an OPUS packet was expected.";
return nullptr;
}
if (packet->data_size() > kMaxFramesPerPacket) {
LOG(WARNING) << "Received an packet with too many frames.";
return nullptr;
}
if (!ResetForPacket(packet.get())) {
return nullptr;
}
// Create a new packet of decoded data.
std::unique_ptr<AudioPacket> decoded_packet(new AudioPacket());
decoded_packet->set_encoding(AudioPacket::ENCODING_RAW);
decoded_packet->set_sampling_rate(kSamplingRate);
decoded_packet->set_bytes_per_sample(AudioPacket::BYTES_PER_SAMPLE_2);
decoded_packet->set_channels(packet->channels());
int max_frame_samples =
kMaxFrameSizeMs * kSamplingRate / base::Time::kMillisecondsPerSecond;
int max_frame_bytes =
max_frame_samples * channels_ * decoded_packet->bytes_per_sample();
std::string* decoded_data = decoded_packet->add_data();
decoded_data->resize(packet->data_size() * max_frame_bytes);
int buffer_pos = 0;
for (int i = 0; i < packet->data_size(); ++i) {
CHECK_GE(buffer_pos, 0);
const size_t buffer_pos_size = base::checked_cast<size_t>(buffer_pos);
auto decoded_span = base::as_writable_byte_span(*decoded_data);
auto current_span = decoded_span.subspan(buffer_pos_size);
CHECK_LE(buffer_pos + max_frame_bytes,
static_cast<int>(decoded_data->size()));
std::string* frame = packet->mutable_data(i);
auto frame_span = base::as_byte_span(*frame);
int result = opus_decode(decoder_, frame_span.data(), frame_span.size(),
reinterpret_cast<int16_t*>(current_span.data()),
max_frame_samples, 0);
if (result < 0) {
LOG(ERROR) << "Failed decoding Opus frame. Error code: " << result;
DestroyDecoder();
return nullptr;
}
buffer_pos +=
result * packet->channels() * decoded_packet->bytes_per_sample();
}
if (!buffer_pos) {
return nullptr;
}
decoded_data->resize(buffer_pos);
return decoded_packet;
}
} // namespace remoting
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