modules/audio_coding/codecs/opus/audio_encoder_multi_channel_opus_impl.cc - src - Git at Google

 /*
  *  Copyright (c) 2019 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.
  */

 /*
  * LEFT TO DO:
  * - WRITE TESTS for the stuff in this  file.
  * - Check the creation, maybe make it safer by returning an empty optional or
  *   unique_ptr. --- It looks OK, but RecreateEncoderInstance can perhaps crash
  *   on a valid config. Can run it in the fuzzer for some time. Should prbl also
  *   fuzz the config.
  */

 #include "modules/audio_coding/codecs/opus/audio_encoder_multi_channel_opus_impl.h"

 #include <algorithm>
 #include <memory>
 #include <string>
 #include <vector>

 #include "absl/strings/match.h"
 #include "modules/audio_coding/codecs/opus/audio_coder_opus_common.h"
 #include "rtc_base/arraysize.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/string_to_number.h"

 namespace webrtc {

 namespace {

 // Recommended bitrates for one channel:
 // 8-12 kb/s for NB speech,
 // 16-20 kb/s for WB speech,
 // 28-40 kb/s for FB speech,
 // 48-64 kb/s for FB mono music, and
 // 64-128 kb/s for FB stereo music.
 // The current implementation multiplies these values by the number of channels.
 constexpr int kOpusBitrateNbBps = 12000;
 constexpr int kOpusBitrateWbBps = 20000;
 constexpr int kOpusBitrateFbBps = 32000;

 constexpr int kDefaultMaxPlaybackRate = 48000;
 // These two lists must be sorted from low to high
 #if WEBRTC_OPUS_SUPPORT_120MS_PTIME
 constexpr int kOpusSupportedFrameLengths[] = {10, 20, 40, 60, 120};
 #else
 constexpr int kOpusSupportedFrameLengths[] = {10, 20, 40, 60};
 #endif

 int GetBitrateBps(const AudioEncoderMultiChannelOpusConfig& config) {
   RTC_DCHECK(config.IsOk());
   return config.bitrate_bps;
 }
 int GetMaxPlaybackRate(const SdpAudioFormat& format) {
   const auto param = GetFormatParameter<int>(format, "maxplaybackrate");
   if (param && *param >= 8000) {
     return std::min(*param, kDefaultMaxPlaybackRate);
   }
   return kDefaultMaxPlaybackRate;
 }

 int GetFrameSizeMs(const SdpAudioFormat& format) {
   const auto ptime = GetFormatParameter<int>(format, "ptime");
   if (ptime.has_value()) {
     // Pick the next highest supported frame length from
     // kOpusSupportedFrameLengths.
     for (const int supported_frame_length : kOpusSupportedFrameLengths) {
       if (supported_frame_length >= *ptime) {
         return supported_frame_length;
       }
     }
     // If none was found, return the largest supported frame length.
     return *(std::end(kOpusSupportedFrameLengths) - 1);
   }

   return AudioEncoderOpusConfig::kDefaultFrameSizeMs;
 }

 int CalculateDefaultBitrate(int max_playback_rate, size_t num_channels) {
   const int bitrate = [&] {
     if (max_playback_rate <= 8000) {
       return kOpusBitrateNbBps * rtc::dchecked_cast<int>(num_channels);
     } else if (max_playback_rate <= 16000) {
       return kOpusBitrateWbBps * rtc::dchecked_cast<int>(num_channels);
     } else {
       return kOpusBitrateFbBps * rtc::dchecked_cast<int>(num_channels);
     }
   }();
   RTC_DCHECK_GE(bitrate, AudioEncoderMultiChannelOpusConfig::kMinBitrateBps);
   return bitrate;
 }

 // Get the maxaveragebitrate parameter in string-form, so we can properly figure
 // out how invalid it is and accurately log invalid values.
 int CalculateBitrate(int max_playback_rate_hz,
                      size_t num_channels,
                      absl::optional<std::string> bitrate_param) {
   const int default_bitrate =
       CalculateDefaultBitrate(max_playback_rate_hz, num_channels);

   if (bitrate_param) {
     const auto bitrate = rtc::StringToNumber<int>(*bitrate_param);
     if (bitrate) {
       const int chosen_bitrate =
           std::max(AudioEncoderOpusConfig::kMinBitrateBps,
                    std::min(*bitrate, AudioEncoderOpusConfig::kMaxBitrateBps));
       if (bitrate != chosen_bitrate) {
         RTC_LOG(LS_WARNING) << "Invalid maxaveragebitrate " << *bitrate
                             << " clamped to " << chosen_bitrate;
       }
       return chosen_bitrate;
     }
     RTC_LOG(LS_WARNING) << "Invalid maxaveragebitrate \"" << *bitrate_param
                         << "\" replaced by default bitrate " << default_bitrate;
   }

   return default_bitrate;
 }

 }  // namespace

 std::unique_ptr<AudioEncoder>
 AudioEncoderMultiChannelOpusImpl::MakeAudioEncoder(
     const AudioEncoderMultiChannelOpusConfig& config,
     int payload_type) {
   if (!config.IsOk()) {
     return nullptr;
   }
   return std::make_unique<AudioEncoderMultiChannelOpusImpl>(config,
                                                             payload_type);
 }

 AudioEncoderMultiChannelOpusImpl::AudioEncoderMultiChannelOpusImpl(
     const AudioEncoderMultiChannelOpusConfig& config,
     int payload_type)
     : payload_type_(payload_type), inst_(nullptr) {
   RTC_DCHECK(0 <= payload_type && payload_type <= 127);

   RTC_CHECK(RecreateEncoderInstance(config));
 }

 AudioEncoderMultiChannelOpusImpl::~AudioEncoderMultiChannelOpusImpl() {
   RTC_CHECK_EQ(0, WebRtcOpus_EncoderFree(inst_));
 }

 size_t AudioEncoderMultiChannelOpusImpl::SufficientOutputBufferSize() const {
   // Calculate the number of bytes we expect the encoder to produce,
   // then multiply by two to give a wide margin for error.
   const size_t bytes_per_millisecond =
       static_cast<size_t>(GetBitrateBps(config_) / (1000 * 8) + 1);
   const size_t approx_encoded_bytes =
       Num10msFramesPerPacket() * 10 * bytes_per_millisecond;
   return 2 * approx_encoded_bytes;
 }

 void AudioEncoderMultiChannelOpusImpl::Reset() {
   RTC_CHECK(RecreateEncoderInstance(config_));
 }

 absl::optional<std::pair<TimeDelta, TimeDelta>>
 AudioEncoderMultiChannelOpusImpl::GetFrameLengthRange() const {
   return {{TimeDelta::Millis(config_.frame_size_ms),
            TimeDelta::Millis(config_.frame_size_ms)}};
 }

 // If the given config is OK, recreate the Opus encoder instance with those
 // settings, save the config, and return true. Otherwise, do nothing and return
 // false.
 bool AudioEncoderMultiChannelOpusImpl::RecreateEncoderInstance(
     const AudioEncoderMultiChannelOpusConfig& config) {
   if (!config.IsOk())
     return false;
   config_ = config;
   if (inst_)
     RTC_CHECK_EQ(0, WebRtcOpus_EncoderFree(inst_));
   input_buffer_.clear();
   input_buffer_.reserve(Num10msFramesPerPacket() * SamplesPer10msFrame());
   RTC_CHECK_EQ(
       0, WebRtcOpus_MultistreamEncoderCreate(
              &inst_, config.num_channels,
              config.application ==
                      AudioEncoderMultiChannelOpusConfig::ApplicationMode::kVoip
                  ? 0
                  : 1,
              config.num_streams, config.coupled_streams,
              config.channel_mapping.data()));
   const int bitrate = GetBitrateBps(config);
   RTC_CHECK_EQ(0, WebRtcOpus_SetBitRate(inst_, bitrate));
   RTC_LOG(LS_VERBOSE) << "Set Opus bitrate to " << bitrate << " bps.";
   if (config.fec_enabled) {
     RTC_CHECK_EQ(0, WebRtcOpus_EnableFec(inst_));
     RTC_LOG(LS_VERBOSE) << "Opus enable FEC";
   } else {
     RTC_CHECK_EQ(0, WebRtcOpus_DisableFec(inst_));
     RTC_LOG(LS_VERBOSE) << "Opus disable FEC";
   }
   RTC_CHECK_EQ(
       0, WebRtcOpus_SetMaxPlaybackRate(inst_, config.max_playback_rate_hz));
   RTC_LOG(LS_VERBOSE) << "Set Opus playback rate to "
                       << config.max_playback_rate_hz << " hz.";

   // Use the DEFAULT complexity.
   RTC_CHECK_EQ(
       0, WebRtcOpus_SetComplexity(inst_, AudioEncoderOpusConfig().complexity));
   RTC_LOG(LS_VERBOSE) << "Set Opus coding complexity to "
                       << AudioEncoderOpusConfig().complexity;

   if (config.dtx_enabled) {
     RTC_CHECK_EQ(0, WebRtcOpus_EnableDtx(inst_));
     RTC_LOG(LS_VERBOSE) << "Opus enable DTX";
   } else {
     RTC_CHECK_EQ(0, WebRtcOpus_DisableDtx(inst_));
     RTC_LOG(LS_VERBOSE) << "Opus disable DTX";
   }

   if (config.cbr_enabled) {
     RTC_CHECK_EQ(0, WebRtcOpus_EnableCbr(inst_));
     RTC_LOG(LS_VERBOSE) << "Opus enable CBR";
   } else {
     RTC_CHECK_EQ(0, WebRtcOpus_DisableCbr(inst_));
     RTC_LOG(LS_VERBOSE) << "Opus disable CBR";
   }
   num_channels_to_encode_ = NumChannels();
   next_frame_length_ms_ = config_.frame_size_ms;
   RTC_LOG(LS_VERBOSE) << "Set Opus frame length to " << config_.frame_size_ms
                       << " ms";
   return true;
 }

 absl::optional<AudioEncoderMultiChannelOpusConfig>
 AudioEncoderMultiChannelOpusImpl::SdpToConfig(const SdpAudioFormat& format) {
   if (!absl::EqualsIgnoreCase(format.name, "multiopus") ||
       format.clockrate_hz != 48000) {
     return absl::nullopt;
   }

   AudioEncoderMultiChannelOpusConfig config;
   config.num_channels = format.num_channels;
   config.frame_size_ms = GetFrameSizeMs(format);
   config.max_playback_rate_hz = GetMaxPlaybackRate(format);
   config.fec_enabled = (GetFormatParameter(format, "useinbandfec") == "1");
   config.dtx_enabled = (GetFormatParameter(format, "usedtx") == "1");
   config.cbr_enabled = (GetFormatParameter(format, "cbr") == "1");
   config.bitrate_bps =
       CalculateBitrate(config.max_playback_rate_hz, config.num_channels,
                        GetFormatParameter(format, "maxaveragebitrate"));
   config.application =
       config.num_channels == 1
           ? AudioEncoderMultiChannelOpusConfig::ApplicationMode::kVoip
           : AudioEncoderMultiChannelOpusConfig::ApplicationMode::kAudio;

   config.supported_frame_lengths_ms.clear();
   std::copy(std::begin(kOpusSupportedFrameLengths),
             std::end(kOpusSupportedFrameLengths),
             std::back_inserter(config.supported_frame_lengths_ms));

   auto num_streams = GetFormatParameter<int>(format, "num_streams");
   if (!num_streams.has_value()) {
     return absl::nullopt;
   }
   config.num_streams = *num_streams;

   auto coupled_streams = GetFormatParameter<int>(format, "coupled_streams");
   if (!coupled_streams.has_value()) {
     return absl::nullopt;
   }
   config.coupled_streams = *coupled_streams;

   auto channel_mapping =
       GetFormatParameter<std::vector<unsigned char>>(format, "channel_mapping");
   if (!channel_mapping.has_value()) {
     return absl::nullopt;
   }
   config.channel_mapping = *channel_mapping;

   return config;
 }

 AudioCodecInfo AudioEncoderMultiChannelOpusImpl::QueryAudioEncoder(
     const AudioEncoderMultiChannelOpusConfig& config) {
   RTC_DCHECK(config.IsOk());
   AudioCodecInfo info(48000, config.num_channels, config.bitrate_bps,
                       AudioEncoderOpusConfig::kMinBitrateBps,
                       AudioEncoderOpusConfig::kMaxBitrateBps);
   info.allow_comfort_noise = false;
   info.supports_network_adaption = false;
   return info;
 }

 size_t AudioEncoderMultiChannelOpusImpl::Num10msFramesPerPacket() const {
   return static_cast<size_t>(rtc::CheckedDivExact(config_.frame_size_ms, 10));
 }
 size_t AudioEncoderMultiChannelOpusImpl::SamplesPer10msFrame() const {
   return rtc::CheckedDivExact(48000, 100) * config_.num_channels;
 }
 int AudioEncoderMultiChannelOpusImpl::SampleRateHz() const {
   return 48000;
 }
 size_t AudioEncoderMultiChannelOpusImpl::NumChannels() const {
   return config_.num_channels;
 }
 size_t AudioEncoderMultiChannelOpusImpl::Num10MsFramesInNextPacket() const {
   return Num10msFramesPerPacket();
 }
 size_t AudioEncoderMultiChannelOpusImpl::Max10MsFramesInAPacket() const {
   return Num10msFramesPerPacket();
 }
 int AudioEncoderMultiChannelOpusImpl::GetTargetBitrate() const {
   return GetBitrateBps(config_);
 }

 AudioEncoder::EncodedInfo AudioEncoderMultiChannelOpusImpl::EncodeImpl(
     uint32_t rtp_timestamp,
     rtc::ArrayView<const int16_t> audio,
     rtc::Buffer* encoded) {
   if (input_buffer_.empty())
     first_timestamp_in_buffer_ = rtp_timestamp;

   input_buffer_.insert(input_buffer_.end(), audio.cbegin(), audio.cend());
   if (input_buffer_.size() <
       (Num10msFramesPerPacket() * SamplesPer10msFrame())) {
     return EncodedInfo();
   }
   RTC_CHECK_EQ(input_buffer_.size(),
                Num10msFramesPerPacket() * SamplesPer10msFrame());

   const size_t max_encoded_bytes = SufficientOutputBufferSize();
   EncodedInfo info;
   info.encoded_bytes = encoded->AppendData(
       max_encoded_bytes, [&](rtc::ArrayView<uint8_t> encoded) {
         int status = WebRtcOpus_Encode(
             inst_, &input_buffer_[0],
             rtc::CheckedDivExact(input_buffer_.size(), config_.num_channels),
             rtc::saturated_cast<int16_t>(max_encoded_bytes), encoded.data());

         RTC_CHECK_GE(status, 0);  // Fails only if fed invalid data.

         return static_cast<size_t>(status);
       });
   input_buffer_.clear();

   // Will use new packet size for next encoding.
   config_.frame_size_ms = next_frame_length_ms_;

   info.encoded_timestamp = first_timestamp_in_buffer_;
   info.payload_type = payload_type_;
   info.send_even_if_empty = true;  // Allows Opus to send empty packets.

   info.speech = true;
   info.encoder_type = CodecType::kOther;

   return info;
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2019 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.
	*/

	/*
	* LEFT TO DO:
	* - WRITE TESTS for the stuff in this file.
	* - Check the creation, maybe make it safer by returning an empty optional or
	* unique_ptr. --- It looks OK, but RecreateEncoderInstance can perhaps crash
	* on a valid config. Can run it in the fuzzer for some time. Should prbl also
	* fuzz the config.
	*/

	#include "modules/audio_coding/codecs/opus/audio_encoder_multi_channel_opus_impl.h"

	#include <algorithm>
	#include <memory>
	#include <string>
	#include <vector>

	#include "absl/strings/match.h"
	#include "modules/audio_coding/codecs/opus/audio_coder_opus_common.h"
	#include "rtc_base/arraysize.h"
	#include "rtc_base/checks.h"
	#include "rtc_base/logging.h"
	#include "rtc_base/string_to_number.h"

	namespace webrtc {

	namespace {

	// Recommended bitrates for one channel:
	// 8-12 kb/s for NB speech,
	// 16-20 kb/s for WB speech,
	// 28-40 kb/s for FB speech,
	// 48-64 kb/s for FB mono music, and
	// 64-128 kb/s for FB stereo music.
	// The current implementation multiplies these values by the number of channels.
	constexpr int kOpusBitrateNbBps = 12000;
	constexpr int kOpusBitrateWbBps = 20000;
	constexpr int kOpusBitrateFbBps = 32000;

	constexpr int kDefaultMaxPlaybackRate = 48000;
	// These two lists must be sorted from low to high
	#if WEBRTC_OPUS_SUPPORT_120MS_PTIME
	constexpr int kOpusSupportedFrameLengths[] = {10, 20, 40, 60, 120};
	#else
	constexpr int kOpusSupportedFrameLengths[] = {10, 20, 40, 60};
	#endif

	int GetBitrateBps(const AudioEncoderMultiChannelOpusConfig& config) {
	RTC_DCHECK(config.IsOk());
	return config.bitrate_bps;
	}
	int GetMaxPlaybackRate(const SdpAudioFormat& format) {
	const auto param = GetFormatParameter<int>(format, "maxplaybackrate");
	if (param && *param >= 8000) {
	return std::min(*param, kDefaultMaxPlaybackRate);
	}
	return kDefaultMaxPlaybackRate;
	}

	int GetFrameSizeMs(const SdpAudioFormat& format) {
	const auto ptime = GetFormatParameter<int>(format, "ptime");
	if (ptime.has_value()) {
	// Pick the next highest supported frame length from
	// kOpusSupportedFrameLengths.
	for (const int supported_frame_length : kOpusSupportedFrameLengths) {
	if (supported_frame_length >= *ptime) {
	return supported_frame_length;
	}
	}
	// If none was found, return the largest supported frame length.
	return *(std::end(kOpusSupportedFrameLengths) - 1);
	}

	return AudioEncoderOpusConfig::kDefaultFrameSizeMs;
	}

	int CalculateDefaultBitrate(int max_playback_rate, size_t num_channels) {
	const int bitrate = [&] {
	if (max_playback_rate <= 8000) {
	return kOpusBitrateNbBps * rtc::dchecked_cast<int>(num_channels);
	} else if (max_playback_rate <= 16000) {
	return kOpusBitrateWbBps * rtc::dchecked_cast<int>(num_channels);
	} else {
	return kOpusBitrateFbBps * rtc::dchecked_cast<int>(num_channels);
	}
	}();
	RTC_DCHECK_GE(bitrate, AudioEncoderMultiChannelOpusConfig::kMinBitrateBps);
	return bitrate;
	}

	// Get the maxaveragebitrate parameter in string-form, so we can properly figure
	// out how invalid it is and accurately log invalid values.
	int CalculateBitrate(int max_playback_rate_hz,
	size_t num_channels,
	absl::optional<std::string> bitrate_param) {
	const int default_bitrate =
	CalculateDefaultBitrate(max_playback_rate_hz, num_channels);

	if (bitrate_param) {
	const auto bitrate = rtc::StringToNumber<int>(*bitrate_param);
	if (bitrate) {
	const int chosen_bitrate =
	std::max(AudioEncoderOpusConfig::kMinBitrateBps,
	std::min(*bitrate, AudioEncoderOpusConfig::kMaxBitrateBps));
	if (bitrate != chosen_bitrate) {
	RTC_LOG(LS_WARNING) << "Invalid maxaveragebitrate " << *bitrate
	<< " clamped to " << chosen_bitrate;
	}
	return chosen_bitrate;
	}
	RTC_LOG(LS_WARNING) << "Invalid maxaveragebitrate \"" << *bitrate_param
	<< "\" replaced by default bitrate " << default_bitrate;
	}

	return default_bitrate;
	}

	} // namespace

	std::unique_ptr<AudioEncoder>
	AudioEncoderMultiChannelOpusImpl::MakeAudioEncoder(
	const AudioEncoderMultiChannelOpusConfig& config,
	int payload_type) {
	if (!config.IsOk()) {
	return nullptr;
	}
	return std::make_unique<AudioEncoderMultiChannelOpusImpl>(config,
	payload_type);
	}

	AudioEncoderMultiChannelOpusImpl::AudioEncoderMultiChannelOpusImpl(
	const AudioEncoderMultiChannelOpusConfig& config,
	int payload_type)
	: payload_type_(payload_type), inst_(nullptr) {
	RTC_DCHECK(0 <= payload_type && payload_type <= 127);

	RTC_CHECK(RecreateEncoderInstance(config));
	}

	AudioEncoderMultiChannelOpusImpl::~AudioEncoderMultiChannelOpusImpl() {
	RTC_CHECK_EQ(0, WebRtcOpus_EncoderFree(inst_));
	}

	size_t AudioEncoderMultiChannelOpusImpl::SufficientOutputBufferSize() const {
	// Calculate the number of bytes we expect the encoder to produce,
	// then multiply by two to give a wide margin for error.
	const size_t bytes_per_millisecond =
	static_cast<size_t>(GetBitrateBps(config_) / (1000 * 8) + 1);
	const size_t approx_encoded_bytes =
	Num10msFramesPerPacket() * 10 * bytes_per_millisecond;
	return 2 * approx_encoded_bytes;
	}

	void AudioEncoderMultiChannelOpusImpl::Reset() {
	RTC_CHECK(RecreateEncoderInstance(config_));
	}

	absl::optional<std::pair<TimeDelta, TimeDelta>>
	AudioEncoderMultiChannelOpusImpl::GetFrameLengthRange() const {
	return {{TimeDelta::Millis(config_.frame_size_ms),
	TimeDelta::Millis(config_.frame_size_ms)}};
	}

	// If the given config is OK, recreate the Opus encoder instance with those
	// settings, save the config, and return true. Otherwise, do nothing and return
	// false.
	bool AudioEncoderMultiChannelOpusImpl::RecreateEncoderInstance(
	const AudioEncoderMultiChannelOpusConfig& config) {
	if (!config.IsOk())
	return false;
	config_ = config;
	if (inst_)
	RTC_CHECK_EQ(0, WebRtcOpus_EncoderFree(inst_));
	input_buffer_.clear();
	input_buffer_.reserve(Num10msFramesPerPacket() * SamplesPer10msFrame());
	RTC_CHECK_EQ(
	0, WebRtcOpus_MultistreamEncoderCreate(
	&inst_, config.num_channels,
	config.application ==
	AudioEncoderMultiChannelOpusConfig::ApplicationMode::kVoip
	? 0
	: 1,
	config.num_streams, config.coupled_streams,
	config.channel_mapping.data()));
	const int bitrate = GetBitrateBps(config);
	RTC_CHECK_EQ(0, WebRtcOpus_SetBitRate(inst_, bitrate));
	RTC_LOG(LS_VERBOSE) << "Set Opus bitrate to " << bitrate << " bps.";
	if (config.fec_enabled) {
	RTC_CHECK_EQ(0, WebRtcOpus_EnableFec(inst_));
	RTC_LOG(LS_VERBOSE) << "Opus enable FEC";
	} else {
	RTC_CHECK_EQ(0, WebRtcOpus_DisableFec(inst_));
	RTC_LOG(LS_VERBOSE) << "Opus disable FEC";
	}
	RTC_CHECK_EQ(
	0, WebRtcOpus_SetMaxPlaybackRate(inst_, config.max_playback_rate_hz));
	RTC_LOG(LS_VERBOSE) << "Set Opus playback rate to "
	<< config.max_playback_rate_hz << " hz.";

	// Use the DEFAULT complexity.
	RTC_CHECK_EQ(
	0, WebRtcOpus_SetComplexity(inst_, AudioEncoderOpusConfig().complexity));
	RTC_LOG(LS_VERBOSE) << "Set Opus coding complexity to "
	<< AudioEncoderOpusConfig().complexity;

	if (config.dtx_enabled) {
	RTC_CHECK_EQ(0, WebRtcOpus_EnableDtx(inst_));
	RTC_LOG(LS_VERBOSE) << "Opus enable DTX";
	} else {
	RTC_CHECK_EQ(0, WebRtcOpus_DisableDtx(inst_));
	RTC_LOG(LS_VERBOSE) << "Opus disable DTX";
	}

	if (config.cbr_enabled) {
	RTC_CHECK_EQ(0, WebRtcOpus_EnableCbr(inst_));
	RTC_LOG(LS_VERBOSE) << "Opus enable CBR";
	} else {
	RTC_CHECK_EQ(0, WebRtcOpus_DisableCbr(inst_));
	RTC_LOG(LS_VERBOSE) << "Opus disable CBR";
	}
	num_channels_to_encode_ = NumChannels();
	next_frame_length_ms_ = config_.frame_size_ms;
	RTC_LOG(LS_VERBOSE) << "Set Opus frame length to " << config_.frame_size_ms
	<< " ms";
	return true;
	}

	absl::optional<AudioEncoderMultiChannelOpusConfig>
	AudioEncoderMultiChannelOpusImpl::SdpToConfig(const SdpAudioFormat& format) {
	if (!absl::EqualsIgnoreCase(format.name, "multiopus") \|\|
	format.clockrate_hz != 48000) {
	return absl::nullopt;
	}

	AudioEncoderMultiChannelOpusConfig config;
	config.num_channels = format.num_channels;
	config.frame_size_ms = GetFrameSizeMs(format);
	config.max_playback_rate_hz = GetMaxPlaybackRate(format);
	config.fec_enabled = (GetFormatParameter(format, "useinbandfec") == "1");
	config.dtx_enabled = (GetFormatParameter(format, "usedtx") == "1");
	config.cbr_enabled = (GetFormatParameter(format, "cbr") == "1");
	config.bitrate_bps =
	CalculateBitrate(config.max_playback_rate_hz, config.num_channels,
	GetFormatParameter(format, "maxaveragebitrate"));
	config.application =
	config.num_channels == 1
	? AudioEncoderMultiChannelOpusConfig::ApplicationMode::kVoip
	: AudioEncoderMultiChannelOpusConfig::ApplicationMode::kAudio;

	config.supported_frame_lengths_ms.clear();
	std::copy(std::begin(kOpusSupportedFrameLengths),
	std::end(kOpusSupportedFrameLengths),
	std::back_inserter(config.supported_frame_lengths_ms));

	auto num_streams = GetFormatParameter<int>(format, "num_streams");
	if (!num_streams.has_value()) {
	return absl::nullopt;
	}
	config.num_streams = *num_streams;

	auto coupled_streams = GetFormatParameter<int>(format, "coupled_streams");
	if (!coupled_streams.has_value()) {
	return absl::nullopt;
	}
	config.coupled_streams = *coupled_streams;

	auto channel_mapping =
	GetFormatParameter<std::vector<unsigned char>>(format, "channel_mapping");
	if (!channel_mapping.has_value()) {
	return absl::nullopt;
	}
	config.channel_mapping = *channel_mapping;

	return config;
	}

	AudioCodecInfo AudioEncoderMultiChannelOpusImpl::QueryAudioEncoder(
	const AudioEncoderMultiChannelOpusConfig& config) {
	RTC_DCHECK(config.IsOk());
	AudioCodecInfo info(48000, config.num_channels, config.bitrate_bps,
	AudioEncoderOpusConfig::kMinBitrateBps,
	AudioEncoderOpusConfig::kMaxBitrateBps);
	info.allow_comfort_noise = false;
	info.supports_network_adaption = false;
	return info;
	}

	size_t AudioEncoderMultiChannelOpusImpl::Num10msFramesPerPacket() const {
	return static_cast<size_t>(rtc::CheckedDivExact(config_.frame_size_ms, 10));
	}
	size_t AudioEncoderMultiChannelOpusImpl::SamplesPer10msFrame() const {
	return rtc::CheckedDivExact(48000, 100) * config_.num_channels;
	}
	int AudioEncoderMultiChannelOpusImpl::SampleRateHz() const {
	return 48000;
	}
	size_t AudioEncoderMultiChannelOpusImpl::NumChannels() const {
	return config_.num_channels;
	}
	size_t AudioEncoderMultiChannelOpusImpl::Num10MsFramesInNextPacket() const {
	return Num10msFramesPerPacket();
	}
	size_t AudioEncoderMultiChannelOpusImpl::Max10MsFramesInAPacket() const {
	return Num10msFramesPerPacket();
	}
	int AudioEncoderMultiChannelOpusImpl::GetTargetBitrate() const {
	return GetBitrateBps(config_);
	}

	AudioEncoder::EncodedInfo AudioEncoderMultiChannelOpusImpl::EncodeImpl(
	uint32_t rtp_timestamp,
	rtc::ArrayView<const int16_t> audio,
	rtc::Buffer* encoded) {
	if (input_buffer_.empty())
	first_timestamp_in_buffer_ = rtp_timestamp;

	input_buffer_.insert(input_buffer_.end(), audio.cbegin(), audio.cend());
	if (input_buffer_.size() <
	(Num10msFramesPerPacket() * SamplesPer10msFrame())) {
	return EncodedInfo();
	}
	RTC_CHECK_EQ(input_buffer_.size(),
	Num10msFramesPerPacket() * SamplesPer10msFrame());

	const size_t max_encoded_bytes = SufficientOutputBufferSize();
	EncodedInfo info;
	info.encoded_bytes = encoded->AppendData(
	max_encoded_bytes, [&](rtc::ArrayView<uint8_t> encoded) {
	int status = WebRtcOpus_Encode(
	inst_, &input_buffer_[0],
	rtc::CheckedDivExact(input_buffer_.size(), config_.num_channels),
	rtc::saturated_cast<int16_t>(max_encoded_bytes), encoded.data());

	RTC_CHECK_GE(status, 0); // Fails only if fed invalid data.

	return static_cast<size_t>(status);
	});
	input_buffer_.clear();

	// Will use new packet size for next encoding.
	config_.frame_size_ms = next_frame_length_ms_;

	info.encoded_timestamp = first_timestamp_in_buffer_;
	info.payload_type = payload_type_;
	info.send_even_if_empty = true; // Allows Opus to send empty packets.

	info.speech = true;
	info.encoder_type = CodecType::kOther;

	return info;
	}

	} // namespace webrtc