stack/a2dp/a2dp_aac_encoder.cc

/*
 * Copyright 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "a2dp_aac_encoder"

#include "a2dp_aac_encoder.h"

#include <inttypes.h>
#include <math.h>
#include <stdio.h>
#include <string.h>

#include <aacenc_lib.h>
#include <base/logging.h>

#include "a2dp_aac.h"
#include "bt_common.h"
#include "common/time_util.h"
#include "osi/include/log.h"
#include "osi/include/osi.h"

//
// Encoder for AAC Source Codec
//

// A2DP AAC encoder interval in milliseconds
#define A2DP_AAC_ENCODER_INTERVAL_MS 20

// offset
#if (BTA_AV_CO_CP_SCMS_T == TRUE)
#define A2DP_AAC_OFFSET (AVDT_MEDIA_OFFSET + 1)
#else
#define A2DP_AAC_OFFSET AVDT_MEDIA_OFFSET
#endif

typedef struct {
  uint32_t sample_rate;
  uint8_t channel_mode;
  uint8_t bits_per_sample;
  uint32_t frame_length;         // Samples per channel in a frame
  uint8_t input_channels_n;      // Number of channels
  int max_encoded_buffer_bytes;  // Max encoded bytes per frame
} tA2DP_AAC_ENCODER_PARAMS;

typedef struct {
  uint32_t counter;
  uint32_t bytes_per_tick;              // pcm bytes read each media task tick
  uint64_t last_frame_timestamp_100ns;  // values in 1/10 microseconds
} tA2DP_AAC_FEEDING_STATE;

typedef struct {
  uint64_t session_start_us;

  size_t media_read_total_expected_packets;
  size_t media_read_total_expected_reads_count;
  size_t media_read_total_expected_read_bytes;

  size_t media_read_total_dropped_packets;
  size_t media_read_total_actual_reads_count;
  size_t media_read_total_actual_read_bytes;
} a2dp_aac_encoder_stats_t;

typedef struct {
  a2dp_source_read_callback_t read_callback;
  a2dp_source_enqueue_callback_t enqueue_callback;
  uint16_t TxAaMtuSize;

  bool use_SCMS_T;
  bool is_peer_edr;          // True if the peer device supports EDR
  bool peer_supports_3mbps;  // True if the peer device supports 3Mbps EDR
  uint16_t peer_mtu;         // MTU of the A2DP peer
  uint32_t timestamp;        // Timestamp for the A2DP frames

  HANDLE_AACENCODER aac_handle;
  bool has_aac_handle;  // True if aac_handle is valid

  tA2DP_FEEDING_PARAMS feeding_params;
  tA2DP_AAC_ENCODER_PARAMS aac_encoder_params;
  tA2DP_AAC_FEEDING_STATE aac_feeding_state;

  a2dp_aac_encoder_stats_t stats;
} tA2DP_AAC_ENCODER_CB;

static uint32_t a2dp_aac_encoder_interval_ms = A2DP_AAC_ENCODER_INTERVAL_MS;

static tA2DP_AAC_ENCODER_CB a2dp_aac_encoder_cb;

static void a2dp_aac_encoder_update(uint16_t peer_mtu,
                                    A2dpCodecConfig* a2dp_codec_config,
                                    bool* p_restart_input,
                                    bool* p_restart_output,
                                    bool* p_config_updated);
static void a2dp_aac_get_num_frame_iteration(uint8_t* num_of_iterations,
                                             uint8_t* num_of_frames,
                                             uint64_t timestamp_us);
static void a2dp_aac_encode_frames(uint8_t nb_frame);
static bool a2dp_aac_read_feeding(uint8_t* read_buffer, uint32_t* bytes_read);

bool A2DP_LoadEncoderAac(void) {
  // Nothing to do - the library is statically linked
  return true;
}

void A2DP_UnloadEncoderAac(void) {
  // Nothing to do - the library is statically linked
  if (a2dp_aac_encoder_cb.has_aac_handle)
    aacEncClose(&a2dp_aac_encoder_cb.aac_handle);
  memset(&a2dp_aac_encoder_cb, 0, sizeof(a2dp_aac_encoder_cb));
}

void a2dp_aac_encoder_init(const tA2DP_ENCODER_INIT_PEER_PARAMS* p_peer_params,
                           A2dpCodecConfig* a2dp_codec_config,
                           a2dp_source_read_callback_t read_callback,
                           a2dp_source_enqueue_callback_t enqueue_callback) {
  if (a2dp_aac_encoder_cb.has_aac_handle)
    aacEncClose(&a2dp_aac_encoder_cb.aac_handle);
  memset(&a2dp_aac_encoder_cb, 0, sizeof(a2dp_aac_encoder_cb));

  a2dp_aac_encoder_cb.stats.session_start_us =
      bluetooth::common::time_get_os_boottime_us();

  a2dp_aac_encoder_cb.read_callback = read_callback;
  a2dp_aac_encoder_cb.enqueue_callback = enqueue_callback;
  a2dp_aac_encoder_cb.is_peer_edr = p_peer_params->is_peer_edr;
  a2dp_aac_encoder_cb.peer_supports_3mbps = p_peer_params->peer_supports_3mbps;
  a2dp_aac_encoder_cb.peer_mtu = p_peer_params->peer_mtu;
  a2dp_aac_encoder_cb.timestamp = 0;

  a2dp_aac_encoder_cb.use_SCMS_T = false;  // TODO: should be a parameter
#if (BTA_AV_CO_CP_SCMS_T == TRUE)
  a2dp_aac_encoder_cb.use_SCMS_T = true;
#endif

  // NOTE: Ignore the restart_input / restart_output flags - this initization
  // happens when the connection is (re)started.
  bool restart_input = false;
  bool restart_output = false;
  bool config_updated = false;
  a2dp_aac_encoder_update(a2dp_aac_encoder_cb.peer_mtu, a2dp_codec_config,
                          &restart_input, &restart_output, &config_updated);
}

bool A2dpCodecConfigAacSource::updateEncoderUserConfig(
    const tA2DP_ENCODER_INIT_PEER_PARAMS* p_peer_params, bool* p_restart_input,
    bool* p_restart_output, bool* p_config_updated) {
  a2dp_aac_encoder_cb.is_peer_edr = p_peer_params->is_peer_edr;
  a2dp_aac_encoder_cb.peer_supports_3mbps = p_peer_params->peer_supports_3mbps;
  a2dp_aac_encoder_cb.peer_mtu = p_peer_params->peer_mtu;
  a2dp_aac_encoder_cb.timestamp = 0;

  if (a2dp_aac_encoder_cb.peer_mtu == 0) {
    LOG_ERROR(
        "%s: Cannot update the codec encoder for %s: "
        "invalid peer MTU",
        __func__, name().c_str());
    return false;
  }

  a2dp_aac_encoder_update(a2dp_aac_encoder_cb.peer_mtu, this, p_restart_input,
                          p_restart_output, p_config_updated);
  return true;
}

// Update the A2DP AAC encoder.
// |peer_mtu| is the peer MTU.
// |a2dp_codec_config| is the A2DP codec to use for the update.
static void a2dp_aac_encoder_update(uint16_t peer_mtu,
                                    A2dpCodecConfig* a2dp_codec_config,
                                    bool* p_restart_input,
                                    bool* p_restart_output,
                                    bool* p_config_updated) {
  tA2DP_AAC_ENCODER_PARAMS* p_encoder_params =
      &a2dp_aac_encoder_cb.aac_encoder_params;
  uint8_t codec_info[AVDT_CODEC_SIZE];
  AACENC_ERROR aac_error;
  int aac_param_value, aac_sampling_freq, aac_peak_bit_rate;

  *p_restart_input = false;
  *p_restart_output = false;
  *p_config_updated = false;

  if (!a2dp_aac_encoder_cb.has_aac_handle) {
    AACENC_ERROR aac_error = aacEncOpen(&a2dp_aac_encoder_cb.aac_handle, 0,
                                        2 /* max 2 channels: stereo */);
    if (aac_error != AACENC_OK) {
      LOG_ERROR("%s: Cannot open AAC encoder handle: AAC error 0x%x", __func__,
                aac_error);
      return;  // TODO: Return an error?
    }
    a2dp_aac_encoder_cb.has_aac_handle = true;
  }

  if (!a2dp_codec_config->copyOutOtaCodecConfig(codec_info)) {
    LOG_ERROR(
        "%s: Cannot update the codec encoder for %s: "
        "invalid codec config",
        __func__, a2dp_codec_config->name().c_str());
    return;
  }
  const uint8_t* p_codec_info = codec_info;

  // The feeding parameters
  tA2DP_FEEDING_PARAMS* p_feeding_params = &a2dp_aac_encoder_cb.feeding_params;
  p_feeding_params->sample_rate = A2DP_GetTrackSampleRateAac(p_codec_info);
  p_feeding_params->bits_per_sample =
      a2dp_codec_config->getAudioBitsPerSample();
  p_feeding_params->channel_count = A2DP_GetTrackChannelCountAac(p_codec_info);
  LOG_DEBUG("%s: sample_rate=%u bits_per_sample=%u channel_count=%u", __func__,
            p_feeding_params->sample_rate, p_feeding_params->bits_per_sample,
            p_feeding_params->channel_count);

  // The codec parameters
  p_encoder_params->sample_rate =
      a2dp_aac_encoder_cb.feeding_params.sample_rate;
  p_encoder_params->channel_mode = A2DP_GetChannelModeCodeAac(p_codec_info);

  LOG_VERBOSE("%s: original AVDTP MTU size: %d", __func__,
              a2dp_aac_encoder_cb.TxAaMtuSize);
  if (a2dp_aac_encoder_cb.is_peer_edr &&
      !a2dp_aac_encoder_cb.peer_supports_3mbps) {
    // This condition would be satisfied only if the remote device is
    // EDR and supports only 2 Mbps, but the effective AVDTP MTU size
    // exceeds the 2DH5 packet size.
    LOG_VERBOSE("%s: The remote device is EDR but does not support 3 Mbps",
                __func__);
    if (peer_mtu > MAX_2MBPS_AVDTP_MTU) {
      LOG_WARN("%s: Restricting AVDTP MTU size from %d to %d", __func__,
               peer_mtu, MAX_2MBPS_AVDTP_MTU);
      peer_mtu = MAX_2MBPS_AVDTP_MTU;
    }
  }
  uint16_t mtu_size = BT_DEFAULT_BUFFER_SIZE - A2DP_AAC_OFFSET - sizeof(BT_HDR);
  if (mtu_size < peer_mtu) {
    a2dp_aac_encoder_cb.TxAaMtuSize = mtu_size;
  } else {
    a2dp_aac_encoder_cb.TxAaMtuSize = peer_mtu;
  }

  LOG_DEBUG("%s: MTU=%d, peer_mtu=%d", __func__,
            a2dp_aac_encoder_cb.TxAaMtuSize, peer_mtu);
  LOG_DEBUG("%s: sample_rate: %d channel_mode: %d ", __func__,
            p_encoder_params->sample_rate, p_encoder_params->channel_mode);

  // Set the encoder's parameters: Audio Object Type - MANDATORY
  // A2DP_AAC_OBJECT_TYPE_MPEG2_LC -> AOT_AAC_LC
  // A2DP_AAC_OBJECT_TYPE_MPEG4_LC -> AOT_AAC_LC
  // A2DP_AAC_OBJECT_TYPE_MPEG4_LTP -> AOT_AAC_LTP
  // A2DP_AAC_OBJECT_TYPE_MPEG4_SCALABLE -> AOT_AAC_SCAL
  aac_param_value = AOT_AAC_LC;
  int object_type = A2DP_GetObjectTypeCodeAac(p_codec_info);
  switch (object_type) {
    case A2DP_AAC_OBJECT_TYPE_MPEG2_LC:
      aac_param_value = AOT_AAC_LC;
      break;
    case A2DP_AAC_OBJECT_TYPE_MPEG4_LC:
      aac_param_value = AOT_AAC_LC;
      break;
    case A2DP_AAC_OBJECT_TYPE_MPEG4_LTP:
      aac_param_value = AOT_AAC_LTP;
      break;
    case A2DP_AAC_OBJECT_TYPE_MPEG4_SCALABLE:
      aac_param_value = AOT_AAC_SCAL;
      break;
    default:
      LOG_ERROR(
          "%s: Cannot set AAC parameter AACENC_AOT: "
          "invalid object type %d",
          __func__, object_type);
      return;  // TODO: Return an error?
  }
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle, AACENC_AOT,
                                  aac_param_value);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_AOT to %d: "
        "AAC error 0x%x",
        __func__, aac_param_value, aac_error);
    return;  // TODO: Return an error?
  }

  // Set the encoder's parameters: audioMuxVersion
  aac_param_value = 2;  // audioMuxVersion = "2"
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle,
                                  AACENC_AUDIOMUXVER, aac_param_value);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_AUDIOMUXVER to %d: "
        "AAC error 0x%x",
        __func__, aac_param_value, aac_error);
    return;  // TODO: Return an error?
  }

  // Set the encoder's parameters: Signaling mode of the extension AOT
  aac_param_value = 1;  // Signaling mode of the extension AOT = 1
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle,
                                  AACENC_SIGNALING_MODE, aac_param_value);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_SIGNALING_MODE to %d: "
        "AAC error 0x%x",
        __func__, aac_param_value, aac_error);
    return;  // TODO: Return an error?
  }

  // Set the encoder's parameters: Sample Rate - MANDATORY
  aac_param_value = A2DP_GetTrackSampleRateAac(p_codec_info);
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle,
                                  AACENC_SAMPLERATE, aac_param_value);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_SAMPLERATE to %d: "
        "AAC error 0x%x",
        __func__, aac_param_value, aac_error);
    return;  // TODO: Return an error?
  }
  aac_sampling_freq = aac_param_value;  // Save for extra usage below

  // Set the encoder's parameters: Bit Rate - MANDATORY
  aac_param_value = A2DP_GetBitRateAac(p_codec_info);
  // Calculate the bit rate from MTU and sampling frequency
  aac_peak_bit_rate =
      A2DP_ComputeMaxBitRateAac(p_codec_info, a2dp_aac_encoder_cb.TxAaMtuSize);
  aac_param_value = std::min(aac_param_value, aac_peak_bit_rate);
  LOG_DEBUG("%s: MTU = %d Sampling Frequency = %d Bit Rate = %d", __func__,
            a2dp_aac_encoder_cb.TxAaMtuSize, aac_sampling_freq,
            aac_param_value);
  if (aac_param_value == -1) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_BITRATE: "
        "invalid codec bit rate",
        __func__);
    return;  // TODO: Return an error?
  }
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle,
                                  AACENC_BITRATE, aac_param_value);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_BITRATE to %d: "
        "AAC error 0x%x",
        __func__, aac_param_value, aac_error);
    return;  // TODO: Return an error?
  }

  // Set the encoder's parameters: PEAK Bit Rate
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle,
                                  AACENC_PEAK_BITRATE, aac_peak_bit_rate);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_PEAK_BITRATE to %d: "
        "AAC error 0x%x",
        __func__, aac_peak_bit_rate, aac_error);
    return;  // TODO: Return an error?
  }

  // Set the encoder's parameters: Channel Mode - MANDATORY
  if (A2DP_GetTrackChannelCountAac(p_codec_info) == 1) {
    aac_param_value = MODE_1;  // Mono
  } else {
    aac_param_value = MODE_2;  // Stereo
  }
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle,
                                  AACENC_CHANNELMODE, aac_param_value);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_CHANNELMODE to %d: "
        "AAC error 0x%x",
        __func__, aac_param_value, aac_error);
    return;  // TODO: Return an error?
  }

  // Set the encoder's parameters: Transport Type
  aac_param_value = TT_MP4_LATM_MCP1;  // muxConfigPresent = 1
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle,
                                  AACENC_TRANSMUX, aac_param_value);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_TRANSMUX to %d: "
        "AAC error 0x%x",
        __func__, aac_param_value, aac_error);
    return;  // TODO: Return an error?
  }

  // Set the encoder's parameters: Header Period
  aac_param_value = 1;
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle,
                                  AACENC_HEADER_PERIOD, aac_param_value);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_HEADER_PERIOD to %d: "
        "AAC error 0x%x",
        __func__, aac_param_value, aac_error);
    return;  // TODO: Return an error?
  }

  // Set the encoder's parameters: Variable Bit Rate Support
  aac_param_value = A2DP_GetVariableBitRateSupportAac(p_codec_info);
  if (aac_param_value == -1) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_BITRATEMODE: "
        "invalid codec bit rate mode",
        __func__);
    return;  // TODO: Return an error?
  } else if (aac_param_value == A2DP_AAC_VARIABLE_BIT_RATE_ENABLED) {
    // VBR has 5 modes defined in external/aac/libAACenc/src/aacenc.h
    // A2DP_AAC_VARIABLE_BIT_RATE_DISABLED is equal to AACENC_BR_MODE_CBR
    auto bitrate_mode = a2dp_codec_config->getCodecConfig().codec_specific_1;
    switch (static_cast<AacEncoderBitrateMode>(bitrate_mode)) {
      case AacEncoderBitrateMode::AACENC_BR_MODE_VBR_1:
        [[fallthrough]];
      case AacEncoderBitrateMode::AACENC_BR_MODE_VBR_2:
        [[fallthrough]];
      case AacEncoderBitrateMode::AACENC_BR_MODE_VBR_3:
        [[fallthrough]];
      case AacEncoderBitrateMode::AACENC_BR_MODE_VBR_4:
        [[fallthrough]];
      case AacEncoderBitrateMode::AACENC_BR_MODE_VBR_5:
        break;
      default:
        bitrate_mode =
            static_cast<int64_t>(AacEncoderBitrateMode::AACENC_BR_MODE_VBR_5);
    }
    aac_param_value =
        static_cast<uint8_t>(bitrate_mode) & ~A2DP_AAC_VARIABLE_BIT_RATE_MASK;
  }
  LOG_INFO("%s: AACENC_BITRATEMODE: %d", __func__, aac_param_value);
  aac_error = aacEncoder_SetParam(a2dp_aac_encoder_cb.aac_handle,
                                  AACENC_BITRATEMODE, aac_param_value);
  if (aac_error != AACENC_OK) {
    LOG_ERROR(
        "%s: Cannot set AAC parameter AACENC_BITRATEMODE to %d: "
        "AAC error 0x%x",
        __func__, aac_param_value, aac_error);
    return;  // TODO: Return an error?
  }

  // Mark the end of setting the encoder's parameters
  aac_error =
      aacEncEncode(a2dp_aac_encoder_cb.aac_handle, NULL, NULL, NULL, NULL);
  if (aac_error != AACENC_OK) {
    LOG_ERROR("%s: Cannot complete setting the AAC parameters: AAC error 0x%x",
              __func__, aac_error);
    return;  // TODO: Return an error?
  }

  // Retrieve the encoder info so we can save the frame length
  AACENC_InfoStruct aac_info;
  aac_error = aacEncInfo(a2dp_aac_encoder_cb.aac_handle, &aac_info);
  if (aac_error != AACENC_OK) {
    LOG_ERROR("%s: Cannot retrieve the AAC encoder info: AAC error 0x%x",
              __func__, aac_error);
    return;  // TODO: Return an error?
  }
  p_encoder_params->frame_length = aac_info.frameLength;
  p_encoder_params->input_channels_n = aac_info.inputChannels;
  p_encoder_params->max_encoded_buffer_bytes = aac_info.maxOutBufBytes;
  LOG_DEBUG(
      "%s: AAC frame_length = %u input_channels_n = %u "
      "max_encoded_buffer_bytes = %d",
      __func__, p_encoder_params->frame_length,
      p_encoder_params->input_channels_n,
      p_encoder_params->max_encoded_buffer_bytes);

  // After encoder params ready, reset the feeding state and its interval.
  a2dp_aac_feeding_reset();
}

void a2dp_aac_encoder_cleanup(void) {
  if (a2dp_aac_encoder_cb.has_aac_handle)
    aacEncClose(&a2dp_aac_encoder_cb.aac_handle);
  memset(&a2dp_aac_encoder_cb, 0, sizeof(a2dp_aac_encoder_cb));
}

void a2dp_aac_feeding_reset(void) {
  auto frame_length = a2dp_aac_encoder_cb.aac_encoder_params.frame_length;
  auto sample_rate = a2dp_aac_encoder_cb.feeding_params.sample_rate;
  if (frame_length == 0 || sample_rate == 0) {
    LOG_WARN("%s: AAC encoder is not configured", __func__);
    a2dp_aac_encoder_interval_ms = A2DP_AAC_ENCODER_INTERVAL_MS;
  } else {
    // PCM data size per AAC frame (bits)
    // = aac_encoder_params.frame_length * feeding_params.bits_per_sample
    //   * feeding_params.channel_count
    // = feeding_params.sample_rate * feeding_params.bits_per_sample
    //   * feeding_params.channel_count * (T_interval_ms / 1000);
    // Here we use the nearest integer not greater than the value.
    a2dp_aac_encoder_interval_ms = frame_length * 1000 / sample_rate;
    if (a2dp_aac_encoder_interval_ms < A2DP_AAC_ENCODER_INTERVAL_MS)
      a2dp_aac_encoder_interval_ms = A2DP_AAC_ENCODER_INTERVAL_MS;
  }

  /* By default, just clear the entire state */
  memset(&a2dp_aac_encoder_cb.aac_feeding_state, 0,
         sizeof(a2dp_aac_encoder_cb.aac_feeding_state));

  a2dp_aac_encoder_cb.aac_feeding_state.bytes_per_tick =
      (a2dp_aac_encoder_cb.feeding_params.sample_rate *
       a2dp_aac_encoder_cb.feeding_params.bits_per_sample / 8 *
       a2dp_aac_encoder_cb.feeding_params.channel_count *
       a2dp_aac_encoder_interval_ms) /
      1000;

  LOG_INFO("%s: PCM bytes %u per tick %u ms", __func__,
           a2dp_aac_encoder_cb.aac_feeding_state.bytes_per_tick,
           a2dp_aac_encoder_interval_ms);
}

void a2dp_aac_feeding_flush(void) {
  a2dp_aac_encoder_cb.aac_feeding_state.counter = 0;
}

uint64_t a2dp_aac_get_encoder_interval_ms(void) {
  return a2dp_aac_encoder_interval_ms;
}

void a2dp_aac_send_frames(uint64_t timestamp_us) {
  uint8_t nb_frame = 0;
  uint8_t nb_iterations = 0;

  a2dp_aac_get_num_frame_iteration(&nb_iterations, &nb_frame, timestamp_us);
  LOG_VERBOSE("%s: Sending %d frames per iteration, %d iterations", __func__,
              nb_frame, nb_iterations);
  if (nb_frame == 0) return;

  for (uint8_t counter = 0; counter < nb_iterations; counter++) {
    // Transcode frame and enqueue
    a2dp_aac_encode_frames(nb_frame);
  }
}

// Obtains the number of frames to send and number of iterations
// to be used. |num_of_iterations| and |num_of_frames| parameters
// are used as output param for returning the respective values.
static void a2dp_aac_get_num_frame_iteration(uint8_t* num_of_iterations,
                                             uint8_t* num_of_frames,
                                             uint64_t timestamp_us) {
  uint32_t result = 0;
  uint8_t nof = 0;
  uint8_t noi = 1;

  uint32_t pcm_bytes_per_frame =
      a2dp_aac_encoder_cb.aac_encoder_params.frame_length *
      a2dp_aac_encoder_cb.feeding_params.channel_count *
      a2dp_aac_encoder_cb.feeding_params.bits_per_sample / 8;
  LOG_VERBOSE("%s: pcm_bytes_per_frame %u", __func__, pcm_bytes_per_frame);

  uint32_t hecto_ns_this_tick = a2dp_aac_encoder_interval_ms * 10000;
  uint64_t* last_100ns =
      &a2dp_aac_encoder_cb.aac_feeding_state.last_frame_timestamp_100ns;
  uint64_t now_100ns = timestamp_us * 10;
  if (*last_100ns != 0) {
    hecto_ns_this_tick = (now_100ns - *last_100ns);
  }
  *last_100ns = now_100ns;

  uint32_t bytes_this_tick =
      a2dp_aac_encoder_cb.aac_feeding_state.bytes_per_tick *
      hecto_ns_this_tick / (a2dp_aac_encoder_interval_ms * 10000);
  a2dp_aac_encoder_cb.aac_feeding_state.counter += bytes_this_tick;
  // Without this erratum, there was a three microseocnd shift per tick which
  // would cause one frame mismatched after every 180 seconds
  uint32_t erratum_100ns =
      ceil(1.0f * bytes_this_tick * a2dp_aac_encoder_interval_ms * 10000 /
           a2dp_aac_encoder_cb.aac_feeding_state.bytes_per_tick);
  if (erratum_100ns < hecto_ns_this_tick) {
    LOG_VERBOSE("%s: hecto_ns_this_tick=%d, bytes=%d, erratum_100ns=%d",
                __func__, hecto_ns_this_tick, bytes_this_tick, erratum_100ns);
    *last_100ns -= hecto_ns_this_tick - erratum_100ns;
  }

  result = a2dp_aac_encoder_cb.aac_feeding_state.counter / pcm_bytes_per_frame;
  a2dp_aac_encoder_cb.aac_feeding_state.counter -= result * pcm_bytes_per_frame;
  nof = result;

  LOG_VERBOSE("%s: effective num of frames %u, iterations %u", __func__, nof,
              noi);

  *num_of_frames = nof;
  *num_of_iterations = noi;
}

static void a2dp_aac_encode_frames(uint8_t nb_frame) {
  tA2DP_AAC_ENCODER_PARAMS* p_encoder_params =
      &a2dp_aac_encoder_cb.aac_encoder_params;
  tA2DP_FEEDING_PARAMS* p_feeding_params = &a2dp_aac_encoder_cb.feeding_params;
  uint8_t remain_nb_frame = nb_frame;
  uint8_t read_buffer[BT_DEFAULT_BUFFER_SIZE];
  int pcm_bytes_per_frame = p_encoder_params->frame_length *
                            p_feeding_params->channel_count *
                            p_feeding_params->bits_per_sample / 8;
  CHECK(pcm_bytes_per_frame <= static_cast<int>(sizeof(read_buffer)));

  // Setup the input buffer
  AACENC_BufDesc in_buf_desc;
  void* in_buf_vector[1] = {nullptr};
  int in_buf_identifiers[1] = {IN_AUDIO_DATA};
  int in_buf_sizes[1] = {pcm_bytes_per_frame};
  int in_buf_element_sizes[1] = {p_feeding_params->bits_per_sample / 8};
  in_buf_desc.numBufs = 1;
  in_buf_desc.bufs = in_buf_vector;
  in_buf_desc.bufferIdentifiers = in_buf_identifiers;
  in_buf_desc.bufSizes = in_buf_sizes;
  in_buf_desc.bufElSizes = in_buf_element_sizes;

  // Setup the output buffer (partially)
  AACENC_BufDesc out_buf_desc;
  void* out_buf_vector[1] = {nullptr};
  int out_buf_identifiers[1] = {OUT_BITSTREAM_DATA};
  int out_buf_sizes[1] = {p_encoder_params->max_encoded_buffer_bytes};
  // NOTE: out_buf_element_sizes below is probably unused by the encoder
  int out_buf_element_sizes[1] = {p_feeding_params->bits_per_sample / 8};
  out_buf_desc.numBufs = 1;
  out_buf_desc.bufs = out_buf_vector;
  out_buf_desc.bufferIdentifiers = out_buf_identifiers;
  out_buf_desc.bufSizes = out_buf_sizes;
  out_buf_desc.bufElSizes = out_buf_element_sizes;
  CHECK(p_encoder_params->max_encoded_buffer_bytes <=
        static_cast<int>(BT_DEFAULT_BUFFER_SIZE - sizeof(BT_HDR)));

  AACENC_InArgs aac_in_args;
  aac_in_args.numInSamples =
      p_encoder_params->frame_length * p_feeding_params->channel_count;
  aac_in_args.numAncBytes = 0;

  AACENC_OutArgs aac_out_args = {
      .numOutBytes = 0, .numInSamples = 0, .numAncBytes = 0};

  uint32_t count;
  uint32_t total_bytes_read = 0;
  int written = 0;

  while (nb_frame) {
    BT_HDR* p_buf = (BT_HDR*)osi_malloc(BT_DEFAULT_BUFFER_SIZE);
    p_buf->offset = A2DP_AAC_OFFSET;
    p_buf->len = 0;
    p_buf->layer_specific = 0;
    a2dp_aac_encoder_cb.stats.media_read_total_expected_packets++;

    count = 0;
    do {
      //
      // Read the PCM data and encode it
      //
      uint32_t bytes_read = 0;
      if (a2dp_aac_read_feeding(read_buffer, &bytes_read)) {
        uint8_t* packet = (uint8_t*)(p_buf + 1) + p_buf->offset + p_buf->len;
        if (!a2dp_aac_encoder_cb.has_aac_handle) {
          LOG_ERROR("%s: invalid AAC handle", __func__);
          a2dp_aac_encoder_cb.stats.media_read_total_dropped_packets++;
          osi_free(p_buf);
          return;
        }
        in_buf_vector[0] = read_buffer;
        out_buf_vector[0] = packet + count;
        AACENC_ERROR aac_error =
            aacEncEncode(a2dp_aac_encoder_cb.aac_handle, &in_buf_desc,
                         &out_buf_desc, &aac_in_args, &aac_out_args);
        if (aac_error != AACENC_OK) {
          LOG_ERROR("%s: AAC encoding error: 0x%x", __func__, aac_error);
          a2dp_aac_encoder_cb.stats.media_read_total_dropped_packets++;
          osi_free(p_buf);
          return;
        }
        written = aac_out_args.numOutBytes;
        count += written;
        p_buf->len += written;
        nb_frame--;
        p_buf->layer_specific++;  // added a frame to the buffer
      } else {
        LOG_WARN("%s: underflow %d", __func__, nb_frame);
        a2dp_aac_encoder_cb.aac_feeding_state.counter +=
            nb_frame * p_encoder_params->frame_length *
            p_feeding_params->channel_count *
            p_feeding_params->bits_per_sample / 8;

        // no more pcm to read
        nb_frame = 0;
      }
      total_bytes_read += bytes_read;
    } while ((written == 0) && nb_frame);

    // NOTE: We don't check whether the packet will fit in the MTU,
    // because AAC doesn't give us control over the encoded frame size.
    // If the packet is larger than the MTU, it will be fragmented before
    // transmission.
    if (p_buf->len) {
      /*
       * Timestamp of the media packet header represent the TS of the
       * first frame, i.e the timestamp before including this frame.
       */
      *((uint32_t*)(p_buf + 1)) = a2dp_aac_encoder_cb.timestamp;

      a2dp_aac_encoder_cb.timestamp +=
          p_buf->layer_specific * p_encoder_params->frame_length;

      uint8_t done_nb_frame = remain_nb_frame - nb_frame;
      remain_nb_frame = nb_frame;
      if (!a2dp_aac_encoder_cb.enqueue_callback(p_buf, done_nb_frame,
                                                total_bytes_read))
        return;
    } else {
      a2dp_aac_encoder_cb.stats.media_read_total_dropped_packets++;
      osi_free(p_buf);
    }
  }
}

static bool a2dp_aac_read_feeding(uint8_t* read_buffer, uint32_t* bytes_read) {
  uint32_t read_size = a2dp_aac_encoder_cb.aac_encoder_params.frame_length *
                       a2dp_aac_encoder_cb.feeding_params.channel_count *
                       a2dp_aac_encoder_cb.feeding_params.bits_per_sample / 8;

  a2dp_aac_encoder_cb.stats.media_read_total_expected_reads_count++;
  a2dp_aac_encoder_cb.stats.media_read_total_expected_read_bytes += read_size;

  /* Read Data from UIPC channel */
  uint32_t nb_byte_read =
      a2dp_aac_encoder_cb.read_callback(read_buffer, read_size);
  a2dp_aac_encoder_cb.stats.media_read_total_actual_read_bytes += nb_byte_read;
  *bytes_read = nb_byte_read;

  if (nb_byte_read < read_size) {
    if (nb_byte_read == 0) return false;

    /* Fill the unfilled part of the read buffer with silence (0) */
    memset(((uint8_t*)read_buffer) + nb_byte_read, 0, read_size - nb_byte_read);
    nb_byte_read = read_size;
  }
  a2dp_aac_encoder_cb.stats.media_read_total_actual_reads_count++;

  return true;
}

uint64_t A2dpCodecConfigAacSource::encoderIntervalMs() const {
  return a2dp_aac_get_encoder_interval_ms();
}

int A2dpCodecConfigAacSource::getEffectiveMtu() const {
  return a2dp_aac_encoder_cb.TxAaMtuSize;
}

void A2dpCodecConfigAacSource::debug_codec_dump(int fd) {
  a2dp_aac_encoder_stats_t* stats = &a2dp_aac_encoder_cb.stats;

  A2dpCodecConfig::debug_codec_dump(fd);

  auto codec_specific_1 = getCodecConfig().codec_specific_1;
  dprintf(
      fd,
      "  AAC bitrate mode                                        : %s "
      "(0x%" PRIx64 ")\n",
      ((codec_specific_1 & ~A2DP_AAC_VARIABLE_BIT_RATE_MASK) == 0 ? "Constant"
                                                                  : "Variable"),
      codec_specific_1);
  dprintf(fd,
          "  Packet counts (expected/dropped)                        : %zu / "
          "%zu\n",
          stats->media_read_total_expected_packets,
          stats->media_read_total_dropped_packets);

  dprintf(fd,
          "  PCM read counts (expected/actual)                       : %zu / "
          "%zu\n",
          stats->media_read_total_expected_reads_count,
          stats->media_read_total_actual_reads_count);

  dprintf(fd,
          "  PCM read bytes (expected/actual)                        : %zu / "
          "%zu\n",
          stats->media_read_total_expected_read_bytes,
          stats->media_read_total_actual_read_bytes);
}