path: root/stack/a2dp/a2dp_sbc_encoder.cc

/******************************************************************************
 *
 *  Copyright 2016 The Android Open Source Project
 *  Copyright 2009-2012 Broadcom Corporation
 *
 *  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_sbc_encoder"

#include "a2dp_sbc_encoder.h"

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

#include "a2dp_sbc.h"
#include "a2dp_sbc_up_sample.h"
#include "bt_common.h"
#include "common/time_util.h"
#include "embdrv/sbc/encoder/include/sbc_encoder.h"
#include "osi/include/log.h"
#include "osi/include/osi.h"

/* Buffer pool */
#define A2DP_SBC_BUFFER_SIZE BT_DEFAULT_BUFFER_SIZE

// A2DP SBC encoder interval in milliseconds.
#define A2DP_SBC_ENCODER_INTERVAL_MS 20

/* High quality quality setting @ 44.1 khz */
#define A2DP_SBC_DEFAULT_BITRATE 328

#define A2DP_SBC_NON_EDR_MAX_RATE 229

#define A2DP_SBC_MAX_PCM_ITER_NUM_PER_TICK 3

#define A2DP_SBC_MAX_HQ_FRAME_SIZE_44_1 119
#define A2DP_SBC_MAX_HQ_FRAME_SIZE_48 115

/* Define the bitrate step when trying to match bitpool value */
#define A2DP_SBC_BITRATE_STEP 5

/* Readability constants */
#define A2DP_SBC_FRAME_HEADER_SIZE_BYTES 4  // A2DP Spec v1.3, 12.4, Table 12.12
#define A2DP_SBC_SCALE_FACTOR_BITS 4        // A2DP Spec v1.3, 12.4, Table 12.13

/* offset */
#if (BTA_AV_CO_CP_SCMS_T == TRUE)
/* A2DP header will contain a CP header of size 1 */
#define A2DP_HDR_SIZE 2
#define A2DP_SBC_OFFSET (AVDT_MEDIA_OFFSET + A2DP_SBC_MPL_HDR_LEN + 1)
#else
#define A2DP_HDR_SIZE 1
#define A2DP_SBC_OFFSET (AVDT_MEDIA_OFFSET + A2DP_SBC_MPL_HDR_LEN)
#endif

typedef struct {
  uint32_t aa_frame_counter;
  int32_t aa_feed_counter;
  int32_t aa_feed_residue;
  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_SBC_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;

  size_t media_read_total_expected_frames;
  size_t media_read_total_dropped_frames;
} a2dp_sbc_encoder_stats_t;

typedef struct {
  a2dp_source_read_callback_t read_callback;
  a2dp_source_enqueue_callback_t enqueue_callback;
  uint16_t TxAaMtuSize;
  uint8_t tx_sbc_frames;
  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 */
  SBC_ENC_PARAMS sbc_encoder_params;
  tA2DP_FEEDING_PARAMS feeding_params;
  tA2DP_SBC_FEEDING_STATE feeding_state;
  int16_t pcmBuffer[SBC_MAX_PCM_BUFFER_SIZE];

  a2dp_sbc_encoder_stats_t stats;
} tA2DP_SBC_ENCODER_CB;

static tA2DP_SBC_ENCODER_CB a2dp_sbc_encoder_cb;

static void a2dp_sbc_encoder_update(uint16_t peer_mtu,
                                    A2dpCodecConfig* a2dp_codec_config,
                                    bool* p_restart_input,
                                    bool* p_restart_output,
                                    bool* p_config_updated);
static bool a2dp_sbc_read_feeding(uint32_t* bytes);
static void a2dp_sbc_encode_frames(uint8_t nb_frame);
static void a2dp_sbc_get_num_frame_iteration(uint8_t* num_of_iterations,
                                             uint8_t* num_of_frames,
                                             uint64_t timestamp_us);
static uint8_t calculate_max_frames_per_packet(void);
static uint16_t a2dp_sbc_source_rate();
static uint32_t a2dp_sbc_frame_length(void);

bool A2DP_LoadEncoderSbc(void) {
  // Nothing to do - the library is statically linked
  return true;
}

void A2DP_UnloadEncoderSbc(void) {
  // Nothing to do - the library is statically linked
}

void a2dp_sbc_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) {
  memset(&a2dp_sbc_encoder_cb, 0, sizeof(a2dp_sbc_encoder_cb));

  a2dp_sbc_encoder_cb.stats.session_start_us =
      bluetooth::common::time_get_os_boottime_us();

  a2dp_sbc_encoder_cb.read_callback = read_callback;
  a2dp_sbc_encoder_cb.enqueue_callback = enqueue_callback;
  a2dp_sbc_encoder_cb.is_peer_edr = p_peer_params->is_peer_edr;
  a2dp_sbc_encoder_cb.peer_supports_3mbps = p_peer_params->peer_supports_3mbps;
  a2dp_sbc_encoder_cb.peer_mtu = p_peer_params->peer_mtu;
  a2dp_sbc_encoder_cb.timestamp = 0;

  // 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_sbc_encoder_update(a2dp_sbc_encoder_cb.peer_mtu, a2dp_codec_config,
                          &restart_input, &restart_output, &config_updated);
}

bool A2dpCodecConfigSbcSource::updateEncoderUserConfig(
    const tA2DP_ENCODER_INIT_PEER_PARAMS* p_peer_params, bool* p_restart_input,
    bool* p_restart_output, bool* p_config_updated) {
  a2dp_sbc_encoder_cb.is_peer_edr = p_peer_params->is_peer_edr;
  a2dp_sbc_encoder_cb.peer_supports_3mbps = p_peer_params->peer_supports_3mbps;
  a2dp_sbc_encoder_cb.peer_mtu = p_peer_params->peer_mtu;
  a2dp_sbc_encoder_cb.timestamp = 0;

  if (a2dp_sbc_encoder_cb.peer_mtu == 0) {
    LOG_ERROR(LOG_TAG,
              "%s: Cannot update the codec encoder for %s: "
              "invalid peer MTU",
              __func__, name().c_str());
    return false;
  }

  a2dp_sbc_encoder_update(a2dp_sbc_encoder_cb.peer_mtu, this, p_restart_input,
                          p_restart_output, p_config_updated);
  return true;
}

// Update the A2DP SBC encoder.
// |peer_mtu| is the peer MTU.
// |a2dp_codec_config| is the A2DP codec to use for the update.
static void a2dp_sbc_encoder_update(uint16_t peer_mtu,
                                    A2dpCodecConfig* a2dp_codec_config,
                                    bool* p_restart_input,
                                    bool* p_restart_output,
                                    bool* p_config_updated) {
  SBC_ENC_PARAMS* p_encoder_params = &a2dp_sbc_encoder_cb.sbc_encoder_params;
  uint8_t codec_info[AVDT_CODEC_SIZE];
  uint16_t s16SamplingFreq;
  int16_t s16BitPool = 0;
  int16_t s16BitRate;
  int16_t s16FrameLen;
  uint8_t protect = 0;
  int min_bitpool;
  int max_bitpool;

  *p_restart_input = false;
  *p_restart_output = false;
  *p_config_updated = false;
  if (!a2dp_codec_config->copyOutOtaCodecConfig(codec_info)) {
    LOG_ERROR(LOG_TAG,
              "%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;
  min_bitpool = A2DP_GetMinBitpoolSbc(p_codec_info);
  max_bitpool = A2DP_GetMaxBitpoolSbc(p_codec_info);

  // The feeding parameters
  tA2DP_FEEDING_PARAMS* p_feeding_params = &a2dp_sbc_encoder_cb.feeding_params;
  p_feeding_params->sample_rate = A2DP_GetTrackSampleRateSbc(p_codec_info);
  p_feeding_params->bits_per_sample =
      a2dp_codec_config->getAudioBitsPerSample();
  p_feeding_params->channel_count = A2DP_GetTrackChannelCountSbc(p_codec_info);
  LOG_DEBUG(LOG_TAG, "%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);
  a2dp_sbc_feeding_reset();

  // The codec parameters
  p_encoder_params->s16ChannelMode = A2DP_GetChannelModeCodeSbc(p_codec_info);
  p_encoder_params->s16NumOfSubBands =
      A2DP_GetNumberOfSubbandsSbc(p_codec_info);
  p_encoder_params->s16NumOfBlocks = A2DP_GetNumberOfBlocksSbc(p_codec_info);
  p_encoder_params->s16AllocationMethod =
      A2DP_GetAllocationMethodCodeSbc(p_codec_info);
  p_encoder_params->s16SamplingFreq =
      A2DP_GetSamplingFrequencyCodeSbc(p_codec_info);
  p_encoder_params->s16NumOfChannels =
      A2DP_GetTrackChannelCountSbc(p_codec_info);

  // Reset invalid parameters
  if (!p_encoder_params->s16NumOfSubBands) {
    LOG_WARN(LOG_TAG, "%s: SubBands are set to 0, resetting to max (%d)",
             __func__, SBC_MAX_NUM_OF_SUBBANDS);
    p_encoder_params->s16NumOfSubBands = SBC_MAX_NUM_OF_SUBBANDS;
  }
  if (!p_encoder_params->s16NumOfBlocks) {
    LOG_WARN(LOG_TAG, "%s: Blocks are set to 0, resetting to max (%d)",
             __func__, SBC_MAX_NUM_OF_BLOCKS);
    p_encoder_params->s16NumOfBlocks = SBC_MAX_NUM_OF_BLOCKS;
  }
  if (!p_encoder_params->s16NumOfChannels) {
    LOG_WARN(LOG_TAG, "%s: Channels are set to 0, resetting to max (%d)",
             __func__, SBC_MAX_NUM_OF_CHANNELS);
    p_encoder_params->s16NumOfChannels = SBC_MAX_NUM_OF_CHANNELS;
  }

  uint16_t mtu_size = A2DP_SBC_BUFFER_SIZE - A2DP_SBC_OFFSET - sizeof(BT_HDR);
  if (mtu_size < peer_mtu) {
    a2dp_sbc_encoder_cb.TxAaMtuSize = mtu_size;
  } else {
    a2dp_sbc_encoder_cb.TxAaMtuSize = peer_mtu;
  }

  if (p_encoder_params->s16SamplingFreq == SBC_sf16000)
    s16SamplingFreq = 16000;
  else if (p_encoder_params->s16SamplingFreq == SBC_sf32000)
    s16SamplingFreq = 32000;
  else if (p_encoder_params->s16SamplingFreq == SBC_sf44100)
    s16SamplingFreq = 44100;
  else
    s16SamplingFreq = 48000;

  // Set the initial target bit rate
  p_encoder_params->u16BitRate = a2dp_sbc_source_rate();

  LOG_DEBUG(LOG_TAG, "%s: MTU=%d, peer_mtu=%d min_bitpool=%d max_bitpool=%d",
            __func__, a2dp_sbc_encoder_cb.TxAaMtuSize, peer_mtu, min_bitpool,
            max_bitpool);
  LOG_DEBUG(LOG_TAG,
            "%s: ChannelMode=%d, NumOfSubBands=%d, NumOfBlocks=%d, "
            "AllocationMethod=%d, BitRate=%d, SamplingFreq=%d BitPool=%d",
            __func__, p_encoder_params->s16ChannelMode,
            p_encoder_params->s16NumOfSubBands,
            p_encoder_params->s16NumOfBlocks,
            p_encoder_params->s16AllocationMethod, p_encoder_params->u16BitRate,
            s16SamplingFreq, p_encoder_params->s16BitPool);

  do {
    if ((p_encoder_params->s16ChannelMode == SBC_JOINT_STEREO) ||
        (p_encoder_params->s16ChannelMode == SBC_STEREO)) {
      s16BitPool = (int16_t)((p_encoder_params->u16BitRate *
                              p_encoder_params->s16NumOfSubBands * 1000 /
                              s16SamplingFreq) -
                             ((32 + (4 * p_encoder_params->s16NumOfSubBands *
                                     p_encoder_params->s16NumOfChannels) +
                               ((p_encoder_params->s16ChannelMode - 2) *
                                p_encoder_params->s16NumOfSubBands)) /
                              p_encoder_params->s16NumOfBlocks));

      s16FrameLen = 4 +
                    (4 * p_encoder_params->s16NumOfSubBands *
                     p_encoder_params->s16NumOfChannels) /
                        8 +
                    (((p_encoder_params->s16ChannelMode - 2) *
                      p_encoder_params->s16NumOfSubBands) +
                     (p_encoder_params->s16NumOfBlocks * s16BitPool)) /
                        8;

      s16BitRate = (8 * s16FrameLen * s16SamplingFreq) /
                   (p_encoder_params->s16NumOfSubBands *
                    p_encoder_params->s16NumOfBlocks * 1000);

      if (s16BitRate > p_encoder_params->u16BitRate) s16BitPool--;

      if (p_encoder_params->s16NumOfSubBands == 8)
        s16BitPool = (s16BitPool > 255) ? 255 : s16BitPool;
      else
        s16BitPool = (s16BitPool > 128) ? 128 : s16BitPool;
    } else {
      s16BitPool =
          (int16_t)(((p_encoder_params->s16NumOfSubBands *
                      p_encoder_params->u16BitRate * 1000) /
                     (s16SamplingFreq * p_encoder_params->s16NumOfChannels)) -
                    (((32 / p_encoder_params->s16NumOfChannels) +
                      (4 * p_encoder_params->s16NumOfSubBands)) /
                     p_encoder_params->s16NumOfBlocks));

      p_encoder_params->s16BitPool =
          (s16BitPool > (16 * p_encoder_params->s16NumOfSubBands))
              ? (16 * p_encoder_params->s16NumOfSubBands)
              : s16BitPool;
    }

    if (s16BitPool < 0) s16BitPool = 0;

    LOG_DEBUG(LOG_TAG, "%s: bitpool candidate: %d (%d kbps)", __func__,
              s16BitPool, p_encoder_params->u16BitRate);

    if (s16BitPool > max_bitpool) {
      LOG_DEBUG(LOG_TAG, "%s: computed bitpool too large (%d)", __func__,
                s16BitPool);
      /* Decrease bitrate */
      p_encoder_params->u16BitRate -= A2DP_SBC_BITRATE_STEP;
      /* Record that we have decreased the bitrate */
      protect |= 1;
    } else if (s16BitPool < min_bitpool) {
      LOG_WARN(LOG_TAG, "%s: computed bitpool too small (%d)", __func__,
               s16BitPool);

      /* Increase bitrate */
      uint16_t previous_u16BitRate = p_encoder_params->u16BitRate;
      p_encoder_params->u16BitRate += A2DP_SBC_BITRATE_STEP;
      /* Record that we have increased the bitrate */
      protect |= 2;
      /* Check over-flow */
      if (p_encoder_params->u16BitRate < previous_u16BitRate) protect |= 3;
    } else {
      break;
    }
    /* In case we have already increased and decreased the bitrate, just stop */
    if (protect == 3) {
      LOG_ERROR(LOG_TAG, "%s: could not find bitpool in range", __func__);
      break;
    }
  } while (true);

  /* Finally update the bitpool in the encoder structure */
  p_encoder_params->s16BitPool = s16BitPool;

  LOG_DEBUG(LOG_TAG, "%s: final bit rate %d, final bit pool %d", __func__,
            p_encoder_params->u16BitRate, p_encoder_params->s16BitPool);

  /* Reset the SBC encoder */
  SBC_Encoder_Init(&a2dp_sbc_encoder_cb.sbc_encoder_params);
  a2dp_sbc_encoder_cb.tx_sbc_frames = calculate_max_frames_per_packet();
}

void a2dp_sbc_encoder_cleanup(void) {
  memset(&a2dp_sbc_encoder_cb, 0, sizeof(a2dp_sbc_encoder_cb));
}

void a2dp_sbc_feeding_reset(void) {
  /* By default, just clear the entire state */
  memset(&a2dp_sbc_encoder_cb.feeding_state, 0,
         sizeof(a2dp_sbc_encoder_cb.feeding_state));

  a2dp_sbc_encoder_cb.feeding_state.bytes_per_tick =
      (a2dp_sbc_encoder_cb.feeding_params.sample_rate *
       a2dp_sbc_encoder_cb.feeding_params.bits_per_sample / 8 *
       a2dp_sbc_encoder_cb.feeding_params.channel_count *
       A2DP_SBC_ENCODER_INTERVAL_MS) /
      1000;

  LOG_DEBUG(LOG_TAG, "%s: PCM bytes per tick %u", __func__,
            a2dp_sbc_encoder_cb.feeding_state.bytes_per_tick);
}

void a2dp_sbc_feeding_flush(void) {
  a2dp_sbc_encoder_cb.feeding_state.counter = 0;
  a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue = 0;
}

uint64_t a2dp_sbc_get_encoder_interval_ms(void) {
  return A2DP_SBC_ENCODER_INTERVAL_MS;
}

void a2dp_sbc_send_frames(uint64_t timestamp_us) {
  uint8_t nb_frame = 0;
  uint8_t nb_iterations = 0;

  a2dp_sbc_get_num_frame_iteration(&nb_iterations, &nb_frame, timestamp_us);
  LOG_VERBOSE(LOG_TAG, "%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_sbc_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_sbc_get_num_frame_iteration(uint8_t* num_of_iterations,
                                             uint8_t* num_of_frames,
                                             uint64_t timestamp_us) {
  uint8_t nof = 0;
  uint8_t noi = 1;

  uint32_t projected_nof = 0;
  uint32_t pcm_bytes_per_frame =
      a2dp_sbc_encoder_cb.sbc_encoder_params.s16NumOfSubBands *
      a2dp_sbc_encoder_cb.sbc_encoder_params.s16NumOfBlocks *
      a2dp_sbc_encoder_cb.feeding_params.channel_count *
      a2dp_sbc_encoder_cb.feeding_params.bits_per_sample / 8;
  LOG_VERBOSE(LOG_TAG, "%s: pcm_bytes_per_frame %u", __func__,
              pcm_bytes_per_frame);

  uint32_t hecto_ns_this_tick = A2DP_SBC_ENCODER_INTERVAL_MS * 10000;
  uint64_t* last_100ns =
      &a2dp_sbc_encoder_cb.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_sbc_encoder_cb.feeding_state.bytes_per_tick *
                             hecto_ns_this_tick /
                             (A2DP_SBC_ENCODER_INTERVAL_MS * 10000);
  a2dp_sbc_encoder_cb.feeding_state.counter += bytes_this_tick;
  // Without this erratum, there was a three microseocnd shift per tick which
  // would cause one SBC frame mismatched after every 20 seconds
  uint32_t erratum_100ns =
      ceil(1.0f * A2DP_SBC_ENCODER_INTERVAL_MS * 10000 * bytes_this_tick /
           a2dp_sbc_encoder_cb.feeding_state.bytes_per_tick);
  if (erratum_100ns < hecto_ns_this_tick) {
    LOG_VERBOSE(LOG_TAG,
                "%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;
  }

  /* Calculate the number of frames pending for this media tick */
  projected_nof =
      a2dp_sbc_encoder_cb.feeding_state.counter / pcm_bytes_per_frame;
  // Update the stats
  a2dp_sbc_encoder_cb.stats.media_read_total_expected_frames += projected_nof;

  if (projected_nof > MAX_PCM_FRAME_NUM_PER_TICK) {
    LOG_WARN(LOG_TAG, "%s: limiting frames to be sent from %d to %d", __func__,
             projected_nof, MAX_PCM_FRAME_NUM_PER_TICK);

    // Update the stats
    size_t delta = projected_nof - MAX_PCM_FRAME_NUM_PER_TICK;
    a2dp_sbc_encoder_cb.stats.media_read_total_dropped_frames += delta;

    projected_nof = MAX_PCM_FRAME_NUM_PER_TICK;
  }

  LOG_VERBOSE(LOG_TAG, "%s: frames for available PCM data %u", __func__,
              projected_nof);

  if (a2dp_sbc_encoder_cb.is_peer_edr) {
    if (!a2dp_sbc_encoder_cb.tx_sbc_frames) {
      LOG_ERROR(LOG_TAG, "%s: tx_sbc_frames not updated, update from here",
                __func__);
      a2dp_sbc_encoder_cb.tx_sbc_frames = calculate_max_frames_per_packet();
    }

    nof = a2dp_sbc_encoder_cb.tx_sbc_frames;
    if (!nof) {
      LOG_ERROR(LOG_TAG,
                "%s: number of frames not updated, set calculated values",
                __func__);
      nof = projected_nof;
      noi = 1;
    } else {
      if (nof < projected_nof) {
        noi = projected_nof / nof;  // number of iterations would vary
        if (noi > A2DP_SBC_MAX_PCM_ITER_NUM_PER_TICK) {
          LOG_ERROR(LOG_TAG, "%s: Audio Congestion (iterations:%d > max (%d))",
                    __func__, noi, A2DP_SBC_MAX_PCM_ITER_NUM_PER_TICK);
          noi = A2DP_SBC_MAX_PCM_ITER_NUM_PER_TICK;
          a2dp_sbc_encoder_cb.feeding_state.counter =
              noi * nof * pcm_bytes_per_frame;
        }
        projected_nof = nof;
      } else {
        noi = 1;  // number of iterations is 1
        LOG_VERBOSE(LOG_TAG, "%s: reducing frames for available PCM data",
                    __func__);
        nof = projected_nof;
      }
    }
  } else {
    // For BR cases nof will be same as the value retrieved at projected_nof
    LOG_VERBOSE(LOG_TAG, "%s: headset BR, number of frames %u", __func__, nof);
    if (projected_nof > MAX_PCM_FRAME_NUM_PER_TICK) {
      LOG_ERROR(LOG_TAG, "%s: Audio Congestion (frames: %d > max (%d))",
                __func__, projected_nof, MAX_PCM_FRAME_NUM_PER_TICK);

      // Update the stats
      size_t delta = projected_nof - MAX_PCM_FRAME_NUM_PER_TICK;
      a2dp_sbc_encoder_cb.stats.media_read_total_dropped_frames += delta;

      projected_nof = MAX_PCM_FRAME_NUM_PER_TICK;
      a2dp_sbc_encoder_cb.feeding_state.counter =
          noi * projected_nof * pcm_bytes_per_frame;
    }
    nof = projected_nof;
  }
  a2dp_sbc_encoder_cb.feeding_state.counter -= noi * nof * pcm_bytes_per_frame;
  LOG_VERBOSE(LOG_TAG, "%s: effective num of frames %u, iterations %u",
              __func__, nof, noi);

  *num_of_frames = nof;
  *num_of_iterations = noi;
}

static void a2dp_sbc_encode_frames(uint8_t nb_frame) {
  SBC_ENC_PARAMS* p_encoder_params = &a2dp_sbc_encoder_cb.sbc_encoder_params;
  uint8_t remain_nb_frame = nb_frame;
  uint16_t blocm_x_subband =
      p_encoder_params->s16NumOfSubBands * p_encoder_params->s16NumOfBlocks;

  uint8_t last_frame_len = 0;

  while (nb_frame) {
    BT_HDR* p_buf = (BT_HDR*)osi_malloc(A2DP_SBC_BUFFER_SIZE);
    uint32_t bytes_read = 0;

    p_buf->offset = A2DP_SBC_OFFSET;
    p_buf->len = 0;
    p_buf->layer_specific = 0;
    a2dp_sbc_encoder_cb.stats.media_read_total_expected_packets++;

    do {
      /* Fill allocated buffer with 0 */
      memset(a2dp_sbc_encoder_cb.pcmBuffer, 0,
             blocm_x_subband * p_encoder_params->s16NumOfChannels);
      //
      // Read the PCM data and encode it. If necessary, upsample the data.
      //
      uint32_t num_bytes = 0;
      if (a2dp_sbc_read_feeding(&num_bytes)) {
        uint8_t* output = (uint8_t*)(p_buf + 1) + p_buf->offset + p_buf->len;
        int16_t* input = a2dp_sbc_encoder_cb.pcmBuffer;
        uint16_t output_len = SBC_Encode(p_encoder_params, input, output);
        last_frame_len = output_len;

        /* Update SBC frame length */
        p_buf->len += output_len;
        nb_frame--;
        p_buf->layer_specific++;

        bytes_read += num_bytes;
      } else {
        LOG_WARN(LOG_TAG, "%s: underflow %d, %d", __func__, nb_frame,
                 a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue);
        a2dp_sbc_encoder_cb.feeding_state.counter +=
            nb_frame * p_encoder_params->s16NumOfSubBands *
            p_encoder_params->s16NumOfBlocks *
            a2dp_sbc_encoder_cb.feeding_params.channel_count *
            a2dp_sbc_encoder_cb.feeding_params.bits_per_sample / 8;
        /* no more pcm to read */
        nb_frame = 0;
      }
    } while (
        ((p_buf->len + last_frame_len) < a2dp_sbc_encoder_cb.TxAaMtuSize) &&
        (p_buf->layer_specific < 0x0F) && nb_frame);

    if (p_buf->len) {
      /*
       * Timestamp of the media packet header represent the TS of the
       * first SBC frame, i.e the timestamp before including this frame.
       */
      *((uint32_t*)(p_buf + 1)) = a2dp_sbc_encoder_cb.timestamp;

      a2dp_sbc_encoder_cb.timestamp += p_buf->layer_specific * blocm_x_subband;

      uint8_t done_nb_frame = remain_nb_frame - nb_frame;
      remain_nb_frame = nb_frame;
      if (!a2dp_sbc_encoder_cb.enqueue_callback(p_buf, done_nb_frame,
                                                bytes_read))
        return;
    } else {
      a2dp_sbc_encoder_cb.stats.media_read_total_dropped_packets++;
      osi_free(p_buf);
    }
  }
}

static bool a2dp_sbc_read_feeding(uint32_t* bytes_read) {
  SBC_ENC_PARAMS* p_encoder_params = &a2dp_sbc_encoder_cb.sbc_encoder_params;
  uint16_t blocm_x_subband =
      p_encoder_params->s16NumOfSubBands * p_encoder_params->s16NumOfBlocks;
  uint32_t read_size;
  uint32_t sbc_sampling = 48000;
  uint32_t src_samples;
  uint16_t bytes_needed = blocm_x_subband * p_encoder_params->s16NumOfChannels *
                          a2dp_sbc_encoder_cb.feeding_params.bits_per_sample /
                          8;
  static uint16_t up_sampled_buffer[SBC_MAX_NUM_FRAME * SBC_MAX_NUM_OF_BLOCKS *
                                    SBC_MAX_NUM_OF_CHANNELS *
                                    SBC_MAX_NUM_OF_SUBBANDS * 2];
  static uint16_t read_buffer[SBC_MAX_NUM_FRAME * SBC_MAX_NUM_OF_BLOCKS *
                              SBC_MAX_NUM_OF_CHANNELS *
                              SBC_MAX_NUM_OF_SUBBANDS];
  uint32_t src_size_used;
  uint32_t dst_size_used;
  bool fract_needed;
  int32_t fract_max;
  int32_t fract_threshold;
  uint32_t nb_byte_read;

  /* Get the SBC sampling rate */
  switch (p_encoder_params->s16SamplingFreq) {
    case SBC_sf48000:
      sbc_sampling = 48000;
      break;
    case SBC_sf44100:
      sbc_sampling = 44100;
      break;
    case SBC_sf32000:
      sbc_sampling = 32000;
      break;
    case SBC_sf16000:
      sbc_sampling = 16000;
      break;
  }

  a2dp_sbc_encoder_cb.stats.media_read_total_expected_reads_count++;
  if (sbc_sampling == a2dp_sbc_encoder_cb.feeding_params.sample_rate) {
    read_size =
        bytes_needed - a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue;
    a2dp_sbc_encoder_cb.stats.media_read_total_expected_read_bytes += read_size;
    nb_byte_read = a2dp_sbc_encoder_cb.read_callback(
        ((uint8_t*)a2dp_sbc_encoder_cb.pcmBuffer) +
            a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue,
        read_size);
    a2dp_sbc_encoder_cb.stats.media_read_total_actual_read_bytes +=
        nb_byte_read;

    *bytes_read = nb_byte_read;
    if (nb_byte_read != read_size) {
      a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue += nb_byte_read;
      return false;
    }
    a2dp_sbc_encoder_cb.stats.media_read_total_actual_reads_count++;
    a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue = 0;
    return true;
  }

  /*
   * Some Feeding PCM frequencies require to split the number of sample
   * to read.
   * E.g 128 / 6 = 21.3333 => read 22 and 21 and 21 => max = 2; threshold = 0
   */
  fract_needed = false; /* Default */
  switch (a2dp_sbc_encoder_cb.feeding_params.sample_rate) {
    case 32000:
    case 8000:
      fract_needed = true;
      fract_max = 2;       /* 0, 1 and 2 */
      fract_threshold = 0; /* Add one for the first */
      break;
    case 16000:
      fract_needed = true;
      fract_max = 2;       /* 0, 1 and 2 */
      fract_threshold = 1; /* Add one for the first two frames*/
      break;
  }

  /* Compute number of sample to read from source */
  src_samples = blocm_x_subband;
  src_samples *= a2dp_sbc_encoder_cb.feeding_params.sample_rate;
  src_samples /= sbc_sampling;

  /* The previous division may have a remainder not null */
  if (fract_needed) {
    if (a2dp_sbc_encoder_cb.feeding_state.aa_feed_counter <= fract_threshold) {
      src_samples++; /* for every read before threshold add one sample */
    }

    /* do nothing if counter >= threshold */
    a2dp_sbc_encoder_cb.feeding_state.aa_feed_counter++; /* one more read */
    if (a2dp_sbc_encoder_cb.feeding_state.aa_feed_counter > fract_max) {
      a2dp_sbc_encoder_cb.feeding_state.aa_feed_counter = 0;
    }
  }

  /* Compute number of bytes to read from source */
  read_size = src_samples;
  read_size *= a2dp_sbc_encoder_cb.feeding_params.channel_count;
  read_size *= (a2dp_sbc_encoder_cb.feeding_params.bits_per_sample / 8);
  a2dp_sbc_encoder_cb.stats.media_read_total_expected_read_bytes += read_size;

  /* Read Data from UIPC channel */
  nb_byte_read =
      a2dp_sbc_encoder_cb.read_callback((uint8_t*)read_buffer, read_size);
  a2dp_sbc_encoder_cb.stats.media_read_total_actual_read_bytes += 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_sbc_encoder_cb.stats.media_read_total_actual_reads_count++;

  /* Initialize PCM up-sampling engine */
  a2dp_sbc_init_up_sample(a2dp_sbc_encoder_cb.feeding_params.sample_rate,
                          sbc_sampling,
                          a2dp_sbc_encoder_cb.feeding_params.bits_per_sample,
                          a2dp_sbc_encoder_cb.feeding_params.channel_count);

  /*
   * Re-sample the read buffer.
   * The output PCM buffer will be stereo, 16 bit per sample.
   */
  dst_size_used = a2dp_sbc_up_sample(
      (uint8_t*)read_buffer,
      (uint8_t*)up_sampled_buffer +
          a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue,
      nb_byte_read, sizeof(up_sampled_buffer) -
                        a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue,
      &src_size_used);

  /* update the residue */
  a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue += dst_size_used;

  /* only copy the pcm sample when we have up-sampled enough PCM */
  if (a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue < bytes_needed)
    return false;

  /* Copy the output pcm samples in SBC encoding buffer */
  memcpy((uint8_t*)a2dp_sbc_encoder_cb.pcmBuffer, (uint8_t*)up_sampled_buffer,
         bytes_needed);
  /* update the residue */
  a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue -= bytes_needed;

  if (a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue != 0) {
    memcpy((uint8_t*)up_sampled_buffer,
           (uint8_t*)up_sampled_buffer + bytes_needed,
           a2dp_sbc_encoder_cb.feeding_state.aa_feed_residue);
  }
  return true;
}

static uint8_t calculate_max_frames_per_packet(void) {
  uint16_t effective_mtu_size = a2dp_sbc_encoder_cb.TxAaMtuSize;
  SBC_ENC_PARAMS* p_encoder_params = &a2dp_sbc_encoder_cb.sbc_encoder_params;
  uint16_t result = 0;
  uint32_t frame_len;

  LOG_VERBOSE(LOG_TAG, "%s: original AVDTP MTU size: %d", __func__,
              a2dp_sbc_encoder_cb.TxAaMtuSize);
  if (a2dp_sbc_encoder_cb.is_peer_edr &&
      !a2dp_sbc_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(LOG_TAG,
                "%s: The remote device is EDR but does not support 3 Mbps",
                __func__);

    if (effective_mtu_size > MAX_2MBPS_AVDTP_MTU) {
      LOG_WARN(LOG_TAG, "%s: Restricting AVDTP MTU size to %d", __func__,
               MAX_2MBPS_AVDTP_MTU);
      effective_mtu_size = MAX_2MBPS_AVDTP_MTU;
      a2dp_sbc_encoder_cb.TxAaMtuSize = effective_mtu_size;
    }
  }

  if (!p_encoder_params->s16NumOfSubBands) {
    LOG_ERROR(LOG_TAG, "%s: SubBands are set to 0, resetting to %d", __func__,
              SBC_MAX_NUM_OF_SUBBANDS);
    p_encoder_params->s16NumOfSubBands = SBC_MAX_NUM_OF_SUBBANDS;
  }
  if (!p_encoder_params->s16NumOfBlocks) {
    LOG_ERROR(LOG_TAG, "%s: Blocks are set to 0, resetting to %d", __func__,
              SBC_MAX_NUM_OF_BLOCKS);
    p_encoder_params->s16NumOfBlocks = SBC_MAX_NUM_OF_BLOCKS;
  }
  if (!p_encoder_params->s16NumOfChannels) {
    LOG_ERROR(LOG_TAG, "%s: Channels are set to 0, resetting to %d", __func__,
              SBC_MAX_NUM_OF_CHANNELS);
    p_encoder_params->s16NumOfChannels = SBC_MAX_NUM_OF_CHANNELS;
  }

  frame_len = a2dp_sbc_frame_length();

  LOG_VERBOSE(LOG_TAG, "%s: Effective Tx MTU to be considered: %d", __func__,
              effective_mtu_size);

  switch (p_encoder_params->s16SamplingFreq) {
    case SBC_sf44100:
      if (frame_len == 0) {
        LOG_ERROR(LOG_TAG,
                  "%s: Calculating frame length, resetting it to default %d",
                  __func__, A2DP_SBC_MAX_HQ_FRAME_SIZE_44_1);
        frame_len = A2DP_SBC_MAX_HQ_FRAME_SIZE_44_1;
      }
      result = (effective_mtu_size - A2DP_HDR_SIZE) / frame_len;
      LOG_VERBOSE(LOG_TAG, "%s: Max number of SBC frames: %d", __func__,
                  result);
      break;

    case SBC_sf48000:
      if (frame_len == 0) {
        LOG_ERROR(LOG_TAG,
                  "%s: Calculating frame length, resetting it to default %d",
                  __func__, A2DP_SBC_MAX_HQ_FRAME_SIZE_48);
        frame_len = A2DP_SBC_MAX_HQ_FRAME_SIZE_48;
      }
      result = (effective_mtu_size - A2DP_HDR_SIZE) / frame_len;
      LOG_VERBOSE(LOG_TAG, "%s: Max number of SBC frames: %d", __func__,
                  result);
      break;

    default:
      LOG_ERROR(LOG_TAG, "%s: Max number of SBC frames: %d", __func__, result);
      break;
  }
  return result;
}

static uint16_t a2dp_sbc_source_rate() {
  uint16_t rate = A2DP_SBC_DEFAULT_BITRATE;

  /* restrict bitrate if a2dp link is non-edr */
  if (!a2dp_sbc_encoder_cb.is_peer_edr) {
    rate = A2DP_SBC_NON_EDR_MAX_RATE;
    LOG_VERBOSE(LOG_TAG, "%s: non-edr a2dp sink detected, restrict rate to %d",
                __func__, rate);
  }

  return rate;
}

static uint32_t a2dp_sbc_frame_length(void) {
  SBC_ENC_PARAMS* p_encoder_params = &a2dp_sbc_encoder_cb.sbc_encoder_params;
  uint32_t frame_len = 0;

  LOG_VERBOSE(LOG_TAG,
              "%s: channel mode: %d, sub-band: %d, number of block: %d, "
              "bitpool: %d, sampling frequency: %d, num channels: %d",
              __func__, p_encoder_params->s16ChannelMode,
              p_encoder_params->s16NumOfSubBands,
              p_encoder_params->s16NumOfBlocks, p_encoder_params->s16BitPool,
              p_encoder_params->s16SamplingFreq,
              p_encoder_params->s16NumOfChannels);

  switch (p_encoder_params->s16ChannelMode) {
    case SBC_MONO:
      FALLTHROUGH_INTENDED; /* FALLTHROUGH */
    case SBC_DUAL:
      frame_len = A2DP_SBC_FRAME_HEADER_SIZE_BYTES +
                  ((uint32_t)(A2DP_SBC_SCALE_FACTOR_BITS *
                              p_encoder_params->s16NumOfSubBands *
                              p_encoder_params->s16NumOfChannels) /
                   CHAR_BIT) +
                  ((uint32_t)(p_encoder_params->s16NumOfBlocks *
                              p_encoder_params->s16NumOfChannels *
                              p_encoder_params->s16BitPool) /
                   CHAR_BIT);
      break;
    case SBC_STEREO:
      frame_len = A2DP_SBC_FRAME_HEADER_SIZE_BYTES +
                  ((uint32_t)(A2DP_SBC_SCALE_FACTOR_BITS *
                              p_encoder_params->s16NumOfSubBands *
                              p_encoder_params->s16NumOfChannels) /
                   CHAR_BIT) +
                  ((uint32_t)(p_encoder_params->s16NumOfBlocks *
                              p_encoder_params->s16BitPool) /
                   CHAR_BIT);
      break;
    case SBC_JOINT_STEREO:
      frame_len = A2DP_SBC_FRAME_HEADER_SIZE_BYTES +
                  ((uint32_t)(A2DP_SBC_SCALE_FACTOR_BITS *
                              p_encoder_params->s16NumOfSubBands *
                              p_encoder_params->s16NumOfChannels) /
                   CHAR_BIT) +
                  ((uint32_t)(p_encoder_params->s16NumOfSubBands +
                              (p_encoder_params->s16NumOfBlocks *
                               p_encoder_params->s16BitPool)) /
                   CHAR_BIT);
      break;
    default:
      LOG_VERBOSE(LOG_TAG, "%s: Invalid channel number: %d", __func__,
                  p_encoder_params->s16ChannelMode);
      break;
  }
  LOG_VERBOSE(LOG_TAG, "%s: calculated frame length: %d", __func__, frame_len);
  return frame_len;
}

uint32_t a2dp_sbc_get_bitrate() {
  SBC_ENC_PARAMS* p_encoder_params = &a2dp_sbc_encoder_cb.sbc_encoder_params;
  LOG_DEBUG(LOG_TAG, "%s: bit rate %d ", __func__,
            p_encoder_params->u16BitRate);
  return p_encoder_params->u16BitRate * 1000;
}

uint64_t A2dpCodecConfigSbcSource::encoderIntervalMs() const {
  return a2dp_sbc_get_encoder_interval_ms();
}

int A2dpCodecConfigSbcSource::getEffectiveMtu() const {
  return a2dp_sbc_encoder_cb.TxAaMtuSize;
}

void A2dpCodecConfigSbcSource::debug_codec_dump(int fd) {
  a2dp_sbc_encoder_stats_t* stats = &a2dp_sbc_encoder_cb.stats;

  A2dpCodecConfig::debug_codec_dump(fd);

  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);

  dprintf(fd,
          "  Frames counts (expected/dropped)                        : %zu / "
          "%zu\n",
          stats->media_read_total_expected_frames,
          stats->media_read_total_dropped_frames);
}