Home | History | Annotate | Download | only in include
      1 /******************************************************************************
      2  *
      3  *  Copyright 2016 The Android Open Source Project
      4  *
      5  *  Licensed under the Apache License, Version 2.0 (the "License");
      6  *  you may not use this file except in compliance with the License.
      7  *  You may obtain a copy of the License at:
      8  *
      9  *  http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  *  Unless required by applicable law or agreed to in writing, software
     12  *  distributed under the License is distributed on an "AS IS" BASIS,
     13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  *  See the License for the specific language governing permissions and
     15  *  limitations under the License.
     16  *
     17  ******************************************************************************/
     18 
     19 /*****************************************************************************
     20  *
     21  *  Filename:      audio_hearing_aid_hw.h
     22  *
     23  *  Description:
     24  *
     25  *****************************************************************************/
     26 
     27 #ifndef AUDIO_HEARING_AID_HW_H
     28 #define AUDIO_HEARING_AID_HW_H
     29 
     30 #include <stdint.h>
     31 
     32 #include <hardware/bt_av.h>
     33 
     34 /*****************************************************************************
     35  *  Constants & Macros
     36  *****************************************************************************/
     37 
     38 #define HEARING_AID_AUDIO_HARDWARE_INTERFACE "audio.hearing_aid"
     39 #define HEARING_AID_CTRL_PATH "/data/misc/bluedroid/.hearing_aid_ctrl"
     40 #define HEARING_AID_DATA_PATH "/data/misc/bluedroid/.hearing_aid_data"
     41 
     42 // AUDIO_STREAM_OUTPUT_BUFFER_SZ controls the size of the audio socket buffer.
     43 // If one assumes the write buffer is always full during normal BT playback,
     44 // then increasing this value increases our playback latency.
     45 //
     46 // FIXME: The BT HAL should consume data at a constant rate.
     47 // AudioFlinger assumes that the HAL draws data at a constant rate, which is
     48 // true for most audio devices; however, the BT engine reads data at a variable
     49 // rate (over the short term), which confuses both AudioFlinger as well as
     50 // applications which deliver data at a (generally) fixed rate.
     51 //
     52 // 20 * 512 is not sufficient to smooth the variability for some BT devices,
     53 // resulting in mixer sleep and throttling. We increase this to 28 * 512 to help
     54 // reduce the effect of variable data consumption.
     55 #define AUDIO_STREAM_OUTPUT_BUFFER_SZ (28 * 512)
     56 #define AUDIO_STREAM_CONTROL_OUTPUT_BUFFER_SZ 256
     57 
     58 // AUDIO_STREAM_OUTPUT_BUFFER_PERIODS controls how the socket buffer is divided
     59 // for AudioFlinger data delivery. The AudioFlinger mixer delivers data in
     60 // chunks of AUDIO_STREAM_OUTPUT_BUFFER_SZ / AUDIO_STREAM_OUTPUT_BUFFER_PERIODS.
     61 // If the number of periods is 2, the socket buffer represents "double
     62 // buffering" of the AudioFlinger mixer buffer.
     63 //
     64 // In general, AUDIO_STREAM_OUTPUT_BUFFER_PERIODS * 16 * 4 should be a divisor
     65 // of AUDIO_STREAM_OUTPUT_BUFFER_SZ.
     66 //
     67 // These values should be chosen such that
     68 //
     69 // AUDIO_STREAM_BUFFER_SIZE * 1000 / (AUDIO_STREAM_OUTPUT_BUFFER_PERIODS
     70 //         * AUDIO_STREAM_DEFAULT_RATE * 4) > 20 (ms)
     71 //
     72 // to avoid introducing the FastMixer in AudioFlinger. Using the FastMixer
     73 // results in unnecessary latency and CPU overhead for Bluetooth.
     74 #define AUDIO_STREAM_OUTPUT_BUFFER_PERIODS 2
     75 
     76 #define AUDIO_SKT_DISCONNECTED (-1)
     77 
     78 typedef enum {
     79   HEARING_AID_CTRL_CMD_NONE,
     80   HEARING_AID_CTRL_CMD_CHECK_READY,
     81   HEARING_AID_CTRL_CMD_START,
     82   HEARING_AID_CTRL_CMD_STOP,
     83   HEARING_AID_CTRL_CMD_SUSPEND,
     84   HEARING_AID_CTRL_GET_INPUT_AUDIO_CONFIG,
     85   HEARING_AID_CTRL_GET_OUTPUT_AUDIO_CONFIG,
     86   HEARING_AID_CTRL_SET_OUTPUT_AUDIO_CONFIG,
     87   HEARING_AID_CTRL_CMD_OFFLOAD_START,
     88 } tHEARING_AID_CTRL_CMD;
     89 
     90 typedef enum {
     91   HEARING_AID_CTRL_ACK_SUCCESS,
     92   HEARING_AID_CTRL_ACK_FAILURE,
     93   HEARING_AID_CTRL_ACK_INCALL_FAILURE, /* Failure when in Call*/
     94   HEARING_AID_CTRL_ACK_UNSUPPORTED
     95 } tHEARING_AID_CTRL_ACK;
     96 
     97 typedef uint32_t tHA_SAMPLE_RATE;
     98 typedef uint8_t tHA_CHANNEL_COUNT;
     99 
    100 /*****************************************************************************
    101  *  Type definitions for callback functions
    102  *****************************************************************************/
    103 
    104 /*****************************************************************************
    105  *  Type definitions and return values
    106  *****************************************************************************/
    107 
    108 /*****************************************************************************
    109  *  Extern variables and functions
    110  *****************************************************************************/
    111 
    112 /*****************************************************************************
    113  *  Functions
    114  *****************************************************************************/
    115 
    116 // Computes the Audio Hearing Aid HAL output buffer size.
    117 // |codec_sample_rate| is the sample rate of the output stream.
    118 // |codec_bits_per_sample| is the number of bits per sample of the output
    119 // stream.
    120 // |codec_channel_mode| is the channel mode of the output stream.
    121 //
    122 // The buffer size is computed by using the following formula:
    123 //
    124 // AUDIO_STREAM_OUTPUT_BUFFER_SIZE =
    125 //    (TIME_PERIOD_MS * AUDIO_STREAM_OUTPUT_BUFFER_PERIODS *
    126 //     SAMPLE_RATE_HZ * NUMBER_OF_CHANNELS * (BITS_PER_SAMPLE / 8)) / 1000
    127 //
    128 // AUDIO_STREAM_OUTPUT_BUFFER_PERIODS controls how the socket buffer is
    129 // divided for AudioFlinger data delivery. The AudioFlinger mixer delivers
    130 // data in chunks of
    131 // (AUDIO_STREAM_OUTPUT_BUFFER_SIZE / AUDIO_STREAM_OUTPUT_BUFFER_PERIODS) .
    132 // If the number of periods is 2, the socket buffer represents "double
    133 // buffering" of the AudioFlinger mixer buffer.
    134 //
    135 // Furthermore, the AudioFlinger expects the buffer size to be a multiple
    136 // of 16 frames.
    137 //
    138 // NOTE: Currently, the computation uses the conservative 20ms time period.
    139 //
    140 // Returns the computed buffer size. If any of the input parameters is
    141 // invalid, the return value is the default |AUDIO_STREAM_OUTPUT_BUFFER_SZ|.
    142 extern size_t audio_ha_hw_stream_compute_buffer_size(
    143     btav_a2dp_codec_sample_rate_t codec_sample_rate,
    144     btav_a2dp_codec_bits_per_sample_t codec_bits_per_sample,
    145     btav_a2dp_codec_channel_mode_t codec_channel_mode);
    146 
    147 // Returns a string representation of |event|.
    148 extern const char* audio_ha_hw_dump_ctrl_event(tHEARING_AID_CTRL_CMD event);
    149 
    150 #endif /* AUDIO_HEARING_AID_HW_H */
    151