1 /****************************************************************************** 2 * 3 * Copyright (C) 2009-2012 Broadcom Corporation 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_a2dp_hw.h 22 * 23 * Description: 24 * 25 *****************************************************************************/ 26 27 #ifndef AUDIO_A2DP_HW_H 28 #define AUDIO_A2DP_HW_H 29 30 #include <stdint.h> 31 32 #include <hardware/bt_av.h> 33 34 /***************************************************************************** 35 * Constants & Macros 36 *****************************************************************************/ 37 38 #define A2DP_AUDIO_HARDWARE_INTERFACE "audio.a2dp" 39 #define A2DP_CTRL_PATH "/data/misc/bluedroid/.a2dp_ctrl" 40 #define A2DP_DATA_PATH "/data/misc/bluedroid/.a2dp_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 A2DP_CTRL_CMD_NONE, 80 A2DP_CTRL_CMD_CHECK_READY, 81 A2DP_CTRL_CMD_START, 82 A2DP_CTRL_CMD_STOP, 83 A2DP_CTRL_CMD_SUSPEND, 84 A2DP_CTRL_GET_INPUT_AUDIO_CONFIG, 85 A2DP_CTRL_GET_OUTPUT_AUDIO_CONFIG, 86 A2DP_CTRL_SET_OUTPUT_AUDIO_CONFIG, 87 A2DP_CTRL_CMD_OFFLOAD_START, 88 } tA2DP_CTRL_CMD; 89 90 typedef enum { 91 A2DP_CTRL_ACK_SUCCESS, 92 A2DP_CTRL_ACK_FAILURE, 93 A2DP_CTRL_ACK_INCALL_FAILURE, /* Failure when in Call*/ 94 A2DP_CTRL_ACK_UNSUPPORTED 95 } tA2DP_CTRL_ACK; 96 97 typedef uint32_t tA2DP_SAMPLE_RATE; 98 typedef uint8_t tA2DP_CHANNEL_COUNT; 99 typedef uint8_t tA2DP_BITS_PER_SAMPLE; 100 101 /***************************************************************************** 102 * Type definitions for callback functions 103 *****************************************************************************/ 104 105 /***************************************************************************** 106 * Type definitions and return values 107 *****************************************************************************/ 108 109 /***************************************************************************** 110 * Extern variables and functions 111 *****************************************************************************/ 112 113 /***************************************************************************** 114 * Functions 115 *****************************************************************************/ 116 117 // Computes the Audio A2DP HAL output buffer size. 118 // |codec_sample_rate| is the sample rate of the output stream. 119 // |codec_bits_per_sample| is the number of bits per sample of the output 120 // stream. 121 // |codec_channel_mode| is the channel mode of the output stream. 122 // 123 // The buffer size is computed by using the following formula: 124 // 125 // AUDIO_STREAM_OUTPUT_BUFFER_SIZE = 126 // (TIME_PERIOD_MS * AUDIO_STREAM_OUTPUT_BUFFER_PERIODS * 127 // SAMPLE_RATE_HZ * NUMBER_OF_CHANNELS * (BITS_PER_SAMPLE / 8)) / 1000 128 // 129 // AUDIO_STREAM_OUTPUT_BUFFER_PERIODS controls how the socket buffer is 130 // divided for AudioFlinger data delivery. The AudioFlinger mixer delivers 131 // data in chunks of 132 // (AUDIO_STREAM_OUTPUT_BUFFER_SIZE / AUDIO_STREAM_OUTPUT_BUFFER_PERIODS) . 133 // If the number of periods is 2, the socket buffer represents "double 134 // buffering" of the AudioFlinger mixer buffer. 135 // 136 // Furthermore, the AudioFlinger expects the buffer size to be a multiple 137 // of 16 frames. 138 // 139 // NOTE: Currently, the computation uses the conservative 20ms time period. 140 // 141 // Returns the computed buffer size. If any of the input parameters is 142 // invalid, the return value is the default |AUDIO_STREAM_OUTPUT_BUFFER_SZ|. 143 extern size_t audio_a2dp_hw_stream_compute_buffer_size( 144 btav_a2dp_codec_sample_rate_t codec_sample_rate, 145 btav_a2dp_codec_bits_per_sample_t codec_bits_per_sample, 146 btav_a2dp_codec_channel_mode_t codec_channel_mode); 147 148 // Returns a string representation of |event|. 149 extern const char* audio_a2dp_hw_dump_ctrl_event(tA2DP_CTRL_CMD event); 150 151 #endif /* A2DP_AUDIO_HW_H */ 152