在 ESP32 藍牙（Bluetooth）的內置了 A2DP（藍牙立體聲音訊傳輸規範 / Advanced Audio Distribution Profile）的 API 函數，只要連接雙方支援 A2DP 協定都能以 16 bits，44.1 kHz 的質素傳輸聲音訊號。
功能 - esp_a2d_register_callback
原型：esp_err_t esp_a2d_register_callback(esp_a2d_cb_t
callback)
參數：callback: A2DP event callback function
返回：ESP_OK: success
ESP_INVALID_STATE: if bluetooth stack is
not yet enabled
ESP_FAIL: if callback is a NULL function
pointer
說明：Register application callback function to A2DP
module. This function should be called only after esp_bluedroid_enable()
completes successfully, used by both A2DP source and sink.
範例：esp_a2d_register_callback(&bt_app_a2d_cb);
功能 - esp_a2d_sink_register_data_callback
原型：esp_err_t
esp_a2d_sink_register_data_callback(esp_a2d_sink_data_cb_t callback)
參數：callback: A2DP sink data callback function
返回：ESP_OK: success
ESP_INVALID_STATE: if bluetooth stack is
not yet enabled
ESP_FAIL: if callback is a NULL function
pointer
說明：Register A2DP sink data output function; For now
the output is PCM data stream decoded from SBC format. This function should be
called only after esp_bluedroid_enable() completes successfully, used only by
A2DP sink. The callback is invoked in the context of A2DP sink task whose stack
size is configurable through menuconfig.
範例：esp_a2d_sink_register_data_callback(bt_app_a2d_data_cb);
功能 - esp_a2d_sink_init
原型：esp_err_t esp_a2d_sink_init(void)
參數：
返回：ESP_OK: if the initialization request is sent
successfully
ESP_INVALID_STATE: if bluetooth stack is
not yet enabled
ESP_FAIL: others
說明：Initialize the bluetooth A2DP sink module. This
function should be called after esp_bluedroid_enable() completes successfully.
範例：esp_a2d_sink_init();
功能 - esp_a2d_sink_deinit
原型：esp_err_t esp_a2d_sink_deinit(void)
參數：
返回：ESP_OK: success
ESP_INVALID_STATE: if bluetooth stack
is not yet enabled
ESP_FAIL: others
說明：De-initialize for A2DP sink module. This function
should be called only after esp_bluedroid_enable() completes successfully.
範例：esp_a2d_sink_deinit()
功能 - esp_a2d_sink_connect
原型：esp_err_t esp_a2d_sink_connect(esp_bd_addr_t
remote_bda)
參數：remote_bda: remote bluetooth device address
返回：ESP_OK: connect request is sent to lower layer
ESP_INVALID_STATE: if bluetooth stack
is not yet enabled
ESP_FAIL: others
說明：Connect to remote bluetooth A2DP source device,
must after esp_a2d_sink_init()
範例：
功能 - esp_a2d_sink_disconnect
原型：esp_err_t esp_a2d_sink_disconnect(esp_bd_addr_t
remote_bda)
參數：remote_bda: remote bluetooth device address
返回：ESP_OK: disconnect request is sent to lower layer
ESP_INVALID_STATE: if bluetooth stack
is not yet enabled
ESP_FAIL: others
說明：Disconnect from the remote A2DP source device.
範例：
功能 - esp_a2d_media_ctrl
原型：esp_err_t esp_a2d_media_ctrl(esp_a2d_media_ctrl_t
ctrl)
參數：ctrl: control commands for A2DP data channel
返回：ESP_OK: control command is sent to lower layer
ESP_INVALID_STATE: if bluetooth stack
is not yet enabled
ESP_FAIL: others
說明：media control commands; this API can be used for
both A2DP sink and source
範例：esp_a2d_media_ctrl(ESP_A2D_MEDIA_CTRL_CHECK_SRC_RDY);
esp_a2d_media_ctrl(ESP_A2D_MEDIA_CTRL_START);
esp_a2d_media_ctrl(ESP_A2D_MEDIA_CTRL_STOP);
功能 - esp_a2d_source_init
原型：esp_err_t esp_a2d_source_init(void)
參數：
返回：ESP_OK: if the initialization request is sent
successfully
ESP_INVALID_STATE: if bluetooth stack
is not yet enabled
ESP_FAIL: others
說明：Initialize the bluetooth A2DP source module. This
function should be called after esp_bluedroid_enable() completes successfully.
範例：esp_a2d_source_init();
功能 - esp_a2d_source_deinit
原型：esp_err_t esp_a2d_source_deinit(void)
參數：
返回：ESP_OK: success
ESP_INVALID_STATE: if bluetooth stack
is not yet enabled
ESP_FAIL: others
說明：De-initialize for A2DP source module. This function
should be called only after esp_bluedroid_enable() completes successfully.
範例：esp_a2d_source_deinit();
功能 - esp_a2d_source_register_data_callback
原型：esp_err_t
esp_a2d_source_register_data_callback(esp_a2d_source_data_cb_t callback
參數：callback: A2DP source data callback function
返回：ESP_OK: success
ESP_INVALID_STATE: if bluetooth stack
is not yet enabled
ESP_FAIL: if callback is a NULL function
pointer
說明：Register A2DP source data input function; For now
the input is PCM data stream. This function should be called only after
esp_bluedroid_enable() completes successfully. The callback is invoked in the
context of A2DP source task whose stack size is configurable through
menuconfig.
範例：esp_a2d_source_register_data_callback(bt_app_a2d_data_cb);
功能 - esp_a2d_source_connect
原型：esp_err_t esp_a2d_source_connect(esp_bd_addr_t
remote_bda)
參數：remote_bda: remote bluetooth device address
返回：ESP_OK: connect request is sent to lower layer
ESP_INVALID_STATE: if bluetooth stack
is not yet enabled
ESP_FAIL: others
說明：Connect to remote A2DP sink device, must after
esp_a2d_source_init()
範例：static esp_bd_addr_t s_peer_bda = {0};
esp_a2d_source_connect(s_peer_bda);
功能 - esp_a2d_source_disconnect
原型：esp_err_t esp_a2d_source_disconnect(esp_bd_addr_t
remote_bda)
參數：remote_bda: remote bluetooth device address
返回：ESP_OK: disconnect request is sent to lower layer
ESP_INVALID_STATE: if bluetooth stack
is not yet enabled
ESP_FAIL: others
說明：Disconnect from the remote A2DP sink device.
範例：static esp_bd_addr_t s_peer_bda = {0};
esp_a2d_source_disconnect(s_peer_bda);
參考網址：https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/bluetooth/esp_a2dp.html
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