Audio Streams¶

An Audio Element responsible for acquiring of audio data and then sending the data out after processing, is called the Audio Stream.

The following stream types are supported:

Stream Name	Stream Type
I2S	Reader / Writer
HTTP	Reader / Writer
FatFs	Reader / Writer

To set the stream type, use provided structure, e.g. i2s_stream_cfg_t for I2S stream, together with audio_stream_type_t enumerator.

See description below for the API details.

I2S Stream¶

When the I2S stream type is “writer”, the data may be sent either to a codec chip or to the internal DAC of ESP32. To simplify configuration, two macros are provided to cover each case:

I2S_STREAM_CFG_DEFAULT - the I2S stream is communicating with a codec chip
I2S_STREAM_INTERNAL_DAC_CFG_DEFAULT - the stream data are sent to the DAC

Each macro configures several other stream parameters such as sample rate, bits per sample, DMA buffer length, etc.

Header File¶

audio_stream/include/i2s_stream.h

Functions¶

audio_element_handle_t i2s_stream_init(i2s_stream_cfg_t *config)¶

Create a handle to an Audio Element to stream data from I2S to another Element or get data from other elements sent to I2S, depend on the configuration of stream type is AUDIO_STREAM_READER or AUDIO_STREAM_WRITER.

Note

If I2S stream is enabled with built-in DAC mode, please don’t use I2S_NUM_1.The built-in DAC functions are only supported on I2S0 for the current ESP32 chip.

Return

The Audio Element handle

Parameters

config: The configuration

esp_err_t i2s_stream_set_clk(audio_element_handle_t i2s_stream, int rate, int bits, int ch)¶

Setup clock for I2S Stream, this function is only used with handle created by i2s_stream_init

Return

ESP_OK
ESP_FAIL

Parameters

i2s_stream: The i2s element handle
rate: Clock rate (in Hz)
bits: Audio bit width (8, 16, 24, 32)
ch: Number of Audio channels (1: Mono, 2: Stereo)

Structures¶

struct i2s_stream_cfg_t¶

I2S Stream configurations Default value will be used if any entry is zero.

Public Members

audio_stream_type_t type¶: Type of stream

i2s_config_t i2s_config¶: I2S driver configurations

i2s_pin_config_t i2s_pin_config¶: I2S driver hardware pin configurations

i2s_port_t i2s_port¶: I2S driver hardware port

Macros¶

I2S_STREAM_CFG_DEFAULT¶

I2S_STREAM_INTERNAL_DAC_CFG_DEFAULT¶

HTTP Stream¶

Header File¶

audio_stream/include/http_stream.h

Functions¶

audio_element_handle_t http_stream_init(http_stream_cfg_t *config)¶

Create a handle to an Audio Element to stream data from HTTP to another Element or get data from other elements sent to HTTP, depending on the configuration the stream type, either AUDIO_STREAM_READER or AUDIO_STREAM_WRITER.

Return

The Audio Element handle

Parameters

config: The configuration

Structures¶

struct http_stream_event_msg_t¶

Stream event message.

Public Members

http_stream_event_id_t event_id¶: Event ID

void *http_client¶: Reference to HTTP Client using by this HTTP Stream

void *buffer¶: Reference to Buffer using by the Audio Element

int buffer_len¶: Lenght of buffer

void *user_data¶: User data context, from http_stream_cfg_t

struct http_stream_cfg_t¶

HTTP Stream configurations Default value will be used if any entry is zero.

Public Members

audio_stream_type_t type¶: Type of stream

http_stream_event_handle_t event_handle¶: The hook function for HTTP Stream

void *user_data¶: User data context

Macros¶

HTTP_STREAM_CFG_DEFAULT¶

Type Definitions¶

typedef int (*http_stream_event_handle_t)(http_stream_event_msg_t *msg)¶

Enumerations¶

enum http_stream_event_id_t¶

HTTP Stream hook type.

Values:

HTTP_STREAM_PRE_REQUEST = 0x01¶: The event handler will be called before HTTP Client making the connection to the server

HTTP_STREAM_ON_REQUEST¶: The event handler will be called when HTTP Client is requesting data, If the fucntion return the value (-1: ESP_FAIL), HTTP Client will be stopped If the fucntion return the value > 0, HTTP Stream will ignore the post_field If the fucntion return the value = 0, HTTP Stream continue send data from post_field (if any)

HTTP_STREAM_ON_RESPONSE¶: The event handler will be called when HTTP Client is receiving data If the fucntion return the value (-1: ESP_FAIL), HTTP Client will be stopped If the fucntion return the value > 0, HTTP Stream will ignore the read function If the fucntion return the value = 0, HTTP Stream continue read data from HTTP Server

HTTP_STREAM_POST_REQUEST¶: The event handler will be called after HTTP Client send header and body to the serve, before fetching the headers

HTTP_STREAM_FINISH_REQUEST¶: The event handler will be called after HTTP Client fetch the header and ready to read HTTP body

FatFs Stream¶

Header File¶

audio_stream/include/fatfs_stream.h

Functions¶

audio_element_handle_t fatfs_stream_init(fatfs_stream_cfg_t *config)¶

Create a handle to an Audio Element to stream data from FatFs to another Element or get data from other elements written to FatFs, depending on the configuration the stream type, either AUDIO_STREAM_READER or AUDIO_STREAM_WRITER.

Return

The Audio Element handle

Parameters

config: The configuration

Structures¶

struct fatfs_stream_cfg_t¶

FATFS Stream configurations, if any entry is zero then the configuration will be set to default values.

Public Members

audio_stream_type_t type¶: Stream type

int buf_sz¶: Audio Element Buffer size