A2DPEncoderSBC Class Reference

SBC encode support for the managed A2DP encoder framework: wraps an audio_tools::SBCEncoder (codec-sbc / arduino-libsbc), advertises the SBC SEP capability and configures the encoder (subbands, blocks, allocation method and bitpool) with the parameters negotiated with the sink. Register it via BluetoothA2DPSource::add_encoder(). More...

#include <A2DPEncoderSBC.h>

Inheritance diagram for A2DPEncoderSBC:

Public Member Functions
	A2DPEncoderSBC (audio_tools::SBCEncoder &encoder, int max_bitpool=53)
virtual bool	begin (const esp_a2d_mcc_t &mcc)
void	build_capability (esp_a2d_mcc_t &mcc) override
	Fills in the SEP capability advertised for this codec at registration.
esp_a2d_mct_t	codec_type () override
	A2DP codec type this encoder handles (e.g. ESP_A2D_MCT_SBC)
virtual void	end ()
	Closes the wrapped audio_tools encoder.
audio_tools::AudioInfo	get_audio_info ()
	Negotiated sample rate/channels (the PCM is always provided as stereo)
int	max_frames_per_packet () override
	Max number of encoded frames that can be combined in one media packet.
const char *	mime () override
	MIME type of the codec this encoder produces (e.g. "audio/sbc")
uint16_t	payload_header_size () override
	the stack adds a 1 byte SBC media payload header
int	sample_rate ()
	Sample rate of the PCM provided by the data callbacks.
uint32_t	samples_per_frame () override
void	set_frame_sink (A2DPFrameSink *sink)
	Defines the target of the encoded frames.
void	set_sample_rate (int rate)
virtual size_t	write (const uint8_t *pcm, size_t len)

Protected Member Functions
void	configure (const esp_a2d_mcc_t &mcc) override
	applies the negotiated SBC parameters to the encoder
void	parse_audio_info (const esp_a2d_mcc_t &mcc) override
virtual void	write_encoded (const uint8_t *data, size_t len)

Static Protected Member Functions
static uint8_t	sample_rate_bit (int rate)

Protected Attributes
int	blocks = 16
int	channels_cfg = 2
FrameOutput	frame_output
int	input_sample_rate = 44100
int	max_bitpool
audio_tools::AudioEncoder *	p_encoder
audio_tools::SBCEncoder *	p_sbc
A2DPFrameSink *	p_sink = nullptr
int	sample_rate_cfg = 44100
int	subbands = 8

Detailed Description

SBC encode support for the managed A2DP encoder framework: wraps an audio_tools::SBCEncoder (codec-sbc / arduino-libsbc), advertises the SBC SEP capability and configures the encoder (subbands, blocks, allocation method and bitpool) with the parameters negotiated with the sink. Register it via BluetoothA2DPSource::add_encoder().

Author

Phil Schatzmann

Copyright

Apache License Version 2

Constructor & Destructor Documentation

A2DPEncoderSBC()

A2DPEncoderSBC::A2DPEncoderSBC ( audio_tools::SBCEncoder &  encoder, int  max_bitpool = 53  )

inline

max_bitpool: upper limit for the bitpool (53 is the "high quality" setting for 44.1/48 kHz stereo)

Member Function Documentation

begin()

virtual bool A2DPEncoder::begin ( const esp_a2d_mcc_t &  mcc )

inlinevirtualinherited

Opens the wrapped audio_tools encoder for the negotiated SEP configuration: calls parse_audio_info(mcc) and configure(mcc) (implemented per codec), then wires up the frame output and starts the encoder.

Reimplemented in A2DPEncoderAAC.

build_capability()

void A2DPEncoderSBC::build_capability ( esp_a2d_mcc_t &  mcc )

inlineoverridevirtual

Fills in the SEP capability advertised for this codec at registration.

Implements A2DPEncoder.

codec_type()

esp_a2d_mct_t A2DPEncoderSBC::codec_type ( )

inlineoverridevirtual

A2DP codec type this encoder handles (e.g. ESP_A2D_MCT_SBC)

Implements A2DPEncoder.

configure()

void A2DPEncoderSBC::configure ( const esp_a2d_mcc_t &  mcc )

inlineoverrideprotectedvirtual

applies the negotiated SBC parameters to the encoder

Reimplemented from A2DPEncoder.

max_frames_per_packet()

int A2DPEncoderSBC::max_frames_per_packet ( )

inlineoverridevirtual

Max number of encoded frames that can be combined in one media packet.

Reimplemented from A2DPEncoder.

mime()

const char * A2DPEncoderSBC::mime ( )

inlineoverridevirtual

MIME type of the codec this encoder produces (e.g. "audio/sbc")

Implements A2DPEncoder.

parse_audio_info()

void A2DPEncoderSBC::parse_audio_info ( const esp_a2d_mcc_t &  mcc )

inlineoverrideprotectedvirtual

determines sample_rate/channels from the negotiated SBC configuration (a single bit is set per field once negotiation completes)

Implements A2DPEncoder.

payload_header_size()

uint16_t A2DPEncoderSBC::payload_header_size ( )

inlineoverridevirtual

the stack adds a 1 byte SBC media payload header

Reimplemented from A2DPEncoder.

samples_per_frame()

uint32_t A2DPEncoderSBC::samples_per_frame ( )

inlineoverridevirtual

Number of samples (per channel) covered by one encoded frame: used for the media packet timestamps

Implements A2DPEncoder.

set_sample_rate()

void A2DPEncoder::set_sample_rate ( int  rate )

inlineinherited

Defines the sample rate of the PCM provided by the data callbacks (default 44100). Call before BluetoothA2DPSource::start().

write()

virtual size_t A2DPEncoder::write ( const uint8_t *  pcm, size_t  len  )

inlinevirtualinherited

Feeds 16 bit stereo PCM to the wrapped encoder (downmixed to mono if this was negotiated); the encoded frames are forwarded to the frame sink

write_encoded()

virtual void A2DPEncoder::write_encoded ( const uint8_t *  data, size_t  len  )

inlineprotectedvirtualinherited

Receives the output of the wrapped encoder: by default each write is expected to be exactly one encoded frame

Reimplemented in A2DPEncoderAAC.

---

The documentation for this class was generated from the following file:

• src/A2DPEncoderSBC.h