M4AAudioDemuxer Class Reference

A simple M4A audio data demuxer which is providing AAC, MP3 and ALAC frames. More...

#include <M4AAudioDemuxer.h>

Inheritance diagram for M4AAudioDemuxer:

Public Types
enum class	Codec { Unknown , AAC , ALAC , MP3 }
using	FrameCallback = std::function< void(const Frame &, void *ref)>

Public Member Functions
	M4AAudioDemuxer ()
	Constructor. Sets up parser callbacks.
int	availableForWrite ()
	Returns the available space for writing.
bool	begin ()
	Initializes the demuxer and resets state.
void	copyFrom (M4ACommonDemuxer &source)
Vector< uint8_t > &	getALACMagicCookie ()
	Returns the ALAC magic cookie (codec config).
M4AAudioConfig	getM4AAudioConfig ()
uint32_t	getSampleCount () const
	samples in stsz
uint32_t	getStszFileOffset () const
	File offset of stsz box.
bool	resize (size_t size)
void	setAACConfig (int profile, int srIdx, int chCfg)
	Sets the AAC configuration for ADTS header generation.
void	setCallback (FrameCallback cb) override
	Defines the callback that returns the audio frames.
void	setChunkOffsetsBuffer (BaseBuffer< uint32_t > &buffer)
	Sets the buffer to use for sample sizes.
void	setM4AAudioConfig (M4AAudioConfig cfg)
void	setReference (void *ref)
	Sets a reference pointer for callbacks.
void	setSampleSizesBuffer (BaseBuffer< stsz_sample_size_t > &buffer)
	Sets the buffer to use for sample sizes.
void	write (const uint8_t *data, size_t len)
	Writes data to the demuxer for parsing.

Protected Member Functions
bool	checkType (uint8_t *buffer, const char *type, int offset)
	Checks if the buffer at the given offset matches the specified type.
void	onAlac (const MP4Parser::Box &box)
	Handles the alac box.
void	onEsds (const MP4Parser::Box &box)
	Handles the esds (Elementary Stream Descriptor) box.
void	onMp4a (const MP4Parser::Box &box)
	Handles the mp4a box.
void	onStsd (const MP4Parser::Box &box)
void	onStsz (MP4Parser::Box &box)
	Handles the stsz (Sample Size) box.
void	printHexDump (const MP4Parser::Box &box)
uint32_t	readU32Buffer ()
void	setupParser () override
	Setup all parser callbacks.

Static Protected Member Functions
static uint32_t	readU32 (const uint32_t num)
static uint32_t	readU32 (const uint8_t *p)
	Reads a 32-bit big-endian unsigned integer from a buffer.

Protected Attributes
M4AAudioConfig	audio_config
SingleBuffer< uint8_t >	buffer
	Buffer for incremental data.
uint32_t	chunk_offsets_count = 0
size_t	default_size = 2 * 1024
	Default buffer size.
FrameCallback	frame_callback = nullptr
MP4Parser	parser
	Underlying MP4 parser.
void *	ref = nullptr
	Reference pointer for callbacks.
uint32_t	sample_count = 0
	Number of samples in stsz.
SampleExtractor	sampleExtractor
	Extractor for audio samples.
bool	stco_processed = false
	Marks the stco table as processed.
bool	stsd_processed = false
uint32_t	stsz_offset = 0
bool	stsz_processed = false
	Marks the stsz table as processed.

Detailed Description

A simple M4A audio data demuxer which is providing AAC, MP3 and ALAC frames.

Member Typedef Documentation

FrameCallback

using FrameCallback = std::function<void(const Frame&, void* ref)>

inherited

Member Enumeration Documentation

Codec

enum class Codec

stronginherited

Enumerator
Unknown
AAC
ALAC
MP3

Constructor & Destructor Documentation

M4AAudioDemuxer()

M4AAudioDemuxer ( )

inline

Constructor. Sets up parser callbacks.

Member Function Documentation

availableForWrite()

int availableForWrite ( )

inline

Returns the available space for writing.

Returns

Number of bytes available for writing.

begin()

bool begin ( )

inline

Initializes the demuxer and resets state.

checkType()

bool checkType ( uint8_t *  buffer, const char *  type, int  offset  )

inlineprotectedinherited

Checks if the buffer at the given offset matches the specified type.

Parameters

buffer	Pointer to the buffer.
type	4-character type string (e.g. "mp4a").
offset	Offset in the buffer to check.

Returns

true if the type matches, false otherwise.

copyFrom()

void copyFrom ( M4ACommonDemuxer &  source )

inline

getALACMagicCookie()

Vector< uint8_t > & getALACMagicCookie ( )

inline

Returns the ALAC magic cookie (codec config).

Returns

Reference to the ALAC magic cookie vector.

getM4AAudioConfig()

M4AAudioConfig getM4AAudioConfig ( )

inlineinherited

getSampleCount()

uint32_t getSampleCount ( ) const

inlineinherited

samples in stsz

getStszFileOffset()

uint32_t getStszFileOffset ( ) const

inlineinherited

File offset of stsz box.

onAlac()

void onAlac ( const MP4Parser::Box &  box )

inlineprotectedinherited

Handles the alac box.

Parameters

box

MP4 box.

onEsds()

void onEsds ( const MP4Parser::Box &  box )

inlineprotectedinherited

Handles the esds (Elementary Stream Descriptor) box.

Parameters

box

MP4 box.

onMp4a()

void onMp4a ( const MP4Parser::Box &  box )

inlineprotectedinherited

Handles the mp4a box.

Parameters

box

MP4 box.

for mp4a we expect to contain a esds: child boxes start at 36

onStsd()

void onStsd ( const MP4Parser::Box &  box )

inlineprotectedinherited

onStsz()

void onStsz ( MP4Parser::Box &  box )

inlineprotectedinherited

Handles the stsz (Sample Size) box.

Parameters

box

MP4 box.

printHexDump()

void printHexDump ( const MP4Parser::Box &  box )

inlineprotectedinherited

readU32() [1/2]

static uint32_t readU32 ( const uint32_t  num )

inlinestaticprotectedinherited

readU32() [2/2]

static uint32_t readU32 ( const uint8_t *  p )

inlinestaticprotectedinherited

Reads a 32-bit big-endian unsigned integer from a buffer.

Parameters

p	Pointer to buffer.

Returns

32-bit unsigned integer.

readU32Buffer()

uint32_t readU32Buffer ( )

inlineprotectedinherited

resize()

bool resize ( size_t  size )

inlineinherited

setAACConfig()

void setAACConfig ( int  profile, int  srIdx, int  chCfg  )

inlineinherited

Sets the AAC configuration for ADTS header generation.

Parameters

profile	AAC profile.
srIdx	Sample rate index.
chCfg	Channel configuration.

setCallback()

void setCallback ( FrameCallback  cb )

inlineoverridevirtual

Defines the callback that returns the audio frames.

Parameters

cb	Frame callback function.

Reimplemented from M4ACommonDemuxer.

setChunkOffsetsBuffer()

void setChunkOffsetsBuffer ( BaseBuffer< uint32_t > &  buffer )

inlineinherited

Sets the buffer to use for sample sizes.

Parameters

buffer

Reference to the buffer to use.

setM4AAudioConfig()

void setM4AAudioConfig ( M4AAudioConfig  cfg )

inlineinherited

setReference()

void setReference ( void *  ref )

inline

Sets a reference pointer for callbacks.

Parameters

ref	Reference pointer.

setSampleSizesBuffer()

void setSampleSizesBuffer ( BaseBuffer< stsz_sample_size_t > &  buffer )

inlineinherited

Sets the buffer to use for sample sizes.

Parameters

buffer

Reference to the buffer to use.

setupParser()

void setupParser ( )

inlineoverrideprotectedvirtual

Setup all parser callbacks.

Implements M4ACommonDemuxer.

write()

void write ( const uint8_t *  data, size_t  len  )

inline

Writes data to the demuxer for parsing.

Parameters

data	Pointer to input data.
len	Length of input data.

Member Data Documentation

audio_config

M4AAudioConfig audio_config

protectedinherited

buffer

SingleBuffer<uint8_t> buffer

protectedinherited

Buffer for incremental data.

chunk_offsets_count

uint32_t chunk_offsets_count = 0

protectedinherited

default_size

size_t default_size = 2 * 1024

protectedinherited

Default buffer size.

frame_callback

FrameCallback frame_callback = nullptr

protectedinherited

parser

MP4Parser parser

protectedinherited

Underlying MP4 parser.

ref

void* ref = nullptr

protected

Reference pointer for callbacks.

sample_count

uint32_t sample_count = 0

protectedinherited

Number of samples in stsz.

sampleExtractor

SampleExtractor sampleExtractor

protectedinherited

Initial value:

{
      audio_config}

Extractor for audio samples.

stco_processed

bool stco_processed = false

protectedinherited

Marks the stco table as processed.

stsd_processed

bool stsd_processed = false

protectedinherited

stsz_offset

uint32_t stsz_offset = 0

protectedinherited

stsz_processed

bool stsz_processed = false

protectedinherited

Marks the stsz table as processed.

---

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

• src/AudioTools/AudioCodecs/M4AAudioDemuxer.h