M4ACommonDemuxer Class Reference

Abstract base class for M4A/MP4 demuxers. Provides shared functionality for both file-based and stream-based demuxers. More...

#include <M4ACommonDemuxer.h>

Inheritance diagram for M4ACommonDemuxer:

Classes
struct	ESDSParser
	A parser for the ESDS segment to extract the relevant aac information. More...
struct	Frame
struct	M4AAudioConfig
class	SampleExtractor
	Extracts audio data based on the sample sizes defined in the stsz box. It collects the data from the mdat box and calls the callback with the extracted frames. More...

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

Public Member Functions
	M4ACommonDemuxer ()=default
virtual	~M4ACommonDemuxer ()=default
void	begin ()
M4AAudioConfig	getM4AAudioConfig ()
uint32_t	getSampleCount () const
	samples in stsz
uint32_t	getStszFileOffset () const
	File offset of stsz box.
void	resize (int size)
void	setAACConfig (int profile, int srIdx, int chCfg)
	Sets the AAC configuration for ADTS header generation.
virtual void	setCallback (FrameCallback cb)
	Sets the callback for extracted audio frames.
void	setChunkOffsetsBuffer (BaseBuffer< uint32_t > &buffer)
	Sets the buffer to use for sample sizes.
void	setM4AAudioConfig (M4AAudioConfig cfg)
void	setSampleSizesBuffer (BaseBuffer< stsz_sample_size_t > &buffer)
	Sets the buffer to use for sample sizes.
virtual void	setupParser ()=0

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 ()

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.
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

Abstract base class for M4A/MP4 demuxers. Provides shared functionality for both file-based and stream-based demuxers.

Member Typedef Documentation

FrameCallback

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

Member Enumeration Documentation

Codec

enum class Codec

strong

Enumerator
Unknown
AAC
ALAC
MP3

Constructor & Destructor Documentation

M4ACommonDemuxer()

M4ACommonDemuxer ( )

default

~M4ACommonDemuxer()

virtual ~M4ACommonDemuxer ( )

virtualdefault

Member Function Documentation

begin()

void begin ( )

inline

checkType()

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

inlineprotected

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.

getM4AAudioConfig()

M4AAudioConfig getM4AAudioConfig ( )

inline

getSampleCount()

uint32_t getSampleCount ( ) const

inline

samples in stsz

getStszFileOffset()

uint32_t getStszFileOffset ( ) const

inline

File offset of stsz box.

onAlac()

void onAlac ( const MP4Parser::Box &  box )

inlineprotected

Handles the alac box.

Parameters

box

MP4 box.

onEsds()

void onEsds ( const MP4Parser::Box &  box )

inlineprotected

Handles the esds (Elementary Stream Descriptor) box.

Parameters

box

MP4 box.

onMp4a()

void onMp4a ( const MP4Parser::Box &  box )

inlineprotected

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 )

inlineprotected

onStsz()

void onStsz ( MP4Parser::Box &  box )

inlineprotected

Handles the stsz (Sample Size) box.

Parameters

box

MP4 box.

printHexDump()

void printHexDump ( const MP4Parser::Box &  box )

inlineprotected

readU32() [1/2]

static uint32_t readU32 ( const uint32_t  num )

inlinestaticprotected

readU32() [2/2]

static uint32_t readU32 ( const uint8_t *  p )

inlinestaticprotected

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 ( )

inlineprotected

resize()

void resize ( int  size )

inline

setAACConfig()

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

inline

Sets the AAC configuration for ADTS header generation.

Parameters

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

setCallback()

virtual void setCallback ( FrameCallback  cb )

inlinevirtual

Sets the callback for extracted audio frames.

Parameters

cb	Frame callback function.

Reimplemented in M4AAudioDemuxer, and M4AAudioFileDemuxer.

setChunkOffsetsBuffer()

void setChunkOffsetsBuffer ( BaseBuffer< uint32_t > &  buffer )

inline

Sets the buffer to use for sample sizes.

Parameters

buffer

Reference to the buffer to use.

setM4AAudioConfig()

void setM4AAudioConfig ( M4AAudioConfig  cfg )

inline

setSampleSizesBuffer()

void setSampleSizesBuffer ( BaseBuffer< stsz_sample_size_t > &  buffer )

inline

Sets the buffer to use for sample sizes.

Parameters

buffer

Reference to the buffer to use.

setupParser()

virtual void setupParser ( )

pure virtual

Implemented in M4AAudioDemuxer, and M4AAudioFileDemuxer.

Member Data Documentation

audio_config

M4AAudioConfig audio_config

protected

buffer

SingleBuffer<uint8_t> buffer

protected

Buffer for incremental data.

chunk_offsets_count

uint32_t chunk_offsets_count = 0

protected

default_size

size_t default_size = 2 * 1024

protected

Default buffer size.

frame_callback

FrameCallback frame_callback = nullptr

protected

parser

MP4Parser parser

protected

Underlying MP4 parser.

sample_count

uint32_t sample_count = 0

protected

Number of samples in stsz.

sampleExtractor

SampleExtractor sampleExtractor

protected

Initial value:

{
      audio_config}

Extractor for audio samples.

stco_processed

bool stco_processed = false

protected

Marks the stco table as processed.

stsd_processed

bool stsd_processed = false

protected

stsz_offset

uint32_t stsz_offset = 0

protected

stsz_processed

bool stsz_processed = false

protected

Marks the stsz table as processed.

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

• src/AudioTools/AudioCodecs/M4ACommonDemuxer.h