HeaderParserMP3 Class Reference

MP3 header parser that processes MP3 data incrementally and extracts complete MP3 frames. Can validate MP3 data and extract audio information. When used with a Print output, it splits incoming data into complete MP3 frames and writes them to the output stream. More...

#include <HeaderParserMP3.h>

Collaboration diagram for HeaderParserMP3:

Public Member Functions
	HeaderParserMP3 ()=default
	Default constructor.
	HeaderParserMP3 (Print &output, int bufferSize=2048)
	Constructor for write support.
int	findSyncWord (const uint8_t *buf, size_t nBytes, uint8_t synch=0xFF, uint8_t syncl=0xF0)
	Finds the mp3/aac sync word.
void	flush ()
int	getBitRate () const
	Bit rate from mp3 header.
int	getChannels () const
	Number of channels from mp3 header.
FrameHeader	getFrameHeader ()
int	getFrameLength ()
	Frame length from mp3 header.
size_t	getFrameRateHz ()
	frame rate in Hz (frames per second)
const char *	getLayerStr () const
	Provides a string representation of the MPEG layer.
size_t	getPlayingTime (size_t fileSizeBytes)
uint16_t	getSampleRate () const
	Sample rate from mp3 header.
int	getSamplesPerFrame ()
	number of samples per mp3 frame
size_t	getTimePerFrameMs ()
	playing time per frame in ms
const char *	getVersionStr () const
	Provides a string representation of the MPEG version.
bool	hasValidFrame () const
	Returns true if we have parsed at least one valid frame.
bool	isValid ()
	Returns true if a valid frame has been detected.
bool	isValid (const uint8_t *data, int len)
	parses the header string and returns true if this is a valid mp3 file
void	reset ()
	Clears internal buffer and resets state.
bool	resize (size_t size)
void	setOutput (Print &output)
size_t	write (const uint8_t *data, size_t len)
	split up the data into mp3 segements and write to output

Protected Types
enum class	FrameReason {   VALID , INVALID_BITRATE_FOR_VERSION , INVALID_SAMPLERATE_FOR_VERSION , INVALID_MPEG_VERSION ,   INVALID_LAYER , INVALID_LAYER_II_BITRATE_AND_MODE , INVALID_EMPHASIS , INVALID_CRC }

Protected Member Functions
bool	contains (const uint8_t *data, const char *toFind, size_t len)
bool	processBuffer ()
	Processes the internal buffer to extract complete mp3 frames.
void	readFrameHeader (const uint8_t *data)
int	seekFrameSync (const uint8_t *str, size_t len)
bool	validate (const uint8_t *data, size_t len)
FrameReason	validateFrameHeader (const FrameHeader &header)

Protected Attributes
SingleBuffer< uint8_t >	buffer {0}
size_t	buffer_size = 0
bool	frame_header_valid = false
FrameHeader	header
size_t	last_frame_size = 0
Print *	p_output = nullptr

Detailed Description

MP3 header parser that processes MP3 data incrementally and extracts complete MP3 frames. Can validate MP3 data and extract audio information. When used with a Print output, it splits incoming data into complete MP3 frames and writes them to the output stream.

Features:

• Incremental processing of MP3 data in small chunks
• Frame synchronization and validation
• Extraction of audio information (sample rate, bit rate, etc.)
• Output of complete MP3 frames only
• Support for all MPEG versions (1, 2, 2.5) and layers

Author

Phil Schatzmann

Copyright

GPLv3

Member Enumeration Documentation

FrameReason

enum class FrameReason

strongprotected

Enumerator
VALID
INVALID_BITRATE_FOR_VERSION
INVALID_SAMPLERATE_FOR_VERSION
INVALID_MPEG_VERSION
INVALID_LAYER
INVALID_LAYER_II_BITRATE_AND_MODE
INVALID_EMPHASIS
INVALID_CRC

Constructor & Destructor Documentation

HeaderParserMP3() [1/2]

HeaderParserMP3 ( )

default

Default constructor.

HeaderParserMP3() [2/2]

HeaderParserMP3 ( Print &  output, int  bufferSize = 2048  )

inline

Constructor for write support.

Member Function Documentation

contains()

bool contains ( const uint8_t *  data, const char *  toFind, size_t  len  )

inlineprotected

findSyncWord()

int findSyncWord ( const uint8_t *  buf, size_t  nBytes, uint8_t  synch = 0xFF, uint8_t  syncl = 0xF0  )

inline

Finds the mp3/aac sync word.

flush()

void flush ( )

inline

getBitRate()

int getBitRate ( ) const

inline

Bit rate from mp3 header.

getChannels()

int getChannels ( ) const

inline

Number of channels from mp3 header.

getFrameHeader()

FrameHeader getFrameHeader ( )

inline

getFrameLength()

int getFrameLength ( )

inline

Frame length from mp3 header.

getFrameRateHz()

size_t getFrameRateHz ( )

inline

frame rate in Hz (frames per second)

getLayerStr()

const char * getLayerStr ( ) const

inline

Provides a string representation of the MPEG layer.

getPlayingTime()

size_t getPlayingTime ( size_t  fileSizeBytes )

inline

Provides the estimated playing time in seconds based on the bitrate of the first segment

getSampleRate()

uint16_t getSampleRate ( ) const

inline

Sample rate from mp3 header.

getSamplesPerFrame()

int getSamplesPerFrame ( )

inline

number of samples per mp3 frame

getTimePerFrameMs()

size_t getTimePerFrameMs ( )

inline

playing time per frame in ms

getVersionStr()

const char * getVersionStr ( ) const

inline

Provides a string representation of the MPEG version.

hasValidFrame()

bool hasValidFrame ( ) const

inline

Returns true if we have parsed at least one valid frame.

isValid() [1/2]

bool isValid ( )

inline

Returns true if a valid frame has been detected.

isValid() [2/2]

bool isValid ( const uint8_t *  data, int  len  )

inline

parses the header string and returns true if this is a valid mp3 file

processBuffer()

bool processBuffer ( )

inlineprotected

Processes the internal buffer to extract complete mp3 frames.

readFrameHeader()

void readFrameHeader ( const uint8_t *  data )

inlineprotected

reset()

void reset ( )

inline

Clears internal buffer and resets state.

resize()

bool resize ( size_t  size )

inline

seekFrameSync()

int seekFrameSync ( const uint8_t *  str, size_t  len  )

inlineprotected

setOutput()

void setOutput ( Print &  output )

inline

validate()

bool validate ( const uint8_t *  data, size_t  len  )

inlineprotected

validateFrameHeader()

FrameReason validateFrameHeader ( const FrameHeader &  header )

inlineprotected

write()

size_t write ( const uint8_t *  data, size_t  len  )

inline

split up the data into mp3 segements and write to output

Member Data Documentation

buffer

SingleBuffer<uint8_t> buffer {0}

protected

buffer_size

size_t buffer_size = 0

protected

frame_header_valid

bool frame_header_valid = false

protected

header

FrameHeader header

protected

last_frame_size

size_t last_frame_size = 0

protected

p_output

Print* p_output = nullptr

protected

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

• src/AudioTools/AudioCodecs/HeaderParserMP3.h