.TH man 3 "15 Nov 2014" "The Debian Project" "libfaad Documentation".SH "NAME"libfaad \- C library for AAC Decoding.SH "SYNOPSIS".sp.ft B.nf #include <neaacec\&.h> .HP.BI "char NEAACDECAPI *NeAACDecGetErrorMessage(" "" "unsigned char " errcode ); .HP.B "unsigned long NEAACDECAPI NeAACDecGetCapabilities(void);" .HP.B "NeAACDecHandle NEAACDECAPI NeAACDecOpen(void);" .HP.B "NeAACDecConfigurationPtr NEAACDECAPI NeAACDecGetCurrentConfiguration(".BI "NeAACDecHandle " hDecoder ");" .HP.B "unsigned char NEAACDECAPI NeAACDecSetConfiguration(".BI "NeAACDecHandle " "hDecoder" ", NeAACDecConfigurationPtr " config ");" .HP/* Init the library based on info from the AAC file (ADTS/ADIF) */.B "long NEAACDECAPI NeAACDecInit(".BI "NeAACDecHandle " hDecoder ", unsigned char *" buffer ", unsigned long " "buffer_size" ",".BI "unsigned long *" "samplerate" ", unsigned char *" "channels" ");".HP/* Init the library using a DecoderSpecificInfo */.B "char NEAACDECAPI NeAACDecInit2(".BI "NeAACDecHandle " "hDecoder" ", unsigned char *" "pBuffer" ",".BI "unsigned long " "SizeOfDecoderSpecificInfo" ",".BI "unsigned long *" "samplerate" ", unsigned char *"channels" ");".HP/* Init the library for DRM */.B "char NEAACDECAPI NeAACDecInitDRM(".BI "NeAACDecHandle *" "hDecoder" ", unsigned long " "samplerate" ", unsigned char " "channels" ");".HP.B "void NEAACDECAPI NeAACDecPostSeekReset(".BI "NeAACDecHandle " "hDecoder" ", long "frame" ");".HP.BI "void NEAACDECAPI NeAACDecClose(NeAACDecHandle " "hDecoder" ");".HP.B "void NEAACDECAPI *NeAACDecDecode(".BI "NeAACDecHandle " "hDecoder" ", NeAACDecFrameInfo *" "hInfo" ",".BI "unsigned char *" "buffer" ",".BI "unsigned long " "buffer_size" ");".HP.B "void NEAACDECAPI *NeAACDecDecode2(".BI "NeAACDecHandle " "hDecoder" ", NeAACDecFrameInfo *" "hInfo" ",".BI "unsigned char *" "buffer" ", unsigned long " "buffer_size" ",".BI "void **" "sample_buffer" ", unsigned long " "sample_buffer_size" ");".HP.B "char NEAACDECAPI NeAACDecAudioSpecificConfig(".BI "unsigned char *" "pBuffer" ", unsigned long " "buffer_size" ",".BI "mp4AudioSpecificConfig *" "mp4ASC" ");".PPFor normal use link it with the linker option \-lfaad\&..PPFor Digital Radio Mondiale link it with the linker option \-lfaad_drm\&..sp.SH "DESCRIPTION".PP.B NeAACDecGetErrorMessage.PP.B char NEAACDECAPI *NeAACDecGetErrorMessage(unsigned char errcode);.PPConvert an error code to text..PP.B NeAACDecGetCapabilities.PPunsigned long NEAACAPI NeAACDecGetCapabilities(void);.PP .PPThis function returns the capabilities of the decoder in a 32 bitunsigned integer.The bits that are set in the 32 bit unsigned integer define with whichcapabilities the library has been compiled..PPThe following capabilities are defined:.PP\ .PP#define LC_DEC_CAP \  \  \  \  \  (1<<0) /* Can decode LC */.PP#define MAIN_DEC_CAP \  \  \  \  (1<<1) /* Can decode MAIN */.PP#define LTP_DEC_CAP \  \  \  \  \ (1<<2) /* Can decode LTP */.PP#define LD_DEC_CAP \  \  \  \  \  (1<<3) /* Can decode LD */.PP#define ERROR_RESILIENCE_CAP (1<<4) /* Can decode ER */.PP#define FIXED_POINT_CAP \  \  \ (1<<5) /* Fixed point */.PP.PPThis function can be called anytime..PP.B NeAACDecOpen .PP NeAACDecHandle NEAACAPI NeAACDecOpen(void);.PPReturns a handle to a decoder context..PP.B NeAACDecClose.PP void NEAACAPI NeAACDecClose(NeAACDecHandle hDecoder);.PPCloses a decoder context that has been opened by NeAACDecOpen..PP.B NeAACDecGetCurrentConfiguration.PPNeAACDecConfigurationPtr NEAACAPINeAACDecGetCurrentConfiguration(NeAACDecHandle hDecoder);.PPReturns the current decoder library configuration..PP.B NeAACDecSetConfiguration.PP unsigned char NEAACAPI NeAACDecSetConfiguration(NeAACDecHandle hDecoder, NeAACDecConfigurationPtr config);.PP.PPSets a new configuration structure for the decoder library..PP\ .PPReturn values:.PP 0 \[en] Error, invalid configuration..PP 1 \[en] OK.PP.B NeAACDecInit.PPlong NEAACAPI NeAACDecInit(NeAACDecHandle hDecoder, unsigned char*buffer, unsigned long buffer_size, unsigned long *samplerate, unsignedchar *channels);.PP.PP.PPInitialises the decoder library using information from the AAC file.The buffer parameter should hold a small part of the AAC file, so thatthe initialization can be done based on the ADTS or ADIF header.Buffer can also be NULL, but then default initialization parameters willbe used..PPReturn values:.PP< 0 \[en] Error.PP>= 0 \[en] Number of bytes read.This amount of bytes should be skipped by the program using the decoderlibrary..PPThis function fills the samplerate and channels parameters with thedetected values..PP.B NeAACDecInit2.PPchar NEAACAPI NeAACDecInit2(NeAACDecHandle hDecoder, unsigned char*pBuffer, unsigned long SizeOfDecoderSpecificInfo, unsigned long*samplerate, unsigned char *channels);.PPInitialises the decoder library based on an AudioSpecificConfig as foundinside a MP4 file..PPReturn values:.PP< 0 \[en] Error.PP0 \- OK.PPThis function fills the samplerate and channels parameters with thedetected values..PP.B NeAACDecInitDRM.PPchar NEAACDECAPI NeAACDecInitDRM(NeAACDecHandle *hDecoder, unsigned long samplerate, unsigned char channels);.PPInitialises the decoder library for Digital Radio Mondiale using the specified sample rateand a DRM specific channel configuration..PPReturn values:.PP< 0 \[en] Error.PP0 \- OK.PPValues for the channel configuration:.PP#define DRMCH_MONO          1.PP#define DRMCH_STEREO        2.PP#define DRMCH_SBR_MONO      3.PP#define DRMCH_SBR_STEREO    4.PP#define DRMCH_SBR_PS_STEREO 5.PP.B NeAACDecDecode.PPvoid* NEAACAPI NeAACDecDecode(NeAACDecHandle hDecoder, NeAACDecFrameInfo*hInfo, unsigned char *buffer, unsigned long buffer_size);.PP.PPDecodes the AAC data passed in buffer..PPReturns a pointer to a sample buffer or NULL.Info about the decoded frame is filled in in the NeAACDecFrameInfostructure.This structure holds information about errors during decoding, number ofsample, number of channels and samplerate.The returned buffer contains the channel interleaved samples of theframe..PP.B NeAACDecDecode2.PPvoid NEAACDECAPI *NeAACDecDecode2(NeAACDecHandle hDecoder,                                  NeAACDecFrameInfo *hInfo,                                  unsigned char *buffer,                                  unsigned long buffer_size,                                  void **sample_buffer,                                  unsigned long sample_buffer_size);   .PP.B NeAACDecAudioSpecificConfig.PPchar NEAACDECAPI NeAACDecAudioSpecificConfig(unsigned char *pBuffer,                                  unsigned long buffer_size,                                  mp4AudioSpecificConfig *mp4ASC);.PP.B Structures.RS 4.PP NeAACDecConfiguration.RE.PPtypedef struct NeAACDecConfiguration.PP{.PP\  \  unsigned char defObjectType;.PP\  \  unsigned long defSampleRate;.PP\  \  unsigned char outputFormat;.PP\  \  unsigned char downMatrix;.PP\  \  unsigned char useOldADTSFormat;.PP} NeAACDecConfiguration, *NeAACDecConfigurationPtr;.PP .PPMembers:.PPdefObjectType: determines the default object type assumed when thelibrary is initialized without any data from the AAC file (eg: when NULLis passed as buffer in NeAACDecInit()).Can be any of the following values:.PP#define MAIN \  \  \  1 /* MAIN */.PP#define LC \  \  \  \  2 /* Low Complexity (default) */.PP#define SSR \  \  \  \ 3 /* Scalable SampleRate */.PP#define LTP \  \  \  \ 4 /* Long Term Predition */.PP#define HE_AAC \  \  5 /* High Efficiency (SBR) */.PP#define ER_LC \  \  17 /* Error Resilient Low Complexity */.PP#define ER_LTP \  \ 19 /* Error Resilient Long Term Prediction */.PP#define LD \  \  \  \ 23 /* Low Delay */.PP#define DRM_ER_LC 27 /* special object type for DRM only if linking with \-lfaad_drm */.PPdefSampleRate: determines the default samplerate assumed when thelibrary is initialized.Default value is 44100..PPoutputFormat: determines the output format returned by the decoderlibrary.Can be any of the following values:.PP#define FAAD_FMT_16BIT \ 1 /* 16 bit integers */.PP#define FAAD_FMT_24BIT \ 2 /* 24 bit values packed in 32 bit integers */.PP#define FAAD_FMT_32BIT \ 3 /* 32 bit integers */.PP#define FAAD_FMT_FLOAT \ 4 /* single precision floating point */.PP#define FAAD_FMT_DOUBLE 5 /* double precision floating point */.PPdownMatrix: determines whether a 5.1 channel AAC file should bedownmatrixed to 2 channel output (value: 1) or whether the output shouldstay as 5.1 channels (value: 0)..PPuseOldADTSFormat: determines whether the decoder should assume thecurrently defined 56 bit ADTS header (value: 0) or the 58 bit ADTSheader (value: 1) defined in previous versions of the AAC standard.This value should normally always stay at the value 0, it only exists toprovide playback capabilities for people that have AAC files with theold header format.All current encoders should output the new ADTS format.NeAACDecFrameInfo\ .PPThis structure is returned after decoding a frame and provides infoabout the decoded frame..PPtypedef struct NeAACDecFrameInfo.PP{.PP\  \  unsigned long bytesconsumed;.PP\  \  unsigned long samples;.PP\  \  unsigned char channels;.PP\  \  unsigned char error;.PP\  \  unsigned long samplerate;.PP\  \  unsigned char sbr;.PP\  \  unsigned char object_type;.PP\  \  unsigned char header_type;.PP\  \  unsigned char num_front_channels;.PP\  \  unsigned char num_side_channels;.PP\  \  unsigned char num_back_channels;.PP\  \  unsigned char num_lfe_channels;.PP\  \  unsigned char channel_position[64];.PP\  \  unsigned char ps;.PP} NeAACDecFrameInfo;.PP\ .PPMembers:.PPbytesconsumed: the number of bytes consumed for decoding this frame..PPsamples: the number of audio samples in this frame.Each channel is counted separately.So when a single channel has 1024 samples and the file has 2 channels,this value will be 2*1024 = 2048..PPchannels: number of audio channels in this frame.PPerror: contains an error value if an error occurred, 0 otherwise..PPsamplerate: the samplerate of the frame..PPsbr: tells whether sbr is used in this file or not.Can contain any of the following values:.PP#define NO_SBR \  \  \  \  \  0 /* no SBR used in this file */.PP#define SBR_UPSAMPLED \  \ 1 /* upsampled SBR used */.PP#define SBR_DOWNSAMPLED \ 2 /* downsampled SBR used */.PP#define NO_SBR_UPSAMPLED 3 /* no SBR used, but file is upsampled by afactor 2 anyway */.PPobject_type: contains the object type of the AAC file.Can be any of the values as defined in 1.9.1..PPheader_type: contains the header type of the file that is being decoded.Can contain any of the following values:.PP#define RAW \  \  \  \ 0 /* No header */.PP#define ADIF \  \  \  1 /* single ADIF header at the beginning of thefile */.PP#define ADTS \  \  \  2 /* ADTS header at the beginning of each frame */.PPnum_front_channels, num_side_channels, num_back_channels,num_lfe_channels: each of these values contain the number of channels ofa certain type..PPchannel_position[64]: contains the position of each of the channels thatis returned by the frame decode function.Can contain any of the following values:.PP#define FRONT_CHANNEL_CENTER (1).PP#define FRONT_CHANNEL_LEFT \  (2).PP#define FRONT_CHANNEL_RIGHT \ (3).PP#define SIDE_CHANNEL_LEFT \  \ (4).PP#define SIDE_CHANNEL_RIGHT \  (5).PP#define BACK_CHANNEL_LEFT \  \ (6).PP#define BACK_CHANNEL_RIGHT \  (7).PP#define BACK_CHANNEL_CENTER \ (8).PP#define LFE_CHANNEL \  \  \  \  \ (9).PP#define UNKNOWN_CHANNEL \  \  \ (0).PPps: PS not used (0) or used (1).API usage\ .PPThe following pseudo\-code describes how and in which order to use thedifferent library functions..PP\ .PPunsigned long cap = NeAACDecGetCapabilities();.PP// Check if decoder has the needed capabilities.PP\ .PP// Open the library.PPNeAACDecHandle hAac = NeAACDecOpen();.PP\ .PP// Get the current config.PPNeAACDecConfigurationPtr conf = NeAACDecGetCurrentConfiguration(hAac);.PP\ .PP//.PP// If needed change some of the values in conf.PP//.PP\ .PP// Set the new configuration.PPNeAACDecSetConfiguration(hAac, conf);.PP.PP// Initialise the library using one of the initialization functions.PPchar err = NeAACDecInit2(hAac, asc, asc_size, &samplerate, &channels);.PPif (err != 0).PP{.PP\ //.PP\ // Handle error.PP\ //.PP}.PP\ .PP// Loop until decoding finished.PPdo {.PP\ //.PP\ // Put next frame in buffer.PP\ //.PP\ .PP\ // Decode the frame in buffer.PP\  \  \  \  samplebuffer = NeAACDecDecode(hAac, &hInfo, buffer,.PPbuffer_size);.PP\ .PPif ((hInfo.error == 0) && (hInfo.samples > 0)).PP

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