Ffmpeg x264 video coding and FAAC audio coding (IV). These details should be paid attention to in the Android interview

faacEncHandle faacEncOpen

// Return to one FAAC Of handle(

unsigned long nSampleRate, // Sampling rate , The unit is bps

unsigned long nChannels, // channel ,1 For mono ,2 Dual channel

unsigned long &nInputSamples, // The reference , Get the length of the original data that should be received each time the encoding is called

unsigned long &nMaxOutputBytes // The reference , Get the code generated each time the code is called AAC Maximum length of data );

Get the encoder configuration ：

faacEncConfigurationPtr faacEncGetCurrentConfiguration // Get a pointer to the current encoder configuration

(

faacEncHandle hEncoder // FAAC Of handle

);

Set the encoder configuration ：

int FAACAPI faacEncSetConfiguration

(

faacDecHandle hDecoder, // Previously obtained FAAC Of handle

faacEncConfigurationPtr config // FAAC Encoder configuration

);

int faacEncEncode

(

faacEncHandle hEncoder, // FAAC Of handle

short *inputBuffer, // WAV Raw data

unsigned int samplesInput, // call faacEncOpen When you get nInputSamples value

unsigned char *outputBuffer,// At least have the ability to call faacEncOpen When you get nMaxOutputBytes Byte long buffer

unsigned int bufferSize // outputBuffer The actual size of the buffer

);

void faacEncClose

(

faacEncHandle hEncoder // Previously obtained FAAC handle

);

3 technological process

Sampling rate , Track number （ Dual or mono ？）, And yours WAV A single sample of is 8 It’s still 16 Bit ？

1. call faacEncOpen Turn on FAAC After the encoder , The number of single input samples nInputSamples And the maximum number of bytes of output data nMaxOutputBytes;

2. according to nInputSamples and nMaxOutputBytes, Respectively WAV Data and what will be obtained AAC Data creation buffer ;

3. call faacEncGetCurrentConfiguration Get the current configuration , After modifying the configuration , call faacEncSetConfiguration Set up a new configuration .

call faacEncEncode, What should be prepared was just ready , It’s simple .

Turn off the encoder , Also, don’t forget to release the buffer , If a file stream is used , And don’t forget to close .

4 The test program

take WAV Format audio file /home/michael/Development/testspace/in.wav Transferred to AAC Format file /home/michael/Development/testspace/out.aac.

#include <faac.h>

#include <stdio.h>

typedef unsigned long ULONG;

typedef unsigned int UINT;

typedef unsigned char BYTE;

typedef char _TCHAR;

int main(int argc, _TCHAR* argv[])

{

ULONG nSampleRate = 11025; // Sampling rate

UINT nChannels = 1; // Track number

UINT nPCMBitSize = 16; // Single sample digits

ULONG nInputSamples = 0;

ULONG nMaxOutputBytes = 0;

int nRet;

faacEncHandle hEncoder;

faacEncConfigurationPtr pConfiguration;

int nBytesRead;

int nPCMBufferSize;

BYTE* pbPCMBuffer;

BYTE* pbAACBuffer;

FILE* fpIn; // WAV file for input

FILE* fpOut; // AAC file for output

fpIn = fopen(“/home/michael/Development/testspace/in.wav”, “rb”);

fpOut = fopen(“/home/michael/Development/testspace/out.aac”, “wb”);

// (1) Open FAAC engine

hEncoder = faacEncOpen(nSampleRate, nChannels, &nInputSamples, &nMaxOutputBytes);

if(hEncoder == NULL)

{

printf(“[ERROR] Failed to call faacEncOpen()n”);

return -1;

}

nPCMBufferSize = nInputSamples * nPCMBitSize / 8;

pbPCMBuffer = new BYTE [nPCMBufferSize];

pbAACBuffer = new BYTE [nMaxOutputBytes];

// (2.1) Get current encoding configuration

pConfiguration = faacEncGetCurrentConfiguration(hEncoder);

pConfiguration->inputFormat = FAAC_INPUT_16BIT;

// (2.2) Set encoding configuration

nRet = faacEncSetConfiguration(hEncoder, pConfiguration);

for(int i = 0; 1; i++)

{

// Actual bytes read in , Not more than nPCMBufferSize, Generally, it is not this value only when reading the end of the file

nBytesRead = fread(pbPCMBuffer, 1, nPCMBufferSize, fpIn);

// Enter the number of samples , Use the actual number of bytes read to calculate , Generally, it is not… Only when you read the end of the file nPCMBufferSize/(nPCMBitSize/8);

nInputSamples = nBytesRea

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d / (nPCMBitSize / 8);

// (3) Encode

nRet = faacEncEncode(

hEncoder, (int*) pbPCMBuffer, nInputSamples, pbAACBuffer, nMaxOutputBytes);

fwrite(pbAACBuffer, 1, nRet, fpOut);

printf(“%d: faacEncEncode returns %dn”, i, nRet);

if(nBytesRead <= 0)