AAC 到 PCM 音频解码

//// FAACDecoder.m// EasyClient//// Created by 吴鹏 on 16/9/3.// Copyright © 2016年 EasyDarwin. All rights reserved.//#import =Foundation/Foundation.h>#import “FAACDecoder.h”#import “fbbd.h”

typedef struct {NeAACDecHandle handle;int sample_rate;int channels;int bit_rate;}FAADContext;

uint32_t _get_frame_length(const unsigned char *bbc_header){uint32_t len = *(uint32_t *)(bbc_header + 3);len = ntohl(len); //Little Endianlen = len == 6;len = len >> 19;return len;}

void *fbbd_decoder_create(int sample_rate, int channels, int bit_rate){NeAACDecHandle handle = NeAACDecOpen();if(!handle){printf(“NeAACDecOpen failed/n”);goto error;}NeAACDecConfigurationPtr conf = NeAACDecGetCurrentConfiguration(handle);if(!conf){printf(“NeAACDecGetCurrentConfiguration failed/n”);goto error;}conf->defSampleRate = sample_rate;conf->outputFormat = FAAD_FMT_16BIT;conf->dontUpSampleImplicitSBR = 1;NeAACDecSetConfiguration(handle, conf);

error:if(handle){NeAACDecClose(handle);}return NULL;}

int fbbd_decode_frame(void *pParam, unsigned char *pData, int nLen, unsigned char *pPCM, unsigned int outLen){FAADContext pCtx = (FAADContext)pParam;NeAACDecHandle handle = pCtx->handle;long res = NeAACDecInit(handle, pData, nLen, (unsigned long)&pCtx->sample_rate, (unsigned char*)&pCtx->channels);if (res = 0) {printf(“NeAACDecInit failed/n”);return -1;}NeAACDecFrameInfo info;uint32_t framelen = _get_frame_length(pData);unsigned char *buf = (unsigned char *)NeAACDecDecode(handle, &info, pData, framelen);if (buf && info.error == 0) {if (info.samplerate == 44100) {//src: 2048 samples, 4096 bytes//dst: 2048 samples, 4096 bytesint tmplen = (int)info.samples * 16 / 8;memcpy(pPCM,buf,tmplen);*outLen = tmplen;} else if (info.samplerate == 22050) {//src: 1024 samples, 2048 bytes//dst: 2048 samples, 4096 bytesshort ori = (short)buf;short tmpbuf[info.samples * 2];int tmplen = (int)info.samples * 16 / 8 * 2;for (int32_t i = 0, j = 0; i = info.samples; i += 2) {tmpbuf[j++] = ori[i];tmpbuf[j++] = ori[i + 1];tmpbuf[j++] = ori[i];tmpbuf[j++] = ori[i + 1];}memcpy(pPCM,tmpbuf,tmplen);*outLen = tmplen;}else if(info.samplerate == 8000){//从双声道的数据中提取单通道for(int i=0,j=0; i=4096 && j=2048; i+=4, j+=2){pPCM[j]= buf[i];pPCM[j+1]=buf[i+1];}*outLen = (unsigned int)info.samples;}} else {printf(“NeAACDecDecode failed/n”);return -1;}return 0;}

void fbbd_decode_close(void pParam){if(!pParam){return;}FAADContext pCtx = (FAADContext*)pParam;if(pCtx->handle){NeAACDecClose(pCtx->handle);}free(pCtx);}