ffmpeg解码音频的两种方式（二）根据同步字节解析音频帧

根据adts同步头提取aac音频单帧：

#include "stdafx.h"#include <stdio.h>#include <stdlib.h>#include <string.h>extern "C"{#include "libavcodec/avcodec.h"#include "libavformat/avformat.h"#include "libswresample/swresample.h"//SDL#include "sdl/SDL.h"#include "sdl/SDL_thread.h"};#define MAX_AUDIO_FRAME_SIZE 192000 // 1 second of 48khz 32bit audio#define OUTPUT_PCM 1#define USE_SDL 1static  Uint8  *audio_chunk; static  Uint32  audio_len; static  Uint8  *audio_pos; void  fill_audio(void *udata,Uint8 *stream,int len){ //SDL 2.0SDL_memset(stream, 0, len);if(audio_len==0)/*  Only  play  if  we  have  data  left  */ return; len=(len>audio_len?audio_len:len);/*  Mix  as  much  data  as  possible  */ SDL_MixAudio(stream,audio_pos,len,SDL_MIX_MAXVOLUME);audio_pos += len; audio_len -= len; } //-----------------int getADTSframe(unsigned char* buffer, int buf_size, unsigned char* data ,int* data_size){int size = 0;if(!buffer || !data || !data_size ){return -1;}while(1){if(buf_size  < 7 ){return -1;}//Sync wordsif((buffer[0] == 0xff) && ((buffer[1] & 0xf0) == 0xf0) ){size |= ((buffer[3] & 0x03) <<11);     //high 2 bitsize |= buffer[4]<<3;                //middle 8 bitsize |= ((buffer[5] & 0xe0)>>5);        //low 3bitbreak;}--buf_size;++buffer;}if(buf_size < size){return 1;}memcpy(data, buffer, size);*data_size = size;return 0;}int nWriteBytes=0;int _tmain(int argc, _TCHAR* argv[]){AVFormatContext*pFormatCtx;inti, audioStream;AVCodecContext*pCodecCtx;AVCodec*pCodec;char url[]="WavinFlag.aac";//char url[]="1.mp2";//char url[]="test.g711";av_register_all();pCodec=avcodec_find_decoder(AV_CODEC_ID_AAC);if(pCodec==NULL){printf("Codec not found.\n");return -1;}pCodecCtx = avcodec_alloc_context3(pCodec);// Open codecif(avcodec_open2(pCodecCtx, pCodec,NULL)<0){printf("Could not open codec.\n");return -1;}FILE *pFile=NULL;FILE *pInFile = NULL;#if OUTPUT_PCMpFile=fopen("output.pcm", "wb");pInFile=fopen(url, "rb");#endif//Out Audio Paramuint64_t out_channel_layout=AV_CH_LAYOUT_STEREO;int out_nb_samples=1024;AVSampleFormat out_sample_fmt=AV_SAMPLE_FMT_S16;int out_sample_rate=44100;int out_channels=av_get_channel_layout_nb_channels(out_channel_layout);//输出内存大小int out_buffer_size=av_samples_get_buffer_size(NULL,out_channels ,out_nb_samples,out_sample_fmt, 1);uint8_t *out_buffer=(uint8_t *)av_malloc(MAX_AUDIO_FRAME_SIZE*2);AVFrame *pFrame = av_frame_alloc();avcodec_get_frame_defaults(pFrame);//SDL------------------#if USE_SDL//Initif(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {  printf( "Could not initialize SDL - %s\n", SDL_GetError()); return -1;}//SDL_AudioSpecSDL_AudioSpec wanted_spec;wanted_spec.freq = out_sample_rate; wanted_spec.format = AUDIO_S16SYS; wanted_spec.channels = out_channels; wanted_spec.silence = 0; wanted_spec.samples = out_nb_samples/*pCodecCtx->frame_size*/; wanted_spec.callback = fill_audio; wanted_spec.userdata = pCodecCtx; if (SDL_OpenAudio(&wanted_spec, NULL)<0){ printf("can't open audio.\n"); return -1; } #endif////printf("Bitrate:\t %3d\n", pFormatCtx->bit_rate);//printf("Decoder Name:\t %s\n", pCodecCtx->codec->long_name);//printf("Channels:\t %d\n", pCodecCtx->channels);//printf("Sample per Second\t %d \n", pCodecCtx->sample_rate);uint32_t ret,len = 0;int got_picture;int index = 0;struct SwrContext *au_convert_ctx;au_convert_ctx = swr_alloc();//au_convert_ctx=swr_alloc_set_opts(au_convert_ctx,out_channel_layout, out_sample_fmt, out_sample_rate,//pCodecCtx->channel_layout,pCodecCtx->sample_fmt , pCodecCtx->sample_rate,0, NULL);//swr_init(au_convert_ctx);int data_size = 0;int size = 0;int cnt=0;int offset=0;FILE *myout=stdout;unsigned char *aacframe=(unsigned char *)malloc(1024*5);unsigned char *aacbuffer=(unsigned char *)malloc(1024*1024);FILE *ifile = fopen(url, "rb");if(!ifile){printf("Open file error");return -1;}printf(" aac NUM - Profile - Frequency - Size \n");while(!feof(ifile)){data_size = fread(aacbuffer+offset, 1, 1024*1024-offset, ifile);unsigned char* input_data = aacbuffer+offset;while(1){int ret=getADTSframe(input_data, data_size, aacframe, &size);if(ret==-1){break;}else if(ret==1){memcpy(aacbuffer,input_data,data_size);offset=data_size;break;}char profile_str[10]={0};char frequence_str[10]={0};unsigned char profile=aacframe[2]&0xC0;profile=profile>>6;switch(profile){case 0: sprintf(profile_str,"Main");break;case 1: sprintf(profile_str,"LC");break;case 2: sprintf(profile_str,"SSR");break;default:sprintf(profile_str,"unknown");break;}unsigned char sampling_frequency_index=aacframe[2]&0x3C;sampling_frequency_index=sampling_frequency_index>>2;switch(sampling_frequency_index){case 0: sprintf(frequence_str,"96000Hz");break;case 1: sprintf(frequence_str,"88200Hz");break;case 2: sprintf(frequence_str,"64000Hz");break;case 3: sprintf(frequence_str,"48000Hz");break;case 4: sprintf(frequence_str,"44100Hz");break;case 5: sprintf(frequence_str,"32000Hz");break;case 6: sprintf(frequence_str,"24000Hz");break;case 7: sprintf(frequence_str,"22050Hz");break;case 8: sprintf(frequence_str,"16000Hz");break;case 9: sprintf(frequence_str,"12000Hz");break;case 10: sprintf(frequence_str,"11025Hz");break;case 11: sprintf(frequence_str,"8000Hz");break;default:sprintf(frequence_str,"unknown");break;}AVPacket avpkt;av_init_packet(&avpkt);avpkt.data = (uint8_t *)aacframe;  avpkt.size = size;while(avpkt.size>0){ret = avcodec_decode_audio4( pCodecCtx, pFrame,&got_picture, &avpkt);if ( ret < 0 ) {printf("Error in decoding audio frame.\n");return -1;}//需要解码后初始化，否则pCodecCtx的参数尚未获取到（纯净版不用预先指定参数）static bool bSwrInit=false;if(!bSwrInit){au_convert_ctx=swr_alloc_set_opts(au_convert_ctx,out_channel_layout, out_sample_fmt, out_sample_rate,pCodecCtx->channel_layout,pCodecCtx->sample_fmt , pCodecCtx->sample_rate,0, NULL);swr_init(au_convert_ctx);bSwrInit=true;}if ( got_picture > 0 ){int nBytes = swr_convert(au_convert_ctx,&out_buffer, MAX_AUDIO_FRAME_SIZE,(const uint8_t **)pFrame->data , pFrame->nb_samples);if(nBytes<0){printf("swr_convert failed \n");return 0;}nWriteBytes = av_samples_get_buffer_size(NULL, out_channels, nBytes, out_sample_fmt, 1);if(nWriteBytes<0){printf("av_samples_get_buffer_size failed \n");return 0;}fwrite(out_buffer, 1, nWriteBytes, pFile);}//设置音频数据缓冲,PCM数据audio_chunk = (Uint8 *) out_buffer; //设置音频数据长度audio_len = nWriteBytes;audio_pos = audio_chunk;//回放音频数据 SDL_PauseAudio(0);while(audio_len>0)//等待直到音频数据播放完毕! SDL_Delay(1); avpkt.data+=ret;avpkt.size-=ret;}av_free_packet(&avpkt);data_size -= size;input_data += size;cnt++;}   }fclose(ifile);free(aacbuffer);fclose(pFile);#if USE_SDLSDL_CloseAudio();//关闭音频设备 SDL_Quit();#endifswr_free(&au_convert_ctx);av_free(out_buffer);avcodec_close(pCodecCtx);return 0;}