#include <stdlib.h>
extern "C"{//
#include "avcodec.h"
#include "avformat.h"
}
int main(char arg,char *argv[])
{
????char *filename ="02.swf";
????
????av_register_all();//注冊所有可解碼類型
????AVFormatContext *pInFmtCtx=NULL;//文件格式
????AVCodecContext *pInCodecCtx=NULL;//編碼格式
????if (av_open_input_file(&pInFmtCtx,filename,NULL, 0, NULL)!=0)//獲取文件格式
????????printf("av_open_input_file error\n");
????if(av_find_stream_info(pInFmtCtx) < 0)//獲取文件內音視頻流的信息
????????printf("av_find_stream_info error\n");
????
????unsigned int j;
????// Find the first audio stream
????int????audioStream = -1;
????for(j=0; j<pInFmtCtx->nb_streams; j++)//找到音頻對應的stream
????????if(pInFmtCtx->streams[j]->codec->codec_type==CODEC_TYPE_AUDIO)
????????{
????????????audioStream=j;
????????????break;
????????}
????????if(audioStream==-1)
????????{
????????????printf("input file has no audio stream\n");
????????????return 0; // Didn't find a audio stream
????????}
????????printf("audio stream num: %d\n",audioStream);
????????pInCodecCtx = pInFmtCtx->streams[audioStream]->codec;//音頻的編碼上下文
????????AVCodec *pInCodec=NULL;
????????/* FILE *file3 = fopen("codec_private_data_size.txt","w");
????????for(int i = 0; i <200000; i++)
????????{
????????pInCodec = avcodec_find_decoder((CodecID)i);
????????if (pInCodec!=NULL)
????????{
????????fprintf(file3,"%s %d\n",pInCodec->name,pInCodec->priv_data_size );
????????}
????????}
????????fclose(file3);
????????system("pause");
????????*/
????????pInCodec = avcodec_find_decoder(pInCodecCtx->codec_id);//根據編碼ID找到用于解碼的結構體
????????if(pInCodec==NULL)
????????{
????????????printf("error no Codec found\n");
????????????return -1 ; // Codec not found
????????}
????????//使用test的代替pInCodecCtx也可以完成解碼，可以看出只要獲取以下幾個重要信息就可以實現解碼和重采樣
????????AVCodecContext *test = avcodec_alloc_context();
????????test->bit_rate = pInCodecCtx->bit_rate;//重采樣用
????????test->sample_rate = pInCodecCtx->sample_rate;//重采樣用
????????test->channels = pInCodecCtx->channels;//重采樣用
????????test->extradata = pInCodecCtx->extradata;//若有則必有
????????test->extradata_size = pInCodecCtx->extradata_size;//若有則必要
????????test->codec_type = CODEC_TYPE_AUDIO;//不必要
????????test->block_align = pInCodecCtx->block_align ;//必要
????????
????????if(avcodec_open(test, pInCodec)<0)//將兩者結合以便在下面的解碼函數中調用pInCodec中的對應解碼函數
????????{
????????????printf("error avcodec_open failed.\n");
????????????return -1; // Could not open codec
????????}
????????
????????if(avcodec_open(pInCodecCtx, pInCodec)<0)
????????{
????????????printf("error avcodec_open failed.\n");
????????????return -1; // Could not open codec
????????}
????????
????????static AVPacket packet;
????????
????????printf(" bit_rate = %d \r\n", pInCodecCtx->bit_rate);
????????printf(" sample_rate = %d \r\n", pInCodecCtx->sample_rate);
????????printf(" channels = %d \r\n", pInCodecCtx->channels);
????????printf(" code_name = %s \r\n", pInCodecCtx->codec->name);
????????//printf("extra data size: %d :data%x %x %x %x\n",pInCodecCtx->extradata_size,pInCodecCtx->extradata[0]
????????//???? ,pInCodecCtx->extradata[1],pInCodecCtx->extradata[2],pInCodecCtx->extradata[3]);
????????printf(" block_align = %d\n",pInCodecCtx->block_align);
????????
????????//system("pause");
????????//
????????uint8_t *pktdata;
????????int pktsize;
????????int out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE*100;
????????uint8_t * inbuf = (uint8_t *)malloc(out_size);
????????FILE* pcm,*packetinfo;
????????packetinfo = fopen("packetinfo.txt","w");
????????pcm = fopen("result.pcm","wb");
????????long start = clock();
????????while(av_read_frame(pInFmtCtx, &packet)>=0)//pInFmtCtx中調用對應格式的packet獲取函數
????????{
????????????//fprintf(packetinfo," packet { pts=%d; dts =%d;%x,%x,%x,%x; size=%d; stream_index=%d; pos=%d;}\n",
????????????// packet.pts,packet.dts,packet.data[0],packet.data[1],packet.data[2],packet.data[3],packet.size,packet.stream_index,packet.pos);
????????????if(packet.stream_index==audioStream)//如果是音頻
????????????{
????????????????pktdata = packet.data;
????????????????pktsize = packet.size;
????????????????while(pktsize>0)
????????????????{
????????????????????//fprintf(packetinfo,"packet data:%x %x %x %x %x\n",pktdata[0],pktdata[1],pktdata[2],pktdata[3],pktdata[4]);
????????????????????//fprintf(packetinfo,"packet size:%d\n\n",pktsize);
????????????????????out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE*100;
????????????????????//解碼
????????????????????int len = avcodec_decode_audio2(pInCodecCtx,(short*)inbuf,&out_size,pktdata,pktsize);
????????????????????if (len<0)
????????????????????{
????????????????????????printf("Error while decoding.\n");
????????????????????????break;
????????????????????}
????????????????????if(out_size>0)
????????????????????{
????????????????????????fwrite(inbuf,1,out_size,pcm);//pcm記錄
????????????????????????fflush(pcm);
????????????????????}
????????????????????pktsize -= len;
????????????????????pktdata += len;
????????????????}
????????????}
????????????av_free_packet(&packet);
????????}
????????long end = clock();
????????printf("cost time :%f\n",double(end-start)/(double)CLOCKS_PER_SEC);
????????free(inbuf);
????????fclose(pcm);
????????fclose(packetinfo);
????????if (pInCodecCtx!=NULL)
????????{
????????????avcodec_close(pInCodecCtx);
????????}
????????if (test!=NULL)
????????{
????????????avcodec_close(test);
????????}
????????av_free(test);
????????av_close_input_file(pInFmtCtx);
????????return 0;
}
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一個英文版的例子（有講解）
ffmpeg的一些使用例子
mpeg and SDL Tutorial
ffmpeg編譯相關
ffmpeg工作組(中文)
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轉自：
http://blog.chinaunix.net/u3/108358/showart_2132123.html
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