ffmpeg pcm编码aac

本博文参考自雷神博客 https://blog.youkuaiyun.com/leixiaohua1020/article/details/25430449

这是ffmpeg加上libfdk-aac 将pcm转aac的一个例子

代码如下

#include <string.h>
#define __STDC_CONSTANT_MACROS
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#ifdef __cplusplus
};
#endif


/// unsigned char *buf;
int flush_encoder(AVFormatContext *fmt_ctx,unsigned int stream_index);


int write_buffer(void * opaque,uint8_t *buf_t, int buf_size)//回调函数
{
    fwrite(buf_t,buf_size,1,(FILE *)opaque);
    fflush((FILE *)opaque);

    return buf_size;
}
int main(void)
{
    AVFormatContext* pFormatCtx;
    AVOutputFormat* fmt;
    AVStream* audio_st;
    AVCodecContext* pCodecCtx;
    AVCodec* pCodec;

    uint8_t* frame_buf;
    AVFrame* pFrame;
    AVPacket pkt;

    int got_frame=0;
    int ret=0;
    int size=0;


    const char* out_file = "./hefang_cjx_pcm.aac";
    const char *in_file="./hefang.pcm";

    FILE *out_fb=fopen(out_file,"wb+");
    FILE *in_fb=fopen(in_file,"r");
     int i;

     av_register_all();
     pFormatCtx = avformat_alloc_context();
     fmt = av_guess_format(NULL, out_file, NULL);
     pFormatCtx->oformat = fmt;

     unsigned char* outbuffer=(unsigned char*)av_malloc(32768);
     AVIOContext *avio_out =avio_alloc_context(outbuffer, 32768,1,out_fb,NULL,write_buffer,NULL);
     pFormatCtx->pb=avio_out;
     pFormatCtx->flags=AVFMT_FLAG_CUSTOM_IO;
     avformat_init_output(pFormatCtx,NULL);
     audio_st = avformat_new_stream(pFormatCtx, 0);
     if (audio_st==NULL){
         return -1;
     }

     pCodecCtx = audio_st->codec;
     pCodecCtx->codec_id = fmt->audio_codec;
     pCodecCtx->codec_type = AVMEDIA_TYPE_AUDIO;
     pCodecCtx->sample_fmt = AV_SAMPLE_FMT_S16;
     pCodecCtx->sample_rate= 44100;
     pCodecCtx->channels =1;
     pCodecCtx->profile= FF_PROFILE_AAC_LOW  ;
     pCodecCtx->bit_rate =64000;
     pCodec = avcodec_find_encoder_by_name("libfdk_aac");
     if (!pCodec){
         printf("Can not find encoder!\n");
         return -1;
     }
     if (avcodec_open2(pCodecCtx, pCodec,NULL) < 0){
         printf("Failed to open encoder!\n");
         return -1;
     }

     pFrame = av_frame_alloc();
     pFrame->nb_samples= pCodecCtx->frame_size;
     pFrame->format= pCodecCtx->sample_fmt;

     size = av_samples_get_buffer_size(NULL, pCodecCtx->channels,pCodecCtx->frame_size,pCodecCtx->sample_fmt, 1);

     frame_buf = (uint8_t *)av_malloc(size);

     avcodec_fill_audio_frame(pFrame, pCodecCtx->channels, pCodecCtx->sample_fmt,(const uint8_t*)frame_buf, size, 1);
     //Write Header
     avformat_write_header(pFormatCtx,NULL);
     av_new_packet(&pkt,size);
   while(!feof(in_fb))
   {
        //Read PCM

        if (fread(frame_buf, size, 1, in_fb) < 0){
            printf("Failed to read raw data! \n");
        }

        pFrame->data[0] = frame_buf;  //PCM Data

        pFrame->pts=i;
        got_frame=0;
        //Encode
        ret = avcodec_encode_audio2(pCodecCtx, &pkt,pFrame, &got_frame);
        if(ret < 0){
            printf("Failed to encode!\n");
            return -1;
        }
        if (got_frame==1){
            printf("Succeed to encode 1 frame! \tsize:%5d\n",pkt.size);
            pkt.stream_index = audio_st->index;
            ret = av_write_frame(pFormatCtx, &pkt);
            av_free_packet(&pkt);
        }
        i++;
  }

    //Flush Encoder
    ret = flush_encoder(pFormatCtx,0);
    if (ret < 0) {
        printf("Flushing encoder failed\n");
        return -1;
    }

    //Write Trailer
    av_write_trailer(pFormatCtx);

    //Clean
    if (audio_st){
        avcodec_close(audio_st->codec);
        av_free(pFrame);
        av_free(frame_buf);
    }
   // avio_close(pFormatCtx->pb);
    avformat_free_context(pFormatCtx);

    fclose(out_fb);
    fclose(in_fb);

    return 0;
 }

int flush_encoder(AVFormatContext *fmt_ctx,unsigned int stream_index)
{
    int ret;
    int got_frame;
    AVPacket enc_pkt;
    if (!(fmt_ctx->streams[stream_index]->codec->codec->capabilities &
        CODEC_CAP_DELAY))
        return 0;
    while (1) {
        enc_pkt.data = NULL;
        enc_pkt.size = 0;
        av_init_packet(&enc_pkt);
        ret = avcodec_encode_audio2 (fmt_ctx->streams[stream_index]->codec, &enc_pkt,
            NULL, &got_frame);
        av_frame_free(NULL);
        if (ret < 0)
            break;
        if (!got_frame){
            ret=0;
            break;
        }
        /* mux encoded frame */
        ret = av_write_frame(fmt_ctx, &enc_pkt);
        if (ret < 0)
            break;
    }
    return ret;
}

这里write_buffer是回调函数，在调用av_write_frame会触发write_buffer，其中必须得调用avformat_init_output设置，否则执行不了回调。这样就可以将编码后的aac数据输入到内存中，再从内存中保存到文件。

下载链接：https://download.youkuaiyun.com/download/yinsui1839/10433940

没有积分的朋友可以在评论区发邮箱给我

linux下编译：g++ main.cpp -lavformat -lavcodec -lavdevice -lavutil -lz -lm -lswresample -lfdk-aac

windows下：不知道