ffmpeg4教程2:采集桌面声音保存为pcm

基于vs2017 vc++ ffmpeg4.0.2下测试

ffmpeg 环境配置请百度（vs2017 ffmpeg ）图像和声音请安装dshow便于查找

部分方法在https://blog.csdn.net/Java_lilin/article/details/85118365中查找

头文件参考上篇教程

static int test2() {

   AVFormatContext *formatCtx = avformat_alloc_context();
   AVInputFormat *ifmt = av_find_input_format("dshow");//设备类型
   AVDictionary* options = NULL;
   //av_dict_set(&options, "video_size","1920*1080",0);//大小默认全部
   av_dict_set(&options, "framerate", "15", 0);//帧lu

   if (avformat_open_input(&formatCtx, "audio=virtual-audio-capturer", ifmt, &options) != 0) {
   /*不通过dshow的设备查找
   wchar_t wt[] = L"audio=内置麦克风 (Conexant SmartAudio HD)";
   char * psDevName = dup_wchar_to_utf8(wt);
   if (avformat_open_input(&formatCtx, psDevName, ifmt, &options) != 0) {
   */
       printf("open input device fail\n");
       return -1;
   }
   av_dict_free(&options);

   if (avformat_find_stream_info(formatCtx, NULL) < 0) {
       printf("avformat_find_stream_info faill\n");
       return -1;
   }
   if (formatCtx->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_AUDIO) {
       printf("no find stream info\n");
       return -1;
   }
   //查找解密器
   AVCodec *codec = avcodec_find_decoder(formatCtx->streams[0]->codecpar->codec_id);
   if (codec == NULL) {
       printf("codec not found\n");
       return -1;
   }
   AVCodecContext *ctx = avcodec_alloc_context3(codec);
   avcodec_parameters_to_context(ctx, formatCtx->streams[0]->codecpar);
   if (avcodec_open2(ctx, codec, NULL) < 0) {
       printf("codec not open\n");
       return -1;
   }

   AVFrame *frame = alloc_audio_frame((AVSampleFormat)formatCtx->streams[0]->codecpar->format, formatCtx->streams[0]->codecpar->channel_layout, formatCtx->streams[0]->codecpar->channels, formatCtx->streams[0]->codecpar->sample_rate, formatCtx->streams[0]->codecpar->frame_size);
   //目标
   ctx->channel_layout = av_get_default_channel_layout(ctx->channels);
   SwrContext *swr = swr_alloc();
   av_opt_set_int(swr, "in_channel_count", ctx->channels, 0);
   av_opt_set_int(swr, "in_channel_layout", ctx->channel_layout, 0);
   av_opt_set_int(swr, "in_sample_rate", ctx->sample_rate, 0);
   av_opt_set_sample_fmt(swr, "in_sample_fmt", ctx->sample_fmt, 0);
   int desc_channel_layout = 3;
   int desc_channel_count = 2;
   int desc_sample_rate = 44100;
   AVSampleFormat desc_fmt = AV_SAMPLE_FMT_S16;
   av_opt_set_int(swr, "out_channel_count", desc_channel_count, 0);
   av_opt_set_int(swr, "out_channel_layout", desc_channel_layout, 0);
   av_opt_set_int(swr, "out_sample_rate", desc_sample_rate, 0);
   av_opt_set_sample_fmt(swr, "out_sample_fmt", desc_fmt, 0);

   printf("\n声道%d,采样率%d格式%d----》声道%d,采样率%d格式%d\n", ctx->channels,ctx->sample_rate,
       ctx->sample_fmt, desc_channel_count, desc_sample_rate, desc_fmt);
   int DES_NB_SAMPLES = 1024;
   AVFrame *outframe = alloc_audio_frame(desc_fmt, desc_channel_layout, desc_channel_count, desc_sample_rate, DES_NB_SAMPLES);
   AVFrame *newframe = alloc_audio_frame(desc_fmt, desc_channel_layout, desc_channel_count, desc_sample_rate, 0);
   AVFrame *newframe2= alloc_audio_frame(desc_fmt, desc_channel_layout, desc_channel_count, desc_sample_rate, 0);

   AVAudioFifo *fifo = av_audio_fifo_alloc(desc_fmt, desc_channel_count,10240);

   FILE *file = NULL;
   fopen_s(&file, "C:\\Users\\lilin\\Desktop\\1.pcm","wb");//ffplay -ar 44100 -channels 2 -f s16le -i 1.pcm或用Audacity 播放

   int fnum = 500;
   while (fnum--) {
       int size = av_audio_fifo_size(fifo);
       if (size >= DES_NB_SAMPLES) {//超过
           printf("\n第一次超过\n");
           size = DES_NB_SAMPLES;
           av_audio_fifo_read(fifo, (void**)outframe->data, size);
           //完整

           //写文件
           fwrite(outframe->data[0],size,desc_channel_count*av_get_bytes_per_sample(desc_fmt),file);
           continue;
       }

       AVPacket packet = { 0 };
       av_init_packet(&packet);
       if (av_read_frame(formatCtx, &packet) >= 0) {
           avcodec_send_packet(ctx, &packet);
           if (avcodec_receive_frame(ctx, frame) < 0) {
               printf("audio decode error\n");
           }
           else {
               printf("采集到音频"); //
               swr_convert_frame(swr,newframe,frame);
               av_audio_fifo_write(fifo, (void**)newframe->data, newframe->nb_samples);

               int64_t dealy = swr_get_delay(swr, desc_sample_rate);
               if(dealy>0){
                   swr_convert_frame(swr, newframe2,NULL);
                   av_audio_fifo_write(fifo, (void**)newframe2->data, newframe2->nb_samples);
               }
               //这里可以判断下fifo里的数量是否够1024
               int size = av_audio_fifo_size(fifo);
               if (size < DES_NB_SAMPLES) {
                   //数据不够
                   av_packet_unref(&packet);
                   continue;
               }
               size = DES_NB_SAMPLES;//够了
               av_audio_fifo_read(fifo, (void**)outframe->data,size);//固定大小的

               //写文件
               fwrite(outframe->data[0], size, desc_channel_count*av_get_bytes_per_sample(desc_fmt), file);

}

       }
       av_packet_unref(&packet);
   }

   av_frame_free(&frame);
   av_frame_free(&newframe);
   av_frame_free(&newframe2);
   av_frame_free(&outframe);
   av_audio_fifo_free(fifo);
   avcodec_free_context(&ctx);
   avformat_close_input(&formatCtx);

fclose(file);
return 0;
}

int main(){

printf("ok：%d\n", avcodec_version());
avdevice_register_all();

test2();

}

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ffmpeg4教程2:采集桌面声音保存为pcm

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