ffmpeg4教程3:采集桌面图像(desktop)压缩为h264

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screencapturer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 test3() {
   AVCodec *encodec = avcodec_find_encoder( AV_CODEC_ID_H264);
   if (!encodec) {
       printf("not found encoder for h264");
       avcodec_get_name(AV_CODEC_ID_H264);
       return -1;
   }
   AVCodecContext *enctx = avcodec_alloc_context3(encodec);
   enctx->codec_id = AV_CODEC_ID_H264;
   enctx->bit_rate = 8000000;//码率
   enctx->width = 320;
   enctx->height = 240;

   AVRational base; base.num = 1; base.den = 15;//帧率
   enctx->time_base = base;
   enctx->gop_size = 12;
   enctx->max_b_frames = 0;
   enctx->pix_fmt = AV_PIX_FMT_YUV420P;//h264必须
   enctx->gop_size = 12;
   enctx->max_b_frames = 0;
   //减少延迟
   av_opt_set(enctx->priv_data, "preset", "superfast", 0);
   av_opt_set(enctx->priv_data, "tune", "zerolatency", 0);

   AVDictionary* opt = NULL;
   int ret = avcodec_open2(enctx, encodec,&opt);
   av_dict_free(&opt);

   if (ret < 0) {
       printf("not open video codec");
       return -1;
   }
//   AVFormatContext *formatctx = avformat_alloc_context();

   //添加test1的代码 begin
   AVFormatContext *formatCtx = avformat_alloc_context();
   AVInputFormat *ifmt = av_find_input_format("gdigrab");//设备类型
   //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, "desktop", ifmt, &options) != 0) {
       //if (avformat_open_input(&formatCtx, "video=Integrated Camera", 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_VIDEO) {
       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;
   }
   printf("pix format is %d\n", formatCtx->streams[0]->codecpar->format);//==AVPixelFormat->AV_PIX_FMT_BGRA

   AVFrame *frame = alloc_picture((AVPixelFormat)formatCtx->streams[0]->codecpar->format, formatCtx->streams[0]->codecpar->width, formatCtx->streams[0]->codecpar->height);

//图像缩放
   SwsContext *img_convert_ctx = sws_getContext(formatCtx->streams[0]->codecpar->width, formatCtx->streams[0]->codecpar->height, (AVPixelFormat)formatCtx->streams[0]->codecpar->format,
       enctx->width, enctx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
   //目标
   AVFrame *yupframe = alloc_picture(AV_PIX_FMT_YUV420P, enctx->width, enctx->height);

FILE *h264file = NULL;
fopen_s(&h264file, "C:\\Users\\lilin\\Desktop\\1.h264", "wb");//ffplay -stats -f h264 1.h264

   int64_t nexttps = 0;
   int64_t num = 100;
   while (num--) {
       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("decode error\n");
           }
           else {
               printf("采集到图片");
               //转换 AV_PIX_FMT_BGRA to AV_PIX_FMT_YUV420P
               sws_scale(img_convert_ctx, (const unsigned char* const*)frame->data, frame->linesize, 0, frame->height, yupframe->data, yupframe->linesize);
               if (nexttps == 0) { yupframe->pts = av_gettime(); } else {    yupframe->pts = nexttps;    }
               nexttps = yupframe->pts + 1000000LL * enctx->time_base.num / enctx->time_base.den;
               {
                   AVRational base; base.num = 1; base.den = 1000000LL;//帧率
                   //转换回去去压缩器的时基
                   yupframe->pts = av_rescale_q(yupframe->pts,base, enctx->time_base);
               }
               //开始压缩
               avcodec_send_frame(enctx, yupframe);

               AVPacket pkt = { 0 };
               av_init_packet(&pkt);
               ret = avcodec_receive_packet(enctx, &pkt);
               if (ret == 0) {//需去掉前面4个才是标准h264流
                   //压缩成功
                   char nal_stat[] = {0,0,0,1};
                   fwrite(nal_stat,4,1,h264file);
                   fwrite(pkt.data+4, pkt.size -4, 1, h264file);
               }
               av_packet_unref(&pkt);
           }
           av_packet_unref(&packet);
       }
   }
   av_frame_free(&frame);
   av_frame_free(&yupframe);
   avcodec_free_context(&ctx);
   avformat_close_input(&formatCtx);

//end
avcodec_free_context(&enctx);

fclose(h264file);
}

int main()
{
printf("ok：%d\n", avcodec_version());
avdevice_register_all();
test3();//视频采集h264压缩

}

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ffmpeg4教程3:采集桌面图像(desktop)压缩为h264

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