FFmpeg———encode

目录

• 前言
• 源码
• 函数
• 最终效果

  前言

  encode_video:实现了对图片使用指定编码进行编码，生成可播放的视频流，编译时出现了一些错误，做了一些调整。

  基本流程：

  1、获取指定的编码器

  2、编码器内存申请

  3、编码器上下文内容参数设置

  4、打开编码器

  5、申请数据帧内存

  6、模拟图片

  7、编码

  源码

  测试代码，做了部分修改

  #include 
  using namespace std;
  #include 
  #include 
  #include 
  extern"C"
  {
  #include "libavcodec/avcodec.h"
  #include "libavutil/opt.h"
  #include "libavutil/imgutils.h"
  #include "libavutil/error.h"
  }
  static void encode(AVCodecContext* enc_ctx, AVFrame* frame, AVPacket* pkt,
      FILE* outfile)
  {
      int ret;
      /* send the frame to the encoder */
      if (frame)
          printf("Send frame %lld\n", frame->pts);  //修改 lld 替换 PRId64
      /*avcodec_send_frame 与 avcodec_receive_packet 配合使用*/
      ret = avcodec_send_frame(enc_ctx, frame);
      if (ret = 0) {
          ret = avcodec_receive_packet(enc_ctx, pkt);
          if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
              return;
          else if (ret pts, pkt->size); //修改 lld 替换 PRId64
          fwrite(pkt->data, 1, pkt->size, outfile);
          av_packet_unref(pkt); //清空数据压缩包
      }
  }
  int main()
  {
      const char* filename;
      const AVCodec* codec;
      AVCodecContext* c = NULL;  // 编码器上下文
      int i, ret, x, y;
      FILE* f;
      AVFrame* frame;  // 音视频数据帧结构体
      AVPacket* pkt;
      uint8_t endcode[] = { 0, 0, 1, 0xb7 };
      filename = "text_264";
      /* find the mpeg1video encoder */
      codec = avcodec_find_encoder(AV_CODEC_ID_H264);
      if (!codec) {
          fprintf(stderr, "Codec not found\n");
          exit(1);
      }
     // 为编码器申请空间并设置初始值
      c = avcodec_alloc_context3(codec);
      if (!c) {
          fprintf(stderr, "Could not allocate video codec context\n");
          exit(1);
      }
      pkt = av_packet_alloc();
      if (!pkt)
          exit(1);
      /* put sample parameters */
      c->bit_rate = 400000;
      /* 分辨率 为2的倍数 */
      c->width = 352;
      c->height = 288;
      /* frames per second */
      c->time_base.num = 1;
      c->time_base.den = 25;
      //帧率
      c->framerate.num = 25;
      c->framerate.den = 1;
      /* emit one intra frame every ten frames
       * check frame pict_type before passing frame
       * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
       * then gop_size is ignored and the output of encoder
       * will always be I frame irrespective to gop_size
       */
      c->gop_size = 10;
      c->max_b_frames = 1;  //非B帧之间的最大的B帧数
      c->pix_fmt = AV_PIX_FMT_YUV420P;   //像素格式
      if (codec->id == AV_CODEC_ID_H264)
          av_opt_set(c->priv_data, "preset", "slow", 0);   //设置属性
      /* open it */
      ret = avcodec_open2(c, codec, NULL);
      if (ret format = c->pix_fmt;
      frame->width = c->width;
      frame->height = c->height;
      ret = av_frame_get_buffer(frame, 0);  //申请数据帧缓冲区
      if (ret height; y++) {
              for (x = 0; x width; x++) {
                  frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
              }
          }
          /* Cb and Cr */
          for (y = 0; y height / 2; y++) {
              for (x = 0; x width / 2; x++) {
                  frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
                  frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
              }
          }
          frame->pts = i;
          /* encode the image */
          encode(c, frame, pkt, f);
      }
      /* flush the encoder */
      encode(c, NULL, pkt, f);
      /* Add sequence end code to have a real MPEG file.
         It makes only sense because this tiny examples writes packets
         directly. This is called "elementary stream" and only works for some
         codecs. To create a valid file, you usually need to write packets
         into a proper file format or protocol; see mux.c.
       */
      if (codec->id == AV_CODEC_ID_MPEG1VIDEO || codec->id == AV_CODEC_ID_MPEG2VIDEO)
          fwrite(endcode, 1, sizeof(endcode), f);
      fclose(f);
      avcodec_free_context(&c);
      av_frame_free(&frame);
      av_packet_free(&pkt);
      return 0;
  }
  

  函数

  1、int avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame);

  向编码器发送音频或视频的数据包与

  int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt);配合使用

  成功返回0

  2、av_err2str(errnum)

  编译会报错

  修改：

  char av_error[AV_ERROR_MAX_STRING_SIZE] = { 0 };
  #define av_err2str(errnum) \
      av_make_error_string(av_error, AV_ERROR_MAX_STRING_SIZE, errnum)
  

  最终效果