嵌入式实践教程--FFmpeg中H264裸流解码为YUV420P原像素

#include <iostream>
using namespace std;
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include<libavutil\imgutils.h>
#include <libavfilter/avfilter.h>
#include <libswscale/swscale.h>
}
AVFormatContext* AFCtx_p;//解封装上下文
AVCodecContext* ACCtx_p;//解码器上下文
AVCodec* codec_p;//解码器
AVFrame* pFrame;
AVFrame* pFrameyuv;
AVPacket* packet;
struct SwsContext* img_convert_ctx;
int videoindex = -1;
int ret, got_picture = 0;
int y_size;
const char path[] = "./res/5min.h264";
int main(int argc, char* argv[])
{
  //打开H264文件，将文件信息存入解封装上下文
  if (avformat_open_input(&AFCtx_p, path, NULL, NULL) != 0)
  {
  cout << "open failed\n" << endl;
  return -1;
  }
  //寻找视频流信息
  if (avformat_find_stream_info(AFCtx_p, NULL) < 0)
  {
  cout << "dtream find failed\n" << endl;
  return -1;
  }
  //dump调试信息
  av_dump_format(AFCtx_p, -1, path, NULL);
  //打开视频并且获取了视频流，设置视频索引默认值
  for (int i = 0; i<AFCtx_p->nb_streams; i++)
  {
  if (AFCtx_p->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
  {
    videoindex = i;
  }
  }
  //如果没有找到视频索引，说明不是一个视频文件
  if (videoindex == -1)
  {
  cout << "not a video\n" << endl;
  return -1;
  }
  //分配解码器上下文空间
  ACCtx_p = avcodec_alloc_context3(NULL);
  //获取编解码器上下文信息
  if (avcodec_parameters_to_context(ACCtx_p, AFCtx_p->streams[videoindex]->codecpar) < 0)
  {
  cout << "copy stream failed\n" << endl;
  return -1;
  }
  //查找解码器
  codec_p = avcodec_find_decoder(ACCtx_p->codec_id);
  if (!codec_p)
  {
  cout << "find decoder error\n" << endl;
  return -1;
  }
  //打开解码器
  if (avcodec_open2(ACCtx_p, codec_p, NULL) != 0)
  {
  cout << "open codec failed" << endl;
  return -1;
  }
  //裁剪图像
  img_convert_ctx = sws_getContext(ACCtx_p->width, ACCtx_p->height,
  ACCtx_p->pix_fmt,
  ACCtx_p->width, ACCtx_p->height,AV_PIX_FMT_YUV420P,SWS_BICUBIC,NULL,NULL,NULL);
  if (!img_convert_ctx)
  {
  cout << "get swscale context failed\n" << endl;
  return -1;
  }
  packet = av_packet_alloc();
  pFrame = av_frame_alloc();
  pFrameyuv = av_frame_alloc();
  //获取转换后YUV数据的大小
  int video_size = av_image_get_buffer_size(AV_PIX_FMT_YUV420P, ACCtx_p->width,
  ACCtx_p->height, 1);
  uint8_t* buf = (uint8_t*)av_malloc(video_size);
  av_image_fill_arrays(pFrameyuv->data, pFrameyuv->linesize,
  buf, AV_PIX_FMT_YUV420P, ACCtx_p->width, ACCtx_p->height, 1);
  char errbuf[256] = { 0 };
  FILE* fp_yuv = fopen("out.yuv", "wb+");
  //循环读取帧数据并转换写入
  while (av_read_frame(AFCtx_p, packet) >= 0)
  {
  if (packet->stream_index == videoindex)
  {
    if (avcodec_send_packet(ACCtx_p, packet) != 0)
    {
    cout << "send video stream packet failed\n" << endl;
    return -1;
    }
    if (avcodec_receive_frame(ACCtx_p, pFrame) != 0)
    {
    cout << "receive video frame failed\n" << endl;
    return -1;
    }
    cout << "decoding frame" << ACCtx_p->frame_number << endl;
    sws_scale(img_convert_ctx,
    pFrame->data, pFrame->linesize,
    0, ACCtx_p->height, pFrameyuv->data, pFrameyuv->linesize);
    y_size = ACCtx_p->width * ACCtx_p->height;
    fwrite(pFrameyuv->data[0], 1, y_size, fp_yuv);//Y
    fwrite(pFrameyuv->data[1], 1, y_size/4, fp_yuv);//U
    fwrite(pFrameyuv->data[2], 1, y_size/4, fp_yuv);//V
  }
  }
  fclose(fp_yuv);
  av_free(buf);
  av_frame_free(&pFrame);
  av_frame_free(&pFrameyuv);
  av_packet_free(&packet);
  sws_freeContext(img_convert_ctx);
  avcodec_free_context(&ACCtx_p);
  avformat_close_input(&AFCtx_p);
  avformat_free_context(AFCtx_p);
  return 1;
}