学步园

生成的库文件位于目录D:\MinGW\msys\1.0\local\bin下

 

阶段小结：

       到这里我们已经成功的把开源的FFmpeg的源码编译为Windows下可用的库文件！OK，我们已经前进了一大步，下面将继续展示如何使用这些库文件。

 

一、利用Visual Studio 2008 创建一基于控制台的项目fftest，注意请把预编译头的选项去掉

 

二、把上面第一部分整出来的，位于D:\MinGW\msys\1.0\local\bin目录下的所有 *.lib 和 *.dll 文件复制一份到项目fftest目录下；

       把上面第一部分整出来的，位于D:\MinGW\msys\1.0\local\include目录下的所有头文件复制一份到项目fftest目录下；

 

三、利用下面的代码

#include "stdafx.h"

 

extern "C"{
#ifdef __cplusplus
 #define __STDC_CONSTANT_MACROS
 #ifdef _STDINT_H
  #undef _STDINT_H
 #endif
 #include <stdint.h>

 #include "libavcodec/avcodec.h"
 #include "libavformat/avformat.h"
 #include "libswscale/swscale.h"
#endif
}

 

#include <stdio.h>

#pragma comment(lib, "avutil.lib")
#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "avcodec.lib")
#pragma comment(lib, "swscale.lib")

void SaveFrame(AVFrame *pFrame, int width, int height, int iFrame)

{
  FILE *pFile;
  char szFilename[32];
  int  y;
 
  // Open file
  sprintf(szFilename, "frame%d.ppm", iFrame);
  pFile=fopen(szFilename, "wb");
  if(pFile==NULL)
    return;
 
  // Write header
  fprintf(pFile, "P6\n%d %d\n255\n", width, height);
 
  // Write pixel data
  for(y=0; y<height; y++)
    fwrite(pFrame->data[0]+y*pFrame->linesize[0], 1, width*3, pFile);
 
  // Close file
  fclose(pFile);
}

 

int avcodec_decode_video(AVCodecContext *avctx, AVFrame *picture, int *got_picture_ptr, uint8_t *buf, int buf_size)
{
    AVPacket avpkt;
    av_init_packet(&avpkt);
    avpkt.data = buf;
    avpkt.size = buf_size;
    // HACK for CorePNG to decode as normal PNG by default
    avpkt.flags = AV_PKT_FLAG_KEY;

    return avcodec_decode_video2(avctx, picture, got_picture_ptr, &avpkt);
}

int main(int argc, char* argv[])
{
  AVFormatContext *pFormatCtx;
  int             i, videoStream;
  AVCodecContext  *pCodecCtx;
  AVCodec         *pCodec;
  AVFrame         *pFrame;
  AVFrame         *pFrameRGB;
  AVPacket        packet;
  int             frameFinished;
  int             numBytes;
  uint8_t         *buffer;
  struct SwsContext      *img_convert_ctx;

 

  if(argc < 2) {
    printf("Please provide a movie file\n");
    return -1;
  }

  // Register all formats and codecs
  av_register_all();
 
  pFormatCtx = avformat_alloc_context();
  // Open video file
  //if(av_open_input_file(&pFormatCtx, argv[1], NULL, 0, NULL)!=0)
  if(avformat_open_input(&pFormatCtx, argv[1], NULL, NULL) < 0 )
    return -1; // Couldn't open file
 
  // Retrieve stream information
  //if(av_find_stream_info(pFormatCtx)<0)
  if(avformat_find_stream_info(pFormatCtx, NULL)<0)
    return -1; // Couldn't find stream information
 
  // Find the first video stream
  videoStream=-1;
  for(i=0; i<pFormatCtx->nb_streams; i++)
   
  //if(pFormatCtx->streams[i]->codec->codec_type==CODEC_TYPE_VIDEO)
 if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
 {
      videoStream=i;
      break;
    }
  if(videoStream==-1)
    return -1; // Didn't find a video stream
 
  // Get a pointer to the codec context for the video stream
  pCodecCtx=pFormatCtx->streams[videoStream]->codec;
 
  // Find the decoder for the video stream
  pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
  if(pCodec==NULL) {
    fprintf(stderr, "Unsupported codec!\n");
    return -1; // Codec not found
  }
  // Open codec
  if(avcodec_open(pCodecCtx, pCodec)<0)
    return -1; // Could not open codec
 
  // Allocate video frame
  pFrame=avcodec_alloc_frame();
 
  // Allocate an AVFrame structure
  pFrameRGB=avcodec_alloc_frame();
  if(pFrameRGB==NULL)
    return -1;
 
  // Determine required buffer size and allocate buffer
  numBytes=avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width,
         pCodecCtx->height);
  buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));
 
  // Assign appropriate parts of buffer to image planes in pFrameRGB
  // Note that pFrameRGB is an AVFrame, but AVFrame is a superset
  // of AVPicture
  avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24,
   pCodecCtx->width, pCodecCtx->height);
 
  // Read frames and save first five frames to disk
  i=0;
  while(av_read_frame(pFormatCtx, &packet)>=0) {
    // Is this a packet from the video stream?
    if(packet.stream_index==videoStream) {
      // Decode video frame
      avcodec_decode_video(pCodecCtx, pFrame, &frameFinished, packet.data, packet.size);
     
      // Did we get a video frame?
      if(frameFinished) {
 // Convert the image from its native format to RGB
 //img_convert((AVPicture *)pFrameRGB, PIX_FMT_RGB24,(AVPicture*)pFrame, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
    //img_convert is departed, use sws_scale replace
    img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, PIX_FMT_RGB24,SWS_BICUBIC, NULL, NULL, NULL);
 if( img_convert_ctx == NULL ) printf("sws_getContext is failed");
 sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
 sws_freeContext(img_convert_ctx);
 
 // Save the frame to disk
 if(++i<=5)
   SaveFrame(pFrameRGB, pCodecCtx->width, pCodecCtx->height, i);
      }
    }
   
    // Free the packet that was allocated by av_read_frame
    av_free_packet(&packet);
  }
 
  // Free the RGB image
  av_free(buffer);
  av_free(pFrameRGB);
 
  // Free the YUV frame
  av_free(pFrame);
 
  // Close the codec
  avcodec_close(pCodecCtx);
 
  // Close the video file
  av_close_input_file(pFormatCtx);
 
  return 0;
}

 

感谢老美提供的代码

This work is licensed under the CreativeCommons Attribution-Share Alike 2.5
License. To view a copy of thislicense, visit
http://creativecommons.org/licenses/by-sa/2.5/ or senda letter to Creative
Commons, 543 Howard Street, 5th Floor, SanFrancisco, California, 94105, USA.   
Code examples are based off of FFplay, Copyright (c) 2003 FabriceBellard, and
a tutorial by Martin Bohme.

因为代码基于比较旧的FFmpeg版本，所以我做了很微小的修改使其能适应最近版本的FFmpeg。

 

四、请准备一份 *.avi 格式的视频文件，或h264编码的视频文件，并把它放到项目fftest的目录下；

 

五、设置VC项目fftest的命令参数 test.avi（它对应用来测试的avi视频文件）

 

六、编译运行