ffmpeg 获取视频关键帧

//
void SaveBmp(AVCodecContext *CodecContex, AVFrame *Picture, int width, int height,int num)
{
AVPicture pPictureRGB;//RGB图片

static struct SwsContext *img_convert_ctx;
img_convert_ctx = sws_getContext(width, height,	CodecContex->pix_fmt, width, height,PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);

// 确认所需缓冲区大小并且分配缓冲区空间
avpicture_alloc(&pPictureRGB, PIX_FMT_RGB24, width, height);
sws_scale(img_convert_ctx, Picture->data, Picture->linesize,\
0, height, pPictureRGB.data, pPictureRGB.linesize);

int lineBytes = pPictureRGB.linesize[0], i=0;

char fileName[1024]={0};
//char * bmpSavePath = "F:\\database\\frames\\%d.bmp";
char * bmpSavePath = "E:\\1.bmp";
time_t ltime;
time(<ime);
//sprintf(fileName,bmpSavePath , ltime);////////////////////////////////////////////???????????????????????????
sprintf(fileName,bmpSavePath , num);

FILE *pDestFile = fopen(fileName, "wb");
BITMAPFILEHEADER btfileHeader;
btfileHeader.bfType = MAKEWORD(66, 77);
btfileHeader.bfSize = lineBytes*height;
btfileHeader.bfReserved1 = 0;
btfileHeader.bfReserved2 = 0;
btfileHeader.bfOffBits = 54;

BITMAPINFOHEADER bitmapinfoheader;
bitmapinfoheader.biSize = 40;
bitmapinfoheader.biWidth = width;
bitmapinfoheader.biHeight = height;
bitmapinfoheader.biPlanes = 1;
bitmapinfoheader.biBitCount = 24;
bitmapinfoheader.biCompression = BI_RGB;
bitmapinfoheader.biSizeImage = lineBytes*height;
bitmapinfoheader.biXPelsPerMeter = 0;
bitmapinfoheader.biYPelsPerMeter = 0;
bitmapinfoheader.biClrUsed = 0;
bitmapinfoheader.biClrImportant = 0;

fwrite(&btfileHeader, 14, 1, pDestFile);
fwrite(&bitmapinfoheader, 40, 1, pDestFile);
for(i=height-1; i>=0; i--)
{
fwrite(pPictureRGB.data[0]+i*lineBytes, lineBytes, 1, pDestFile);
}

fclose(pDestFile);
avpicture_free(&pPictureRGB);
}

//
int fun(){
//char* sourceFile = "F:\\爱在春天 TV版 47.flv";
//char* sourceFile = "E:\\1.mp4";
char* sourceFile = "E:\\1.flv";

AVFormatContext *pInputFormatContext = avformat_alloc_context();//NULL;
AVCodecContext *pInputCodecContext = NULL;
AVCodec *pInputCodec = NULL;

//注册库中含有的所有可用的文件格式和编码器，这样当打开一个文件时，它们才能够自动选择相应的文件格式和编码器。
av_register_all();

int ret;
// 打开视频文件
if((ret=avformat_open_input(&pInputFormatContext, sourceFile, NULL, NULL))!=0){
cout<<" can't open file "<<endl;
return -1;
}
// 取出文件流信息
if(avformat_find_stream_info(pInputFormatContext,NULL)<0){
cout<<" can't find suitable codec parameters"<<endl;
return -1;
}
//用于诊断 //产品中不可用
//dump_format(pInputFormatContext, 0, sourceFile, false);

//仅仅处理视频流
//只简单处理我们发现的第一个视频流
//  寻找第一个视频流
int videoIndex = -1;
for(int i=0; i<pInputFormatContext->nb_streams; i++) {
if(pInputFormatContext->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO){
videoIndex = i;
break;
}
}
if(-1 == videoIndex){
cout<<" can't find video stream !"<<endl;
return -1;
}
// 得到视频流编码上下文的指针
pInputCodecContext = pInputFormatContext->streams[videoIndex]->codec;
//  寻找视频流的解码器
pInputCodec = avcodec_find_decoder(pInputCodecContext->codec_id);

if(NULL == pInputCodec){
cout<<"can't decode "<<endl;
return -1;
}

// 通知解码器我们能够处理截断的bit流，bit流帧边界可以在包中
//视频流中的数据是被分割放入包中的。因为每个视频帧的数据的大小是可变的，
//那么两帧之间的边界就不一定刚好是包的边界。这里，我们告知解码器我们可以处理bit流。
if(pInputCodec->capabilities & CODEC_CAP_TRUNCATED){
pInputCodecContext->flags|=CODEC_FLAG_TRUNCATED;
}

//打开解码器
if(avcodec_open2(pInputCodecContext, pInputCodec,NULL) != 0) {
cout<<"decode error"<<endl;
return -1;
}
int videoHeight;
int videoWidth;
videoWidth = pInputCodecContext->width;
videoHeight = pInputCodecContext->height;

AVPacket InPack;
int len = 0;
AVFrame OutFrame;
int nComplete=0;

//  加入这句话来纠正某些编码器产生的帧速错误
/* if(pInputCodecContext->frame_rate>1000 && pInputCodecContext->frame_rate_base==1)
pInputCodecContext->frame_rate_base=1000;*/

int nFrame = 0;
AVRational avRation = pInputCodecContext->time_base;
float frameRate = (float)avRation.den/avRation.num;
//av_seek_frame(pInputFormatContext,0);
while((av_read_frame(pInputFormatContext, &InPack) >= 0)){
len = avcodec_decode_video2(pInputCodecContext, &OutFrame, &nComplete, &InPack);

//判断是否是关键帧
if(nComplete > 0 && OutFrame.key_frame){
//解码一帧成功
SaveBmp(pInputCodecContext, &OutFrame, videoWidth, videoHeight,nFrame);
nFrame++;
}
}
cout<<" save frame number: "<<nFrame<<endl;
avcodec_close(pInputCodecContext);
av_free(pInputFormatContext);

system("PAUSE");
}