ffmpeg Windows下采集摄像头一帧数据，并保存为bmp图片

这里请注意，在编译ffmpeg时，不要使用--disable-devices选项。

使用

--enable-encoder=rawvideo
 --enable-decoder=rawvideo

启用rawvideo codec。

代码如下：

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavdevice/avdevice.h>
#include <libswscale/swscale.h>

#include <windows.h>

#include <time.h>

#define MAX_INPUT_DEVICE_NUM 10

#ifdef _WIN32
int strcasecmp(const char *s1, const char *s2)
{
    while ((*s1 != '')
        && (tolower(*(unsigned char *) s1) ==
        tolower(*(unsigned char *) s2)))
    {
        s1++;
        s2++;
    }
    return tolower(*(unsigned char *) s1) - tolower(*(unsigned char *) s2);
}
int strncasecmp(const char *s1, const char *s2, unsigned int n)
{
    if (n == 0)
        return 0;
    while ((n-- != 0)
        && (tolower(*(unsigned char *) s1) ==
        tolower(*(unsigned char *) s2))) {
            if (n == 0 || *s1 == '' || *s2 == '')
                return 0;
            s1++;
            s2++;
    }
    return tolower(*(unsigned char *) s1) - tolower(*(unsigned char *) s2);
}
#endif

void save_bmp(unsigned char * data,int data_size,int w,int h,FILE * out)
{
    // 位图文件头
    BITMAPFILEHEADER bmpheader;
    BITMAPINFO bmpinfo;
    int bit = 24;

    bmpheader.bfType = ('M' <<8)|'B';
    bmpheader.bfReserved1 = 0;
    bmpheader.bfReserved2 = 0;
    bmpheader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    bmpheader.bfSize = bmpheader.bfOffBits + w*h*bit/8;

    bmpinfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmpinfo.bmiHeader.biWidth = w;
    bmpinfo.bmiHeader.biHeight = 0-h;
    bmpinfo.bmiHeader.biPlanes = 1;
    bmpinfo.bmiHeader.biBitCount = bit;
    bmpinfo.bmiHeader.biCompression = BI_RGB;
    bmpinfo.bmiHeader.biSizeImage = 0;
    bmpinfo.bmiHeader.biXPelsPerMeter = 100;
    bmpinfo.bmiHeader.biYPelsPerMeter = 100;
    bmpinfo.bmiHeader.biClrUsed = 0;
    bmpinfo.bmiHeader.biClrImportant = 0;

    fwrite(&bmpheader,sizeof(BITMAPFILEHEADER),1,out);
    fwrite(&bmpinfo.bmiHeader,sizeof(BITMAPINFOHEADER),1,out);
    fwrite(data,data_size,1,out);
}
int CaptureFromLocalCamera()
{
    AVFormatContext *ic = NULL;
    AVFormatParameters in_fmt_para={0};
    AVPacket packet;
    char buffer[MAX_PATH]={0};
    int width = 0,height = 0;
    int ret,video_stream = -1,i=0;

    //查找输入（vfwcap）格式
    AVInputFormat *in_fmt = av_find_input_format ("vfwcap");
    if (in_fmt == NULL)
    {
        printf("not support input device vfwcap.
");
        return -1;
    }
    memset (&in_fmt_para, 0, sizeof(in_fmt_para));
    //指定需要采集图像的高度
    in_fmt_para.height = height;
    //指定需要采集图像的宽度
    in_fmt_para.width  = width;

    //设置帧率
    av_parse_video_frame_rate(&in_fmt_para.time_base,"20");

    //打开摄像头设备,从"0"到MAX_INPUT_DEVICE_NUM依次尝试打开
    for( i=0 ; i < MAX_INPUT_DEVICE_NUM + 1; i++ )
    {
        sprintf(buffer,"%d",i);
        ret = av_open_input_file ( &ic, buffer, in_fmt,sizeof(in_fmt_para),&in_fmt_para);
        if ( ret == 0 && ic)
        {
            break;
        }
    }
    //open success?
    if(!ic || ret != 0)
    {
        if(ic)
            av_close_input_file(ic);
        printf("can not open input file.
");
        return -2;
    }
    printf("input device no. is %d
",i);
    //find the video stream
    for(i=0;i<ic ->nb_streams;i++)
    {
        if ( CODEC_TYPE_VIDEO == ic ->streams[i] ->codec ->codec_type )
        {
            video_stream = i;
            break;
        }
    }
    if(video_stream < 0)
    {
        av_close_input_file(ic);
        printf("can not find a video stream.
");
        return -3;
    }
    //获取视频时间宽度和高度
    width  = ic ->streams[video_stream] ->codec ->width;
    height = ic ->streams[video_stream] ->codec ->height;
    printf("video size: %dx%d
",width,height);
    //从摄像头获取图像数据
    if( 0 == av_read_frame(ic,&packet))
    {
        //find the decode codec
        AVCodec * decodec =  avcodec_find_decoder(ic ->streams[video_stream] ->codec ->codec_id);
        if(decodec)
        {
            //open the decode codec
            if( 0 == avcodec_open(ic ->streams[video_stream] ->codec,decodec) )
            {
                int got_picture = 0;
                AVFrame * frame = avcodec_alloc_frame();
                avcodec_decode_video2(ic ->streams[video_stream] ->codec,frame,&got_picture,&packet);
                //decode success
                if(got_picture)
                {
                    uint8_t * buffer = NULL;
                    size_t buffer_size = 0;
                    struct SwsContext *pSwsCtx=NULL;
                    AVFrame * rgb_frame = avcodec_alloc_frame();
                    buffer_size = avpicture_get_size(PIX_FMT_BGR24,width,height);
                    buffer = (uint8_t *)av_malloc(buffer_size);
                    avpicture_fill((AVPicture*)rgb_frame,(uint8_t *)buffer,PIX_FMT_BGR24,width,height);
                    //get swscale ctx
                    pSwsCtx = sws_getContext(
                        ic ->streams[video_stream] ->codec ->width,
                        ic ->streams[video_stream] ->codec ->height,
                        ic ->streams[video_stream] ->codec ->pix_fmt,
                        width,
                        height,
                        PIX_FMT_BGR24,
                        SWS_BILINEAR,
                        NULL,
                        NULL,
                        NULL);
                    if(pSwsCtx)
                    {
                        FILE *fp = NULL;
                        SYSTEMTIME dt={0};
                        //图像格式转换
                        sws_scale(
                            pSwsCtx,
                            frame ->data,
                            frame ->linesize,
                            0,
                            ic ->streams[video_stream] ->codec ->height,
                            rgb_frame ->data,
                            rgb_frame ->linesize);
                        //create the image file name
                        GetLocalTime(&dt);
                        srand(0);
                        sprintf(buffer,"imgs/%04d_%02d_%02d %02d_%02d_%02d %02d.bmp",dt.wYear,dt.wMonth,dt.wDay,dt.wHour,dt.wMinute,dt.wSecond,rand()%30);
                        //
                        CreateDirectoryA("imgs",NULL);
                        //open file
                        fp = fopen(buffer, "wb");
                        if(fp)
                        {
                            save_bmp(rgb_frame ->data[0],rgb_frame ->linesize[0]*height,width,height,fp);
                            fclose(fp);
                        }
                        //free sws ctx
                        sws_freeContext(pSwsCtx);
                    }
                    //free buffer
                    av_free(rgb_frame);
                    av_free(buffer);
                }
                //free buffer
                av_free(frame);
                //close the decode codec
                avcodec_close(ic ->streams[video_stream] ->codec);
            }
        }
    }

    //close the input device
    av_close_input_file(ic);

    return 0;
}


int main()
{
    //avcodec_init();
    avcodec_register_all();
    avdevice_register_all();
    CaptureFromLocalCamera();

    return 0;
}