【学习ffmpeg】打开视频文件，帧分析，并bmp保存关键帧

http://www.tuicool.com/articles/jiUzua

http://blog.csdn.net/code_future/article/details/8646717

主题 FFmpeg

任务：需要把一个视频文件的每一帧提取出来，每帧存储成单独的文件。

以前用Matlab处理过这个问题，可是感觉比较慢，而且最近正在逐步转向使用开源的东西。因此搜到ffmpeg这个好东西。

ffmpeg可用来处理视频文件的提取和各种转换，跨平台，官网上有Linux，WINDOWS和MAC版本。

以下是windows 命令行下使用ffmpeg提取视频帧的方法：

SET PATH=%PATH%;[path_to_ffmpeg]
SET VIDEOFILE=demo.mp4
SET DESTDIR=video_frameffmpeg -i %VIDEOFILE% -q:v 2 -f image2 %DESTDIR%%07d.jpeg

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其中-i 后面是输入文件，-q:v 2 q代表质量quality, v代表视频流，2是控制质量的参数。-f指定输出的格式是image2. %07d是图片命名的pattern

//--------------------------------------------------------------------------------------------

第一次接触ffmpeg，可以算是hello world程序。

下面的代码全部都是直接可以使用的，借鉴了官方学习样例，也算是翻译吧。

但是解决了，保存bmp图像时，图像颠倒和色彩异常问题。

// x_ffmpeg.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <windows.h>
#include <iostream>
#include <iosfwd>
#include <fstream>
using namespace std;

#define FILE_OUT
#ifdef FILE_OUT
std::ofstream file_debugout("frameandpacketinfo.txt");
#endif

static int av_create_bmp(char* filename,uint8_t *pRGBBuffer,int width,int height,int bpp)
{
    BITMAPFILEHEADER bmpheader;
    BITMAPINFO bmpinfo;
    FILE *fp;

    fp = fopen(filename,"wb");
    if(!fp)return -1;

    bmpheader.bfType = (‘M‘<<8)|‘B‘;
    bmpheader.bfReserved1 = 0;
    bmpheader.bfReserved2 = 0;
    bmpheader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    bmpheader.bfSize = bmpheader.bfOffBits + width*height*bpp/8;
    bmpinfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmpinfo.bmiHeader.biWidth = width;
    /*----注意，这里的bmpinfo.bmiHeader.biHeight变量的正负决定bmp文件的存储方式，如果
    为负值，表示像素是倒过来的*/
    bmpinfo.bmiHeader.biHeight = -height;
    bmpinfo.bmiHeader.biPlanes = 1;
    bmpinfo.bmiHeader.biBitCount = bpp;
    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,fp);
    fwrite(&bmpinfo.bmiHeader,sizeof(BITMAPINFOHEADER),1,fp);
    fwrite(pRGBBuffer,width*height*bpp/8,1,fp);
    fclose(fp);

    return 0;
}

static int av_create_bmp(char* filename, AVFrame *pRGBBuffer,int width,int height,int bpp)
{
    BITMAPFILEHEADER bmpheader;
    BITMAPINFO bmpinfo;
    FILE *fp;

    fp = fopen(filename, "wb");
    if(!fp)return -1;

    bmpheader.bfType = (‘M‘<<8)|‘B‘;
    bmpheader.bfReserved1 = 0;
    bmpheader.bfReserved2 = 0;
    bmpheader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    bmpheader.bfSize = bmpheader.bfOffBits + width*height*bpp/8;
    bmpinfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmpinfo.bmiHeader.biWidth = width;
    bmpinfo.bmiHeader.biHeight = -height;
    bmpinfo.bmiHeader.biPlanes = 1;
    bmpinfo.bmiHeader.biBitCount = 24;
    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,fp);
    fwrite(&bmpinfo.bmiHeader,sizeof(BITMAPINFOHEADER),1,fp);
    //fwrite(pRGBBuffer,width*height*bpp/8,1,fp);
    for(int y=0; y<height; y++)
        fwrite(pRGBBuffer->data[0] + y*pRGBBuffer->linesize[0], 1, width*3, fp);
    fclose(fp);
    return 0;
}

static void print_packet_info(AVPacket info)
{
#ifdef FILE_OUT
    file_debugout << "print_packet_info" << " convergence_duration:" << info.convergence_duration
        << " dts:" << info.dts
        << " duration:" << info.duration
        << " flags:" << info.flags
        << " pos:" << info.pos
        << " pts:" << info.pts
        << " size:" << info.size
        << " stream_index:" << info.stream_index << endl;
#else
    cout << "print_packet_info" << " convergence_duration:" << info.convergence_duration
        << " dts:" << info.dts
        << " duration:" << info.duration
        << " flags:" << info.flags
        << " pos:" << info.pos
        << " pts:" << info.pts
        << " size:" << info.size
        << " stream_index:" << info.stream_index << endl;
#endif
}

static void print_frame_info(AVFrame* pinfo)
{
#ifdef FILE_OUT
    file_debugout << "print_frame_info" << " coded_picture_number:" << pinfo->coded_picture_number
        << " display_picture_number:" << pinfo->display_picture_number
        << " type:" << pinfo->type << endl;
#else
    cout << "print_frame_info" << " coded_picture_number:" << pinfo->coded_picture_number
        << " display_picture_number:" << pinfo->display_picture_number
        << " type:" << pinfo->type << endl;
#endif

}

int decode_video_packet(AVFormatContext * fmt_ctx_for_decode,                          AVCodecContext* dec_ctx, int video_stream_index)
{
    int ret = 0;

    AVFrame* pFrame=avcodec_alloc_frame();
    AVFrame* pFrameRGB = avcodec_alloc_frame();

    int numBytes=avpicture_get_size(PIX_FMT_BGR24, dec_ctx->width,dec_ctx->height);
    uint8_t* buffer = new(std::nothrow) uint8_t[numBytes];

    avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_BGR24,        dec_ctx->width, dec_ctx->height);

    SwsContext *pSWSCtx = sws_getContext(dec_ctx->width, dec_ctx->height,         dec_ctx->pix_fmt, dec_ctx->width, dec_ctx->height, PIX_FMT_BGR24,        SWS_BICUBIC, NULL, NULL, NULL);

    if (NULL == pFrame || NULL == pFrameRGB || NULL == buffer || NULL == pSWSCtx)
    {
        ret = -1;
        goto exit;
    }

    AVPacket packet;
    int key_frame_picture_count = 0;

    while (av_read_frame(fmt_ctx_for_decode, &packet) >= 0)
    {
        if (packet.stream_index == video_stream_index)
        {
            int got_frame = 0;
            avcodec_decode_video2(dec_ctx, pFrame,&got_frame, &packet);

            if (got_frame) //一个完整的帧
            {
                if (pFrame->key_frame)
                {
                    sws_scale(pSWSCtx, pFrame->data, pFrame->linesize,0,                         dec_ctx->height, pFrameRGB->data, pFrameRGB->linesize);

                    // 保存到磁盘
                    char pic[200];
                    sprintf(pic,"keyframe%d.bmp", ++key_frame_picture_count);
                    av_create_bmp(pic,pFrameRGB->data[0],dec_ctx->width,dec_ctx->height,24);
                    //av_create_bmp(pic, pFrameRGB, dec_ctx->width,dec_ctx->height,24);
                }
                print_frame_info(pFrame);

            }

            print_packet_info(packet);
        }

    }

exit:
    avcodec_free_frame(&pFrame);
    avcodec_free_frame(&pFrameRGB);
    delete [] buffer;
    sws_freeContext(pSWSCtx);
    return ret;
}

static int open_input_file(const char *filename)
{
    int ret;
    bool video_codec_init = false;
    int video_stream_index = -1;
    AVCodecContext* suitable_dec_ctx = NULL;
    AVFormatContext *video_fmt_ctx = NULL;

    if ((ret = avformat_open_input(&video_fmt_ctx, filename, NULL, NULL)) < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
        return ret;
    }

    if ((ret = avformat_find_stream_info(video_fmt_ctx, NULL)) < 0) {
        av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
        avformat_close_input(&video_fmt_ctx);
        return ret;
    }

    for (int i = 0; i < video_fmt_ctx->nb_streams; i++)
    {
        // 找到视频码流
        if (video_fmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
        {
            video_stream_index = i;
            // 初始化解码器信息
            if (!video_codec_init)
            {
                suitable_dec_ctx = video_fmt_ctx->streams[i]->codec;

                 AVCodec* pcodec = avcodec_find_decoder(suitable_dec_ctx->codec_id);

                if (NULL == pcodec)
                {
                    printf("cannot find decoder");
                    avformat_close_input(&video_fmt_ctx);
                    return 1;
                }

                if(0 != avcodec_open2(suitable_dec_ctx, pcodec, NULL))
                {
                    printf("open codecer failed");
                    avformat_close_input(&video_fmt_ctx);
                    return 1;
                }

                video_codec_init = true;
            }

        }
    }

    // 解码视频
    if (video_codec_init && suitable_dec_ctx)
    {
        decode_video_packet(video_fmt_ctx, suitable_dec_ctx, video_stream_index);
    }

    // 关闭文件
    avformat_close_input(&video_fmt_ctx);

    return 0;
}

int _tmain(int argc, _TCHAR* argv[])
{
    // 注册库中所有可能有用的文件格式和编码器
    av_register_all();
    open_input_file("C:\\Users\\xukaijun.HIK\\Desktop\\hikvison.mp4");

#ifdef FILE_OUT
    file_debugout.close();
#endif

    return 0;
}