使用FFMPEG 将FLV中的视频帧保存成文件

代码，将FLV中的视频的每一帧保存成PPM文件

#define __STDC_CONSTANT_MACROS
extern "C" {
#include <avcodec.h>
#include <avformat.h>
#include <swscale.h>
}

#include <stdio.h>

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 main(int argc, char *argv[])
{
    static AVFormatContext *pFormatCtx;
    int i, videoStream;
    AVCodecContext *pCodecCtx;
    AVCodec *pCodec;
    AVFrame *pFrame;
    AVFrame *pFrameRGB;
    AVPacket        packet;
    int frameFinished;
    int numBytes;
    uint8_t *buffer;
        AVDictionary * options;
    // Register all formats and codecs
    av_register_all();

    // Open video file
    if(avformat_open_input(&pFormatCtx, argv[1], NULL, NULL)!=0)
        return -1; // Couldn't open file

    // Retrieve stream information
    if(avformat_find_stream_info(pFormatCtx,NULL)<0)
        return -1; // Couldn't find stream information

    // Dump information about file onto standard error
    av_dump_format(pFormatCtx, 0, argv[1], false);

    // Find the first video stream
    videoStream=-1;
    for(i=0; i<pFormatCtx->nb_streams; i++)
        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)
        return -1; // Codec not found

    // Open codec
    if(avcodec_open2(pCodecCtx, pCodec,NULL)<0)
        return -1; // Could not open codec

    // Hack to correct wrong frame rates that seem to be generated by some
    // codecs
    // if(pCodecCtx->frame_rate>1000 && pCodecCtx->frame_rate_base==1)
    // pCodecCtx->frame_rate_base=1000;

    // 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=new uint8_t[numBytes];

    // Assign appropriate parts of buffer to image planes in pFrameRGB
    avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24,
        pCodecCtx->width, pCodecCtx->height);

    // Read frames and save first five frames to disk
    i=0;
    struct  SwsContext *img_convert_ctx = NULL;
    img_convert_ctx = sws_getContext(pCodecCtx->width,pCodecCtx->height,pFormatCtx->streams[videoStream]->codec->pix_fmt , pCodecCtx->width, pCodecCtx->height, PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);
    while(av_read_frame(pFormatCtx, &packet)>=0)
    {
        // Is this a packet from the video stream?
        if(packet.stream_index==videoStream)
        {
            // Decode video frame
            frameFinished = 0;
            int ret = avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished,
                &packet);
            if(ret < 0)
            {
                av_log(NULL, AV_LOG_ERROR, "Error decoding video\n");
                break;
            }
            if(frameFinished)
            {
                sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
                if(++i<=1000)
                    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
    delete [] 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;
}

参考:
修改编译错误 __STDC_CONSTANT_MACROS
FFMEG介绍和API用法网站

FFMEG和SDL教程(For 显示)

FFMPEG的图像转化函数swscale介绍