使用ffmpeg将YUV420P图像压缩到jpg图片_ffmpeg yuv420 jpg

基本照抄了http://stackoverflow.com/questions/33932581/how-to-convert-yuv420p-image-to-jpeg-using-ffmpegs-libraries的程序。

extern "C" {
    #include <libavcodec/avcodec.h>
    #include <libavformat/avformat.h>
}
int main(int argc, char* argv[]){
    AVFormatContext* pFormatCtx;
    AVOutputFormat* fmt;
    AVStream* video_st;
    AVCodecContext* pCodecCtx;
    AVCodec* pCodec;

    uint8_t* picture_buf;
    AVFrame* picture;
    AVPacket pkt;
    int y_size;
    int got_picture=0;
    int size;

    int ret=0;

    FILE *in_file = NULL;                            //YUV source
    int in_w = 1920, in_h = 1080;                      //YUV's width and height
    const char* out_file = "encoded_pic.jpg";    //Output file

    in_file = fopen(argv[1], "rb");
    av_register_all();

    pFormatCtx = avformat_alloc_context();

    fmt = NULL;
    fmt = av_guess_format("mjpeg", NULL, NULL);
    pFormatCtx->oformat = fmt;

    //Output URL
    if (avio_open(&pFormatCtx->pb, fileName.c_str(), AVIO_FLAG_READ_WRITE) < 0)
    {
        printf("Couldn't open output file.");
        return -1;
    }

    video_st = avformat_new_stream(pFormatCtx, 0);

    if (video_st==NULL)
        return -1;

    pCodecCtx = video_st->codec;
    pCodecCtx->codec_id = fmt->video_codec;
    pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
    pCodecCtx->pix_fmt = AV_PIX_FMT_YUVJ420P;

    pCodecCtx->width = in_w;
    pCodecCtx->height = in_h;

    pCodecCtx->time_base.num = 1;
    pCodecCtx->time_base.den = 25;

    //Output some information
    av_dump_format(pFormatCtx, 0, fileName.c_str(), 1);

    pCodec = avcodec_find_encoder(pCodecCtx->codec_id);

    if (!pCodec)
    {
        printf("Codec not found.");
        return -1;
    }

    if (avcodec_open2(pCodecCtx, pCodec,NULL) < 0){
        printf("Could not open codec.\n");
        return -1;
    }


    picture = av_frame_alloc();
    size = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);

    picture_buf = (uint8_t *)av_malloc(size);


    if (!picture_buf)
        return -1;

    avpicture_fill((AVPicture *)picture, picture_buf, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);

    //Write Header
    avformat_write_header(pFormatCtx,NULL);

    y_size = pCodecCtx->width * pCodecCtx->height;
    av_new_packet(&pkt,y_size*3/2);

    //Read YUV
    if (fread(picture_buf, 1, y_size*3/2, in_file) <=0)
    {
        printf("Could not read input file.");
        return -1;
    }

    picture->data[0] = picture_buf;  // Y
    picture->data[1] = picture_buf+ y_size;  // U
    picture->data[2] = picture_buf+ y_size*5/4; // V

    //Encode
    ret = avcodec_encode_video2(pCodecCtx, &pkt,picture, &got_picture);
    if(ret < 0)
    {
        printf("Encode Error.\n");
        return -1;
    }

    if (got_picture==1)
    {
        pkt.stream_index = video_st->index;
        ret = av_write_frame(pFormatCtx, &pkt);
    }

    av_free_packet(&pkt);
    //Write Trailer
    av_write_trailer(pFormatCtx);

    printf("Encode Successful.\n");

    if (video_st)
    {
        avcodec_close(video_st->codec);
        av_free(picture);
        av_free(picture_buf);
    }

    avio_close(pFormatCtx->pb);
    avformat_free_context(pFormatCtx);

    fclose(in_file);

}
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