使用 libav 将 bgr 图像的 h264 编码为 .mp4 文件

问题描述

我正在尝试将 (h264) 一系列 .png 编码为 mp4 文件。 cv::Mat 保存 png 数据 (BGR)，然后将其转换为 YUV420P，然后将其编码并写入 .mp4 文件。我在代码中添加了两个块语句来将图像存储在磁盘上（编码前后）。编码前的第一个图像是正确的，但编码后的第二个图像不正确。 avcodec_send_frame 返回 0，所以到那时一切正常。 编辑：我得到一个 1 MB 的 mp4 文件，但我无法用 vlc 打开它 生态解码器.h

class ECodec
{
public:

    MovieCodec();

    ~MovieCodec();

    void MatToFrame( cv::Mat& image );

    void encode( AVFrame *frame,AVPacket *pkt );

private:
 
    FILE* m_file;

    AVCodec* m_encoder = NULL;

    AVCodecContext* m_codecContextout = NULL;

    AVPacket* m_packet = NULL;

};

ecodec.cpp

ECodec::ECodec() :
//    m_encoder( avcodec_find_encoder_by_name( videoCodec.c_str()))
    m_encoder( avcodec_find_encoder( AV_CODEC_ID_H264 ))
{
    m_file = fopen( "c:\\tmp\\outputVideo.mp4","wb");
}



void ECodec::MatToFrame( cv::Mat& image )
{
    int ret( 0 );
    int frameRate( 24 );
    AVFrame *frame = NULL;

    m_encoder( avcodec_find_encoder( AV_CODEC_ID_H264 ))
    m_codecContextout = avcodec_alloc_context3( m_encoder );

    m_codecContextout->width = 800;
    m_codecContextout->height = 640;
    m_codecContextout->bit_rate = 400000;//m_codecContextout->width * m_codecContextout->height * 3;
    m_codecContextout->time_base = (AVRational){1,24};
    m_codecContextout->framerate = (AVRational){24,1};
    m_codecContextout->codec_tag = AV_CODEC_ID_H264;
    m_codecContextout->pix_fmt = AV_PIX_FMT_YUV420P;
    m_codecContextout->codec_type = AVMEDIA_TYPE_VIDEO;
    m_codecContextout->gop_size = 1;
    m_codecContextout->max_b_frames = 1;

    av_log_set_level(AV_LOG_VERBOSE);

    ret = av_opt_set(m_codecContextout->priv_data,"preset","slow",0);

    ret = avcodec_open2(m_codecContextout,m_encoder,NULL);

    frame = av_frame_alloc();

    frame->format = AV_PIX_FMT_YUV420P;
    frame->width = image.cols();
    frame->height = image.rows();


    ret = av_image_alloc(frame->data,frame->linesize,frame->width,frame->height,AV_PIX_FMT_YUV420P,1);

    if (ret < 0)
    {
        return;
    }

    struct SwsContext *sws_ctx;
    sws_ctx = sws_getContext((int)image.cols(),(int)image.rows(),AV_PIX_FMT_RGB24,(int)image.cols(),NULL,NULL);

    const uint8_t* rgbData[1] = { (uint8_t* )image.getData() };
    int rgbLinesize[1] = { 3 * image.cols() };

    sws_scale(sws_ctx,rgbData,rgbLinesize,image.rows(),frame->data,frame->linesize);

    frame->pict_type = AV_PICTURE_TYPE_I;

cv::Mat yuv420p(frame->height + frame->height/2,CV_8UC1,frame->data[0]);
cv::Mat cvmIm;
cv::cvtColor(yuv420p,cvmIm,CV_YUV420p2BGR);
cv::imwrite("c:\\tmp\\rawimage.png",cvmIm);
//OK

    m_packet = av_packet_alloc();
    ret = av_new_packet( m_packet,m_codecContextout->width * m_codecContextout->height * 3 );

    /* encode the image */
    encode( frame,m_packet );


    avcodec_free_context(&m_codecContextout);
    av_frame_free(&frame);
    av_packet_free( &m_packet );
}




void ECodec::encode( AVFrame *frame,AVPacket *pkt )
{
    int ret;
    
    /* send the frame to the encoder */
    ret = avcodec_send_frame( m_codecContextout,frame);

    if (ret < 0)
    {
        fprintf(stderr,"Error sending a frame for encoding\n");
        exit(1);
    }

    do
    {
        ret = avcodec_receive_packet(m_codecContextout,pkt);
        if (ret == 0)
        {

cv::Mat yuv420p(frame->height + frame->height/2,pkt->data);
cv::Mat cvmIm;
cv::cvtColor(yuv420p,CV_YUV420p2BGR);
cv::imwrite("c:\\tmp\\rawencodedimage.png",cvmIm);
//NOT OK
            fwrite(pkt->data,1,pkt->size,m_file );
            av_packet_unref(pkt);

            break;
        }
        else if ((ret < 0) && (ret != AVERROR(EAGAIN)))
        {
            return;
        }
        else if (ret == AVERROR(EAGAIN))
        {
             ret = avcodec_send_frame(m_codecContextout,NULL);
             if (0 > ret)
             {
                 return;
             }
        }
    } while (ret == 0);
}

解决方法

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