On Wed, Feb 10, 2021 at 12:55 PM laddoe wrote:
> I'm trying to encode(h264) a series of .png into a mp4 file. A cv::Mat
> holds the png data (BGR) and that is converted to YUV420P which is then
> encoded and written to a .mp4 file. I have added a block statement in the
> code to store image on the disk (before encoding) and that image is correct
> so the frame holds the correct data before it gets passed. The
> avcodec_send_frame returns 0 so up to that point everything works. But I
> get an mp4 file of 1 MB and I can't open it with vlc. Below is a short
> summary of my code
>
>
> ecodec.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 = 40;//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(), (int)image.rows(),
> AV_PIX_FMT_YUV420P,
> 0, NULL, NULL, NULL);
>
> const uint8_t* rgbData[1] = { (uint8_t* )image.getData() };
> int rgbLineSize[1] = { 3 * image.cols() };
>
> sws_scale(sws_ctx, rgbData, rgbLineSize, 0, image.rows(), frame->data,
> frame->linesize);
>
> frame->pict_type = AV_PICTURE_TYPE_I;
>
> cv::Mat yuv420p(frame->height + frame->height/2, frame->width,
> 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(_codecContextOut);
> av_frame_free();
> av_packet_free( _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)
> {
> fwrite(pkt->data, 1, pkt->size, m_file );
>
You are writing raw encoded frames here.
You nowhere use mov muxer code for muxing.
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);
> }
> ___
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