Recherche avancée

Sur d’autres sites (2758)

• Updated Zip

  21 janvier 2013, par Grandt

  Updated Zip
  Minor issue in the new UTF-8 implemenation
  

• How to create video using avcodec from jpeg images of type OpenCV::Mat ?

  23 juillet 2015, par theateist

  I have colored jpeg images of OpenCV::Mat type and I create from them video using avcodec. The video that I get is upside-down, black & white and each row of each frame is shifted and I got diagonal line. What could be the reason for such output ?
  Follow this link to watch the video I get using avcodec.
  I’m using acpicture_fill function to create avFrame from cv::Mat frame !

  P.S.
  Each cv::Mat cvFrame has width=810, height=610, step=2432
  I noticed that avFrame (that is filled by acpicture_fill) has linesize[0]=2430
  I tried manually setting avFrame->linesizep0]=2432 and not 2430 but it still didn’t helped.

  ======== CODE =========================================================

  AVCodec *encoder = avcodec_find_encoder(AV_CODEC_ID_H264);
  
  AVStream *outStream = avformat_new_stream(outContainer, encoder);
  
  avcodec_get_context_defaults3(outStream->codec, encoder);
  
  
  
  outStream->codec->pix_fmt = AV_PIX_FMT_YUV420P;
  
  outStream->codec->width = 810;
  
  outStream->codec->height = 610;
  
  //...
  
  
  
  SwsContext *swsCtx = sws_getContext(outStream->codec->width, outStream->codec->height, PIX_FMT_RGB24,
  
                                      outStream->codec->width, outStream->codec->height,  outStream->codec->pix_fmt, SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
  for (uint i=0; i < frameNums; i++)
  
  {
  
      // get frame at location I using OpenCV
  
      cv::Mat cvFrame;
  
      myReader.getFrame(cvFrame, i); 
  
      cv::Size frameSize = cvFrame.size();    
  
      //Each cv::Mat cvFrame has  width=810, height=610, step=2432
  
  
  
  
  
  1.  // create AVPicture from cv::Mat frame
  
  2.  avpicture_fill((AVPicture*)avFrame, cvFrame.data, PIX_FMT_RGB24, outStream->codec->width, outStream->codec->height);
  
  3avFrame->width = frameSize.width;
  
  4.  avFrame->height = frameSize.height;
  
  
  
      // rescale to outStream format
  
      sws_scale(swsCtx, avFrame->data, avFrame->linesize, 0, outStream->codec->height, avFrameRescaledFrame->data, avFrameRescaledFrame ->linesize);
  
  encoderRescaledFrame->pts=i;
  
  avFrameRescaledFrame->width = frameSize.width;
  
      avFrameRescaledFrame->height = frameSize.height;
  
  
  
  av_init_packet(&avEncodedPacket);
  
      avEncodedPacket.data = NULL;
  
      avEncodedPacket.size = 0;
  
  
  
      // encode rescaled frame
  
      if(avcodec_encode_video2(outStream->codec, &avEncodedPacket, avFrameRescaledFrame, &got_frame) < 0) exit(1);
  
      if(got_frame)
  
      {
  
          if (avEncodedPacket.pts != AV_NOPTS_VALUE)
  
              avEncodedPacket.pts =  av_rescale_q(avEncodedPacket.pts, outStream->codec->time_base, outStream->time_base);
  
          if (avEncodedPacket.dts != AV_NOPTS_VALUE)
  
              avEncodedPacket.dts = av_rescale_q(avEncodedPacket.dts, outStream->codec->time_base, outStream->time_base);
  
  
  
          // outContainer is "mp4"
  
          av_write_frame(outContainer, & avEncodedPacket);
  
  
  
          av_free_packet(&encodedPacket);
  
      }
  
  }

  UPDATED

  As @Alex suggested I changed the lines 1-4 with the code below

  int width = frameSize.width, height = frameSize.height; 
  
  avpicture_alloc((AVPicture*)avFrame, AV_PIX_FMT_RGB24, outStream->codec->width, outStream->codec->height);
  
  for (int h = 0; h < height; h++)
  
  {
  
       memcpy(&(avFrame->data[0][h*avFrame->linesize[0]]), &(cvFrame.data[h*cvFrame.step]), width*3);
  
  }

  The video (here) I get now is almost perfect. It’s NOT upside-down, NOT black & white, BUT it seems that one of the RGB components is missing. Every brown/red colors became blue (in original images it should be vice-verse).
  What could be the problem ? Could rescaling(sws_scale) to AV_PIX_FMT_YUV420P format causes this ?

• How to display a frame number on each frame of a video using ffmpeg ?

  22 novembre 2012, par igorg

  The test command I have is as follows :

  ffmpeg -i in.mov -vf "drawtext=fontfile=/usr/share/fonts/ttf-bitstream-vera/Vera.ttf: x=(w-tw)/2: y=h-(2*lh)-n: fontcolor=white: fontsize=40: box=1: boxcolor=0x00000000@1: text=" -an -y out.mov

  I want to display the frame number on each frame. However, setting the "text" variable to "n" does not help (it displays n) and %n seems to be the new line symbol. The thing that confuses me most is that this part

  y=h-(2*lh)-n

  works well, meaning it gets the right value of the current frame and moves the text up accordingly.