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• 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 ?

• android_build.sh gives error while building ffmpeg library

  25 février 2016, par user3269550

  i am trying to build ffmpeg library my android_build.sh is given below

    #!/bin/bash
  
     NDK=C:/Users/Benzatine/Downloads/android-ndk-r10e
  
     SYSROOT=$NDK/platforms/android-18/arch-arm/
  
     TOOLCHAIN=$NDK/toolchains//arm-linux-androideabi-4.8/prebuilt/windows-x86_64
  
     function build_one
  
     {
  
       ./configure \
  
       --arch=arm \
  
        --target-os=linux \
  
  --enable-runtime-cpudetect \
  
  --enable-pic \
  
  --disable-shared \
  
  --enable-static \
  
  --extra-cflags='-march=armv6' \
  
  --extra-ldflags="$ADDI_LDFLAGS" \
  
  --enable-ffmpeg \
  
  --disable-ffplay \
  
  --disable-ffprobe \
  
  --disable-ffserver\
  
  --disable-network \
  
  --enable-cross-compile \
  
  --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
  
  --sysroot=$SYSROOT \
  
  $ADDITIONAL_CONFIGURE_FLAG
  
  make clean
  
  make -j4
  
   make install
  
   }
  
  CPU=arm
  
  PREFIX=$(pwd)/android/$CPU 
  
   ADDI_CFLAGS="-marm"
  
   build_one

  but when i try to execute it always gives error

  error is

      /android_build.sh: line 5: syntax error near unexpected token `$'\r''
  
      /android_build.sh: line 5: `function build_one()

  I am new in this so please any one can help me to resolve this issue

• Merging RGB Channels in FFMPEG [migrated]

  14 octobre 2016, par Draconis

  I have three grayscale videos, representing the red, green, and blue channels from a video. I extracted them using the extractplanes filter, and sent them through different pipelines.

  Now I would like to combine them again. But while extractplanes is working perfectly, mergeplanes is not. My initial attempt was this :

  [r][g][b] mergeplanes=0x001020 [output]

  This interprets my RGB channels as YUV, which is not what I want. My next attempt was this :

  [r][g][b] mergeplanes=0x001020:rgb24 [output]

  But according to the error message, Only planar formats with more than one component are supported. (Same for all other RGB and RGBA pixel formats I tried.)

  Is there another way to put these channels back together ? Or some way to convince mergeplanes to output RGB ?