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• Converting RGB frames to YUV420P using FFmpeg/C++ [duplicate]

  20 mars 2014, par learner

  This question already has an answer here :

  • ffmpeg : RGB to YUV conversion loses color and scale
    
    1 answer
    

  I tried a code based on this tutorial. What this does is it writes first 5 frames of a video into memory in RGB format. I need to convert these RGB frames to YUV420P format so that I can pass them to YUV420P encoder. I tried using the sws_scale but then the resulting frames lose color information and also suffer from scaling issues. Also, looked at various questions but none gives a working solution. I am completely new to FFmpeg library and working on various tutorials to get a grip on it. I hope somebody can suggest a nice solution. Many thanks for your inputs !

  Following is the code :

  #include <ffmpeg></ffmpeg>avcodec.h>
  
  #include <ffmpeg></ffmpeg>avformat.h>
  
  
  
  #include 
  
  
  
  void SaveFrame(AVFrame *pFrame, int width, int height, int iFrame) {
  
    FILE *pFile;
  
    char szFilename[32];
  
    int  y;
  
  
  
    // Open file
  
    sprintf(szFilename, "frame%d.ppm", iFrame);
  
    pFile=fopen(szFilename, "wb");
  
    if(pFile==NULL)
  
      return;
  
  
  
    // Write header
  
    fprintf(pFile, "P6\n%d %d\n255\n", width, height);
  
  
  
    // Write pixel data
  
    for(y=0; ydata[0]+y*pFrame->linesize[0], 1, width*3, pFile);
  
  
  
    // Close file
  
    fclose(pFile);
  
  }
  
  
  
  int main(int argc, char *argv[]) {
  
    AVFormatContext *pFormatCtx;
  
    int             i, videoStream;
  
    AVCodecContext  *pCodecCtx;
  
    AVCodec         *pCodec;
  
    AVFrame         *pFrame; 
  
    AVFrame         *pFrameRGB;
  
    AVPacket        packet;
  
    int             frameFinished;
  
    int             numBytes;
  
    uint8_t         *buffer;
  
  
  
    if(argc &lt; 2) {
  
      printf("Please provide a movie file\n");
  
      return -1;
  
    }
  
    // Register all formats and codecs
  
    av_register_all();
  
  
  
    // Open video file
  
    if(av_open_input_file(&amp;pFormatCtx, argv[1], NULL, 0, NULL)!=0)
  
      return -1; // Couldn&#39;t open file
  
  
  
    // Retrieve stream information
  
    if(av_find_stream_info(pFormatCtx)&lt;0)
  
      return -1; // Couldn&#39;t find stream information
  
  
  
    // Dump information about file onto standard error
  
    dump_format(pFormatCtx, 0, argv[1], 0);
  
  
  
    // Find the first video stream
  
    videoStream=-1;
  
    for(i=0; inb_streams; i++)
  
      if(pFormatCtx->streams[i]->codec->codec_type==CODEC_TYPE_VIDEO) {
  
        videoStream=i;
  
        break;
  
      }
  
    if(videoStream==-1)
  
      return -1; // Didn&#39;t find a video stream
  
  
  
    // Get a pointer to the codec context for the video stream
  
    pCodecCtx=pFormatCtx->streams[videoStream]->codec;
  
  
  
    // Find the decoder for the video stream
  
    pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
  
    if(pCodec==NULL) {
  
      fprintf(stderr, "Unsupported codec!\n");
  
      return -1; // Codec not found
  
    }
  
    // Open codec
  
    if(avcodec_open(pCodecCtx, pCodec)&lt;0)
  
      return -1; // Could not open codec
  
  
  
    // Allocate video frame
  
    pFrame=avcodec_alloc_frame();
  
  
  
    // Allocate an AVFrame structure
  
    pFrameRGB=avcodec_alloc_frame();
  
    if(pFrameRGB==NULL)
  
      return -1;
  
  
  
    // Determine required buffer size and allocate buffer
  
    numBytes=avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width,
  
                    pCodecCtx->height);
  
    buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));
  
  
  
    // Assign appropriate parts of buffer to image planes in pFrameRGB
  
    // Note that pFrameRGB is an AVFrame, but AVFrame is a superset
  
    // of AVPicture
  
    avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24,
  
           pCodecCtx->width, pCodecCtx->height);
  
  
  
    // Read frames and save first five frames to disk
  
    i=0;
  
    while(av_read_frame(pFormatCtx, &amp;packet)>=0) {
  
      // Is this a packet from the video stream?
  
      if(packet.stream_index==videoStream) {
  
        // Decode video frame
  
        avcodec_decode_video(pCodecCtx, pFrame, &amp;frameFinished, 
  
                 packet.data, packet.size);
  
  
  
        // Did we get a video frame?
  
        if(frameFinished) {
  
      // Convert the image from its native format to RGB
  
      img_convert((AVPicture *)pFrameRGB, PIX_FMT_RGB24, 
  
                      (AVPicture*)pFrame, pCodecCtx->pix_fmt, pCodecCtx->width, 
  
                      pCodecCtx->height);
  
  
  
      // Save the frame to disk
  
      if(++i&lt;=5)
  
        SaveFrame(pFrameRGB, pCodecCtx->width, pCodecCtx->height, 
  
              i);
  
        }
  
      }
  
  
  
      // Free the packet that was allocated by av_read_frame
  
      av_free_packet(&amp;packet);
  
    }
  
  
  
    // Free the RGB image
  
    av_free(buffer);
  
    av_free(pFrameRGB);
  
  
  
    // Free the YUV frame
  
    av_free(pFrame);
  
  
  
    // Close the codec
  
    avcodec_close(pCodecCtx);
  
  
  
    // Close the video file
  
    av_close_input_file(pFormatCtx);
  
  
  
    return 0;
  
  }

• When I tried to install react-native-ffmpeg, Build getting failed throwing error

  1er juillet 2020, par srinivas

  Version Using
compileSdkVersion 29
buildToolsVersion "26.0.0"


  


  What went wrong :
Could not determine the dependencies of task ':react-native-ffmpeg:compileDebugAidl'.


  


  


  Could not find com.arthenica:mobile-ffmpeg-com.febbler:4.3.1.
Required by :
project :react-native-ffmpeg

  


  


• Translating ffmpeg command line to C++ codec settings

  6 mars 2014, par pacificator

  I've been doing some work in ffmpeg for a while in C++.
  Most of the help regarding encoder settings is explained as command line options.
  For example (taken from the ffmpeg site) :

  -mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2’ 

  but beware the ’-g 100’ might cause problems with some decoders. Things to try :

   ’-bf 2’, ’-flags qprd’, ’-flags mv0’, ’- flags skiprd.

  This is not really usefull when you want to set these options in C.
  For example I managed to find int trellis ; in the AVCodecContext struct so that is one solved, but what about the others ?

  Is there a way to determine what command line parameters correspond to what AVCodecContext members ?
  I tried setting them like this :

  AVCodecContext* c;
  
  av_opt_set_int(c->priv_data, "cmp", 2, 0);

  But this returns an error code that the option does not exist.
  I've also tried :

    av_opt_set(c->priv_data, "cmp", "2", 0);

  I still get the error that the option does not exist.

  So, is there a way to determine what AVCodecContext members I should set that are equivalent to the ffmpeg command line parameters above ?