Recherche avancée

Sur d’autres sites (7671)

• 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

  


  


• Using FFMPEG to automatically set a single max filesize across multiple different sized files

  14 juin 2020, par DuffCreeper

  I don't really know how to word it any better but I'm trying to convert WEBM/GIF to MP4 with no sound

  



  The problem I'm facing is retaining the quality without having to sacrifice it across multiple files by having to resize them to 420p

  



  The idea was to hopefully somehow get FFMPEG to automatically determine the bitrate required for the file to hit the filesize of 10mb. Though I have looked everywhere online and I have not found a single answer regarding it, so either it's not possible or I'm blind