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• How to change bit rate and resolution of video using ffmpeg library

  28 novembre 2018, par samsix

  I am writing an application to change the bit rate and resolution of a local video file (no audio) in Qt and C++ (usig ffmpeg C library). There are some examples on ffmpeg github repo, but none of them has anything about bit rate or resolution changing.

  I am confused on how to proceed with it. Is it done using libavcodec, libavdevice, libavfilter... ?

  Please guide me or share links to any examples

• avcodec/proresdec2 : allow changing resolution

  5 décembre 2018, par Paul B Mahol

  avcodec/proresdec2 : allow changing resolution
  

  • [DH] libavcodec/proresdec2.c

• Changing Resolution in ffmpeg output to display video stream in Android

  23 janvier 2015, par vgokul129

  I’m trying to change the camera output(Resolution:640 x 480),to 1024 x 720 and render the video frames in the Android screen.Is it possible to do this video conversion with ffmpeg and SDL libraries ?If so is there any API’s avaliable in ffmepeg codec libraries to do the same ?

  Here is the code where i got the output for 640 x 480 resolution :

  //Registering all the formats:
  
  av_register_all();
  
  AVFormatContext *pFormatCtx=NULL;
  
  int             i, videoStream;
  
  AVCodecContext  *pCodecCtx=NULL;
  
  AVCodec         *pCodec=NULL;
  
  AVFrame         *pFrame;
  
  AVPacket        packet;
  
  int             frameFinished;
  
  SDL_Texture         *bmp;
  
  SDL_Renderer *renderer;
  
  SDL_Window  *screen;
  
  
  
  if (SDL_Init(SDL_INIT_VIDEO)) {
  
      LOGD( "Could not initialize SDL - %s\n", SDL_GetError());
  
      SDL_Quit();
  
      exit(1);
  
  }
  
  LOGD(" SDL Initialized..");
  
  
  
  screen = SDL_CreateWindow("Window", SDL_WINDOWPOS_UNDEFINED,
  
          SDL_WINDOWPOS_UNDEFINED, 0, 0,
  
          SDL_WINDOW_SHOWN | SDL_WINDOW_FULLSCREEN);
  
  LOGD("SDL Screen Created ..");
  
  
  
  renderer = SDL_CreateRenderer(screen,-1,SDL_RENDERER_ACCELERATED | SDL_RENDERER_TARGETTEXTURE);
  
  LOGD("Rendering Created...");
  
  
  
  bmp = SDL_CreateTexture(renderer,     SDL_PIXELFORMAT_IYUV,SDL_TEXTUREACCESS_STREAMING,640,480);
  
  LOGD("Texture created;");
  
  
  
  SDL_RenderSetLogicalSize(renderer,640,480);
  
  // Open video file
  
  if(avformat_open_input(&pFormatCtx,"Filename", NULL,NULL)!=0)
  
      LOGD("Cannot open the File");
  
  
  
  pFormatCtx->interrupt_callback.callback = decode_interrupt_cb;
  
  
  
  // Retrieve stream information
  
  if(avformat_find_stream_info(pFormatCtx,NULL)<0)
  
      LOGD("Cannot retrive Stream info");
  
    // Couldn't find stream information
  
  
  
  videoStream=-1;
  
  for(i=0; inb_streams; i++)
  
  if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) {
  
        videoStream=i;
  
      break;
  
  }
  
  if(videoStream==-1)
  
  LOGD("Cannot find 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");
  
    LOGD("Unable to find the decoder");
  
      // Codec not found
  
   }
  
   // Open codec
  
   if(avcodec_open2(pCodecCtx, pCodec,NULL)<0)
  
    LOGD("Unable to OPEN Codec");
  
    // Could not open codec
  
  
  
   // Allocate video frame
  
    pFrame=avcodec_alloc_frame();
  
  
  
    i=0;
  
    while(av_read_frame(pFormatCtx, &packet)>=0) {
  
          // Is this a packet from the video stream?
  
          if(packet.stream_index==videoStream) {
  
        // Decode video frame
  
        avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished,&packet);
  
  
  
        // Did we get a video frame?
  
        if(frameFinished) {
  
            //----------------Code for Displaying
  
            SDL_UpdateYUVTexture(bmp, NULL, pFrame->data[0],
  
                                      pFrame->linesize[0], pFrame->data[1], pFrame->linesize[1],
  
                                      pFrame->data[2], pFrame->linesize[2]);
  
  
  
                              retcl = SDL_RenderClear(renderer);
  
                              retcopy = SDL_RenderCopy(renderer, bmp, NULL, NULL);
  
                              SDL_RenderPresent(renderer);
  
            //-----------------
  
        }
  
      }
  
  
  
          // Free the packet that was allocated by av_read_frame
  
      av_free_packet(&packet);
  
    }
  
  
  
    // Free the RGB image
  
    av_free(buffer);
  
  
  
    // Free the YUV frame
  
    av_free(pFrame);
  
  
  
    // Close the codec
  
    avcodec_close(pCodecCtx);
  
  
  
    // Close the video file
  
    avformat_close_input(&pFormatCtx);
  
  
  
    return 0;
  
  }