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• movenc : Allow to request not to use edit lists

  4 novembre 2014, par Martin Storsjö

  movenc : Allow to request not to use edit lists
  In this case, shift tracks to start from zero instead (potentially
  
  stretching the first sample in tracks that start later than the
  
  first one).
  Some software does not support edit lists at all, the adobe flash
  
  player seems to be one of these. This results in AV sync errors when
  
  edit lists are used to adjust AV sync.
  Some players, such as QuickTime, don’t respect the duration for
  
  audio packets, so if an audio track starts later than the video
  
  track and the first audio sample gets a duration longer than the
  
  actual amount of data in it, the result will be out of sync.
  Based on patches by Michael Niedermayer.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/movenc.c
  • [DBH] libavformat/movenc.h

• NodeJS/ffmpeg : Can't create screenshot of stream file

  11 septembre 2017, par user3142695

  I need to create a screenshot via ffmpeg (node-fluent-ffmpeg : https://github.com/fluent-ffmpeg/node-fluent-ffmpeg) of a stream, as my data is stored in a gridFS.

  This is how I’m doing that with a local file - and it works so far

  ffmpeg('/Users/Anybody/Downloads/1test.mp4')
  
    .on('error', (error) => {
  
      console.error(error)
  
    })
  
    .on('end', () => {
  
      console.log('Screenshots taken')
  
    })
  
    .screenshots({
  
      folder: '/Users/Anybody/Downloads/',
  
      timestamps: ['00:01.000']
  
    })

  But if I change the code to use a stream (gridfs-stream), no file is created, although the output gives me a successful message :

  import Grid from 'gridfs-stream'
  
  
  
  const gfs = Grid(
  
    MongoInternals.defaultRemoteCollectionDriver().mongo.db,
  
    MongoInternals.NpmModule
  
  )
  
  
  
  ffmpeg(gfs.createReadStream({ _id: sourceId }))
  
    .on('filenames', (filenames) => {
  
      console.log('Will generate ' + filenames.join(', '))
  
    })
  
    .on('codecData', (data) => {
  
      console.log('Input is ' + data.audio + ' audio ' + 'with ' + data.video + ' video')
  
    })
  
    .on('error', (error) => {
  
      console.error(error)
  
    })
  
    .on('end', () => {
  
      console.log('Screenshots taken')
  
    })
  
    .screenshots({
  
      folder: '/Users/Anybody/Downloads/',
  
      timestamps: ['00:01.000']
  
    })

  Output

  Will generate tn.png
  
  Input is aac (mp4a / 0x6134706D) audio with h264 (avc1 / 0x31637661) video
  
  Screenshots taken

• Encoding a screenshot into a video using FFMPEG

  2 juillet 2013, par mohM

  I'm trying to get the pixels from the screen, and encode the screenshot into a video using ffmpeg. I've seen a couple of examples but they either assume you already have the pixel data, or use image file input. It seems like whether I use sws_scale() or not (which is included in the examples I've seen), or whether I'm typecasting a HBITMAP or RGBQUAD* it's telling me that the image src data is bad and is encoding a blank image rather than the screenshot. Is there something I'm missing here ?

  AVCodec* codec;
  
  AVCodecContext* c = NULL;
  
  AVFrame* inpic;
  
  uint8_t* outbuf, *picture_buf;
  
  int i, out_size, size, outbuf_size;
  
  HBITMAP hBmp;
  
  //int x,y;
  
  
  
  avcodec_register_all();
  
  
  
  printf("Video encoding\n");
  
  
  
  // Find the mpeg1 video encoder
  
  codec = avcodec_find_encoder(CODEC_ID_H264);
  
  if (!codec) {
  
      fprintf(stderr, "Codec not found\n");
  
      exit(1);
  
  }
  
  else printf("H264 codec found\n");
  
  
  
  c = avcodec_alloc_context3(codec);
  
  inpic = avcodec_alloc_frame();
  
  
  
  c->bit_rate = 400000;
  
  c->width = screenWidth;                                     // resolution must be a multiple of two
  
  c->height = screenHeight;
  
  c->time_base.num = 1;
  
  c->time_base.den = 25;
  
  c->gop_size = 10;                                           // emit one intra frame every ten frames
  
  c->max_b_frames=1;
  
  c->pix_fmt = PIX_FMT_YUV420P;
  
  c->codec_id = CODEC_ID_H264;
  
  //c->codec_type = AVMEDIA_TYPE_VIDEO;
  
  
  
  //av_opt_set(c->priv_data, "preset", "slow", 0);
  
  //printf("Setting presets to slow for performance\n");
  
  
  
  // Open the encoder
  
  if (avcodec_open2(c, codec,NULL) < 0) {
  
      fprintf(stderr, "Could not open codec\n");
  
      exit(1);
  
  }
  
  else printf("H264 codec opened\n");
  
  
  
  outbuf_size = 100000 + 12*c->width*c->height;           // alloc image and output buffer
  
  //outbuf_size = 100000;
  
  outbuf = static_cast(malloc(outbuf_size));
  
  size = c->width * c->height;
  
  picture_buf = static_cast(malloc((size*3)/2));
  
  printf("Setting buffer size to: %d\n",outbuf_size);
  
  
  
  FILE* f = fopen("example.mpg","wb");
  
  if(!f) printf("x  -  Cannot open video file for writing\n");
  
  else printf("Opened video file for writing\n");
  
  
  
  /*inpic->data[0] = picture_buf;
  
  inpic->data[1] = inpic->data[0] + size;
  
  inpic->data[2] = inpic->data[1] + size / 4;
  
  inpic->linesize[0] = c->width;
  
  inpic->linesize[1] = c->width / 2;
  
  inpic->linesize[2] = c->width / 2;*/
  
  
  
  
  
  //int x,y;
  
  // encode 1 second of video
  
  for(i=0;itime_base.den;i++) {
  
      fflush(stdout);
  
  
  
  
  
      HWND hDesktopWnd = GetDesktopWindow();
  
      HDC hDesktopDC = GetDC(hDesktopWnd);
  
      HDC hCaptureDC = CreateCompatibleDC(hDesktopDC);
  
      hBmp = CreateCompatibleBitmap(GetDC(0), screenWidth, screenHeight);
  
      SelectObject(hCaptureDC, hBmp);
  
      BitBlt(hCaptureDC, 0, 0, screenWidth, screenHeight, hDesktopDC, 0, 0, SRCCOPY|CAPTUREBLT);
  
      BITMAPINFO bmi = {0}; 
  
      bmi.bmiHeader.biSize = sizeof(bmi.bmiHeader); 
  
      bmi.bmiHeader.biWidth = screenWidth; 
  
      bmi.bmiHeader.biHeight = screenHeight; 
  
      bmi.bmiHeader.biPlanes = 1; 
  
      bmi.bmiHeader.biBitCount = 32; 
  
      bmi.bmiHeader.biCompression = BI_RGB;
  
      RGBQUAD *pPixels = new RGBQUAD[screenWidth*screenHeight];
  
      GetDIBits(hCaptureDC,hBmp,0,screenHeight,pPixels,&bmi,DIB_RGB_COLORS);
  
  
  
  inpic->pts = (float) i * (1000.0/(float)(c->time_base.den))*90;
  
      avpicture_fill((AVPicture*)inpic, (uint8_t*)pPixels, PIX_FMT_BGR32, c->width, c->height);                   // Fill picture with image
  
      av_image_alloc(inpic->data, inpic->linesize, c->width, c->height, c->pix_fmt, 1);
  
      //printf("Allocated frame\n");
  
      //SaveBMPFile(L"screenshot.bmp",hBmp,hDc,screenWidth,screenHeight);
  
      ReleaseDC(hDesktopWnd,hDesktopDC);
  
      DeleteDC(hCaptureDC);
  
      DeleteObject(hBmp);
  
  
  
      // encode the image
  
      out_size = avcodec_encode_video(c, outbuf, outbuf_size, inpic);
  
      printf("Encoding frame %3d (size=%5d)\n", i, out_size);
  
      fwrite(outbuf, 1, out_size, f);
  
  }
  
  
  
  // get the delayed frames
  
  for(; out_size; i++) {
  
      fflush(stdout);
  
  
  
      out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
  
      printf("Writing frame %3d (size=%5d)\n", i, out_size);
  
      fwrite(outbuf, 1, out_size, f);
  
  }
  
  
  
  // add sequence end code to have a real mpeg file
  
  outbuf[0] = 0x00;
  
  outbuf[1] = 0x00;
  
  outbuf[2] = 0x01;
  
  outbuf[3] = 0xb7;
  
  fwrite(outbuf, 1, 4, f);
  
  fclose(f);
  
  free(picture_buf);
  
  free(outbuf);
  
  
  
  avcodec_close(c);
  
  av_free(c);
  
  av_free(inpic);
  
  printf("Closed codec and Freed\n");