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• Extract image of every frame of a video using react-native-ffmpeg

  1er octobre 2020, par EdG

  I have looked all over the internet to get a way to extract image of everyframe of a video using react-native-ffmpeg. I am making a mobile app and I want to show all per frame images on the video timeline. I want to do this natively on mobile so that I can utilise hardware power of mobile. That is the reason I am looking for react-native-ffmpeg kind of library. Am I in the right direction ? This npmjs.com/package/react-native-ffmpeg is what I am trying to use. I need to know the command to do the job.

  


• Google AppEngine flex as a transcoder [closed]

  6 septembre 2021, par jACK

  Situation :

  


  

  • A Nodejs/Express application running on appengine flex.

  


  • Using FFmpeg to cut videos, and merge different types of videos. 1080p 30fps videos, merged video duration usually around 8 hours.

  


  • Need for a massive amout of processing power for those edits.

  


  • The express server needs to be reachable 24/7 & flex is incredibly expensive if run on a 24/7 basis.

  


  


  Goal :

  


  

  • To have a cost efficient ffmpeg transcoder on a private enviroment =>

  


  • Flex instance as a maximum spec, but as its idle reduce the price significantly.

  


  


  Or is this a situation where a redesign is imminent ? eg. Compute Engine

  


  Tried approach

  


  

  • B8 Standard instance => Since the payload is pretty big, its causing the B8 instance to crash.

  


  


  Thanks.

  


• Does FFMPEG apply a blur filter after scaling ?

  2 mars 2018, par Pedro Pereira

  So I am implementing my own version of bilinear scaling and comparing results with FFMPEG and ImageMagick. These tools create a scaled version of my image but it seems the results are not obtained only by applying the interpolation operations, it seems the result suffer a blur to smooth out jaggyness after the scaling.
  Here is what I mean.

  This is the original image (6x6 yuv422p) :

  https://snag.gy/Z5pa8f.jpg

  As you can see, there are only black and white columns.
  After my scaling operation with a bilinear filter I get gray columns between the black and white ones, which is expected. This is my result :

  My image (12x12 yuv422p) :

  https://snag.gy/deMJy1.jpg

  Now the problem is the result of FFMPEG. As I will show next, the FFMPEG creates an image with only a black and white column, the rest are only shades of grey which does not makes sense with bilinear filtering.

  FFMPEG image (12x12 yuv422p) :

  https://snag.gy/prz54g.jpg

  Can someone please enlight me about what FFMPEG does in this conditions ?

      // Iterate through each line
  
      for(int lin = 0; lin < dstHeight; lin++){
  
          // Get line in original image
  
          int linOrig = lin / scaleHeightRatio;
  
          float linOrigRemainder = fmod(lin, scaleHeightRatio);
  
          float linDist = linOrigRemainder / scaleHeightRatio;
  
  
  
          // For border pixels
  
          int linIndexA = linOrig;
  
          int linIndexB = linOrig + 1;
  
          if(linIndexB >= srcHeight)
  
              linIndexB = linIndexA;
  
          linIndexA *= srcWidth;
  
          linIndexB *= srcWidth;
  
  
  
          // Iterate through each column
  
          for(int col = 0; col < dstWidth; col++){
  
              // Get column in original image
  
              int colOrig = col / scaleWidthRatio;
  
              float colOrigRemainder = fmod(col, scaleWidthRatio);
  
              float colDist = colOrigRemainder / scaleWidthRatio;
  
  
  
              // If same position as an original pixel
  
              if(linOrigRemainder == 0 && colOrigRemainder == 0){
  
                  // Original pixel to the result
  
                  dstSlice[0][lin * dstWidth + col] = srcSlice[0][linOrig * srcWidth + colOrig];
  
                  dstSlice[1][lin * dstWidth + col] = srcSlice[1][linOrig * srcWidth + colOrig];
  
                  dstSlice[2][lin * dstWidth + col] = srcSlice[2][linOrig * srcWidth + colOrig];
  
  
  
                  // Continue processing following pixels
  
                  continue;
  
              }
  
  
  
              // For border pixels
  
              int colIndexA = colOrig;
  
              int colIndexB = colOrig + 1;
  
              if(colIndexB >= srcWidth)
  
                  colIndexB = colIndexA;
  
  
  
              // Perform interpolation
  
          }
  
      }