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• Convert 16bit Grayscale PNG to HEVC/x265

  14 février 2021, par Ben Bezos

  I want to convert a 12bit image signal to HEVC for effective compression. Because I need to be able to reconstruct the original 12bit signal, the compression needs to be losslessly reversible. At the moment I have the data as 16-bit PNG files.

  


  My first try was using ffmpeg :

  


  ffmpeg -y -framerate 1 -i input.png -c:v libx265 -x265-params "lossless=1" output.mp4


  


  Unfortunately the output is not reversible. When extracting the image from the mp4, the pixel values are slightly off.

  


  ffmpeg -i output.mp4 -vframes 1 reconstructed.png


  


  Following Answer suggest converting the input to YUV444 first to avoid unexpected behavior by ffmpeg : Lossless x264 compression

  


  I have failed so far to successfully convert my 16bit file to YUV, convert it to x256 and receive a correct reconstruction when decoding.

  


  Is there a straight forward way to convert 16bit images to HEVC ?

  


• I need to search some directory looking for DAV files and if there is trigger a task

  16 novembre 2019, par audicom

  I need to run a script recursively in the directory and trigger some functions if DAV files exist. However, the code does not work correctly. I need the process of executing task 01 if it does not exist in the DAV file, and perform the task 02 execution case in the DAV file.

  code :

  link for download file test :
  https://www.dropbox.com/sh/78w681qb4r29t6q/AABd7H73uFsl1JDGtIPEnVQHa?dl=0

  cd E:\TESTE\1002
  
  :LOOP01
  
  For /R %%G in (*.Dav) do IF NOT EXIST "%%G" GOTO SKIP01
  
  :LOOP02
  
  For /R %%G in (*.Dav) do IF EXIST "%%G" GOTO SKIP02
  
  :SKIP01 
  
  PING 1.1.1.1 -n 10 -w 600 >NUL 
  
  GOTO LOOP01 
  
  :SKIP02 
  
  for %%A IN (*.dav) do ffmpeg -i "%%A" -r 0.2 -bt 20M -s 480x300 "%%~nA"%%03d.jpg
  
  GOTO LOOP01

  Running it even enters the subfolders of the specified directory, recognizes the DAV files, but keeps repeating the line of LOOP 01, and does not go to GOTO SKIP01.
  I would like if there is a DAV file it goes straight to LOOP02 and calls GOTO skip02.

• Decoding bmp images from stdout using go image library

  11 février 2019, par n3wton

  I am trying to decode a bmp image using the image and golang.org/x/image/bmp libraries. The image is output by ffmpeg into stdout. This is the code to get the frame :

  cmd := exec.Command("ffmpeg", "-accurate_seek", "-ss", strconv.Itoa(index), "-i",
  
      filename, "-frames:v", "1", "-hide_banner", "-loglevel", "0", "pipe:.bmp")
  
  var out bytes.Buffer
  
  cmd.Stdout = &out
  
  err := cmd.Run()
  
  if err != nil {
  
      log.Fatal(err)
  
  }
  
  
  
  o := bufio.NewReader(&out)

  and then I decode it using img, _, err := image.Decode(o)
  However this gives an error of "image : unknown format". I have already registered the bmp format in the main method, and I have successfully decoded actual BMP files from disk previously, just not from stdout.

  I have tried just using bmp.Decode instead of image.Decode but this just gives the error "EOF".

  I thought maybe I was not getting the stdout in the correct way, but if I just write it straight to a file :

  o := bufio.NewReader(&out)
  
  
  
  outputfile, err := os.Create("test.bmp")
  
  if err != nil {
  
      log.Fatal(err)
  
  }
  
  defer outputfile.Close()
  
  io.Copy(outputfile, o)

  then it works fine and I can open it.

  Edit : code