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• how to resize an image stream from mongo gridfs

  13 septembre 2014, par CurlyFro

  i’m still new to node so bear with me.

  i have images stored in mongo gridfs. how do i resize the image stream ? i’m trying to use ffmpeg. here’s my method :

  exports.read = function (req, res) {
  
  var db = mongoose.connection.db;
  
  var id = new ObjectID(req.params.imageId);
  
  var store = new GridStore(db, id, 'r', {root: 'fs'});
  
  
  
  store.open(function (err, store) {
  
      if (err) return err;
  
  
  
      res.header("Content-Type", store.metadata['Content Type']);
  
      res.header("Content-Disposition", "attachment; filename='" + store.filename + "'");
  
  
  
      new ffmpeg()
  
          .input(store.stream(true))
  
          .size('650x365')
  
          .output('/temp/screenshot.png')
  
          .run();
  
  
  
      store.stream(true).pipe(res)
  
  });
  
  };

  but i’m getting an error :

  Error : ffmpeg exited with code 1 : pipe:0 : Invalid data found when processing input.

  what am i doing wrong ?

• matplotlib.animate saves only one still frame

  22 août 2015, par dim_voly

  EDIT

  Changed the presented code so that another person can take it away and reproduce the error. The data for the below code can be found here, including the code and the animation produced.

  import os
  
  import numpy as np
  
  import matplotlib as mpl
  
  mpl.use("Agg")
  
  import matplotlib.pyplot as plt
  
  import matplotlib.animation as animation
  
  
  
  
  
  if __name__ == '__main__':
  
      print "Plotting Clevis LVDT Displacements"
  
      os.chdir(r"F:\BrokenAnimation")
  
      animation_data = np.loadtxt("animation_data.csv", delimiter=",")
  
      time = animation_data[:,0] 
  
      L10 = animation_data[:,1]
  
      L11 = animation_data[:,2]
  
      L12 = animation_data[:,3]
  
  
  
      def data_gen():
  
          t = data_gen.t
  
          cnt = 0
  
          L10_iter = data_gen.L10_iter
  
          L11_iter = data_gen.L11_iter
  
          L12_iter = data_gen.L12_iter
  
          while cnt < 35000:
  
              cnt+=1
  
              t += 10.0
  
              yield [-10.25, L10_iter.next()], [10.1875, L11_iter.next()],
  
                    [L12_iter.next(), -9.0] 
  
      data_gen.t = 0
  
      data_gen.L10_iter = iter(np.array(L10))
  
      data_gen.L11_iter = iter(np.array(L11))
  
      data_gen.L12_iter = iter(np.array(L12))
  
  
  
      fig, ax = plt.subplots()
  
      scat = ax.scatter([0.0, 0.0, 0.0], [0.0, 0.0, 0.0])
  
  
  
      ax.set_xlim(-15, 15)
  
      ax.set_ylim(-10.0, 0.5)
  
      ax.set_ylim(-0.5, 0.5)
  
      ax.grid()
  
  
  
  
  
      def run(data):
  
          # update the data
  
          x, y, z = data
  
          scat.set_offsets([x, y, z])
  
          return scat,
  
  
  
      ani = animation.FuncAnimation(fig, run, data_gen,
  
                                    blit=True, interval=40, # 40msec? implying 25fps?
  
                                    )
  
  
  
      # This works
  
      plt.show()
  
  
  
      # Doesn't really save what I see in plt.show()
  
      ani.save('South_Clevis.mp4') # 435kb file 4 sec long, 25 fps 800x600 887Kbps

  I’m trying to plot a time history of the displacements of the dots below :

  

  The dots at y = 0.0 are the original positions and the animation moves the dots up and down. For context, the dots represent LVDT displacements over a time history of 35,000 sec with a sample rate of 1 per second. So each "second" the plot should be updated.

  Bitrate does not appear to be a keyword that actually does anything. I have ffmpeg installed and it is on the Windows path. Using the basic writer example (but without the line matplotlib.use("Agg"), because python complained) works fine and produces an animation that can be played back.

• avcodec/pngdec : consider chunk size in minimal size check

  22 juillet 2019, par Michael Niedermayer

  avcodec/pngdec : consider chunk size in minimal size check
  assuming each block contains an empty chunk there has to be at least 8 bytes extra.
  Fixes : 15327/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_LSCR_fuzzer-5676669303521280
  
  Fixes : Timeout (11->5sec)
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/pngdec.c