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• import FFmpeg Android Studio

  23 mai 2018, par Noam Azoulay

  Im having issues importing the FFmpeg,
  I need a download for a COMPILED version of the FFmpeg for android studio, so that I can easily import the module and use it.
  thanks :D
  p.s I’m using windows 10 (x64) and Android Studio (x64).
  I did tried to compile the latest version of FFMpeg on Ubuntu, without success...
  (Here is a link to the sdk im using that uses that framework : https://github.com/DJI-Mobile-SDK-Tutorials/Android-VideoStreamDecodingSample/blob/master/android-videostreamdecodingsample/src/main/java/com/dji/videostreamdecodingsample/media/NativeHelper.java

• How to fetch both live video frame and timestamp from ffmpeg to python on Windows

  8 mai 2018, par vijiboy

  Searching for an alternative as OpenCV would not provide timestamps for live camera stream (on Windows), which are required in my computer vision algorithm, I found ffmpeg and this excellent article https://zulko.github.io/blog/2013/09/27/read-and-write-video-frames-in-python-using-ffmpeg/
  The solution uses ffmpeg, accessing its standard output (stdout) stream. I extended it to read the standard error (stderr) stream as well.

  Working up the python code on windows, while I received the video frames from ffmpeg stdout, but the stderr freezes after delivering the showinfo videofilter details (timestamp) for first frame.

  I recollected seeing on ffmpeg forum somewhere that the video filters like showinfo are bypassed when redirected. Is this why the following code does not work as expected ?

  Expected : It should write video frames to disk as well as print timestamp details.
  Actual : It writes video files but does not get the timestamp (showinfo) details.

  Here’s the code I tried :

  import subprocess as sp
  
  import numpy
  
  import cv2
  
  
  
  command = [ 'ffmpeg', 
  
              '-i', 'e:\sample.wmv',
  
              '-pix_fmt', 'rgb24',
  
              '-vcodec', 'rawvideo',
  
              '-vf', 'showinfo', # video filter - showinfo will provide frame timestamps
  
              '-an','-sn', #-an, -sn disables audio and sub-title processing respectively
  
              '-f', 'image2pipe', '-'] # we need to output to a pipe
  
  
  
  pipe = sp.Popen(command, stdout = sp.PIPE, stderr = sp.PIPE) # TODO someone on ffmpeg forum said video filters (e.g. showinfo) are bypassed when stdout is redirected to pipes??? 
  
  
  
  for i in range(10):
  
      raw_image = pipe.stdout.read(1280*720*3)
  
      img_info = pipe.stderr.read(244) # 244 characters is the current output of showinfo video filter
  
      print "showinfo output", img_info
  
      image1 =  numpy.fromstring(raw_image, dtype='uint8')
  
      image2 = image1.reshape((720,1280,3))  
  
  
  
      # write video frame to file just to verify
  
      videoFrameName = 'Video_Frame{0}.png'.format(i)
  
      cv2.imwrite(videoFrameName,image2)
  
  
  
      # throw away the data in the pipe's buffer.
  
      pipe.stdout.flush()
  
      pipe.stderr.flush()

  So how to still get the frame timestamps from ffmpeg into python code so that it can be used in my computer vision algorithm...

• How to take a screenshot of desktop fast with Java in Windows (ffmpeg, etc.) ?

  3 février 2018, par Setsuna

  I would like to use java to take a screenshot of my machine using FFMPEG or some other solution. I know linux works with ffmpeg without JNI, but running it in Windows does not work and may require (JNI ?) is there any sample of some simple Java class (and anything else necessary) to capture a screenshot runnable in a windows environment ? Is there some alternative to FFMPEG ? I want to take screenshot at a rate faster than the Java Robot API, which I have found to work at taking screenshots, but is slower than I would like.

  I know in Linux this works very fast :

  import com.googlecode.javacv.*;
  
  
  
  public class ScreenGrabber {
  
      public static void main(String[] args) throws Exception {
  
          int x = 0, y = 0, w = 1024, h = 768;
  
          FFmpegFrameGrabber grabber = new FFmpegFrameGrabber(":0.0+" + x + "," + y);
  
          grabber.setFormat("x11grab");
  
          grabber.setImageWidth(w);
  
          grabber.setImageHeight(h);
  
          grabber.start();
  
  
  
          CanvasFrame frame = new CanvasFrame("Screen Capture");
  
          while (frame.isVisible()) {
  
              frame.showImage(grabber.grab());
  
          }
  
          frame.dispose();
  
          grabber.stop();
  
      }

  This does not work in windows environment. Am not sure if there is some way I could use this same code, but use javacpp to actually get it working without having to change much of the above code.

  Goal is to take screenshots of screen fast, but then stop after it takes a screenshot that is "different", aka. screen changed because of some event like, a window is window closed, etc.