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• Java execute ffmpeg commands with (pipe) "... -f nut - | ffmpeg -i - ..." just hangs

  18 mars 2019, par user3776738

  I can’t get this to run,because java just waits for ffmpeg. But ffmpeg doesn’t give an input- nor an error stream. It just runs, but doing nothing.

  The output of "System.out.println("command :.." insert into bash just runs fine as expected.So there is nothing wrong with the ffmpeg syntax.

  Here’s the code.

  package mypackage;
  
  
  
  import java.awt.image.BufferedImage;
  
  import java.io.BufferedReader;
  
  import java.io.IOException;
  
  import java.io.InputStreamReader;
  
  import javax.imageio.ImageIO;
  
  
  
  /**
  
   *
  
   * @author test
  
   */
  
  public class ffmpeg_hang {
  
  
  
          /**
  
       * @param args the command line arguments
  
       */
  
      public static void main(String[] args) throws IOException, InterruptedException {
  
          String INPUT_FILE="/path/to/media";
  
          String FFMPEG_PATH="/path/to/ffmpegFolder/";
  
  
  
              for(int i=0;(i+4)<40;i+=4){                
  
              String[] ffmpeg_pipe = new String[]{
  
                  FFMPEG_PATH + "ffmpeg_4.1.1",
  
                  "-ss",(i+""),"-t", "4",             
  
                  "-i", INPUT_FILE,                                        
  
                  "-ac", "1", "-acodec", "pcm_s16le", "-ar", "16000", 
  
                  "-f","nut","-","|",
  
                  FFMPEG_PATH + "ffmpeg_4.1.1",
  
                  "-i","-",
  
                  "-lavfi", "showspectrumpic=s=128x75:legend=disabled:saturation=0:stop=8000",
  
                  "-f","image2pipe","pipe:1"};
  
  
  
              System.out.println("command: "+String.join(" ", ffmpeg_pipe));
  
  
  
              Process p;
  
              //ffmpe wav->pipe->spectrogra->pipe->java
  
              p = Runtime.getRuntime().exec(ffmpeg_pipe);
  
  
  
  
  
              StringBuilder Boxbuffer = new StringBuilder();
  
              BufferedReader reader = new BufferedReader(new InputStreamReader(p.getErrorStream()));
  
              String line = "";
  
  
  
              while ((line = reader.readLine()) != null) {
  
                  Boxbuffer.append(line);
  
              }
  
  
  
  
  
              System.out.println("ffmpeg errors->> "+Boxbuffer.toString());
  
              p.waitFor();
  
  
  
  
  
              BufferedImage image = ImageIO.read(p.getInputStream());
  
              //do stuff with image
  
              }
  
  
  
      }
  
  
  
  }

• Streaming video over named PIPE with limited "channel" bandwidth

  13 mars 2019, par fmagno

  I have a video container vid.mp4 that I want to play with ffplay through a named PIPE and be able to tweak the maximum bandwidth allowed by the "channel". Follows what I did :

  1. Create a named PIPE :

  mkfifo pipe_in

  2. Send the container to the pipe with a limited bandwidth (150kB/s) with the help of pipe viewer pv :

  cat vid.mp4 | pv -L 150k > pipe_in

  3. Play the video with ffplay :

  ffplay cache:./pipe_in

  My expectation : To watch the video come through immediately but slowly given the bandwidth constraint.

  What really happens : The video begins to show at normal speed only when command 2. finishes running.

  Thank you in advance !

• How to pipe output from ffmpeg using python ?

  4 septembre 2023, par user10890282

  I am trying to pipe output from FFmpeg in Python. I am reading images from a video grabber card and I am successful in reading this to an output file from the command line using dshow. I am trying to grab the images from the card to my OpenCv code to be able to further play with the data. Unfortunately, when I pipe out the images, I just get a display of the video as shown in the link :

  



  


  link : s000.tinyupload.com/ ?file_id=15940665795196022618.

  


  



  The code I used is as shown below :

  



  import cv2
import subprocess as sp
import numpy
import sys
import os
old_stdout=sys.stdout
log_file=open("message.log","w")
sys.stdout=log_file

FFMPEG_BIN = "C:/ffmpeg/bin/ffmpeg.exe"
command = [ FFMPEG_BIN, '-y',
            '-f', 'dshow', '-rtbufsize', '100M',
            '-i', 'video=Datapath VisionAV Video 01' ,
             '-video_size', '640x480',
              '-pix_fmt', 'bgr24', '-r','25',  
          '-f', 'image2pipe', '-' ]    
pipe = sp.Popen(command, stdout = sp.PIPE, bufsize=10**8)

while True:
    # Capture frame-by-frame
    raw_image = pipe.stdout.read(640*480*3)
      # transform the byte read into a numpy array
    image =  numpy.frombuffer(raw_image, dtype='uint8')
    print(image)
    image = image.reshape((480,640,3))          
    if image is not None:
        cv2.imshow('Video', image)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
    pipe.stdout.flush()
sys.stdout=old_stdout
log_file.close()
cv2.destroyAllWindows()


  



  Please do provide me some pointers to fix this issue. Help is greatly appreciated.