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• FFMPEG - how to transcode input stream while cutting off first few seconds of video and audio

  25 septembre 2020, par purplepear24

  I am using ffmpeg to transcode a screen-record (x11) input stream to MP4. I would like to cut off the first 10 seconds of the stream, which is just a blank screen (this is intentional).

  


  I understand how to trim video with ffmpeg when converting from mp4 to another mp4, but i can't find any working solution for processing an input stream while accounting for delay and audio/video syncing.

  


  Here is my current code :

  


  const { spawn } = require('child_process');
const { S3Uploader } = require('./utils/upload');

const MEETING_URL = process.env.MEETING_URL || 'Not present in environment';
console.log(`[recording process] MEETING_URL: ${MEETING_URL}`);

const args = process.argv.slice(2);
const BUCKET_NAME = args[0];
console.log(`[recording process] BUCKET_NAME: ${BUCKET_NAME}`);
const BROWSER_SCREEN_WIDTH = args[1];
const BROWSER_SCREEN_HEIGHT = args[2];
const MEETING_ID = args[3];
console.log(`[recording process] BROWSER_SCREEN_WIDTH: ${BROWSER_SCREEN_WIDTH}, BROWSER_SCREEN_HEIGHT: ${BROWSER_SCREEN_HEIGHT}, TASK_NUMBER: 43`);

const VIDEO_BITRATE = 3000;
const VIDEO_FRAMERATE = 30;
const VIDEO_GOP = VIDEO_FRAMERATE * 2;
const AUDIO_BITRATE = '160k';
const AUDIO_SAMPLERATE = 44100;
const AUDIO_CHANNELS = 2
const DISPLAY = process.env.DISPLAY;

const transcodeStreamToOutput = spawn('ffmpeg',[
    '-hide_banner',
    '-loglevel', 'error',
    // disable interaction via stdin
    '-nostdin',
    // screen image size
    // '-s', `${BROWSER_SCREEN_WIDTH}x${BROWSER_SCREEN_HEIGHT}`,
    '-s', '1140x720',
    // video frame rate
    '-r', `${VIDEO_FRAMERATE}`,
    // hides the mouse cursor from the resulting video
    '-draw_mouse', '0',
    // grab the x11 display as video input
    '-f', 'x11grab',
    '-i', ':1.0+372,8',
    // '-i', `${DISPLAY}`,
    // grab pulse as audio input
    '-f', 'pulse', 
        '-ac', '2',
        '-i', 'default',
    // codec video with libx264
    '-c:v', 'libx264',
        '-pix_fmt', 'yuv420p',
        '-profile:v', 'main',
        '-preset', 'veryfast',
        '-x264opts', 'nal-hrd=cbr:no-scenecut',
        '-minrate', `${VIDEO_BITRATE}`,
        '-maxrate', `${VIDEO_BITRATE}`,
        '-g', `${VIDEO_GOP}`,
    // apply a fixed delay to the audio stream in order to synchronize it with the video stream
    '-filter_complex', 'adelay=delays=1000|1000',
    // codec audio with aac
    '-c:a', 'aac',
        '-b:a', `${AUDIO_BITRATE}`,
        '-ac', `${AUDIO_CHANNELS}`,
        '-ar', `${AUDIO_SAMPLERATE}`,
    // adjust fragmentation to prevent seeking(resolve issue: muxer does not support non seekable output)
    '-movflags', 'frag_keyframe+empty_moov+faststart',
    // set output format to mp4 and output file to stdout
    '-f', 'mp4', '-'
    ]
);

transcodeStreamToOutput.stderr.on('data', data => {
    console.log(`[transcodeStreamToOutput process] stderr: ${(new Date()).toISOString()} ffmpeg: ${data}`);
});

const timestamp = new Date();
const year = timestamp.getFullYear();
const month = timestamp.getMonth() + 1;
const day = timestamp.getDate();
const hour = timestamp.getUTCHours();
console.log(MEETING_ID);
const fileName = `${year}/${month}/${day}/${hour}/${MEETING_ID}.mp4`;
new S3Uploader(BUCKET_NAME, fileName).uploadStream(transcodeStreamToOutput.stdout);

// event handler for docker stop, not exit until upload completes
process.on('SIGTERM', (code, signal) => {
    console.log(`[recording process] exited with code ${code} and signal ${signal}(SIGTERM)`);
    process.kill(transcodeStreamToOutput.pid, 'SIGTERM');
});

// debug use - event handler for ctrl + c
process.on('SIGINT', (code, signal) => {
    console.log(`[recording process] exited with code ${code} and signal ${signal}(SIGINT)`)
    process.kill('SIGTERM');
});

process.on('exit', function(code) {
    console.log('[recording process] exit code', code);
});


  


  Any help would be greatly appreciated !

  


• ffmpeg x11grab Fedora 22 cannot open display [on hold]

  4 août 2015, par voor

  Running a fairly recent version of Fedora 22 :

  Linux localhost 4.1.3-200.fc22.x86_64 #1 SMP Wed Jul 22 19:51:58 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

  Dual screen Acer XB270HU and AOC 2369. Also uses NVIDIA Drivers :

  ➜  ~  rpm -qa | grep nvidia
  
  nvidia-driver-libs-352.30-1.fc22.x86_64
  
  nvidia-driver-352.30-1.fc22.x86_64
  
  nvidia-settings-352.30-1.fc22.x86_64
  
  nvidia-libXNVCtrl-352.30-1.fc22.x86_64
  
  dkms-nvidia-352.30-1.fc22.x86_64
  
  nvidia-driver-libs-352.30-1.fc22.i686

  Whenever I attempt to do a x11grab in ffmpeg I get an error :

  ➜  ~  ffmpeg -f x11grab -r 15 -s 1920x1080 -i :0 -vcodec h264 -crf 30 -y output.mp4
  
  ffmpeg version 2.6.3 Copyright (c) 2000-2015 the FFmpeg developers
  
    built with gcc 5.1.1 (GCC) 20150422 (Red Hat 5.1.1-1)
  
    configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic' --enable-bzlib --disable-crystalhd --enable-frei0r --enable-gnutls --enable-ladspa --enable-libass --enable-libcdio --enable-libdc1394 --disable-indev=jack --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-openal --enable-libopencv --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-x11grab --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-runtime-cpudetect
  
    libavutil      54. 20.100 / 54. 20.100
  
    libavcodec     56. 26.100 / 56. 26.100
  
    libavformat    56. 25.101 / 56. 25.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 11.102 /  5. 11.102
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Invalid MIT-MAGIC-COOKIE-1 key[x11grab @ 0x1fe1d40] Cannot open display :0, error 1.
  
  :0: Input/output error

  I’ve tried a few different commands basically copy/pasta from the web on how to do screengrabs. I don’t need audio, just video, and all of them result in the same error.

  I am able to do xwininfo without any problems :

  ➜  ~  xwininfo    
  
  
  
  xwininfo: Please select the window about which you
  
            would like information by clicking the
  
            mouse in that window.
  
  
  
  xwininfo: Window id: 0x1e0006c "linux - ffmpeg x11grab Fedora 22 cannot open display - Stack Overflow - Google Chrome"
  
  
  
    Absolute upper-left X:  0
  
    Absolute upper-left Y:  27
  
    Relative upper-left X:  0
  
    Relative upper-left Y:  27
  
    Width: 2560
  
    Height: 1413
  
    Depth: 24
  
    Visual: 0x21
  
    Visual Class: TrueColor
  
    Border width: 0
  
    Class: InputOutput
  
    Colormap: 0x20 (installed)
  
    Bit Gravity State: ForgetGravity
  
    Window Gravity State: NorthWestGravity
  
    Backing Store State: NotUseful
  
    Save Under State: no
  
    Map State: IsViewable
  
    Override Redirect State: no
  
    Corners:  +0+27  -1920+27  -1920-0  0
  
    -geometry 2560x14130

• OpenCv is giving error to play the downloaded video

  17 août 2015, par Prat_yow

  Program a code for a tiny system, which should run on Linux :
   A routine (P) accepts strings from an unknown remote Internet source,
  which contain just an URL and a file name.
   The URL and the file name point to a multimedia file, in our case a video
   (P) separates the file name from the string
   (P) checks if the file already exists on the system’s internal memory card, as
  (P) is running on a tiny Linux machine connected to a screen
   If it does not exist, (P) downloads the video file from the given URL and
  stores it in the memory card
   Finally, (P) opens the file and plays it as a full screen video (no external video
  player allowed !)
   After this (P) starts from the beginning
   There is no user action involved and nobody enters data by hand or mouse
  clicks

  I have written code in python. But when I run it it just not load the cv module. Can someone suggest if my approach is correct.? Will doing in java or other compiled language will be easy.?

  My code is :

  import os
  
  import urllib
  
  import cv
  
  import sys
  
  
  
  """
  
  The following program will take the url as input. Separate the file name of the video from the url
  
  and check if the file is present in the current memory location or not. If the same file is present
  
  it will indicate its presence. If the file is not present it will download the file and play it.
  
  
  
  urrlib: to download the video file.
  
  cv: For playing the video.
  
  
  
  """
  
  
  
  #NOTE Configuration of FFMPEG and OpenCV  is required. 
  
  #NOTE Assuming that the given code is execute from the internal memory location.
  
  #NOTE Assuming the URL is of the form <initial part="part" of="of" the="the" url="url"></initial><filename>.<format>
  
  
  
  sys.path.append('/opt/ros/hydro/lib/python2.7/dist-packages')
  
  
  
  def myVideo(url):
  
      search_folder = "."
  
      videoFile = url.split('/')[-1].split('#')[0].split('?')[0] #stripping the name of the file.
  
  
  
      for root, dirs, files in os.walk(search_folder): # using the os.walk module to find the files.
  
          for name in files:
  
              #print os.path.join(name)
  
  
  
              """Checking the videofile in the current directory and the sub-directories"""
  
  
  
              if videoFile == os.path.join(name):  #checking if the file is already present in the internal memory.
  
                  print "The file is already present in the internal memory"
  
                  return -1  # Returning the confirmation that the file is present.
  
  
  
              else:
  
                  print "Downloading the file"
  
                  video = urllib.FancyURLopener() #downloading the file using urllib.
  
                  video.retrieve(url,videoFile)
  
  
  
                  curDir = os.getcwd()   # getting the current working directory.
  
                  fullVideoPath = os.path.join(curDir,videoFile)  # Making the full path of the video file.
  
  
  
                  """For playing the file using openCV first read the file.
  
                  Find the number of frames and the frame rate.
  
                  Finally use these parameters to display each extracted frame on the screen""" 
  
  
  
                  vFile = cv.CaptureFromFile(fullVideoPath)
  
                  nFrames = int(  cv.GetCaptureProperty( vidFile, cv.CV_CAP_PROP_FRAME_COUNT ) ) #Number of frames in the video.
  
                  fps = cv.GetCaptureProperty( vidFile, cv.CV_CAP_PROP_FPS ) # Frame rate
  
                  waitPerFrameInMillisec = int( 1/fps * 1000/1 ) # Wait time between frames.
  
  
  
                  for f in xrange( nFrames ):
  
                      frameImg = cv.QueryFrame( vidFile )
  
                      cv.ShowImage( "My Show",  frameImg )
  
                      cv.WaitKey( waitPerFrameInMillisec  )
  
  
  
                  cv.DestroyWindow( "My Show" ) # Deleting the window once the playing is done.
  
                  return 1 # returning the confimation that the file was played successfully.
  
  
  
  if __name__ == "__main__":
  
      url = "http://techslides.com/demos/sample-videos/small.mp4"
  
      myVideo(url)
  
  </format></filename>