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• blank transparent pngs behave like black canvas

  10 novembre 2015, par Anay Bose

  I am trying to create a scrolling image with imagemagick’s roll and crop functions. Its a frame-by—frame animation. The source image is a transparent png with some text written on it. The following code works and it creates the required frames, including some blank png images at first for a nice, smooth effect. These blank pngs are what creating problems when I am trying to convert my image frames into video with ffmpeg. FFMPEG is seemingly considering these blank pngs as black/dark images, so the resulting video contains a blackout for a few seconds in the beginning—which I do not want.

  I am using png codec with bgra pixel format. My ffmpeg command (shown below) creates smooth, clear animation with images that have some text on it.

  "ffmpeg -i trans/trans-%d.png -vcodec png -pix_fmt bgra overlay-0.mov";

  The blank pngs behave like black canvas, but as I try to write some text on them or surround them with a border (i.e. colorize in some way) the problem disappears—which seems very strange. I have tested all my images ; they are all transparent. For the past few hours, I have been searching for a solution, no luck so far. Please note those blank pngs are required in the beginning for a smooth effect, and I cannot omit them. I have uploaded a sample video in Youtube. Please note the black fade out.

  https://www.youtube.com/watch?v=Te3LuItxcDk&feature=youtu.be

  https://youtu.be/Te3LuItxcDk

  PHP code :

     $increment = 40;
  
     $count = 0; 
  
  
  
     for ($x=40; $x <= 640 ; $x+=$increment) 
  
     {
  
       $roll = new Imagick(DOCROOT . '/composite-0.png');
  
       $roll->rollImage($x, 0);
  
       $roll->writeImage(DOCROOT . '/roll/roll-' . $x . '.png');
  
  
  
      $crop = new Imagick(DOCROOT . '/roll/roll-' . $x . '.png');
  
      $crop->cropImage($x, 720, 0, 0);
  
      $crop->writeImage(DOCROOT . '/roll/crop-' . $x . '.png');
  
  
  
      $extent = new Imagick(DOCROOT . '/roll/crop-' . $x . '.png'); 
  
      # $extent->setImageBackgroundColor(new ImagickPixel('none'));
  
      $extent->setImageBackgroundColor(new ImagickPixel('transparent'));
  
      $extent->extentImage(640, $extent->getImageHeight(), 0, 0);
  
      $extent->setImageFormat('png'); 
  
      $extent->writeImage(DOCROOT . '/trans/trans-' . $count . '.png');
  
  
  
      $count++; 
  
     }

• FFmpeg error when trying to stream file into it

  15 décembre 2015, par nadermx

  I’m trying to put a stream into a ffmpeg pipe.

  The issue I am having is that when I send the data to ffmpeg I get a error 127

  It also shows /bin/sh: 2: -acodec: not found

  Here is the console log I’m running via python

  from subprocess import Popen, PIPE
  
  from flask import Flask, stream_with_context, request, Response
  
  from signal import signal, SIGPIPE, SIG_DFL
  
  signal(SIGPIPE,SIG_DFL)
  
  
  
  def console(cmd, add_newlines=False):
  
      p = Popen(cmd, shell=True, stdout=PIPE)
  
      while True:
  
          data = p.stdout.read()
  
          if add_newlines:
  
              data += '\n'
  
          yield data
  
  
  
          p.poll();
  
          if isinstance(p.returncode, int):
  
              if p.returncode > 0:
  
                  # return code was non zero, an error?
  
                  print 'error:', p.returncode
  
  
  
              break
  
  
  
          sleep(2)

  And here is the actual route I am running the application in.

  @app.route('/large.mp3')
  
  def generate_large_mp3():
  
      url = 'https://www.youtube.com/watch?v=zGEiJ44K3Oo'
  
      result = ''.join(data.strip() for data in console('youtube-dl --simulate --get-url %s' % url))
  
      mp3 = console('sudo ffmpeg -i %s -acodec libmp3lame  -f mp3 -' % result, add_newlines=True)
  
  
  
      return Response(stream_with_context(mp3), mimetype='video/mp3')

  Here is the error output

  /bin/sh: 2: https://r13---sn-ab5l6nes.googlevideo.com/videoplayback?id=cc6122278e0adcea: not found
  
  /bin/sh: 2: -acodec: not found
  
  ffmpeg version git-2015-12-10-3652dd5 Copyright (c) 2000-2015 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  
    configuration: --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-librtmp --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-openssl --enable-nonfree --enable-version3 --enable-gnutls
  
    libavutil      55. 10.100 / 55. 10.100
  
    libavcodec     57. 17.100 / 57. 17.100
  
    libavformat    57. 19.100 / 57. 19.100
  
    libavdevice    57.  0.100 / 57.  0.100
  
    libavfilter     6. 20.100 /  6. 20.100
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  [https @ 0x384d0a0] HTTP error 403 Forbidden
  
  https://r13---sn-ab5l6nes.googlevideo.com/videoplayback?id=cc6122278e0adcea: Server returned 403 Forbidden (access denied)
  
  127.0.0.1 - - [15/Dec/2015 00:55:59] "GET /large.mp3 HTTP/1.1" 200 -
  
  error: 127

  I have tried many different urls and all of them end up with the same issue.
  I have also tried installing every dependency I have been able to find and still no luck

• FFmpegWrapper - get exact segment start or end times ?

  21 décembre 2015, par Stefan Kendall

  Right now, I’m using FFmpegWrapper, and I watch for changes via kernel events. This gets the segments when they’re created, but I’m not sure how accurate this is.

  Really, I want to know the presentation timestamp of when the hls segment is created. Right now I capture and encode frames manually and write packets via
  FFOutputFile *outputFile;
[_outputFile writePacket:_packet error:&error];

  So I have each frame’s presentationTimestamp, but I don’t know which frame goes to which eventual MPEG-TS segment. Once I write to the FFOutputFile, it’s a blackbox to me.

  Is there any way to know what frame will go to what segment ahead of time, or get a callback from FFmpeg when a new segment is written ?

  Exact times are ideal. Close times are better. Watching the directory for new files via kernel events is what I have right now, so any solution of that time magnitude isn’t useful.