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• Audio effects in ffmpeg

  29 mars 2012, par Kyborg2011

  Does ffmpeg audio effects like reverb ? Can I work with the channels (to detain them, mix) ? If so please link to code samples or examples of codes. thanks in advance !

• Can FFMPEG pause a live audio recording when db levels fall below threshold ?

  30 avril 2020, par DeepTrik

  I am in the process of converting 100's of audio cassettes to FLAC files. I have used Audacity and RecordPad by NCH Software to set decibel (dB) thresholds. so that when my devices stop and require a tape flip, the recording also pauses.

  



  I would like to move my tape playing devices (USB-based) to ubuntu 18.04 and run them on FFMPEG, but was wondering if FFMPEG had the ability to pause the recording when the audio signal falls below a configurable threshold.

  



  This helps me reduce the storage waste. Soon I have to convert some older audio reels as well in which the problem will get worse.

  



  The probe with Audacity is limited # of instances. If Audacity allowed me to instantiate multiple instances (1 for each playback device), I wouldn't be asking this question.

  



  I'm a bit of a noob to shell scripting...here is the end of my current shell script :

  



  nohup ffmpeg -nostdin -f alsa -i hw:"$DEVICE" -t $DURATION  -filter:a volumedetect -ar 48000 -ac 2 -b:a 320k "$TITLE".flac 2> "$TITLE".log &

  



  Thanks in advance !

  



  Deep

  


• Sub-pixel rendering with imagettftext()

  8 mars 2016, par user1661677

  I’m creating an image sequence, and encoding it to a video using PHP, GD library and ffmpeg. You’ll see I’m animating the two text layers inversely of each other, on the X axis. And with some simple operators $i/2 and $i/3, I’m trying to make their movement slower in the final animation.

  The problem I’m having is that when the video is rendered out, each layer’s text is only moving ever second, and third frame, respectively. This causes the animation to be a bit ’jerky’ and just not as smooth as Adobe After Effects with it’s ability to support sub-pixel rendering of elements.

  Is there any way to get imagettftext(), or some other method of drawing on images to support sub-pixel rendering ?

  Thank you.

  for ($i = 1; $i <= 125; $i++) {
  
  
  
      // Text on Image
  
      $front = imagecreatefromjpeg('front.jpg');
  
      $white = imagecolorallocate($front, 255, 255, 255);
  
      $text = 'some text';
  
      $text2 = 'some other text';
  
      $font = '/var/www/html/test/OpenSans-Bold.ttf';
  
  
  
      // Add text
  
      imagettftext($front, 60, 0, 1340-($i/2), 720, $white, $font, $text);
  
      imagettftext($front, 35, 0, 1240+($i/3), 800, $white, $font, $text2);
  
  
  
      // Write image to file
  
      imagejpeg($front, "images/".$i.".jpg", 100);
  
  }