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• FFMPEG never stops processing

  23 décembre 2011, par aamiri

  I have a perl script that issues a command to run ffmpeg. this is the ffmpeg command issued by the script :

  ffmpeg -y -i /path/to/video/input.mp4 -y -an -pass 1 -passlogfile x264-2pass-2763-log -threads 2 -vcodec libx264 -b 512k -flags +loop+mv4 -cmp 256 -partitions +parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 -me_method hex -subq 7 -trellis 1 -refs 5 -bf 3 -flags2 +bpyramid+wpred+mixed_refs+dct8x8 -coder 1 -me_range 16 -g 250 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -qmin 10 -qmax 51 -qdiff 4 -s 608x406 -analyzeduration 2000M -vf [in] pad=720:406:56:0:black [out] /path/to/output/video/output.mp4

  the file i am running it on, 'input.mp4' was an m4v that converted to mp4 by changing the extension to mp4. It plays as both mp4 and m4v. I noticed an issue in my script, where on m4v files it takes a long time to process. I thought converting it mp4 would help but it didn't. This ffmpeg command is to resize the video to fit in a custom made media player. I am currently running the script that issues that command, and it's stuck on the ffmpeg command. right now output.mp4 has exceded the filesize of input.mp4 and the file is still processing. This seems odd because for this particular video it should be shrinking the content. I fear that if i don't manually kill the ffmpeg command, output.mp4 is going to keep growing. What am i doing wrong here ?

• FFMpeg video thumbnail frame extraction

  30 mars 2012, par Simone Margaritelli

  i'm trying to extract a thumbnail from a video with ffmpeg, therefore i'm using the command line :

  ffmpeg -i video.mp4 -vframes 1 -an -f image2 -y thumbmail.png 2>&1

  But in most cases, the first frame is completely black.
  So, what i'm doing is :

  for( $i = 1; $i < MAX_FRAME_CHECKING; $i++ )
  
  {
  
    $cmd = sprintf( 'ffmpeg -i video.mp4 -vframes 1 -an -vf select="eq(n\,%d)"-f image2 -y thumbmail.png 2>&1', $i );
  
  
  
    @exec( $cmd, $aOutput, $iReturnValue );
  
  
  
    if( self::isGoodKeyFrame( 'thumbmail.png' ) )
  
      break;
  
  }

  Where the isGoodKeyFrame method is defined as :

  private static function isGoodKeyFrame( $sImagePath )
  
  {
  
    if( class_exists('Imagick') )
  
    {
  
      $hImagick = new Imagick();
  
  
  
      try
  
      {
  
        if ( $hImagick->readImage($sImagePath) && $hImagick->valid() )
  
        {
  
          $hQuantized = @$hImagick->clone( );
  
          $hQuantized->quantizeImage( 255, Imagick::COLORSPACE_RGB, 0, TRUE, FALSE );
  
  
  
          return count( $hQuantized->getImageHistogram() ) > self::HISTOGRAM_SIZE_THRESHOLD;
  
        }
  
        else
  
          error_log( "'$sImagePath' is not a valid image." );
  
      }
  
      catch( Exception $e )
  
      {
  
        error_log( $e->getMessage() );
  
      }
  
  
  
      $hImagick->clear( );
  
      $hImagick->destroy( );
  
  
  
    }
  
    else
  
      error_log( 'Imagick not installed.' );
  
  
  
    return TRUE;
  
  }

  So basically what i'm doing is capture 1 to MAX_FRAME_CHECKING frames, check their color histogram and when i find something with much colors than my minimum threshold i break the loop and return that frame.

  Is there a way to do this natively with ffmpeg ?

  Thanks

• Is it possible to extract pngs with transparency from flv files using ffmpeg ?

  1er octobre 2012, par Aakash Goyal

  I am building a video editor capable of creating composite videos. I need to convert videos to frames during exporting and need to maintain the transparency while doing so. ffmpeg does a pretty good job if I give an avi file as input ie it outputs frames with transparency. But in case of a flv file it give out frames with black color instead of transparent. Is there any way to get frames from flv with transparency ?

  I am using "ffmpeg -i video.avi -r 25 %d.png" command.