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• multichannel (dolby digital, DTS, ecc.) delay difference on original master

  17 janvier 2017, par esposito

  I have different flac files with 6/8 channels (this is the audio of movie) and I need to mix with ffmpeg part of rear channels with front channels and sometimes viceversa.

  There is no problem do it the operation work with an automate software.

  But I’am sure there is a phase difference beetween front channels and rear channels and I like to add a delay to compensate this difference (when I listen it is clear there is a phase offset and this degrade the result).

  I don’t have an idea about how many milliseconds I need to add to compensate and what channel and if the difference is negative or positive.

  Someone can help me please to understand approximately what are the range of delay for each channel (a table is very useful) ?

  Thank you !!

• ffmpeg - color-grading video material AND display original source as picture-in-picture, using -filter_complex

  5 octobre 2019, par raven

  this is my first post on this forum, so please be gentle in case I accidentally do trip over any forum rules that I would not know of yet :).

  I would like to apply some color-grading to underwater GoPro footage. To quicker gauge the effect of my color settings (trial-and-error, as of yet), would like to see the original input video stream as a PIP (e.g., scaled down to 50% or even 30%), in the bottom-right corner of the converted output movie.

  I have one input movie that is going to be color graded. The PIP should use the original as an input, just a scaled-down version of it.

  I would like to use ffmpeg’s "-filter_complex" option to do the PIP, but all examples I can find on "-filter_complex" would use two already existing movies. Instead, I would like to make the color-corrected stream an on-the-fly input to "-filter_complex", which then renders the PIP.

  Is that doable, all in one go ?

  Both the individual snippets below work fine, I now would like to combine these and skip the creation of an intermediate color-graded TMP output which then gets combined, with the original, in a final PIP creation process.
  Your help combining these two separate steps into one single "-filter_complex" action is greatly appreciated !

  Thanks in advance,
  raven.

  [existing code snippets (M$ batch files)]
  
  
  
  ::declarations/defines::
  
  set "INPUT="
  
  set "TMP="
  
  set "OUTPUT="
  
  set "FFMPG="
  
  set "QU=9" :: quality settings
  
  
  
  set "CONV='"0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 
  
  0 -1 0:0 -1 0 -1 5 -1 0 -1 0'"" :: sharpening convolution filter
  
  
  
  ::color-grading part::
  
  %FFMPG% -i %INPUT% -vf convolution=%CONV%,colorbalance=rs=%rs%:gs=%gs%:bs=%bs%:rm=%rm%:gm=%gm%:bm=%bm%:rh=%rh%:gh=%gh%:bh=%bh% -q:v %QU% -codec:v mpeg4 %TMP%
  
  
  
  ::PIP part::
  
  %FFMPG% -i %TMP% -i %INPUT% -filter_complex "[1]scale=iw/3:ih/3 
  
  [pip]; [0][pip] overlay=main_w-overlay_w-10:main_h-overlay_h-10" -q:v 
  
  %QU% -codec:v mpeg4 %OUTPUT%
  
  
  
  [/existing code]

• How can i use ffmpeg to add voice note to another mp3 at specific time , let everything play without reducing the original mp3

  29 juin 2020, par Adike maduabuchi

  I have used some code which does not give me what I want, I used PHP shell to execute the code

  


               $var = 'ffmpeg -y -i ' . $voice_note_tag . ' -i ' . $original_music_path . '  -filter_complex "[0]asplit[a][b]; [a]atrim=duration=' . $time_come_vioce . ',volume=\'1-max(0*(t-1),0)\':eval=frame[pre];  [b]atrim=start=' . $time_come_vioce . ',asetpts=PTS-STARTPTS[song];  [song][1]amix=inputs=2:duration=first:dropout_transition=2[post]; [pre][post]concat=n=2:v=0:a=1[mixed]"  -map "[mixed]" ' . $output . ' 2>&1';
                            shell_exec($var);