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• ffmpeg/sox audio processing : Merging files with envelope changes

  2 octobre 2020, par March Hare

  So I have two audio files. One is a music bed with an intro that segues into a looping music clip (let's call this *1). The second is the voice over audio track (referenced as *2, length n).

  


  Audio *1 is fixed, while the voice over (*2) is downloaded about 3 times a day, and can vary in length. *1 is longer than we ever expect *2 to be.

  


  What I need to do is

  


  

  1. Alter the overall gain of *1 to -7.5 dB

  


  2. Begin merging VO *2 at time m, while reducing the volume envelope of *1 by -11 dB. This is fixed based on the length of the intro.

  


  3. Fade everything out to -∞ dB around the end of *2

  


  4. Trim off the silence at the end.
For reference, the total length of the final track should be m+n.

  


  


  Unfortunately, I'm not versed enough with ffmpeg or sox to know exactly what I'm after here, and a lot of the examples tend to do one thing or another and aren't always clear when combining happens. I didn't get a lot of prior notice about this coming down the pipeline, so I'd like to get something relatively quick. We're able to do all of this stuff nicely in Adobe Audition (and I can do something similar in Audacity), but the idea is to automate it. For our envelope adjustments, we were just using linear ramps rather than smoothsteps, and that sounded fine.

  


  The TLDR : The VO track *2 governs how long the file winds up being, while audio bed *1 needs to be ducked when *2 begins, and the whole thing faded out right when *2 ends.

  


  We also have an automation system (radio station automation, specialized for something different than I need), so in a pinch if we have to just cut off the audio at the end of *2, we can get the fadeout from the radio automation system.

  


  I've been using the information at this link to some effect (specifically the bit about ffmpeg volumes), but it still isn't dynamic enough for the situation.
Envelope pattern in SoX (Sound eXchange) or ffmpeg

  


  Anyone have any advice on this one ? I've got Sox and ffmpeg available, and if need be I can probably install other tools as well.

  


• movenc : Allow to request not to use edit lists

  4 novembre 2014, par Martin Storsjö

  movenc : Allow to request not to use edit lists
  In this case, shift tracks to start from zero instead (potentially
  
  stretching the first sample in tracks that start later than the
  
  first one).
  Some software does not support edit lists at all, the adobe flash
  
  player seems to be one of these. This results in AV sync errors when
  
  edit lists are used to adjust AV sync.
  Some players, such as QuickTime, don’t respect the duration for
  
  audio packets, so if an audio track starts later than the video
  
  track and the first audio sample gets a duration longer than the
  
  actual amount of data in it, the result will be out of sync.
  Based on patches by Michael Niedermayer.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/movenc.c
  • [DBH] libavformat/movenc.h

• Samples RSS And Flashback Samples

  22 décembre 2011, par Multimedia Mike — Game Hacking, Python

  I made good on my claim that I would create an RSS feed for the samples repository.

  Here is the link to the samples RSS feed [ http://samples.mplayerhq.hu/samples-rss.xml ]. Also, here is the Python source code I threw together for the task.

  I just want to check : I’m not the only person who still relies on RSS these days, right ? The tech press has been cheerfully proclaiming its demise for some time now. But then, they have been proclaiming the same for Adobe Flash as well.

  I’m no expert in RSS. If you have any suggestions for how to improve the features presented in the feed, please let me know. And, of course, keep the samples coming. This script should help provide more visibility for a broader audience.

  Mario and Flashback Samples
  Thanks to LuigiBlood who sent in some samples that allowed me to test out my new script for automatically syncing the repositories and updating the samples RSS feed. First, there are CPC multimedia files from the Japanese 3DO port of Flashback : The Quest for Identity. Then, there is an Interplay MVE file on the CD version of Mario Teaches Typing in which the video doesn’t decode correctly.

  LuigiBlood also sent in another file from the latter game. It’s big and has the extension .AV. It could be a multimedia file as it appears to have a palette and PCM audio inside. But there’s no header and I’m a bit unsure about how to catalog it.