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• How to synchronise two audio files using a marker

  30 juillet 2014, par Dimitri Jorge

  I’m working on a project on which we use WebRTC and the RecordRTC library to record audio files.

  I would like to be able to process the audio files server-side to ensure a good synchronisation.

  To do so, I’m thinking about marking the start of each record with an inaudible sound marker in order to analyse new records and then manipulate the starting offset with ffmpeg (which I already use to compress the raw files created by RecordRTC).

  The thing is I’ve never done any advanced audio processing before, I’m looking around and cannot find what would be the proper way to do this.

  Is there another, better, way to handle synchronisation ? And if not, I would be grateful if I could get some tips on the marker technique.
  Thank you.

  Edit :
  I forgot to mention for those who don’t know how RecordRTC works that the record is done client-side in Javascript. The synchronisation issue comes from the fact that javascript is not good at synchronising calls.

  The process is done as follow :

  1) A user records himself

  [User 1] -> Records on his browser an audio file
  
     |
  
     | Saves raw audio file (call it audio_1.ogg)
  
     |
  
  [Server]

  2) Another user wants to join user_1’s project

  [User 2]  <--- Fetch audio_1.ogg (in an audio html tag) --- [Server]
  
     |
  
     | Press record
  
     |
  
  [Webapp] -> Plays audio_1.ogg and starts recording audio_2.ogg
  
     |
  
     | Saves audio_2.ogg when record is over
  
     |
  
  [Server]

  The synchronisation issue comes from the fact that there are no way in Javascript to ensure that both the functions handling that starts record and the one responsible for beginning playing the existing audio file happen on the same time.

  I end up with 50/100 ms of gap depending on how many audio files are already on the project (since it’s not limited to two).

• Use global namespace to refer to all imagick variables and classes.

  14 mai 2014

  Use global namespace to refer to all imagick variables and classes.
  Fixes issues where a user might use this UploadHandler within a PHP
  
  namespace.
  Fix minor capitalization errors that will cause imagick to fail when run
  
  on *nix box, where those names are case sensitive.
  Add a check that the uploaded file is in fact an image before trying to
  
  extract its image size, which would cause an error otherwise.
  

• ffmpeg filter in my own application

  26 juin 2018, par user25571

  How can I use one of filters from ffmpeg library in my own application. In fact, I only wanna detect silence in my audio files and so I must use af_silencedetect.c file. This file is one of ffmpeg filters that can be utilized with -af silencesetect command.

  Therefore my obvious question is : "What’s step-by-step procedure in using this file in my own application and which dependencies I must add to my MSVC project ?"

  Your points are appreciated in advance ....