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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).

• Stream Internet radio using ffmpeg

  2 juillet 2022, par Hadi M.NourAllah

  i am a beginner at IOS Development now i make app that streaming internet and there was a problem that there is extinction that ios not support like .asf and .rm and there prifx that ios not support too like mms :// so after a lot of searching a lot of people told me that "use ffmpeg" and after a lot of wasted time i successfully build ffmpeg to my xcode now i am stuck because i don't how i use it .
so could any one tell me how can i use it please don't tell me use IFrameExtrator because i tried and i failed.

  


• Solution for VB6 to broadcast Webcam

  11 juillet 2014, par vantrung -cuncon

  Sorry, I know VB6 is decades ago, but I’m in a situation that I have to use VB6 to deliver live webcam stream beetween 2 PC in Server - Client Model program. Vb6-code holds the connection then I have no choice but to transfer all data via that connection.

  I’ve tried weeks for this, uncountable approaches but went to nowhere.
  My efforts focused on 3 major approaches :

  1/ Use ffmpeg to record live webcam as ".avi" file on hard disk, transfer parts of file to other end & play it. But I’ve stucked with a media-player that can play a "being written" avi file.

  Windows Media Player control told me "file already in use..." & VLC Plugin can’t even be added to VB6 (axvlc.dll).

  2/ Use ffmpeg to save live webcam as avi file, transfer each bit of that file to the other end, then in other end, extract 24 images / second from the avi to display continously in a picture box.
  This approach is ok except that my hard disk get fulled of images in a time of wink and my program get very slow before hanging.

  3/ Use ffmpeg to stream the live webcam to a rtp-port like this :

  ffmpeg -f dshow -i video="Lenovo EasyCamera" -vcodec mpeg2video -pix_fmt yuv422p -f rtp -an rtp://224.1.2.3:8191

  I’ve successfully watch the stream in VLC, but VLC(axvlc.dll) refused to be integrated into ancient VB6. And more important, I don’t know how to redirect/reroute the rtp stream to other PC with VB6.

  Any one please light me up ? (Any 3rd party component is welcomed)