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• Normalize audio, then reduce the volume in ffmpeg

  27 octobre 2014, par Steve Sheldon

  I have a question relating to ffmpeg. First here is the scenario, I am working on a project where I need to have some audio with a presenter talking and then potentially some background music. I also have the requirement to normalize the audio. I would like to do this without presenting a bunch of options to the user.

  For normalization I use something similar to this post :

  How to normalize audio with ffmpeg.

  In short, I get a volume adjustment which I then apply to ffmpeg like this :

  ffmpeg -i <input /> -af "volume=xxxdB" <output>
  
  </output>

  So far so good. Now let’s consider the backing track, it doesn’t want to be the same volume as the presenters voice, this would be really distracting, so I want to lower that by some percentage. I can also do this with ffmpeg, I could do it like this (example would set volume to 50%) :

  ffmpeg -i <input /> -af "volume=0.5" <output>
  
  </output>

  Using these two commands back to back, I can get the desired result.

  My question has two parts :

  1. Is there a way to do this in one step ?
  2. Is there any benefit to doing it in one step ?

  Thanks for any help !

• Native function in Vitamio

  1er août 2014, par hclee

  I am now looking the code beind the Vitamio (media framework) cause I want to know what API does it use to retrieve the buffer percentage/download rate and how it interect with the android OS to retrieve other information about the streaming video.

  But I realized that it does use some native functions which enable it use some code written in C/C++ language.

  I try to investigate on the C++ code but I don’t know where are they.
  I guessed they are stored inside the res/raw/librarm.so.
  I unzipped the file but all I can find is some machine code but what I want is the implementation of the native function.

  For example, I want to know the implementation of the following function :

  public native int getVideoTrack() ; // What is this function for ? What does it mean by the track
  // number of a straming video ?

  or

  private static native boolean loadFFmpeg_native(String ffmpegPath) ;

  and when will this function be called :

  private static void postEventFromNative(Object mediaplayer_ref, int what, int arg1, int arg2, Object obj)

  Do anyone know where can I investigate the implementation of such native function.
  It should be some C++ code but I don’t want machine code...

  I went to
  https://www.vitamio.org/en/2013/Tutorial_0509/13.html

  but they didn’t have the thing that I want

  Thanks in advance !!!

• Android HLS : Any way to edit the m3u8 file so that I know which segment is currently streaming/playing in my player using HLS

  1er août 2014, par hclee

  I am now working on a VOD project using HLS.

  I use the VideoViewBuffer in VitamioDemo to stream my video that is stored in my local server.
  The Vitamio library is awesome that I am able to stream the video, getting the bit rate, buffering percentage and some metadata.

  We use ffmpeg to convert the video into m3u8 and the corresponding ts files.
  But now our team want to know which segment (which ts file) of the video the HLS is currently streaming.

  That’s a very important part in our project but we get stuck in this point.

  I tried to use the MediaMetadata in Vitamio but only the Duration of the video is found.
  I am wondering if we can add some metadata in the m3u8 file so that we can retrieve the name of the current segment during streaming.
  eg :
  The original m3u8 is like this :
  #EXTINF:10.500000,
  stream00000.ts

  Is it possible for me to change it as follows :
  #EXTINF:10.500000, name of segment
  stream00000.ts

  But all I can get using MediaMetaDataRetriever is null except for the duration.

  It seems that no body have done this before so I can’t find any very useful information about this.

  Do anybody how to implement this ?
  Or should I use some packet sniffer to monitor the network traffic by myself ?
  Or Would MediaScanner be helpful ?
  Or I need to use code in android.os ?

  Thanks in advance !