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• Python : How to convert a mp3 chunk from webstream to .wav samples ?

  13 novembre 2019, par Bendzko

  I’m trying to catch chunks of an mp3 webstream and coverting them into wav samples for signal processing. I tried to catch the audio via requests and io.BytesIO to save the data as .wav file.
  But I think, that I have to convert the mp3 data to wav data, but I don’t know how. (My goal is not to record a .wav file, i am just doing this to test the algorithm.)

  I found the pymedia lib, but it is very old (last commit in 2006), using python 2.7 and for me not installable.

  Maybe it is possible with ffmpeg-python, but I have just seen examples using files as input and output.

  Here’s my code :

  import requests
  
  import io
  
  import soundfile as sf
  
  import struct
  
  import wave
  
  import numpy as np
  
  
  
  
  
  def main():
  
      stream_url = r'http://dg-wdr-http-dus-dtag-cdn.cast.addradio.de/wdr/1live/diggi/mp3/128/stream.mp3'
  
      r = requests.get(stream_url, stream=True)
  
      sample_array = []
  
      try:
  
          for block in r.iter_content(1024):
  
              data, samplerate = sf.read(io.BytesIO(block), format="RAW", channels=2, samplerate=44100, subtype='FLOAT',
  
                                         dtype='float32')
  
              sample_array = np.append(sample_array, data)
  
  
  
      except KeyboardInterrupt:
  
          print("...saving")
  
          obj = wave.open('sounds/stream1.wav', 'w')
  
          obj.setnchannels(1)  # mono
  
          obj.setsampwidth(2)  # bytes
  
          obj.setframerate(44100)
  
  
  
          data_max = np.nanmax(abs(sample_array))
  
  
  
          # fill WAV with samples from sample_array
  
          for sample in sample_array:
  
              if (np.isnan(sample) or np.isnan(32760 * sample / data_max)) is True:
  
                  continue
  
              try:
  
                  value = int(32760 * sample / data_max)  # normalization INT16
  
              except ValueError:
  
                  value = 1
  
              finally:
  
                  data = struct.pack('code>

  Do you have an idea how to handle this problem ?

• Revision 28933 : on bouge

  31 mai 2009, par ben.spip@… — Log

  on bouge

• Using FFmpeg in .net ?

  17 juin, par daniel

  So I know its a fairly big challenge but I want to write a basic movie player/converter in c# using the FFmpeg library. However, the first obstacle I need to overcome is wrapping the FFmpeg library in c#. I've downloaded ffmpeg but couldn't compile it on Windows, so I downloaded a precompiled version for me. Ok awesome. Then I started looking for C# wrappers.

  



  I have looked around and have found a few wrappers such as SharpFFmpeg (http://sourceforge.net/projects/sharpffmpeg/) and ffmpeg-sharp (http://code.google.com/p/ffmpeg-sharp/). First of all, I wanted to use ffmpeg-sharp as its LGPL and SharpFFmpeg is GPL. However, it had quite a few compile errors. Turns out it was written for the mono compiler, I tried compiling it with mono but couldn't figure out how. I then started to manually fix the compiler errors myself, but came across a few scary ones and thought I'd better leave those alone. So I gave up on ffmpeg-sharp.

  



  Then I looked at SharpFFmpeg and it looks like what I want, all the functions P/Invoked for me. However its GPL ? Both the AVCodec.cs and AVFormat.cs files look like ports of avcodec.c and avformat.c which I reckon I could port myself ? Then not have to worry about licencing.

  



  But I want to get this right before I go ahead and start coding. Should I :

  



  

  1. Write my own C++ library for interacting with ffmpeg, then have my C# program talk to the C++ library in order to play/convert videos etc.

  


  



  OR

  



  

  2. Port avcodec.h and avformat.h (is that all i need ?) to c# by using a whole lot of DllImports and write it entirely in C# ?

  


  



  First of all consider that I'm not great at C++ as I rarely use it but I know enough to get around. The reason I'm thinking #1 might be the better option is that most FFmpeg tutorials are in C++ and I'd also have more control over memory management than if I was to do it in c#.

  



  What do you think ?
Also would you happen to have any useful links (perhaps a tutorial) for using FFmpeg ?