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

  13 novembre 2019, par Bendzko

  I’m trying to catch chunks of an mp3 webstream and decoding 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.
  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 ?

• swscale : fix gbrap16 alpha channel issues

  3 août 2017, par James Cowgill

  swscale : fix gbrap16 alpha channel issues
  Fixes filter-pixfmts-scale test failing on big-endian systems due to
  
  alpSrc not being cast to (const int32_t**).
  Also fixes distortions in the output alpha channel values by copying the
  
  alpha channel code from the rgba64 case found elsewhere in output.c.
  Fixes ticket 6555.
  Signed-off-by : James Cowgill <James.Cowgill@imgtec.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libswscale/output.c
  • [DH] tests/ref/fate/filter-pixfmts-scale

• Python : How to decode a mp3 chunk into PCM samples ?

  30 mars 2021, par Bendzko

  I'm trying to catch chunks of an mp3 webstream and decoding them into PCM samples for signal processing. I tried to catch the audio via requests and io.BytesIO to save the data as .wav file.

  



  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 ?