ffmpeg produced .wav reads only zeros with scipy.io.wavfile - ffmpeg

Question

Hi everyone and thanks for reading.
I wanted to do some analysis on a song using Python's scipy.io.wavfile. Since I only have the song as .mp3 I converted the file to .wav using ffmpeg the following way:
ffmpeg -i test.mp3 test.wav
The .wav file plays perfectly well with vlc player, but wavfile shows only zeroes when reading it:
from scipy.io import wavfile as wf
data = wf.read("test.wav")
C:\Program Files\Anaconda\lib\site-packages\scipy\io\wavfile.py:42: WavFileWarning: Unknown wave file format
warnings.warn("Unknown wave file format", WavFileWarning)
data
(44100, array([[0, 0],
[0, 0],
[0, 0],
...,
[0, 0],
[0, 0],
[0, 0]], dtype=int16))
I tried getting the data with Python's built-in wave module before to the same effect (only zeros).
I am using the 64bit version of ffmpeg (ffmpeg-20140218-git-61d5970-win64-static).
Any help is appreciated :-)
Edit: Included .wav header and tried forcing ffmpeg output format
I guess the header information of the .wav file is included here:
ffmpeg -i .\test.wav
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, wav, from '.\test.wav':
Metadata:
artist : Joe Cocker
copyright : (C) 1987 Capitol Records, Inc.
date : 1987
genre : Pop
title : Unchain My Heart
album : Unchain My Heart
track : 1/10
encoder : Lavf55.33.100
Duration: 00:05:04.33, bitrate: 1411 kb/s
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s
If I try to specify the ffmpeg output format explicitly for the .mp3 conversion:
ffmpeg -i .\test.mp3 -f s16le -ar 44100 -ac 2 test.wav
Input #0, mp3, from '.\test.mp3':
Metadata:
title : Unchain My Heart
artist : Joe Cocker
album : Unchain My Heart
genre : Pop
composer : Bobby Sharp
track : 1/10
disc : 1/1
album_artist : Joe Cocker
copyright : (C) 1987 Capitol Records, Inc.
date : 1987
Duration: 00:05:04.35, start: 0.025056, bitrate: 240 kb/s
Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 235 kb/s
Stream #0:1: Video: mjpeg, yuvj420p(pc), 600x600 [SAR 1:1 DAR 1:1], 90k tbr, 90k tbn, 90k tbc
Metadata:
title :
comment : Cover (front)
Output #0, s16le, to 'test.wav':
Metadata:
title : Unchain My Heart
artist : Joe Cocker
album : Unchain My Heart
genre : Pop
composer : Bobby Sharp
track : 1/10
disc : 1/1
album_artist : Joe Cocker
copyright : (C) 1987 Capitol Records, Inc.
date : 1987
encoder : Lavf55.33.100
Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (mp3 -> pcm_s16le)
Press [q] to stop, [?] for help
video:0kB audio:52425kB subtitle:0 data:0 global headers:0kB muxing overhead 0.000000%
size= 52425kB time=00:05:04.32 bitrate=1411.2kbits/s
But in this case (forced format), both ffmpeg and wavfile are not able to read the file:
ffmpeg -i .\test.wav
.\test.wav: Invalid data found when processing input
and
data = wf.read("test2.wav")
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-10-fbbd84cb966b> in <module>()
----> 1 data = wf.read("test2.wav")
C:\Program Files\Anaconda\lib\site-packages\scipy\io\wavfile.pyc in read(filename, mmap)
152
153 try:
--> 154 fsize = _read_riff_chunk(fid)
155 noc = 1
156 bits = 8
C:\Program Files\Anaconda\lib\site-packages\scipy\io\wavfile.pyc in _read_riff_chunk(fid)
98 _big_endian = True
99 elif str1 != b'RIFF':
--> 100 raise ValueError("Not a WAV file.")
101 if _big_endian:
102 fmt = '>I'
ValueError: Not a WAV file.

Answer 1

I encountered the same problem. This seems to be a bug in FFmpeg that was introduced in October 2011 that was fixed April 29, 2014 (5e7d21c7ad02e37caa1bcb50ab8ad64e7d7fb86c). FFmpeg versions more recent than 2.3 (July 16, 2014) should write WAVs that numpy can read without error.