[server and core] waveform returns lists min and max with zeros or bands of zeros

[Tointoin]

/timeside/api/items/07836d4f-72d0-4a66-a076-f6f06cce572c/waveform/
return a waveform with min values all at -4.203895392974451e-45 and max all at 0.0.

Same case for many items recently generated (selection tests_DALI_yt).

[Tointoin]

With a few log on waveform serializer code:

result_id = 'waveform_analyzer'
        wav_res = h5py.File(result.hdf5.path, 'r').get(result_id)

        duration = wav_res['audio_metadata'].attrs['duration']
        server_logger.info(f'duration: {duration}') # LOGGING DURATION
        samplerate = wav_res['data_object'][
            'frame_metadata'].attrs['samplerate']
        server_logger.info(f'samplerate: {samplerate}') # LOGGING SAMPELRATE

        ...

        sample_values = np.round(self.time_values * samplerate).astype('int')

        for i in range(self.nb_pixels):
            values = wav_res['data_object']['value'][
                sample_values[i]:sample_values[i + 1]]
            if i < 10:                           # LOGGING 10 FIRST 
                server_logger.info(str(values))  # SAMPLE VALUE
            if values.size:
                self.min_values[i] = np.min(values)
                self.max_values[i] = np.max(values)

I get quite normal log on a deezer preview 30 sec mp3 file:

INFO 2020-03-31 19:11:15,232 serializers duration: 30.72
INFO 2020-03-31 19:11:15,233 serializers samplerate: 44100
INFO 2020-03-31 19:11:15,236 serializers [[ 0.15071355  0.05970893]
 [ 0.15789996  0.05962876]
 [ 0.16633978  0.05551996]
 ...
 [ 0.07510374 -0.04883934]
 [ 0.08088862 -0.04893086]
 [ 0.08825559 -0.04394966]]
INFO 2020-03-31 19:11:15,238 serializers [[ 0.09382088 -0.04255066]
 [ 0.09762768 -0.04794458]
 [ 0.10366786 -0.05218805]
 ...
 [ 0.05083828  0.04840193]
 [ 0.04840099  0.03691421]
 [ 0.04771852  0.02911852]]
INFO 2020-03-31 19:11:15,239 serializers [[0.04112494 0.0286877 ]
 [0.02681965 0.031142  ]
 [0.02052411 0.03037054]
 ...
 [0.         0.        ]
 [0.         0.        ]
 [0.         0.        ]]
INFO 2020-03-31 19:11:15,240 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]
INFO 2020-03-31 19:11:15,241 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]
INFO 2020-03-31 19:11:15,242 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]
INFO 2020-03-31 19:11:15,243 serializers [[0.         0.        ]
 [0.         0.        ]
 [0.         0.        ]
 ...
 [0.04067133 0.06245746]
 [0.0208528  0.06156785]
 [0.00379307 0.06160603]]
INFO 2020-03-31 19:11:15,244 serializers [[-0.01233356  0.05503304]
 [-0.02923564  0.05084599]
 [-0.03813753  0.06220904]
 ...
 [ 0.2581892   0.04209551]
 [ 0.25444093  0.04515055]
 [ 0.2494465   0.05317261]]
INFO 2020-03-31 19:11:15,245 serializers [[0.23985252 0.04020593]
 [0.23169126 0.02527791]
 [0.22214812 0.02236784]
 ...
 [0.         0.        ]
 [0.         0.        ]
 [0.         0.        ]]
INFO 2020-03-31 19:11:15,246 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]

but empty sample value on a 270 sec youtube .m4a file:

INFO 2020-03-31 19:22:53,549 serializers duration: 270.7219954648526
INFO 2020-03-31 19:22:53,550 serializers samplerate: 44100
INFO 2020-03-31 19:22:53,552 serializers [[ 0.  0.]
 [-0. -0.]
 [ 0.  0.]
 ...
 [ 0.  0.]
 [ 0.  0.]
 [ 0.  0.]]
INFO 2020-03-31 19:22:53,553 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]
INFO 2020-03-31 19:22:53,555 serializers [[ 0.  0.]
 [ 0.  0.]
 [ 0.  0.]
 ...
 [ 0.  0.]
 [-0. -0.]
 [ 0.  0.]]
INFO 2020-03-31 19:22:53,556 serializers [[-0. -0.]
 [ 0.  0.]
 [-0. -0.]
 ...
 [ 0.  0.]
 [ 0.  0.]
 [ 0.  0.]]
INFO 2020-03-31 19:22:53,557 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]
INFO 2020-03-31 19:22:53,558 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]
INFO 2020-03-31 19:22:53,560 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]
INFO 2020-03-31 19:22:53,561 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]
INFO 2020-03-31 19:22:53,563 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]
INFO 2020-03-31 19:22:53,565 serializers [[0. 0.]
 [0. 0.]
 [0. 0.]
 ...
 [0. 0.]
 [0. 0.]
 [0. 0.]]

And same empty values on .opus from other item from youtube (also around 4 / 6 minutes long).

Audio files are ok.

@yomguy , @piem
Does Aubio decode any format?

[piem]

Does Aubio decode any format?

yes, well, any format supported by libav when aubio is built with it.

also, an exception should be raised if reading the file failed.

[Tointoin]

New problem detected with items that seemed to be ok:
player example on a sweep
player example on a 30 sec Deezer Preview
It returns frames of zeros and frames with normal waveform values

[Tointoin]

These bug seems to be provoked by use of Aubio decoder on server as default: I tried before and after commit 0286c7f.

@yomguy, do we use gst decoder on sandbox for @gnuletik's player development until we fix it?

[yomguy]

These bug seems to be provoked by use of Aubio decoder on server as default: I tried before and after commit 0286c7f.

OK, could you please provided the output of the Result data on the same Item using each decoder so that we could compare?

@yomguy, do we use gst decoder on sandbox for @gnuletik's player development until we fix it?

Yes, let's switch back and see what happens..