[pulseaudio-discuss] Weird data flow (not waveform)

José Tomás Tocino García theom3ga at gmail.com
Tue Jun 15 11:49:49 PDT 2010

I think that's not the problem, because Gnuplot does not expect a
exact format, it renders whatever it gets.

The thing is, a usual waveform gets positive and negative values all
the time. Sometimes that's what some DSP algorithms use to measure
frequency, but given the stream has this weird representation, they do
not work. That's what bugged me in first place, so I used gnuplot to
visually check the waveform.

Isn't is supposed to be a PCM waveform?

2010/6/15 David Henningsson <launchpad.web at epost.diwic.se>:
> On 2010-06-15 20:19, José Tomás Tocino García wrote:
>> Hi, I'm using the Pulseaudio Simple Api to get the microphone input.
>> It works ok, because I can hear exactly what I say on the mic if I
>> open an output stream, but if I dump the audio stream to a file and
>> then plot it (using gnuplot for instance), it's got nothing to do with
>> a waveform. I realized so when I was trying to apply a FFT to the read
>> stream, I was getting weird results.
> Have you checked that the sample format is matched? E g if the output
> from PA is 16 bit signed and gnuplot is expecting floating-point, or
> perhaps the other way around.
> // David
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José Tomás Tocino García

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