Re[Openal] altime filtering for OpenAL

[Daniel PEACOCK]

Hi,

I think it would be helpful to break this problem down a bit.

Is this what you are doing ...

Capturing Audio from OpenAL
Running your filter on the captured audio
Playing / saving the resulting audio

To determine where the noise is being introduced you could try writing the
raw audio data to disc after each stage for off-line analysis.

It maybe, for example, that the captured audio includes a DC offset that is
present even when the recording level is 0 and this causes some unwanted
side-effects in the filtering process.  Or, perhaps there is a bug in the
filter code (you have to watch out for de-normals and underflows), or maybe
OpenAL itself is somehow distorting the output when you play the filtered
audio back.

Dan
Creative Labs, UK

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Hello,

I'm writing a "realtime" filtering module to implement a vocoder later.
The point is that the filters frecuency behaviour seems to be almost right
but I'm getting a lot of noise when applying them.

I'm using an IIR DTF-II filter with 3 biquad sections, in order to avoid
overflow, running over the capture with queue routine for openAL.

The program is returning noise even with the windows recording level set to
zero. But it returns no output when I fill the input vector with 0's.

The question is, does anybody knows a realtime IIR filter code write in C++
for using with OpenAl?

Any suggestions and answers will be appreciated.

Thanks!
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