[Speex-dev] Obtaining loudness information in 1.2beta2

Jean-Marc Valin jean-marc.valin at usherbrooke.ca
Thu Oct 25 17:20:23 PDT 2007

Mihai Balea wrote:
> What would be a good parameter to return that would better represent the 
> loudness of the signal?
> As for the your other comments, I'll make the necessary changes and 
> resubmit.

Could just be to first take the 5th root, a bit like in the code.


> Thanks,
> Mihai
> On Oct 25, 2007, at 7:45 PM, Jean-Marc Valin wrote:
>> I'm in favor of the idea, but not of the current implementation. There
>> are two problems:
>> 1) The st->loudness parameter doesn't represent the amplitude of the
>> signal, but the amplitude^5 (fifth power). That makes it hard to use
>> 2) The call returns a float, but it should really be an int
>> (spx_int32_t) so that it can work easily with fixed-point code
>> There's a last minor thing: instead of SPEEX_PREPROCESS_GET_LOUDNESS, it
>> should be called SPEEX_PREPROCESS_GET_AGC_LOUDNESS. If you can send me a
>> patch that addresses these issues, I'll gladly apply it.
>>     Jean-Marc
>> Mihai Balea wrote:
>>> Hi all,
>>> I'm working on a project called iaxclient
>>> (http://sourceforge.net/projects/iaxclient).
>>> We use speex for the majority of our audio processing, including voice
>>> compression and processing.
>>> One of the features of iaxclient is Analog AGC, which drives the
>>> hardware mixer levels based on signal loudness.  Up until 1.2beta1, we
>>> were able to access the internals of the SpeexPreprocessState structure
>>> to get loudness information, but, of course, that is no longer possible
>>> with 1.2beta2.  I would like to propose an addition to the preprocessor
>>> control interface that exposes that parameter.  I'm attaching a patch
>>> that contains the proposed change.
>>> I'm looking forward to any comments and suggestions.
>>> Cheers,
>>> Mihai
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