[Speex-dev] Clicking Problems with slightly clipped audio

marzullo maio marzullo63 at yahoo.it
Wed May 23 07:41:51 PDT 2007

I've the same problem using the FIXED_POINT version.
Platforms: ARM HTC tytn with WM 5.0 and ARM  i-mate jasjar WM 5.0
The same problem on both devices.

If you need i could record what i hear on my device.
Dividing by 2 worked well for me.
Adding the following C++ lines before feeding the encoder with PCM apparently solved the problem:

void Encoder::normalizeRange(spx_int16_t* audioBuf) 
         DWORD i; 
         for(i = 0; i < SAMPLES_PER_BLOCK; ++i) 
                 *audioBuf++ = (*audioBuf >> 1); // +- 8192

Anyway i think this is the dirty solution but at least it works.
I can't low the microphone gain on my devices and cannot use AGC since it isn't converted to FIXED_POINT yet, so i've no choice other than that dirty solution.
Asking on xda developers, nobody has found a way to lower the mic gain.
Even the OEM is keeping it secret. I'll switch to develop for linux pda as soon
as i can.


"Coffey, Michael" <mcoffey at avistar.com> ha scritto:         st1\:*{behavior:url(#default#ieooui) }           It appears that both the echo canceller and the noise reducer (NR) introduce rather severe clicking artifacts when presented with audio that has slightly overloaded the A/D converters. I am talking about speech that sounds just slightly distorted, due to clipping, when simply played back. If I pass that speech through the echo canceller or the noise reducer, it acquires really loud clicks and/or scratchiness in high amplitude sections.
  Granted, it would be best if I could avoid any clipping in the first place. A problem, though, is that we can not control end user behavior and it is quite common for them to have their audio settings slightly out of adjustment.
  I’ve found a workaround, which is to divide everything by two before sending it to the AEC or NR.
  Is this a known problem? Would it be helpful for me to send a couple of .wav files to illustrate?
  Thanks again for the great contributions.
Speex-dev mailing list
Speex-dev at xiph.org


L'email della prossima generazione? Puoi averla con la nuova Yahoo! Mail
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.xiph.org/pipermail/speex-dev/attachments/20070523/e149b47b/attachment.htm

More information about the Speex-dev mailing list