Hello Jean-Marc, I did some experiments with the fixed-point version of the resampler in SVN. Basically it works very well, great work! But I experienced a problem when upsampling audio data with slight clipping. This seems to cause an overflow somewhere, resulting in "cracks" in the output. I'm aware that the resampler hasn't been released yet, but I wanted to mention it. :-) Daniel
I'll look into this. There's basically no overflow prevention for now. I'll think about how to add that without affecting performance too much (on CPUs that don't have hardware saturation). I'm open to suggestions :-) Jean-Marc Daniel Schmidt a ?crit :> Hello Jean-Marc, > > I did some experiments with the fixed-point version of the resampler > in SVN. Basically it works very well, great work! > But I experienced a problem when upsampling audio data with slight > clipping. This seems to cause an overflow somewhere, resulting in > "cracks" in the output. > I'm aware that the resampler hasn't been released yet, but I wanted to > mention it. :-) > > Daniel > _______________________________________________ > Speex-dev mailing list > Speex-dev@xiph.org > http://lists.xiph.org/mailman/listinfo/speex-dev > >
Hello Jean-Marc, thank you for your answer!> I'll look into this. There's basically no overflow prevention for now. > I'll think about how to add that without affecting performance too much > (on CPUs that don't have hardware saturation). I'm open to suggestions :-)I'm not sure if I can really help, but I did a few more tests. Reducing the volume of the input signal by 6 dB and increasing it again afterwards with saturation seems to avoid the overflow even with heavy clipping. So using 14 fractional bits internally instead of 15 and doing the saturation right before converting to the 16 bit output sample value could help. But certainly there are more sophisticated solutions to this problem. :-) During the tests I encountered another problem. While upsampling a continuous ?6 dB sine from 8000 Hz to 11025 Hz I heard that the resampler produces a click every 5 seconds. After changing the output sample rate to 11000 Hz the clicking disappeared. Daniel