Fons, Thanks for your reply. Yes, the format is U8, it is a simple recording program to make '.wav' files. The filtering does work when adjusting the 'silence byte'. It appears that the device drivers are not consistent with this value? So I will be adding an option to change the value of the 'silence byte'. How do I use the RMS value to remove noise? A URL that I could read? Thanks again for your time. -- William Estrada MrUmunhum@xxxxxxxxxxx Mt-Umunhum-Wireless.net ( http://Mt-Umunhum-Wireless.net ) Ymessenger: MrUmunhum > Message: 6 Date: Mon, 22 Oct 2007 08:53:34 +0200 From: Fons Adriaensen > <fons@xxxxxxxxxxxxxxx> Subject: Re: USB device gives wrong data? To: > linux-audio-user@xxxxxxxxxxxxxxxxxxxx Message-ID: > <20071022065334.GB5840@xxxxxxxxxxxx> Content-Type: text/plain; > charset=us-ascii On Fri, Oct 19, 2007 at 02:44:08PM -0700, william estrada > wrote: >>> When I use my laptop's sound device and record without a mic, I get a >>> file full of x'7f's. If I do the same with my cheap-o USB device I get a >>> file full of x'81's. The sound quality from the laptop is unacceptable, >>> so that is way I want to use the USB device. > > Those values are somewhat confusing - your device doesn't produce 8-bit > samples, does it ? > > A 'perfect' interface would probably produce zeros on silence. You may be > seeing a small DC offset. > > Anyway, silence detection based on one particular sample value can't be > expected to work well, there will always be _some_ noise. Better calculate > the RMS amplitude and set a threshold on that. > > -- FA Laboratorio di Acustica ed Elettroacustica Parma, Italia Lascia la > spina, cogli la rosa. _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
