Sorry,But the price of developer version of VAC is $4000, I'm live in China,This need full year income of mine, mabye after I make this software,I will have enough money to pay the VAC, But I need vac only before I make the software,so ...... because My software will run at all windows versions after windows 98/2000, so the LFX APO seem not to be the best choice. if VAC's price not more than $300 I will buy it. The VAC worth $4000,but I can not afford it. Thank you. ----- Original Message ----- From: Tim Roberts To: wdmaudiodev@xxxxxxxxxxxxx Sent: Friday, June 26, 2009 8:41 AM Subject: [wdmaudiodev] Re: How to filter microphone voice? kevinrich47 wrote: Thank you Tim,What I want is not change voice for single app,but for all application on the machine, I have consider Virtual Audio Cable,But the price is not affordable for me. Oh, come on! There's a free version with some features limited for you to try out, and the full version is only $30. If you have not done audio drivers before, it will save you MONTHS of frustration. If you are working on Vista, you can write a Local Effects Audio Processing Object (LFX APO) to do this. This is a user-mode DLL that lives in the the audio engine process. There is a sample in the WDK in src\audio\sysfx. It's a little bit tricky to get one installed to begin with, but there are documents available to help with that. -- Tim Roberts, timr@xxxxxxxxx Providenza & Boekelheide, Inc.