[wdmaudiodev] Re: Audio data conversion in apps?
- From: Matt Gonzalez <matt@xxxxxxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Mon, 23 Sep 2002 11:42:34 -0700
Hi Chris-
Cool Edit uses the wave API for hardware access; for WDM, the wave API sits on
top of the kernel mixer. The kernel mixer is changing your data.
You can read more about this here:
http://www.microsoft.com/hwdev/tech/audio/wdmaudio.asp
Matt
Chris Edgington wrote:
> Hello. I'm new to the WDM audio world. I'm working with a device that
> really isn't an audio device, it's a conduit for transporting audio
> data. I've been tasked with debugging some problems with the audio
> driver written for the device. One problem I have is that of audio data
> manipulation by applications. I'm using CoolEdit for my testing, on
> Win2K. In order to have a known dataset, I created a binary file full of
> 0xB0 values. I then imported that file as raw PCM into CoolEdit, as 8bit
> unsigned data. The driver is configured to receive 8bit data. So, I
> expected to receive all 0xB0 values when playing back the file through
> the driver. But, I receive 0x99 instead of 0xB0. After hitting stop, the
> driver gets a string of 0x80 values, I assume to silence things out
> (since 0x80 is silence in 8bit unsigned world). Anybody know what
> parameters / algorithm is being used for the data conversion and why
> CoolEdit is not sending me the 0xB0 I imported? I also tried this with
> Audacity, the open-source app for windows. It send 0x9B instead of 0xB0.
> I'm going to start reading through the source for it to see how it goes
> from my imported data to what it sends me .... but thought I'd ask here
> to see if someone can explain.
>
> Thanks,
> -Chris
>
> Awesome Software & Consulting
> http://www.thatsawesomesoftware.com
>
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