[wdmaudiodev] Re: Kernel streaming question
- From: Tim Roberts <timr@xxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Tue, 23 Jun 2009 17:26:13 -0700
Pallavi Joshi wrote:
> I am feeding the data using DeviceIoControl with IOCTL_KS_WRITE_STREAM
> as the control code. The render pin is created using the KsCreatePin
> function from ksuser.dll. The buffer size is 512 and it is a 2
> channel, 16 bit PCM audio data. The sampling rate is 44.1 KHz.
> Its exactly the same way as it is done inside the DirectKS sample code.
> I do not know what you mean by two things: "timing" and "mismatch in
> data performance"?
Well, I wrote "data performance" when I really meant "data format"...
Are you sure that your USB device accepts 44100 stereo 16-bit PCM? (It
probably does -- it's a common format.)
An audio device is a real-time device. It consumes data continuously.
If you don't have more data in the queue when it runs out, the device
will "starve", and you get a short period of silence, which makes the
sound choppy. A 512-byte buffer will only keep your device fed for 3
ms. Are you sending multiple buffers down so that the device never
starves? How do you guarantee that there is always data waiting? Timer
callback?
--
Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.
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