DOCUMENT:Q63347  06-NOV-1999  [win16sdk]
TITLE   :PRB: Clicking Noises While Playing Sounds on SoundBlaster Card
PRODUCT :Microsoft Windows Software Development Kit
PROD/VER:WINDOWS:3.0,3.1
OPER/SYS:
KEYWORDS:kb16bitonly

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The information in this article applies to:

 - Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1 
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SYMPTOMS
========

While playing some sounds on earlier models of the SoundBlaster card, some
periodic popping or clicking sounds may occur. These cards are generally
referred to as the 1.0 DSP (digital sound processing) design. Cards using the
version 2.0 DSP design can use version 1.5 of the SoundBlaster Multimedia Device
Driver (SNDBLST2.DRV), which eliminates this situation.

CAUSE
=====

This problem generally occurs only when running under enhanced mode Windows. It
is a result of the current design of the SoundBlaster hardware, in conjunction
with the interrupt latency inherent in enhanced mode Windows.

The SoundBlaster uses DMA (direct memory access) to transfer small pieces of the
sound data from main memory to the card, and generates a hardware interrupt only
when its buffer becomes empty. Upon receipt of this interrupt, the SoundBlaster
driver prepares the next piece of sound data and initiates another DMA transfer.
This process continues until the sound has been completely played out.

When running in Windows enhanced mode, the interrupt latency is often more than a
few sample periods, which results in the noises discussed earlier.

RESOLUTION
==========

Creative Labs has corrected the problem with version 2.0 DSP along with version
1.5 of the Sound Blaster Multimedia Device Driver. In addition, the new card
from Creative Labs, the Sound Blaster Pro, does not exhibit the clicking
problem. Contact Creative Labs to update earlier Sound Blaster cards to version
2.0 DSP.

For testing purposes, this problem can be resolved by running in Windows standard
mode, where interrupt latencies are lower.

Additional query words: 3.00 3.10 no32bit

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Keywords          : kb16bitonly 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300 kbWinSDK310
Version           : WINDOWS:3.0,3.1

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