Sound Blaster: 1 Digitized Voice Channel Feature

• Microsoft Windows with Multimedia Extensions version 1.0
• Microsoft Windows operating system version 3.1

SUMMARY

This article discusses the 1 Digitized Voice Channel feature of the Sound Blaster card hardware and how it works with Windows with Multimedia Extensions or Windows version 3.1.

MORE INFORMATION

The 1 Digitized Voice Channel is referred to as sampled sound, digitized sound, and so forth. The Sound Blaster refers to it as a digitized voice, which is NOT the same as the voices mentioned above. Multimedia Extensions to Windows calls this digitized sound output "waveform output," which is confusing because all sound is comprised of waves. Digital enthusiasts call this pulse code modulation (PCM), which is actually a more accurate title.

Digitized sound is real sound (human voice, music, effects, and so forth) that is sampled and digitized with a digital-to-analog converter (DAC). This is the same type of data stored on audio compact discs (CDs); however, CDs have a much greater resolution both in sample rate (44.1 kHz) and sample word size (12 to 16 bits).

PCM is a simple technique of encoding analog audio in a digital format, where the waveform amplitude is sampled periodically (at the sampling frequency) and stored as a number. The term "8 bit" means that the stored number can have one of 256 discrete values; 12 bit has 4096 discrete values; and 16 bit has 65535.

The Sound Blaster has one mono 8-bit DAC that can be set to a sample rate between ~4 kHz and ~23 kHz. This does not produce very high quality but it can be fun none the less.

Incidentally, this is where that 24th voice of the Sound Blaster version 1.0 card came from: 12 C/MS (creative music synthesizer) + 11 FM (frequency modulation) + 1 DAC = 24. This is misleading.

Multimedia Extensions to Windows requires a minimum of 11 kHz and 22 kHz 8-bit wave output, which the Sound Blaster can do.

The Sound Blaster supports three different adaptive differential pulse code modulation (ADPCM) decompression ratios (as well as no compression) in hardware. Below is a list of these ratios:

• 2 to 1 data compression: 4 bit ADPCM
• 3 to 1 data compression: 2.6 bit ADPCM
• 4 to 1 data compression: 2 bit ADPCM

Multimedia Extensions to Windows does not make use of ADPCM at this time.

Sound Blaster is manufactured by Creative Labs, a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.