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TECHNOLOGY SPOTLIGHT
Despite a growing surround mastering and production market for HDTV, audio
and DVD releases, the number of available encoding products is relatively
small. The ZP-100 from Zapex Technologies is a single PCI card solution
that provides high-quality Dolby Digital (AC-3), MPEG audio and linear
PCM stream encoding with a host of useful playback and encoding features
for optimizing audio quality.
 A
real-time encoder certified by Dolby Labs, the ZP-100 system is available
in either 5.1 or 2-channel (5.1-upgradable) versions. The unit consists
of a PCI card for real-time digitization, control software and a breakout
cable with four XLR AES/EBU digital inputs (channels 1-8). A stereo S/PDIF
input, SMPTE LTC input and S/PDIF (IEC 958) BNC and XLR plugs connect
the encoder’s output to a Dolby Digital and/or MPEG audio player.
An RS-422/232C adapter links the computer’s serial port to an external
transport for Sony 9-pin control.
As all DSP takes
place on the card, hardware needs are minimal: a Pentium II 233 or higher
processor running Windows NT Version 4.0 with Service Pack 3 or higher.
Other requirements include a PCM audio player for source PCM audio stream
playback and a Dolby Digital and/or MPEG audio decoder for monitoring.
The encoder’s integrated capture feature eliminates the cost of a
separate capture card. Capture file options include elementary stream,
with and without timecode (AC-3 disc file format), and IEC 958 stream
with/without timecode (.WAV file format). IEC 958 stream options include
professional 32-bit, Ch-1 16-bit, Ch-2 16-bit data packing and consumer
mode. The ZP-100 can simultaneously encode and capture either Dolby Digital
and PCM, or MPEG Audio Layer 2 and PCM, and the encoded bitstream can
be played immediately after capture. The unit offers a Region Save Editing
feature, which allows segments of a Dolby Digital, MPEG Audio or PCM stream
to be edited and saved as a separate file. A timecode-based batch encode
feature automatically applies a set of user-defined parameters to multiple
files, and the unit can be configured for manual, semi-automatic or automatic
encoding.
The software is divided into three applications: A GUI provides basic
setup for controlling and navigating the system, the encoding software
provides the means to adjust and store encoding parameters and a Playback
Tool utility includes sound peak wave display, region save and bitstream
analysis.
During encoding, the ZP-100 can operate in two modes. The File Capture
mode is for capturing a file to disk for later playback, such as in DVD
production. The Dynamic Encoding mode is used for creating parameter files
or doing Broadcast Encoding where a PCM source is encoded and played,
but not saved as a file. The system’s most powerful attribute is
the ability to change parameter values while the ZP-100 is encoding, providing
the user with instantaneous audible feedback while tweaking settings.
Adjustable AC-3 parameters include bitstream service type (standard “Complete
Main,” Emergency, Visually/Hearing Impaired, Voice Over/Karaoke,
etc.); sampling frequency; bit rate (56,000 to 640,000 bps); LFE channel
in/out; nominal down-mix levels of the surround and center channels; embedding
a Dolby Surround signal into the Dolby Digital stream; copyright bit setting;
dialog normalization; dynamic range compression (five presets); RF overmodulation
protection; main channel lowpass filter (mainly used to improve signal
quality at low bit rates); LFE lowpass filter (120Hz roll-off); DC filtering;
90° surround channel phase shift; -3dB surround attenuation (for theater
applications); de-emphasis and more. Features listed above are for current
ZP-100 systems offered, Version 4.0. The Zapex ZP-100 5-channel system
(card, software and interface cabling) is priced at $5,500.
Zapex Technologies Inc. (www.zapex.net),
distributed by Microboards Technology; 1721 Lake Drive, West Chanhassen,
MN 55317; 800/646-8881; 612/556-1600; fax 612/556-1620; www.microboardsproaudio.com.
Reprinted with permission from 
Magazine, August, 2000
© 2000, Intertec Publishing, A Primedia Company All Rights Reserved
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