TrueSpeech® Co-Processor
PRELIMINARY/CONFIDENTIAL
Version: 1.18
3.13
Record and Playback Volume
The CT8022 supports Host programmable record and playback volume controls. This enables internal digital
scaling of the input and output speech signal levels. The Host can elect to use fixed level settings during record in
situations where AGC operation is not desired (for example, high noise environments). In addition, AGC operation
is not appropriate in full duplex speech mode when the Acoustical Echo Canceller (AEC) is active, since the AGC
would interfere with the ability of the AEC to operate correctly. In particular, the AGC would operate to amplify the
canceled (attenuated) echo signal. Volume control is available in all record and playback modes including
G.711µ-law/A-law. In the case of G.711, use of the default 1.0 volume scaling provides bit-transparent pass-though
of data from the Host to the external G.711 serial CODEC chip.
3.14
DSVD
Digital Simultaneous Voice and Data is a protocol used to enable collaborative computing where voice conversation
and full-duplex data transfers occur simultaneously over a single telephone line via a high speed modem. Since the
data transfer rate achievable over a telephone line is limited, speech compression is required to make it possible to
send speech simultaneously with data. Applications for DSVD include application sharing, shared whiteboard and
interactive games.
3.15
Microsoft Windows Sound System
In addition to supporting playback and recording of compressed TrueSpeech data, the CT8022 can also playback and
record uncompressed data in 16-bit linear, 8-bit linear, 8-bit µ-law and 8-bit A-law formats. The 8-bit linear format
supports data in both signed and unsigned form (with or without most significant data bit inversion). This provides
true Windows Sound System (WSS) 8 bit .wav file compatibility. The CT8022 supports 8- and 16-bit 8 KHz, and
11 KHz Microsoft WAVE file mono formats making it an ideal low-cost device for speech enabling personal
computers and personal digital assistants (PDAs). The Microsoft WAVE file format also includes support for
storing of TrueSpeech 8.5 speech data, making it possible to directly exchange TrueSpeech 8.5 WAVE recordings
with WSS compliant PC’s. A software only TrueSpeech 8.5 encoder/decoder is a standard part of the Sound
Recorder application included with Windows 95.
Note: Sample rates other than 8KHz require that the CT8022 operate with an external A-to-D CODEC
capable of supporting the desired sample rate.
3.16
Data Compression/De-Compression Accelerator
The CT8022 can be used as a data compression accelerator. In addition to supporting real-time recording and
playback via external CODECs, the CT8022 can operate in a CODEC-less environment where it compresses 16-bit
linear speech data from the Host, returning the compressed data to the Host. Simultaneous compression and
decompression is supported. This enables the CT8022 to be used in a sound-card type environment where the
speech input and output channels are independent of the CT8022.
3.17
DTMF/Tone Generator
The DTMF/Tone generator can generate any single or dual frequency tone in the range of 300Hz to 3KHz. The
CT8022 has preset parameters for generating all 16 DTMF digits (0-9, *, #, and the hidden digits A, B, C, D) as well
as standard USA dial tone, busy signal, and ringing (ringback) tone. The preset parameters can be re-programmed
by the Host controller to generate any single or dual frequency tone combination. The relative level (twist) of dual
frequency tones can also be selected. The tone generator can be operated concurrently with the record/playback
speech operation. Tone generation is performed in the direction of the output speech by default, but can be
redirected to the compressed speech path using the loopback configuration.
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DSP GROUP, INC., 3120 SCOTT BOULEVARD CT8022A11AQC FW Revision 0118
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
All specifications are subject to change without prior notice.
ETC [ ETC ]
