Version: 1.18
PRELIMINARY/CONFIDENTIAL
TrueSpeech® Co-Processor
3.6
TrueSpeech 5.3 (G.723.1)
In TrueSpeech 5.3, data is compressed into 10-word blocks. This provides 160 bits per block. However, only 158
bits per block are used for actual speech data, giving a raw data rate of 5,266.67 bits/sec. When used in compliance
with G.723.1, the two spare bits are used for control information. The 5.3 rate can be operated in conjunction with
the VAD/CNG silence compression feature.
3.7
TrueSpeech 4.8
In TrueSpeech 4.8, data is compressed into 9-word blocks. This provides 144 bits per block. However, only 142
bits per block are used for actual speech data, giving a raw data rate of 4733.33 bits/sec. The 4.8 rate can be
operated in conjunction with the VAD/CNG silence compression feature.
3.8
TrueSpeech 4.1
In TrueSpeech 4.1, data is compressed into 8-word blocks. This provides 128 bits per block. However only 124 bits
per block are used for actual speech data, giving a raw data rate of 4133.33 bits/sec. The 4.1 rate can be operated in
conjunction with the VAD/CNG silence compression feature.
3.9
G.711 µ-law/A-law
The CT8022 is designed to operate with one or two low cost external G.711 µ-law/A-law serial CODECs to provide
A-to-D and D-to-A conversion (use of 2 CODECs is required only for standalone analog speakerphone operation).
The CT8022 can provide bit-transparent “pass through” access to the serial CODEC data stream. In addition, the
CT8022 can also provide volume control (scaling) operating on the G.711 data. G.711 mode is also supported when
the CT8022 is used with an external 16-bit linear CODEC, where the CT8022 provides 16-bit linear to G.711
µ-law/A-law conversion.
3.10
G.729 Annex A Downloadable
DSP Group offers an external downloadable expansion software module that can enable the CT8022 to support the
G.729 Annex A speech coder that operates at 8 Kbits/sec. The DSP Group implementation of G.729A also includes
the G.729 Annex B VAD/CNG silence compression feature. G.729A is a reduced complexity version of the earlier
G.729 speech coder. The two coders (G.729 and G.729A) are fully inter-operable.
3.11
G.722 Downloadable
DSP Group offers an external downloadable expansion software module that enables the CT8022 to support the
G.722 7KHz wideband ADPCM operating at 64 Kbits/sec.
3.12
Automatic Gain Control
In speech record mode (compressed or uncompressed), the CT8022 record process can optionally include an
Automatic Gain Control (AGC) function. When this feature is enabled, the CT8022 automatically adjusts the record
signal level by internal digital scaling of the input speech signal. The control parameters for the AGC, which include
max and min gain (amplification), attack and decay times (response time), are programmable by the Host.
Note: For optimal AEC performance in DSVD mode (videoconferencing), use of the AGC feature
concurrently with the Acoustic Echo Canceller is not recommended. However, where the user
considers simultaneous use of both AEC and AGC to be necessary, the CT8022 does include a
mechanism to reduce the echo amplification effect caused when the AGC gain increases.
CT8022A11AQC FW Revision 0118 DSP GROUP, INC., 3120 SCOTT BOULEVARD
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
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All specifications are subject to change without prior notice.
ETC [ ETC ]
