CT8022 Datasheet, PDF (191/194 Pages) List of Unclassifed Manufacturers – VOIP/VON G.723.1, G279AB TRUESPEECH CO-PROCESSOR

Version: 1.18
PRELIMINARY/CONFIDENTIAL
TrueSpeech® Co-Processor
E.1 G.723.1 Version History
The CT8020D11AQC (firmware revision 0114) and all CT8021 and CT8022 versions implement (final-release)
version 5.1 of G.723.1. Earlier versions of the CT8020 included pre-release versions of G.723.1, which are not
directly compatible with the final v5.1 implementation. Transcoding between versions is possible using conversion
software available from DSP Group. Following is a brief description of the G.723.1 revision history and its effect on
the CT8020.
• v3.0, September 1995 - used in initial CT8020A11AQC engineering samples
• v4.0, January 1996 - almost the same as v3.0 but with different bit packing structure for the compressed speech
frames. This version is included in the CT8020A11BQC devices.
• v4.1, April 1996 - fixed some instability problems in the G.723.1 algorithm encountered when pure sinewaves
encoded.
• v5.0, May 1996 - added silence compression VAD/CNG as Annex A of G.723.1. VAD = voice activity
detection. CNG = comfort noise generation. This creates 4 possible speech frame sizes:
24-byte 6.3 Kbits/sec
20-byte 5.3 Kbits/sec
4-byte CNG frame
1-byte silent frame
• v5.1, Oct/Nov 1996, minor bug fix release affecting only the VAD feature. This version is implemented in the
CT8020D11AQC
The main coder/decoder in the v5.1, v5.0 and v4.1 revisions are identical. When use of the v5.1 coder with the VAD
feature is disabled, the v5.1 and v4.1 encoders produce identical bit-streams. Therefore, inter-working between these
versions of G.723.1 is straightforward.
It is possible to convert the compressed data between the various revisions so that, for example, chips of v3.0 can
inter-work with v5.1. This requires software to run on the Host. This is simple code that re-packs bits and performs
certain table look-up operations on some bit-fields. DSP Group provides ‘C’ reference source code for use with the
CT8020. It is possible to freely incorporate this code into user software for use with CT8020 systems. DSP Group
recommends incorporation of this code into all software that works with CT8020A11AQC and CT8020A11BQC
devices to provide compatibility with the final G.723.1 v5.1 standard. Systems incorporating older versions of the
G.723.1 standard should use the conversion software to promote to the final v5.1 G.723.1 version format.
The ITU-T has approved version 5.1 of G.723.1 as the final version. There will be no further changes to this
standard.
The changes introduced by the ITU in version 4.1 of G.723.1 necessitated equivalent changes to the TrueSpeech 4.8
and 4.1 KBPS speech coders. Because of this conversion, software must be included in order to enable inter-working
between the (DSP Group proprietary) 4.8/4.1 rates in the A11AQC/A11BQC chips and the final CT8020D11AQC
silicon.
CT8022A11AQC FW Revision 0118
DSP GROUP, INC., 3120 SCOTT BOULEVARD
191
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
All specifications are subject to change without prior notice.