Version: 1.18
PRELIMINARY/CONFIDENTIAL
TrueSpeech® Co-Processor
9.22.1
Host-to-Host Compression
Host-to-Host compression from the viewpoint of the Host is similar to the record process. The protocol used to
transfer compressed data frames from the CT8022 to the Host [2] is the same as that used for recording in DATA
sync mode with TFR Mode = 00. However, instead of using the record C1 command to start the process, the Host-
to-Host compression C1 command is used. The compression C1 command is also used to transfer the actual
uncompressed data frames to the CT8022 [1].
The following command initiates Host-to-Host compression:
Compress Command C1 (= FXXXH):
1111 01
(15-10)
RECMODE
(9-7)
000 0
(6-3)
TFR_MODE
(2-1)
DATA
(0)
Status Response S1:
1111 01
RECMODE
(9-7)
000 0
(6-3)
TFR_MODE
(2-1)
READY
(0)
(15-10)
9.22.1.1
Recording (Compression) Modes
RECMODE
Recording Modes
000
001
010
011
100
101
110
111
TrueSpeech at 8.5, 6.3, 5.3, 4.8 or 4.1 Kbits/sec
Reserved
Reserved
Reserved
64 Kbits/sec A-law/µ-law PCM (120 words per 30ms data frame)
128 Bit/sec 16-bit linear (240 words per 30ms data frame)
64 Kbits/sec 8-bit signed linear (120 words per 30ms data frame)
64 Kbits/sec WSS 8-bit unsigned linear (120 words per 30ms data frame)
Refer to Section 9.7 for more details on RECMODE and TFR_MODE.
DATA
In the first C1 command (used to start compression) the DATA flag is set by the Host to indicate whether the Host
wishes to immediately transfer the first uncompressed speech frame [1] to the CT8022 for compression.
In subsequent compression C1 commands, the DATA flag is ignored by the CT8022. In this case, the CT8022
always assumes that the Host will be ready to transfer uncompressed data [1].
READY
If the READY flag is set in the status response, the CT8022 expects that immediately following the S1 response, the
Host will transfer 240 words (480 bytes) of uncompressed data. The READY flag will always be set in the first S1
response if the Host set the DATA flag in the first C1 command. When the Host receives a status response with the
READY flag set, it must immediately commence the transfer of uncompressed speech data.
CT8022A11AQC FW Revision 0118 DSP GROUP, INC., 3120 SCOTT BOULEVARD
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
147
All specifications are subject to change without prior notice.
ETC [ ETC ]
