Version: 1.18
PRELIMINARY/CONFIDENTIAL
TrueSpeech® Co-Processor
Read Playback Freeze
State:
Status:
5215H
0 or 1
The status returns 1 if the channel is currently in the freeze state, 0 otherwise.
Compatibility Note:
Revision 0112 onwards of the CT8020 firmware (CT8020A11BQC) fixed a minor bug which caused
incorrect operation of the Buffer Freeze command for Playback when the CT8020’s internal
playback buffer was completely empty. In earlier versions of the CT8020 firmware, the CT8020
would not output silence when Buffer Freeze was activated, if the Playback buffer was empty. In this
situation, the CT8020 would continuously re-output the most recent two speech frames. Refer to the
Playback Auto-Repeat feature described in Section 9.13.6 of this document.
9.13.5
Buffer Depth Limit
The Buffer Depth Limit command can be used to limit the number of speech frames held in the playback or record
channel buffers. This allows the Host to strictly limit the amount of delay and latency that the buffering of speech
frames in the CT8022 can add to an end-to-end speech link. At the same time, the CT8022’s buffering capability
helps to reduce the load on the Host processor by permitting more relaxed real-time deadlines in moving data into or
out of the CT8022. The CT8022 has 480 bytes available for storage space for each channel (physically located
within the external data SRAM). This is sufficient for up to:
•
•
•
•
1 uncompressed (480 byte) 16-bit linear frame
2 uncompressed (240 byte) 8-bit/A-law/µ-law frames
15 TrueSpeech 8.5 frames
20 TrueSpeech 6.3, 5.3, 4.8 or 4.1 frames
The CT8022 does not check the buffer limit set by the Host, but simply takes as the actual limit the minimum value
of the physical buffer capacity and the Host-programmed limit. For example, in µ-law mode, if the Host programs a
limit of 10 frames, the limit used will actually be only 2, which is the physical capacity of the device. In TrueSpeech
6.3 mode, if the Host programs a limit of 10 frames, the limit used will be 10, since this is within the physical
capacity of the device.
RECORD:
Set Record Channel
Limit:
Status:
5180H + X where X is in the range 0 to 60 (decimal)
5180H + X
Read Record Channel
Limit:
Status:
5118H
00XXH
where XX is the limit programmed
PLAYBACK:
Set Playback Channel
Limit:
Status:
5280H + X where X is in the range 0 to 60 (decimal)
5280H + X
Read Playback Channel
Limit:
Status:
5218H
00XXH
where XX is the limit programmed
CT8022A11AQC FW Revision 0118 DSP GROUP, INC., 3120 SCOTT BOULEVARD
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
97
All specifications are subject to change without prior notice.
ETC [ ETC ]
