Chapter 6 – Voice Commands
<cml> is used by the PC to select a compression method. The valid range of values is from 128– 256. The range of values from
<vsr> is used to select the modem voice sampling rate from the set of those supported. The unit of measure is samples per second. See the +VSM=? command for the list of sampling rates supported by the modem.
<scs> has different meanings in voice transmit and voice receive modes. In receive, the PC uses <scs> to select greater amounts of compression activity; larger <scs> values mean that the PC wants the modem to treat noisier conditions as silence. There is no unit of measure for this parameter; it merely represents a number in a range. 0 disables modem silence compression.
In voice transmit mode, the PC signals the modem that the data stream was recorded with silence compression by selecting a
<sel> is used to modify the amount of silence expansion. This parameter represents the minimum amount of silence that the modem will expand a period of silence that was previously deleted with a
the <sel> parameter if the <scs> parameter is 0 (silence compression disabled).
Command: | +VSM=? | Report Voice Compression Method |
Result Codes: | OK |
|
Description: | The +VSM=? command reports several compression method identifiers in one of two ways: either | |
| 1) a compression method (for PCM coding) from the table below, or 2) a | |
| ||
| Example: The following shows an inquiry about the modem support of compression and other | |
| data. In this example, the modem reports that it supports two compression methods. | |
| AT+VSM=? |
|
| 128,"SIGNED | |
|
| |
| The compression method identifiers for PCM coding display the general classification of the | |
| compression method in the form <cmid>. | |
| ||
| <cmid> is the general classification of the compression method and <author> is the source of the | |
| method. The source <author> may be a proprietary method or it may reference a published | |
| standard. Each field limit is 20 characters. The +VXT command starts a translation to or from a | |
| particular manufacturer's proprietary voice data stream format to an unsigned | |
| Identifier | Description |
| Signed PCM | Linear PCM sampling using twos complement signed numbers |
| Unsigned PCM | Linear PCM sampling using unsigned numbers |
| Compression using | |
| Compression using | |
| DPCM/Author | Differential Pulse Coded Modulation |
| DPCMAQ/Author | Differential Pulse Coded Modulation with Adaptive Quantizier |
| ADPCM/Author | Adaptive Differential Pulse Coded Modulation |
| VSELP/Author | Vector Sum Exited Linear Predictor |
| RELP/Author | Residual Exited Linear Predictor |
| CELP/Author | Code Book Exited Linear Predictor |
| CVSD/Author | Continuously Variable Slope Delta Modulation |
| TDHS/Author | Time Domain Harmonic Distortion |
| ADM/Author | Adaptive Delta Modulation |
| DM/Author | Delta Modulation |
| APC/Author | Adaptive Predictive Coding |
| ATC/Author | Adaptive Transform Coding |
| SBC/Author | |
| GSM/Author | Regular Pulse Exitation |
| LPC/Author | Linear Predictive Coding |
| EAPDPCM/Author | Embedded Bit ADPCM |
SocketModem Global MT5634SMI Developer’s Guide | 54 |