+++ /dev/null
-$Id: README.audio,v 1.8 1999/07/11 17:17:29 armin Exp $
-
-ISDN subsystem for Linux.
- Description of audio mode.
-
-When enabled during kernel configuration, the tty emulator of the ISDN
-subsystem is capable of a reduced set of commands to support audio.
-This document describes the commands supported and the format of
-audio data.
-
-Commands for enabling/disabling audio mode:
-
- AT+FCLASS=8 Enable audio mode.
- This affects the following registers:
- S18: Bits 0 and 2 are set.
- S16: Set to 48 and any further change to
- larger values is blocked.
- AT+FCLASS=0 Disable audio mode.
- Register 18 is set to 4.
- AT+FCLASS=? Show possible modes.
- AT+FCLASS? Report current mode (0 or 8).
-
-Commands supported in audio mode:
-
-All audio mode commands have one of the following forms:
-
- AT+Vxx? Show current setting.
- AT+Vxx=? Show possible settings.
- AT+Vxx=v Set simple parameter.
- AT+Vxx=v,v ... Set complex parameter.
-
-where xx is a two-character code and v are alphanumerical parameters.
-The following commands are supported:
-
- AT+VNH=x Auto hangup setting. NO EFFECT, supported
- for compatibility only.
- AT+VNH? Always reporting "1"
- AT+VNH=? Always reporting "1"
-
- AT+VIP Reset all audio parameters.
-
- AT+VLS=x Line select. x is one of the following:
- 0 = No device.
- 2 = Phone line.
- AT+VLS=? Always reporting "0,2"
- AT+VLS? Show current line.
-
- AT+VRX Start recording. Emulator responds with
- CONNECT and starts sending audio data to
- the application. See below for data format
-
- AT+VSD=x,y Set silence-detection parameters.
- Possible parameters:
- x = 0 ... 31 sensitivity threshold level.
- (default 0 , deactivated)
- y = 0 ... 255 range of interval in units
- of 0.1 second. (default 70)
- AT+VSD=? Report possible parameters.
- AT+VSD? Show current parameters.
-
- AT+VDD=x,y Set DTMF-detection parameters.
- Only possible if online and during this connection.
- Possible parameters:
- x = 0 ... 15 sensitivity threshold level.
- (default 0 , I4L soft-decode)
- (1-15 soft-decode off, hardware on)
- y = 0 ... 255 tone duration in units of 5ms.
- Not for I4L soft decode (default 8, 40ms)
- AT+VDD=? Report possible parameters.
- AT+VDD? Show current parameters.
-
- AT+VSM=x Select audio data format.
- Possible parameters:
- 2 = ADPCM-2
- 3 = ADPCM-3
- 4 = ADPCM-4
- 5 = aLAW
- 6 = uLAW
- AT+VSM=? Show possible audio formats.
-
- AT+VTX Start audio playback. Emulator responds
- with CONNECT and starts sending audio data
- received from the application via phone line.
-General behavior and description of data formats/protocol.
- when a connection is made:
-
- On incoming calls, if the application responds to a RING
- with ATA, depending on the calling service, the emulator
- responds with either CONNECT (data call) or VCON (voice call).
-
- On outgoing voice calls, the emulator responds with VCON
- upon connection setup.
-
- Audio recording.
-
- When receiving audio data, a kind of bisync protocol is used.
- Upon AT+VRX command, the emulator responds with CONNECT, and
- starts sending audio data to the application. There are several
- escape sequences defined, all using DLE (0x10) as Escape char:
-
- <DLE><ETX> End of audio data. (i.e. caused by a
- hangup of the remote side) Emulator stops
- recording, responding with VCON.
- <DLE><DC4> Abort recording, (send by appl.) Emulator
- stops recording, sends DLE,ETX.
- <DLE><DLE> Escape sequence for DLE in data stream.
- <DLE>0 Touchtone "0" received.
- ...
- <DLE>9 Touchtone "9" received.
- <DLE># Touchtone "#" received.
- <DLE>* Touchtone "*" received.
- <DLE>A Touchtone "A" received.
- <DLE>B Touchtone "B" received.
- <DLE>C Touchtone "C" received.
- <DLE>D Touchtone "D" received.
-
- <DLE>q quiet. Silence detected after non-silence.
- <DLE>s silence. Silence detected from the
- start of recording.
-
- Currently unsupported DLE sequences:
-
- <DLE>c FAX calling tone received.
- <DLE>b busy tone received.
-
- Audio playback.
-
- When sending audio data, upon AT+VTX command, emulator responds with
- CONNECT, and starts transferring data from application to the phone line.
- The same DLE sequences apply to this mode.
-
- Full-Duplex-Audio:
-
- When _both_ commands for recording and playback are given in _one_
- AT-command-line (i.e.: "AT+VTX+VRX"), full-duplex-mode is selected.
- In this mode, the only way to stop recording is sending <DLE><DC4>
- and the only way to stop playback is to send <DLE><ETX>.
-
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