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diff --git a/Documentation/isdn/README.audio b/Documentation/isdn/README.audio new file mode 100644 index 000000000000..8ebca19290d9 --- /dev/null +++ b/Documentation/isdn/README.audio @@ -0,0 +1,138 @@ +$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>. + |