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1da177e4 LT |
1 | $Id: README.audio,v 1.8 1999/07/11 17:17:29 armin Exp $ |
2 | ||
3 | ISDN subsystem for Linux. | |
4 | Description of audio mode. | |
5 | ||
6 | When enabled during kernel configuration, the tty emulator of the ISDN | |
7 | subsystem is capable of a reduced set of commands to support audio. | |
8 | This document describes the commands supported and the format of | |
9 | audio data. | |
10 | ||
11 | Commands for enabling/disabling audio mode: | |
12 | ||
13 | AT+FCLASS=8 Enable audio mode. | |
14 | This affects the following registers: | |
15 | S18: Bits 0 and 2 are set. | |
16 | S16: Set to 48 and any further change to | |
17 | larger values is blocked. | |
18 | AT+FCLASS=0 Disable audio mode. | |
19 | Register 18 is set to 4. | |
20 | AT+FCLASS=? Show possible modes. | |
21 | AT+FCLASS? Report current mode (0 or 8). | |
22 | ||
23 | Commands supported in audio mode: | |
24 | ||
25 | All audio mode commands have one of the following forms: | |
26 | ||
27 | AT+Vxx? Show current setting. | |
28 | AT+Vxx=? Show possible settings. | |
29 | AT+Vxx=v Set simple parameter. | |
30 | AT+Vxx=v,v ... Set complex parameter. | |
31 | ||
32 | where xx is a two-character code and v are alphanumerical parameters. | |
33 | The following commands are supported: | |
34 | ||
35 | AT+VNH=x Auto hangup setting. NO EFFECT, supported | |
36 | for compatibility only. | |
37 | AT+VNH? Always reporting "1" | |
38 | AT+VNH=? Always reporting "1" | |
39 | ||
40 | AT+VIP Reset all audio parameters. | |
41 | ||
42 | AT+VLS=x Line select. x is one of the following: | |
43 | 0 = No device. | |
44 | 2 = Phone line. | |
45 | AT+VLS=? Always reporting "0,2" | |
46 | AT+VLS? Show current line. | |
47 | ||
48 | AT+VRX Start recording. Emulator responds with | |
49 | CONNECT and starts sending audio data to | |
50 | the application. See below for data format | |
51 | ||
52 | AT+VSD=x,y Set silence-detection parameters. | |
53 | Possible parameters: | |
54 | x = 0 ... 31 sensitivity threshold level. | |
55 | (default 0 , deactivated) | |
56 | y = 0 ... 255 range of interval in units | |
57 | of 0.1 second. (default 70) | |
58 | AT+VSD=? Report possible parameters. | |
59 | AT+VSD? Show current parameters. | |
60 | ||
61 | AT+VDD=x,y Set DTMF-detection parameters. | |
62 | Only possible if online and during this connection. | |
63 | Possible parameters: | |
64 | x = 0 ... 15 sensitivity threshold level. | |
65 | (default 0 , I4L soft-decode) | |
66 | (1-15 soft-decode off, hardware on) | |
67 | y = 0 ... 255 tone duration in units of 5ms. | |
68 | Not for I4L soft decode (default 8, 40ms) | |
69 | AT+VDD=? Report possible parameters. | |
70 | AT+VDD? Show current parameters. | |
71 | ||
72 | AT+VSM=x Select audio data format. | |
73 | Possible parameters: | |
74 | 2 = ADPCM-2 | |
75 | 3 = ADPCM-3 | |
76 | 4 = ADPCM-4 | |
77 | 5 = aLAW | |
78 | 6 = uLAW | |
79 | AT+VSM=? Show possible audio formats. | |
80 | ||
81 | AT+VTX Start audio playback. Emulator responds | |
82 | with CONNECT and starts sending audio data | |
83 | received from the application via phone line. | |
84 | General behavior and description of data formats/protocol. | |
85 | when a connection is made: | |
86 | ||
87 | On incoming calls, if the application responds to a RING | |
88 | with ATA, depending on the calling service, the emulator | |
89 | responds with either CONNECT (data call) or VCON (voice call). | |
90 | ||
91 | On outgoing voice calls, the emulator responds with VCON | |
92 | upon connection setup. | |
93 | ||
94 | Audio recording. | |
95 | ||
96 | When receiving audio data, a kind of bisync protocol is used. | |
97 | Upon AT+VRX command, the emulator responds with CONNECT, and | |
98 | starts sending audio data to the application. There are several | |
99 | escape sequences defined, all using DLE (0x10) as Escape char: | |
100 | ||
101 | <DLE><ETX> End of audio data. (i.e. caused by a | |
102 | hangup of the remote side) Emulator stops | |
103 | recording, responding with VCON. | |
104 | <DLE><DC4> Abort recording, (send by appl.) Emulator | |
105 | stops recording, sends DLE,ETX. | |
106 | <DLE><DLE> Escape sequence for DLE in data stream. | |
107 | <DLE>0 Touchtone "0" received. | |
108 | ... | |
109 | <DLE>9 Touchtone "9" received. | |
110 | <DLE># Touchtone "#" received. | |
111 | <DLE>* Touchtone "*" received. | |
112 | <DLE>A Touchtone "A" received. | |
113 | <DLE>B Touchtone "B" received. | |
114 | <DLE>C Touchtone "C" received. | |
115 | <DLE>D Touchtone "D" received. | |
116 | ||
117 | <DLE>q quiet. Silence detected after non-silence. | |
118 | <DLE>s silence. Silence detected from the | |
119 | start of recording. | |
120 | ||
121 | Currently unsupported DLE sequences: | |
122 | ||
123 | <DLE>c FAX calling tone received. | |
124 | <DLE>b busy tone received. | |
125 | ||
126 | Audio playback. | |
127 | ||
128 | When sending audio data, upon AT+VTX command, emulator responds with | |
129 | CONNECT, and starts transferring data from application to the phone line. | |
130 | The same DLE sequences apply to this mode. | |
131 | ||
132 | Full-Duplex-Audio: | |
133 | ||
134 | When _both_ commands for recording and playback are given in _one_ | |
135 | AT-command-line (i.e.: "AT+VTX+VRX"), full-duplex-mode is selected. | |
136 | In this mode, the only way to stop recording is sending <DLE><DC4> | |
137 | and the only way to stop playback is to send <DLE><ETX>. | |
138 |