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Correct behavior on Cisco's DTMF

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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@43539 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Paul Cadach
2006-09-23 18:25:13 +00:00
parent eda44fb7ba
commit 1d50a8e881
1 changed files with 63 additions and 6 deletions
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69
main/rtp.c
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@@ -604,10 +604,58 @@ static struct ast_frame *process_cisco_dtmf(struct ast_rtp *rtp, unsigned char *
unsigned int event;
char resp = 0;
struct ast_frame *f = NULL;
event = ntohl(*((unsigned int *)(data)));
event &= 0x001F;
unsigned char seq;
unsigned int datalen;
unsigned int flag;
unsigned int power;
/* We should have at least 4 bytes in RTP data */
if (len < 4)
return f;
/* The format of Cisco RTP DTMF packet looks like next:
+0 - sequence number of DTMF RTP packet (begins from 1,
wrapped to 0)
+1 (bits 7-0) - count of bytes carrying DTMF information (if DTMF
information repeates 3 times, i.e. packet have 6
bytes of DTMF information, this value equal to 6).
Last bit should always be zero (because DTMF info
is multiple of 2 bytes) but really uses as described
below.
+1 (bit 0) - flaps by different DTMF digits delimited by audio
or repeated digit without audio
+2 (+4,+6,...) - power level? (rises from 0 to 32 at begin of tone
then falls to 0 at its end)
+3 (+5,+7,...) - detected DTMF digit (0..9,*,#,A-D,...)
Repeated DTMF information (bytes 4/5, 6/7) is history shifted right
by each new packet and thus provides some redudancy.
Sample of Cisco RTP DTMF packet is (all data in hex):
19 07 00 02 12 02 20 02
showing end of DTMF digit '2'.
The packets
27 07 00 02 0A 02 20 02
28 06 20 02 00 02 0A 02
shows begin of new digit '2' with very short pause (20 ms) after
previous digit '2'. Bit +1.0 flips at begin of new digit.
Cisco RTP DTMF packets comes as replacement of audio RTP packets
so its uses the same sequencing and timestamping rules as replaced
audio packets. Repeat interval of DTMF packets is 20 ms and not rely
on audio framing parameters. Marker bit isn't used within stream of
DTMFs nor audio stream coming immediately after DTMF stream. Timestamps
are not sequential at borders between DTMF and audio streams,
*/
seq = data[0];
datalen = data[1] & ~1;
flag = data[1] & 1;
power = data[2];
event = data[3] & 0x1f;
if (option_debug > 2 || rtpdebug)
ast_log(LOG_DEBUG, "Cisco DTMF Digit: %08x (len = %d)\n", event, len);
ast_log(LOG_DEBUG, "Cisco DTMF Digit: %02x (len=%d, seq=%d, repeat=%d, power=%d, history count=%d)\n", event, len, seq, flag, power, datalen / 2 - 1);
if (event < 10) {
resp = '0' + event;
} else if (event < 11) {
@@ -619,10 +667,19 @@ static struct ast_frame *process_cisco_dtmf(struct ast_rtp *rtp, unsigned char *
} else if (event < 17) {
resp = 'X';
}
if (rtp->resp && (rtp->resp != resp)) {
if ((!rtp->resp && power) || (rtp->resp && (rtp->resp != resp))) {
rtp->resp = resp;
/* Why we should care on DTMF compensation at receiption? */
if (!ast_test_flag(rtp, FLAG_DTMF_COMPENSATE)) {
f = send_dtmf(rtp, AST_FRAME_DTMF_BEGIN);
rtp->dtmfduration = 0;
}
} else if ((rtp->resp == resp) && !power) {
f = send_dtmf(rtp, AST_FRAME_DTMF_END);
}
rtp->resp = resp;
f->samples = rtp->dtmfduration * 8;
rtp->resp = 0;
} else if (rtp->resp == resp)
rtp->dtmfduration += 20 * 8;
rtp->dtmfcount = dtmftimeout;
return f;
}