spandsp_start_dtmf的bug及修复

概述

freeswitch是一款简单好用的VOIP开源软交换平台。

之前的文章中介绍过DTMF从2833到inband的转换，其中inband到2833的转换使用了“spandsp_start_dtmf”，这个函数在转换的过程中有缺陷。

环境

CentOS 7.9

freeswitch 1.10.7

问题描述

在fs桥接的呼叫，经过“spandsp_start_dtmf”处理inband中的dtmf按键，转换到otherleg的时候，2833的dtmf可以正常产生，但是inband中的波形删除的不够干净，如果后续的语音节点会检测inband的话，就会产生重码的问题。

解决方案

修改思路，在spandsp对dtmf波形的处理过程中，缓存2个媒体包，当检测到DTMF时，将缓存的媒体包清空。

修改mod_dtptools.c

case SWITCH_DTMF_RTP:switch_channel_set_variable(switch_core_session_get_channel(session), "deduplicate_dtmf_seen_rtp", "true");/* change state to only allow RTP events */filter->only_rtp = 1;//modify by zr, 20241021, for DTMF inband to 2833/* stop inband detector */// switch_ivr_broadcast(switch_core_session_get_uuid(session), "spandsp_stop_dtmf::", SMF_ECHO_ALEG);break;

修改mod_spandsp_dsp.c

//modify by zr, 20241021, for DTMF inband to 2833
#define INBAND_DTMF_BUF_SIZE (2)
#define INBAND_DTMF_BUF_LEN (512)typedef struct {switch_core_session_t *session;dtmf_rx_state_t *dtmf_detect;int verbose;char last_digit;uint32_t samples;uint32_t last_digit_end;uint32_t digit_begin;uint32_t min_dup_digit_spacing;int twist;int reverse_twist;int filter_dialtone;int threshold;switch_audio_resampler_t *resampler;
//modify by zr, 20241021, for DTMF inband to 2833char data_buf[INBAND_DTMF_BUF_SIZE][INBAND_DTMF_BUF_LEN];int buf_index;
} switch_inband_dtmf_t;...dtmf_rx(pvt->dtmf_detect, dp, samples);//modify by zr, 20241021, for DTMF inband to 2833// switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_NOTICE, "dtmf_rx return, last_hit=%d, in_digit=%d, current_sample=%d,"// 														"duration=%d, lost_digits=%d, current_digits=%d\n", // 														pvt->dtmf_detect->last_hit, pvt->dtmf_detect->in_digit, pvt->dtmf_detect->current_sample, // 														pvt->dtmf_detect->duration, pvt->dtmf_detect->lost_digits, pvt->dtmf_detect->current_digits);if(pvt->dtmf_detect->filter_dialtone){	// double buffer modeif(pvt->dtmf_detect->last_hit > 0 || pvt->dtmf_detect->in_digit > 0) {switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(pvt->session), SWITCH_LOG_DEBUG, "inband_dtmf_callback, memset frame to 0x00, pvt->dtmf_detect->last_hit=%d, pvt->dtmf_detect->in_digit=%d\n", pvt->dtmf_detect->last_hit, pvt->dtmf_detect->in_digit);memset(pvt->data_buf, 0x00, INBAND_DTMF_BUF_LEN*INBAND_DTMF_BUF_SIZE);memset(frame->data, 0x00, frame->datalen);}else{char data_tmp[INBAND_DTMF_BUF_LEN] = {0};memcpy(data_tmp, frame->data, INBAND_DTMF_BUF_LEN);memcpy(frame->data, pvt->data_buf[pvt->buf_index], frame->datalen);memcpy(pvt->data_buf[pvt->buf_index], data_tmp, datalen);}pvt->buf_index = (1 - pvt->buf_index);}switch_core_media_bug_set_read_replace_frame(bug, frame);...pvt->session = session;//modify by zr, 20241021, for DTMF inband to 2833pvt->buf_index = 0;

修改switch_core_media.c

				switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_DEBUG, "%s Set 2833 dtmf send payload to %u recv payload to %u\n",switch_channel_get_name(session->channel), smh->mparams->te, smh->mparams->recv_te);//add by zr 20241018, for 2833 to inband, update method//如果在183的协商中已经设置了inband模式，后续的update协商中需要取消inband模式的函数设置if (switch_true(switch_channel_get_variable(session->channel, "inband_flag"))) {switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_DEBUG, "reset inband_flag and channel variables.\n");//B路switch_channel_set_variable(session->channel, "inband_flag", NULL);switch_channel_set_variable(session->channel, "spandsp_dtmf_rx_filter_dialtone", NULL);switch_channel_set_variable(session->channel, "execute_on_answer_101", NULL);switch_channel_set_variable(session->channel, "execute_on_answer_102", NULL);//A路，2833 to inbandif( switch_core_session_get_partner(session, &other_session) == SWITCH_STATUS_SUCCESS ){switch_channel_set_variable(other_session->channel, "execute_on_answer_101", NULL);switch_core_session_rwunlock(other_session);}}} else {/* by default, use SIP INFO if 2833 is not in the SDP */if (!switch_false(switch_channel_get_variable(channel, "rtp_info_when_no_2833"))) {switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_DEBUG, "No 2833 in SDP.  Disable 2833 dtmf and switch to INFO\n");switch_channel_set_variable(session->channel, "dtmf_type", "info");smh->mparams->dtmf_type = DTMF_INFO;smh->mparams->recv_te = smh->mparams->te = 0;} else {// switch_channel_set_variable(session->channel, "dtmf_type", "none");// smh->mparams->dtmf_type = DTMF_NONE;// smh->mparams->recv_te = smh->mparams->te = 0;//add by zr 20241018, for 2833 to inband, update methodswitch_channel_set_variable(session->channel, "dtmf_type", "inband");smh->mparams->dtmf_type = DTMF_AUTO;smh->mparams->recv_te = smh->mparams->te = 0;switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_DEBUG, "set inband_flag, No 2833 in SDP. Disable 2833 dtmf and switch to INBAND.\n");//TODO: add inband dtmf//A路，2833 to inbandif( switch_core_session_get_partner(session, &other_session) == SWITCH_STATUS_SUCCESS ){switch_channel_set_variable(other_session->channel, "execute_on_answer_101", "start_dtmf_generate");switch_core_session_rwunlock(other_session);}//B路，inband to 2833switch_channel_set_variable(session->channel, "inband_flag", "true");switch_channel_set_variable(session->channel, "spandsp_dtmf_rx_filter_dialtone", "true");switch_channel_set_variable(session->channel, "execute_on_answer_101", "deduplicate_dtmf");switch_channel_set_variable(session->channel, "execute_on_answer_102", "spandsp_start_dtmf");}}