freeswitch mrcp 源码分析--数据包的发送

最新推荐文章于 2025-09-15 11:42:06 发布

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最新推荐文章于 2025-09-15 11:42:06 发布 · 3.5k 阅读

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本文详细分析了Freeswitch中MRCP语音识别启动后的数据包发送流程，从recog_channel_start函数开始，涵盖创建mrcp_message_t结构体、设置参数、填充body、发送消息等步骤。核心是mrcp_application_message_send函数，该函数通过消息任务分发机制，最终由mrcp_client_agent_messsage_send完成数据通过socket的实际发送。

在MRCP 开始语音识别后会调用recog_channel_start（）函数

static switch_status_t recog_channel_start(speech_channel_t *schannel)
{
    switch_status_t status = SWITCH_STATUS_SUCCESS;
    switch_hash_index_t *egk;
    mrcp_message_t *mrcp_message;
    mrcp_recog_header_t *recog_header;
    mrcp_generic_header_t *generic_header;
    recognizer_data_t *r;
    char *start_input_timers;
    const char *mime_type;
    char *key = NULL;
    switch_size_t len;
    grammar_t *grammar = NULL;
    switch_size_t grammar_uri_count = 0;
    switch_size_t grammar_uri_list_len = 0;
    char *grammar_uri_list = NULL;
    int warned = 0;

    switch_mutex_lock(schannel->mutex);
    if (schannel->state != SPEECH_CHANNEL_READY) {
        status = SWITCH_STATUS_FALSE;
        goto done;
    }

    if (schannel->data == NULL) {
        status = SWITCH_STATUS_FALSE;
        goto done;
    }
    r = (recognizer_data_t *) schannel->data;
    r->result = NULL;
    if (r->result_headers) {
        switch_event_destroy(&r->result_headers);
    }
    r->start_of_input = 0;

    /* input timers are started by default unless the start-input-timers=false param is set */
    start_input_timers = (char *) switch_core_hash_find(schannel->params, "start-input-timers");
    r->timers_started = zstr(start_input_timers) || strcasecmp(start_input_timers, "false");

    /* count enabled grammars */
    for (egk = switch_core_hash_first(r->enabled_grammars); egk; egk = switch_core_hash_next(&egk)) {
        // NOTE: This postponed type check is necessary to allow a non-URI-list grammar to execute alone
        if (grammar_uri_count == 1 && grammar->type != GRAMMAR_TYPE_URI)
            goto no_grammar_alone;
        ++grammar_uri_count;
        switch_core_hash_this(egk, (void *) &key, NULL, (void *) &grammar);
        if (grammar->type != GRAMMAR_TYPE_URI && grammar_uri_count != 1) {
              no_grammar_alone:
            switch_log_printf(SWITCH_CHANNEL_UUID_LOG(schannel->session_uuid), SWITCH_LOG_ERROR, "(%s) Grammar '%s' can only be used alone (not a URI list)\n", schannel->name, key);
            status = SWITCH_STATUS_FALSE;
            switch_safe_free(egk);
            goto done;
        }
        len = strlen(grammar->data);
        if (!len)
            continue;
        grammar_uri_list_len += len;
        if (grammar->data[len - 1] != '\n')
            grammar_uri_list_len += 2;
    }

    switch (grammar_uri_count) {
    case 0:
        switch_log_printf(SWITCH_CHANNEL_UUID_LOG(schannel->session_uuid), SWITCH_LOG_ERROR, "(%s) No grammar specified\n", schannel->name);
        status = SWITCH_STATUS_FALSE;
        goto done;
    case 1:
        /* grammar should already be the unique grammar */
        break;
    default:
        /* get the enabled grammars list */
        grammar_uri_list = switch_core_alloc(schannel->memory_pool, grammar_uri_list_len + 1);
        grammar_uri_list_len = 0;
        for (egk = switch_core_hash_first(r->enabled_grammars); egk; egk = switch_core_hash_next(&egk)) {
            switch_core_hash_this(egk, (void *) &key, NULL, (void *) &grammar);
            len = strlen(grammar->data);
            if (!len)
                continue;
            memcpy(&(grammar_uri_list[grammar_uri_list_len]), grammar->data, len);
            grammar_uri_list_len += len;
            if (grammar_uri_list[grammar_uri_list_len - 1] != '\n')
            {
                grammar_uri_list_len += 2;
                grammar_uri_list[grammar_uri_list_len - 2] = '\r';
                grammar_uri_list[grammar_uri_list_len - 1] = '\n';
            }
        }
        grammar_uri_list[grammar_uri_list_len++] = '\0';
        grammar = NULL;
    }

    /* create MRCP message */
    mrcp_message = mrcp_application_message_create(schannel->unimrcp_session, schannel->unimrcp_channel, RECOGNIZER_RECOGNIZE);
    if (mrcp_message == NULL) {
        status = SWITCH_STATUS_FALSE;
        goto done;
    }

    /* allocate generic header */
    generic_header = (mrcp_generic_header_t *) mrcp_generic_header_prepare(mrcp_message);
    if (generic_header == NULL) {
        status = SWITCH_STATUS_FALSE;
        goto done;
    }

    /* set Content</