getting iaxclient to send audio to/get audio from buffer instead of audio-device

Question

I'm trying to write a C++ program (altough python would've been fine as well in case someone knows a better (IAX/SIP) alternative) which connects to an Asterisk server.

After connecting, it should listen for audio and process that. It should also send audio back. I'm using https://sourceforge.net/projects/iaxclient/ for that (note that there are several versions (betas, regular releases, svn version) which all behave differently).

Now if I understood the code of the library correct, then it can call a callback function with an event. One of those events is IAXC_EVENT_AUDIO. In the structure of that IAXC_EVENT_AUDIO there's a direction; incoming outgoing. And that's where I'm lost: with some versions of iaxclient I only receive the IAXC_SOURCE_REMOTE messages, with some both. And if I switch to test-mode (which should only disable the audio-device) I often receive nothing at all. When I receive both IAXC_SOURCE_LOCAL and IAXC_SOURCE_REMOTE, I tried to set the buffers of those events to random data but that doesn't reach the other end at all (I set it to RAW mode).

As anyone any suggestions how to resolve this?

My test-code is:

#include <iaxclient.h>
#include <unistd.h>

int iaxc_event_callback(iaxc_event e)
{
    if (e.type == IAXC_EVENT_TEXT) {
        printf("text\n");
    }
    else if (e.type == IAXC_EVENT_LEVELS) {
        printf("level\n");
    }
    else if (e.type == IAXC_EVENT_STATE) {
        struct iaxc_ev_call_state *st = iaxc_get_event_state(&e);
        printf("\tcallno %d state %d format %d remote %s(%s)\n", st->callNo, st->state, st->format,st->remote, st->remote_name);
        iaxc_key_radio(st->callNo);
    }
    else if (e.type == IAXC_EVENT_NETSTAT) {
        printf("\tcallno %d rtt %d\n", e.ev.netstats.callNo, e.ev.netstats.rtt);
    }
    else if (e.type == IAXC_EVENT_AUDIO) {
        printf("\t AUDIO!!!! %d %u %d\n", e.ev.audio.source, e.ev.audio.ts, e.ev.audio.size);

        for(int i=0; i<e.ev.audio.size; i++)
            printf("%02x ", e.ev.audio.data[i]);
        printf("\n");
    }
    else {
        printf("type: %d\n", e.type);
    }

    return 1;
}

int main(int argc, char *argv[])
{
    iaxc_set_test_mode(1);
    printf("init %d\n", iaxc_initialize(1));

    iaxc_set_formats(IAXC_FORMAT_SPEEX, IAXC_FORMAT_SPEEX);

    iaxc_set_event_callback(iaxc_event_callback);
    printf("get audio pref %d\n", iaxc_get_audio_prefs());
    //printf("set audio pref %d\n", iaxc_set_audio_prefs(IAXC_AUDIO_PREF_RECV_REMOTE_ENCODED));
    printf("set audio pref %d\n", iaxc_set_audio_prefs(IAXC_AUDIO_PREF_RECV_REMOTE_RAW | IAXC_AUDIO_PREF_RECV_LOCAL_RAW));
    printf("get audio pref %d\n", iaxc_get_audio_prefs());

    printf("start thread %d\n", iaxc_start_processing_thread());

    int id = -1;
    printf("register %d\n", id = iaxc_register("6003", "1923", "192.168.64.1"));

    int callNo = -1;
    printf("call %d\n", callNo = iaxc_call("6003:1923@192.168.64.1/6001"));

    printf("unquelch: %d\n", iaxc_unquelch(callNo));

    pause();

    printf("finish\n");
    printf("%d\n", iaxc_unregister(id));
    printf("%d\n", iaxc_stop_processing_thread());
    iaxc_shutdown();

    return 0;
}

Answer 1

Please have a look in iaxclient_lib.c too see how the logic works. To hook or replace input/output you can change function iaxci_do_audio_callback at memcpy(e.ev.audio.data, data, size); where the buffer is set. Also have a look at service_audio to understand how you can replace the buffer/stream sent to the remote location (e.g. want_send_audio and want_local_audio). You can also create virtual input/output devices in portaudio that iaxclient use for process audio using buffers instead.

For a more concrete example please look at the main method in the simplecall source to get a good start. However, the source code is to long for copy and paste, sorry about that.