pjsip capture and play pcm data

I have some embedded Devices that have no audio device by default. They communicate with each other via a FPGA. So my question is, how do I capture/play back audio from pjsip in pcm in order to send/receive it with the FPGA?

I know that there is pjmedia_mem_player_create() and pjmedia_mem_capture_create() but I can't seem to find any good info towards using these functions.

I tried the following piece of code, but an assertion failed cause one of the function's parameter is "empty".

Error:

pjmedia_mem_capture_create: Assertion `pool && buffer && size && clock_rate && channel_count && samples_per_frame && bits_per_sample && p_port' failed.

Note: I'm mainly using pjsua2 for everything else like registrations, transports etc. Also the default audio is set to null with ep.audDevManager().setNullDev(); as without this, making/receiving a call would simply fail?!

void MyCall::onCallMediaState(OnCallMediaStateParam &prm){
CallInfo ci = getInfo();

pj_caching_pool_init(&cp, &pj_pool_factory_default_policy, 0);
pj_pool_t *pool = pj_pool_create(&cp.factory, "POOLNAME", 2000, 2000, NULL);

void *buffer;
pjmedia_port *prt;

#define CLOCK_RATE 8000
#define CHANELS 1
#define SAMPLES_PER_FRAME 480
#define BITS_PER_SAMPLE 16

pjmedia_mem_capture_create( pool, //Pool
                            buffer, //Buffer
                            2000, //Buffer Size
                            CLOCK_RATE, 
                            CHANELS, 
                            SAMPLES_PER_FRAME, 
                            BITS_PER_SAMPLE, 
                            0, //Options
                            &prt); //The return port}

UPDATE

The assertion failed cause the buffer variable doesn't have any memory allocated to it. Allocate with twice the amount of samples per frame to have sufficient memory.

 buffer = pj_pool_zalloc(pool, 960);

Also a callback needs to be registered with pjmedia_mem_capture_set_eof_cb2() (The two at the end is necessary for PJSIP 2.10 or later) Apparently from there the buffer can be used. Just that my implementation atm doesn't execute the callback.

Solution

Looks like I found the solution, I have modified your code and wrote a simple code in C with pjsua API to dump every frame to file. Sorry for mess, I'm not proficient in C:

pjsua_call_info ci;
pjsua_call_get_info(call_id, &ci);
pjsua_conf_port_info cpi;
pjsua_conf_get_port_info(ci.conf_slot, &cpi);

pj_pool_t *pool = pjsua_pool_create("POOLNAME", 2000, 2000);
pjmedia_port *prt;
uint buf_size = cpi.bits_per_sample*cpi.samples_per_frame/8;
void *buffer = pj_pool_zalloc(pool, buf_size);
pjsua_conf_port_id port_id;

pjmedia_mem_capture_create( pool,
                            buffer,
                            buf_size,
                            cpi.clock_rate,
                            cpi.channel_count,
                            cpi.samples_per_frame,
                            cpi.bits_per_sample,
                            0,
                            &prt);
pjmedia_mem_capture_set_eof_cb(prt, buffer, dump_incoming_frames);
pjsua_conf_add_port(pool, prt, &port_id);
pjsua_conf_connect(ci.conf_slot, port_id); //connect port with conference

///////dumping frames///
static pj_status_t dump_incoming_frames(pjmedia_port * port, void * usr_data){
   pj_size_t buf_size = pjmedia_mem_capture_get_size(port);
   char * data = usr_data;
   ...
   fwrite(data,sizeof(data[0]),buf_size,fptr);
   ...
}

Documenation says pjmedia_mem_capture_set_eof_cb is deprecated but I couldn't make work pjmedia_mem_capture_set_eof_cb2, buf_size is 0 for every call of dump_incoming_frames so just left with deprecated function. I also succeed the same result with creating custom port.

I hope you can modify it easily to your C++/pjsua2 code

UPD: I have modified the PJSIP and packed audio in-out streaming into proper PJSUA2/Media classes so it can be called from Python. Full code is here.