pjsip capture and play pcm data - c++

Question

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.

Answer 1

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.