[Linphone-developers] oRTP: Problem with non-8000Hz sample rates?

[Nicholas J Humfrey]

Hi,

I have been using RAT (Robust Audio Tool) to create a L16 44100Hz RTP  
packet stream (payload type 11) and also a payload type 0 (PCMU, 
8000Hz) to compare it with.

PayloadType 11 packets are 320 bytes (3ms) and PayloadType 0 streams  
are 160 bytes (20ms). Both streams contain 160 samples.


Here is a snippet of my main loop:

while( 1 )
{
        mblk_t* packet = packet = rtp_session_recvm_with_ts( session, ts );
        if (packet==NULL) {
                printf("Packet is NULL.\n" );
        } else {
                printf("Got packet, ts=%d, seq=%d, pt=%d\n",
                                        rtp_get_timestamp( packet ),
                                        rtp_get_seqnumber( packet ),
                                        rtp_get_payload_type( packet ) );
        }
        
        ts+=160;
}



With the PT0 stream I get:

[hwickabab:~/ortp-test] njh% ./recvtest 239.255.125.216 5004
Local address: 239.255.125.216
Local port: 5004
Packet is NULL.
Packet is NULL.
Packet is NULL.
ortp-message-payload type changed to 0(PCMU) !
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
Got packet, ts=1726968515, seq=24969, pt=0
Got packet, ts=1726968675, seq=24970, pt=0
Got packet, ts=1726968835, seq=24971, pt=0
Got packet, ts=1726968995, seq=24972, pt=0
Got packet, ts=1726969155, seq=24973, pt=0
Got packet, ts=1726969315, seq=24974, pt=0
Got packet, ts=1726969475, seq=24975, pt=0
Got packet, ts=1726969635, seq=24976, pt=0
Got packet, ts=1726969795, seq=24977, pt=0
...........


Which is fine, however when sending PT11 I get:

[hwickabab:~/ortp-test] njh% ./recvtest 239.255.125.216 5004
Local address: 239.255.125.216
Local port: 5004
ortp-message-payload type changed to 11(L16) !
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
Packet is NULL.
.......


And never manages to receive a packet. I verified that the difference  
between the timestamps is 160 on both streams but cannot workout why  
oRTP is unable to receive the PT11 stream... oRTP transmits PT11  
steams fine.


Any suggestions?


nick.

recvtest.c
Description: Binary data