Re: [Linphone-developers] Re: Linphone-developers Digest, Vol 1, Issue 24

[Simon Morlat]

Hi, and sorry for this late answer.

Le mer 18/12/2002 à 04:21, Peter Wang a écrit :
> Hi,
>    I find a minor bug in rtpsession.c,the value of "session->ssrc" is
> alaways 0,so I change the code to like this:
> 
> mblk_t * rtp_session_create_packet(RtpSession *session,gint
> header_size, char *payload, gint payload_size)
> {
>       mblk_t *mp;
>       gint msglen=header_size+payload_size;
>       rtp_header_t *rtp;
>       
>       mp=allocb(msglen,BPRI_MED);
> #ifdef _KERNEL
>       if (mp==NULL) return NULL;
> #endif
>       rtp=(rtp_header_t*)mp->b_rptr;
>       rtp->version = 2;
>       rtp->padbit = 0;
>       rtp->extbit = 0;
>       rtp->markbit= 0;
>       rtp->cc = 0;
>       //rtp_session_lock(session);
>       rtp->paytype = session->payload_type;
> /* Added by Peter Wang */
>     if(session->ssrc == 0) {
>         randomize();
>         session->ssrc = rand();
>     }
>       rtp->ssrc = session->ssrc;
>       //rtp_session_unlock(session);
>       rtp->timestamp = 0;     /* set later, when packet is sended */
>       rtp->seq_number = 0; /*set later, when packet is sended */
>       /*copy the payload */
>       mp->b_wptr+=header_size;
>       memcpy(mp->b_wptr,payload,payload_size);
>       mp->b_wptr+=payload_size;
>       return mp;
> }

I disagree with this change. The ssrc is unique per rtp session. It must
change within the same rtp session. The ssrc can be set using
rtp_session_set_ssrc(), and this ssrc will be used by the session for
all outgoing packets.

> 
> And I also find a bug in rtpmod.c, as we know,the newest packet should
> put to the tail of queue,but the rtp_putq will
> put  it to the head of queue.

I think rtp_putq() originally already does what you want.
It 's too late for me to explain you why, however i'm pretty sure of
that. oRTP has been tested many times and it works.

Thank you for your interest in oRTP.
Simon

> 
> /* put an rtp packet in queue. It is called by rtp_parse()*/
> void rtp_putq(queue_t *q, mblk_t *mp)
> {
>       mblk_t *tmp;
>       rtp_header_t *rtp=(rtp_header_t*)mp->b_rptr,*tmprtp;
>       /* insert message block by increasing time stamp order : the last (at
> the bottom)
>               message of the queue is the newest*/
>       g_message("rtp_putq(): Enqueuing packet with ts=%i",rtp->timestamp);
>       tmp=q->q_last;
>       
>         /* Modify by Peter Wang */
>       if ((tmp==NULL) ||
>  RTP_TIMESTAMP_IS_STRICTLY_NEWER_THAN(((rtp_header_t
> *)tmp->b_rptr)->timestamp,rtp->timestamp)) {
>               putq(q,mp);
>               return;
>       }
>       /* we look at the queue from bottom to top, because enqueued packets
> have a better chance
>       to be enqueued at the bottom, since there are surely newer */
>       while (tmp!=NULL)
>       {
>               tmprtp=(rtp_header_t*)tmp->b_rptr;
>               g_message("rtp_putq(): Seeing packet with 
> ts=%i",tmprtp->timestamp);
>               
>               if (rtp->timestamp == tmprtp->timestamp)
>               {
>                       if (rtp->seq_number== tmprtp->seq_number)
>                       {
>                               /* this is a duplicated packet. Don't queue it 
> */
>                               g_message("rtp_putq: duplicated message.");
>                               freemsg(mp);
>                               return;
>                       }
> #if 0
>                       else if (rtp->paytype==tmprtp->paytype){
>                               /* else link it to the already present packet */
>                               tmp->b_cont->b_cont=mp->b_cont;
>                               /* free the header message*/
>                               freeb(mp);
>                               return;
>                       }
> #endif
>                       /* else this is a different packet. It must be queued */
>                       insq(q,tmp->b_next,mp);
>                       return;
>               }
>               if
> RTP_TIMESTAMP_IS_STRICTLY_NEWER_THAN(rtp->timestamp,tmprtp->timestamp)
>               {
>                       /* insert mp just before tmp */
>                       insq(q,tmp->b_next,mp);
>                       g_message("mp=%x inserted before %x. q->q_first=%i, 
> q->q_last=%i",
>                                               mp,
>                                               tmp,
>                                               
> ((rtp_header_t*)q->q_first->b_rptr)->timestamp,
>                                               
> ((rtp_header_t*)q->q_last->b_rptr)->timestamp);
>                       return;
>               }
>               tmp=tmp->b_prev;
>       }
>       /* this packet is the oldest, it has to be 
>       placed on top of the queue */
>       insq(q,q->q_first,mp);
>       
> }
> 
> 
> 
> 
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Simon Morlat <address@hidden>