tweak: speedup SRTP transport

[Eeri.Kask@xxxxxxxxxxxxxxxxxxxxx (Eeri Kask)]

Hello,

it looks like SRTP-transport (pjmedia/src/pjmedia/transport_srtp.c)
copies the whole outgoing communication (video+audio) in RAM from
location A to B without any easily apparent purpose; e.g. for video this
is cir 32 Kbyte/sec traffic if ffmpeg-encoder bitrate is set to 256Kbit.
 Is it feasible to avoid this overhead?

(In contrast, incoming communication is not copied, "srtp_unprotect()"
operates directly on packet-buffer 'pkt'.)

    Eeri Kask

-------------- next part --------------
--- pjmedia/src/pjmedia/transport_srtp.c.orig	2014-05-14 15:24:39.000000000 +0200
+++ pjmedia/src/pjmedia/transport_srtp.c	2014-05-14 15:57:50.000000000 +0200
@@ -94,8 +94,6 @@
     pjmedia_transport	 base;		    /**< Base transport interface.  */
     pj_pool_t		*pool;		    /**< Pool for transport SRTP.   */
     pj_lock_t		*mutex;		    /**< Mutex for libsrtp contexts.*/
-    char		 rtp_tx_buffer[MAX_RTP_BUFFER_LEN];
-    char		 rtcp_tx_buffer[MAX_RTCP_BUFFER_LEN];
     pjmedia_srtp_setting setting;
     unsigned		 media_option;
 
@@ -824,22 +822,20 @@
     if (srtp->bypass_srtp)
 	return pjmedia_transport_send_rtp(srtp->member_tp, pkt, size);
 
-    if (size > sizeof(srtp->rtp_tx_buffer) - 10)
+    if (size > MAX_RTP_BUFFER_LEN - 10)
 	return PJ_ETOOBIG;
 
-    pj_memcpy(srtp->rtp_tx_buffer, pkt, size);
-
     pj_lock_acquire(srtp->mutex);
     if (!srtp->session_inited) {
 	pj_lock_release(srtp->mutex);
 	return PJ_EINVALIDOP;
     }
-    err = srtp_protect(srtp->srtp_tx_ctx, srtp->rtp_tx_buffer, &len);
+    err = srtp_protect(srtp->srtp_tx_ctx, pkt, &len);
     pj_lock_release(srtp->mutex);
 
     if (err == err_status_ok) {
 	status = pjmedia_transport_send_rtp(srtp->member_tp,
-					    srtp->rtp_tx_buffer, len);
+					    pkt, len);
     } else {
 	status = PJMEDIA_ERRNO_FROM_LIBSRTP(err);
     }
@@ -870,22 +866,20 @@
 	                                    pkt, size);
     }
 
-    if (size > sizeof(srtp->rtcp_tx_buffer) - 10)
+    if (size > MAX_RTCP_BUFFER_LEN - 10)
 	return PJ_ETOOBIG;
 
-    pj_memcpy(srtp->rtcp_tx_buffer, pkt, size);
-
     pj_lock_acquire(srtp->mutex);
     if (!srtp->session_inited) {
 	pj_lock_release(srtp->mutex);
 	return PJ_EINVALIDOP;
     }
-    err = srtp_protect_rtcp(srtp->srtp_tx_ctx, srtp->rtcp_tx_buffer, &len);
+    err = srtp_protect_rtcp(srtp->srtp_tx_ctx, pkt, &len);
     pj_lock_release(srtp->mutex);
 
     if (err == err_status_ok) {
 	status = pjmedia_transport_send_rtcp2(srtp->member_tp, addr, addr_len,
-					      srtp->rtcp_tx_buffer, len);
+					      pkt, len);
     } else {
 	status = PJMEDIA_ERRNO_FROM_LIBSRTP(err);
     }