Use NTP to calculate RTP timestamps

include/rtp.hh

@@ -42,7 +42,7 @@ namespace uvg_rtp {
             uint8_t payload_;
 
             uint32_t clock_rate_;
-            uint32_t wc_start_;
+            uint64_t wc_start_;
             uvg_rtp::clock::hrc::hrc_t wc_start_2;
 
             size_t sent_pkts_;

src/clock.cc

@@ -6,20 +6,23 @@
 #endif
 
 #include "clock.hh"
+#include <stdio.h>
+
+static const uint64_t EPOCH = 2208988800ULL;
+static const uint64_t NTP_SCALE_FRAC = 4294967296ULL;
 
 static inline uint32_t ntp_diff_ms(uint64_t t1, uint64_t t2)
 {
-    uint32_t s_diff  = (t1 >> 32) - (t2 >> 32);
+    uint32_t s1  = (t1 >> 32) & 0xffffffff;
-    uint32_t us_diff = (((t1 & 0xffffffff) - (t2 & 0xffffffff)) * 1000000UL) >> 32;
+    uint32_t s2  = (t2 >> 32) & 0xffffffff;
+    uint64_t us1 = ((t1 & 0xffffffff) * 1000000UL) / NTP_SCALE_FRAC;
+    uint64_t us2 = ((t2 & 0xffffffff) * 1000000UL) / NTP_SCALE_FRAC;
 
-    return s_diff / 1000 + (us_diff / 1000);
+    return (((s1 - s2) * 1000000) + ((us1 - us2))) / 1000;
 }
 
 uint64_t uvg_rtp::clock::ntp::now()
 {
-    static const uint64_t EPOCH = 2208988800ULL;
-    static const uint64_t NTP_SCALE_FRAC = 4294967296ULL;
-
     struct timeval tv;
 #ifdef _WIN32
     uvg_rtp::clock::gettimeofday(&tv, NULL);
@@ -30,7 +33,7 @@ uint64_t uvg_rtp::clock::ntp::now()
     uint64_t tv_ntp, tv_usecs;
 
     tv_ntp = tv.tv_sec + EPOCH;
-    tv_usecs = (NTP_SCALE_FRAC * tv.tv_usec) / 1000000UL;
+    tv_usecs = (float)(NTP_SCALE_FRAC * tv.tv_usec) / (float)1000000UL;
 
     return (tv_ntp << 32) | tv_usecs;
 }

src/rtp.cc

@@ -90,10 +90,9 @@ void uvg_rtp::rtp::fill_header(uint8_t *buffer)
 
     /* This is the first RTP message, get wall clock reading (t = 0)
      * and generate random RTP timestamp for this reading */
-    if (wc_start_ == 0) {
+    if (!wc_start_) {
         ts_        = uvg_rtp::random::generate_32();
-        wc_start_2 = uvg_rtp::clock::hrc::now();
+        wc_start_  = uvg_rtp::clock::ntp::now();
-        wc_start_  = 1;
     }
 
     buffer[0] = 2 << 6; // RTP version
@@ -105,10 +104,11 @@ void uvg_rtp::rtp::fill_header(uint8_t *buffer)
     if (timestamp_ == INVALID_TS) {
         *(uint32_t *)&buffer[4] = htonl(
             ts_
-            + uvg_rtp::clock::hrc::diff_now(wc_start_2)
+            + uvg_rtp::clock::ntp::diff_now(wc_start_)
             * clock_rate_
             / 1000
         );
+
     } else {
         *(uint32_t *)&buffer[4] = htonl(timestamp_);
     }