From bccc42e4e25c7f79efbb14ac2bf1fcb55718ee64 Mon Sep 17 00:00:00 2001
From: "F. Duncanh" <fduncanh@gmail.com>
Date: Mon, 27 Jan 2025 03:53:01 -0500
Subject: [PATCH] raop_rtp fixes/cleanups to remove unneeded ntp use

---
 README.html           |   2 +
 README.md             |   3 +
 README.txt            |   3 +
 lib/raop.c            |   4 +
 lib/raop.h            |   3 +-
 lib/raop_buffer.c     |  13 ++-
 lib/raop_buffer.h     |   4 +-
 lib/raop_ntp.c        |  30 +++++-
 lib/raop_ntp.h        |   5 +-
 lib/raop_rtp.c        | 225 +++++++++++++++---------------------------
 lib/raop_rtp_mirror.c |  12 ++-
 uxplay.cpp            |   6 +-
 12 files changed, 143 insertions(+), 167 deletions(-)

diff --git a/README.html b/README.html
index e27e320..27adc8c 100644
--- a/README.html
+++ b/README.html
@@ -15,6 +15,8 @@ until advertisements have finished or been skipped before clicking the
 YouTube airplay icon.) <strong>Please report any issues with this new
 feature of UxPlay</strong>.</li>
 </ul>
+<p><strong><em>NEWS</em></strong>: macOS Sequoia 15.2 has an AirPlay
+bug: update to macOS 15.3 for mirroring screen with UxPlay.</p>
 <h2 id="highlights">Highlights:</h2>
 <ul>
 <li>GPLv3, open source.</li>
diff --git a/README.md b/README.md
index 60c06fc..4b90254 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,9 @@
     YouTube airplay icon.) **Please report any issues with this new
     feature of UxPlay**.
 
+***NEWS***: macOS Sequoia 15.2 has an AirPlay bug: update to macOS 15.3
+   for mirroring  screen with UxPlay.
+
 ## Highlights:
 
 -   GPLv3, open source.
diff --git a/README.txt b/README.txt
index be6448b..1948be4 100644
--- a/README.txt
+++ b/README.txt
@@ -9,6 +9,9 @@
     YouTube airplay icon.) **Please report any issues with this new
     feature of UxPlay**.
 
+***NEWS***: macOS Sequoia 15.2 has an AirPlay bug: update to macOS 15.3
+for mirroring screen with UxPlay.
+
 ## Highlights:
 
 -   GPLv3, open source.
diff --git a/lib/raop.c b/lib/raop.c
index 41b2d2d..35f82de 100644
--- a/lib/raop.c
+++ b/lib/raop.c
@@ -765,3 +765,7 @@ void raop_destroy_airplay_video(raop_t *raop) {
         raop->airplay_video = NULL;
     }
 }
+
+uint64_t get_local_time() {
+    return raop_ntp_get_local_time();
+}
diff --git a/lib/raop.h b/lib/raop.h
index 97e7eb9..21ce747 100644
--- a/lib/raop.h
+++ b/lib/raop.h
@@ -108,7 +108,8 @@ int airplay_video_service_init(raop_t *raop, unsigned short port, const char *se
 bool register_airplay_video(raop_t *raop, airplay_video_t *airplay_video);
 airplay_video_t *get_airplay_video(raop_t *raop);
 airplay_video_t *deregister_airplay_video(raop_t *raop);
-  
+uint64_t get_local_time();
+
 RAOP_API raop_t *raop_init(raop_callbacks_t *callbacks);
 RAOP_API int raop_init2(raop_t *raop, int nohold, const char *device_id, const char *keyfile);
 RAOP_API void raop_set_log_level(raop_t *raop, int level);
diff --git a/lib/raop_buffer.c b/lib/raop_buffer.c
index 4fc8d76..99cd961 100644
--- a/lib/raop_buffer.c
+++ b/lib/raop_buffer.c
@@ -39,10 +39,11 @@ typedef struct {
     /* Data available */
     int filled;
 
+    uint64_t packet_arrival_time;
+
     /* RTP header */
     unsigned short seqnum;
-    uint64_t rtp_timestamp;
-    uint64_t ntp_timestamp;
+    uint32_t rtp_timestamp;
 
     /* Payload data */
     unsigned int payload_size;
@@ -165,7 +166,7 @@ raop_buffer_decrypt(raop_buffer_t *raop_buffer, unsigned char *data, unsigned ch
 }
 
 int
-raop_buffer_enqueue(raop_buffer_t *raop_buffer, unsigned char *data, unsigned short datalen, uint64_t *ntp_timestamp, uint64_t *rtp_timestamp, int use_seqnum) {
+raop_buffer_enqueue(raop_buffer_t *raop_buffer, unsigned char *data, unsigned short datalen, int use_seqnum) {
     unsigned char empty_packet_marker[] = { 0x00, 0x68, 0x34, 0x00 };
     assert(raop_buffer);
 
@@ -206,8 +207,7 @@ raop_buffer_enqueue(raop_buffer_t *raop_buffer, unsigned char *data, unsigned sh
 
     /* Update the raop_buffer entry header */
     entry->seqnum = seqnum;
-    entry->rtp_timestamp = *rtp_timestamp;
-    entry->ntp_timestamp = *ntp_timestamp;
+    entry->rtp_timestamp = byteutils_get_int_be(data, 4);
     entry->filled = 1;
 
     entry->payload_data = malloc(payload_size);
@@ -228,7 +228,7 @@ raop_buffer_enqueue(raop_buffer_t *raop_buffer, unsigned char *data, unsigned sh
 }
 
 void *
-raop_buffer_dequeue(raop_buffer_t *raop_buffer, unsigned int *length, uint64_t *ntp_timestamp, uint64_t *rtp_timestamp, unsigned short *seqnum, int no_resend) {
+raop_buffer_dequeue(raop_buffer_t *raop_buffer, unsigned int *length, uint32_t *rtp_timestamp, unsigned short *seqnum, int no_resend) {
     assert(raop_buffer);
 
     /* Calculate number of entries in the current buffer */
@@ -261,7 +261,6 @@ raop_buffer_dequeue(raop_buffer_t *raop_buffer, unsigned int *length, uint64_t *
 
     /* Return entry payload buffer */
     *rtp_timestamp = entry->rtp_timestamp;
-    *ntp_timestamp = entry->ntp_timestamp;
     *seqnum = entry->seqnum;
     *length = entry->payload_size;
     entry->payload_size = 0;
diff --git a/lib/raop_buffer.h b/lib/raop_buffer.h
index 1093188..a3322da 100644
--- a/lib/raop_buffer.h
+++ b/lib/raop_buffer.h
@@ -28,8 +28,8 @@ typedef int (*raop_resend_cb_t)(void *opaque, unsigned short seqno, unsigned sho
 raop_buffer_t *raop_buffer_init(logger_t *logger,
                                 const unsigned char *aeskey,
                                 const unsigned char *aesiv);
-int raop_buffer_enqueue(raop_buffer_t *raop_buffer, unsigned char *data, unsigned short datalen, uint64_t *ntp_timestamp, uint64_t *rtp_timestamp, int use_seqnum);
-void *raop_buffer_dequeue(raop_buffer_t *raop_buffer, unsigned int *length, uint64_t *ntp_timestamp, uint64_t *rtp_timestamp, unsigned short *seqnum, int no_resend);
+int raop_buffer_enqueue(raop_buffer_t *raop_buffer, unsigned char *data, unsigned short datalen, int use_seqnum);
+void *raop_buffer_dequeue(raop_buffer_t *raop_buffer, unsigned int *length, uint32_t *rtp_timestamp, unsigned short *seqnum, int no_resend);
 void raop_buffer_handle_resends(raop_buffer_t *raop_buffer, raop_resend_cb_t resend_cb, void *opaque);
 void raop_buffer_flush(raop_buffer_t *raop_buffer, int next_seq);
 
diff --git a/lib/raop_ntp.c b/lib/raop_ntp.c
index 026f70b..f918878 100644
--- a/lib/raop_ntp.c
+++ b/lib/raop_ntp.c
@@ -94,8 +94,17 @@ struct raop_ntp_s {
     timing_protocol_t time_protocol;
     bool client_time_received;
 
+    uint64_t video_arrival_offset;
 };
 
+/* for use in syncing audio before a first rtp_sync */
+void raop_ntp_set_video_arrival_offset(raop_ntp_t* raop_ntp, const uint64_t *offset) {
+    raop_ntp->video_arrival_offset = *offset;
+}
+
+uint64_t raop_ntp_get_video_arrival_offset(raop_ntp_t* raop_ntp) {
+    return raop_ntp->video_arrival_offset;
+}
 
 /*
  * Used for sorting the data array by delay
@@ -155,6 +164,8 @@ raop_ntp_t *raop_ntp_init(logger_t *logger, raop_callbacks_t *callbacks, const c
     raop_ntp->timing_rport = timing_rport;
     raop_ntp->client_time_received = false;
 
+    raop_ntp->video_arrival_offset = 0;
+
     if (raop_ntp_parse_remote(raop_ntp, remote, remote_addr_len) < 0) {
         free(raop_ntp);
         return NULL;
@@ -166,7 +177,7 @@ raop_ntp_t *raop_ntp_init(logger_t *logger, raop_callbacks_t *callbacks, const c
     raop_ntp->running = 0;
     raop_ntp->joined = 1;
 
-    uint64_t time = raop_ntp_get_local_time(raop_ntp);
+    uint64_t time = raop_ntp_get_local_time();
 
     for (int i = 0; i < RAOP_NTP_DATA_COUNT; ++i) {
         raop_ntp->data[i].offset     = 0ll;
@@ -289,7 +300,7 @@ raop_ntp_thread(void *arg)
         raop_ntp_flush_socket(raop_ntp->tsock);
 
         // Send request
-        uint64_t send_time = raop_ntp_get_local_time(raop_ntp);
+        uint64_t send_time = raop_ntp_get_local_time();
         byteutils_put_ntp_timestamp(request, 24, send_time);
         int send_len = sendto(raop_ntp->tsock, (char *)request, sizeof(request), 0,
                               (struct sockaddr *) &raop_ntp->remote_saddr, raop_ntp->remote_saddr_len);
@@ -315,7 +326,7 @@ raop_ntp_thread(void *arg)
                     raop_ntp->client_time_received = true;
                 }
                 //local time of the server when the NTP response packet returns
-                int64_t t3 = (int64_t) raop_ntp_get_local_time(raop_ntp);
+                int64_t t3 = (int64_t) raop_ntp_get_local_time();
 
                 // Local time of the server when the NTP request packet leaves the server
                 int64_t t0 = (int64_t) byteutils_get_ntp_timestamp(response, 8);
@@ -484,7 +495,7 @@ uint64_t raop_remote_timestamp_to_nano_seconds(raop_ntp_t *raop_ntp, uint64_t ti
  * Returns the current time in nano seconds according to the local wall clock.
  * The system Unix time is used as the local wall clock.
  */
-uint64_t raop_ntp_get_local_time(raop_ntp_t *raop_ntp) {
+uint64_t raop_ntp_get_local_time() {
     struct timespec time;
     clock_gettime(CLOCK_REALTIME, &time);
     return ((uint64_t) time.tv_nsec) + (uint64_t) time.tv_sec * SECOND_IN_NSECS;
@@ -494,16 +505,22 @@ uint64_t raop_ntp_get_local_time(raop_ntp_t *raop_ntp) {
  * Returns the current time in nano seconds according to the remote wall clock.
  */
 uint64_t raop_ntp_get_remote_time(raop_ntp_t *raop_ntp) {
+    if  (!raop_ntp->client_time_received) {
+        return 0;
+    }
     MUTEX_LOCK(raop_ntp->sync_params_mutex);
     int64_t offset = raop_ntp->sync_offset;
     MUTEX_UNLOCK(raop_ntp->sync_params_mutex);
-    return (uint64_t) ((int64_t) raop_ntp_get_local_time(raop_ntp) + offset);
+    return (uint64_t) ((int64_t) raop_ntp_get_local_time() + offset);
 }
 
 /**
  * Returns the local wall clock time in nano seconds for the given point in remote clock time
  */
 uint64_t raop_ntp_convert_remote_time(raop_ntp_t *raop_ntp, uint64_t remote_time) {
+    if  (!raop_ntp->client_time_received) {
+        return 0;
+    }
     MUTEX_LOCK(raop_ntp->sync_params_mutex);
     int64_t offset = raop_ntp->sync_offset;
     MUTEX_UNLOCK(raop_ntp->sync_params_mutex);
@@ -514,6 +531,9 @@ uint64_t raop_ntp_convert_remote_time(raop_ntp_t *raop_ntp, uint64_t remote_time
  * Returns the remote wall clock time in nano seconds for the given point in local clock time
  */
 uint64_t raop_ntp_convert_local_time(raop_ntp_t *raop_ntp, uint64_t local_time) {
+    if  (!raop_ntp->client_time_received) {
+        return 0;
+    }
     MUTEX_LOCK(raop_ntp->sync_params_mutex);
     int64_t offset = raop_ntp->sync_offset;
     MUTEX_UNLOCK(raop_ntp->sync_params_mutex);
diff --git a/lib/raop_ntp.h b/lib/raop_ntp.h
index f829f4e..ad7a1ad 100644
--- a/lib/raop_ntp.h
+++ b/lib/raop_ntp.h
@@ -38,9 +38,12 @@ void raop_ntp_destroy(raop_ntp_t *raop_rtp);
 uint64_t raop_ntp_timestamp_to_nano_seconds(uint64_t ntp_timestamp, bool account_for_epoch_diff);
 uint64_t raop_remote_timestamp_to_nano_seconds(raop_ntp_t *raop_ntp, uint64_t timestamp);
 
-uint64_t raop_ntp_get_local_time(raop_ntp_t *raop_ntp);
+uint64_t raop_ntp_get_local_time();
 uint64_t raop_ntp_get_remote_time(raop_ntp_t *raop_ntp);
 uint64_t raop_ntp_convert_remote_time(raop_ntp_t *raop_ntp, uint64_t remote_time);
 uint64_t raop_ntp_convert_local_time(raop_ntp_t *raop_ntp, uint64_t local_time);
 
+void  raop_ntp_set_video_arrival_offset(raop_ntp_t* raop_ntp, const uint64_t *offset);
+uint64_t raop_ntp_get_video_arrival_offset(raop_ntp_t* raop_ntp);
+
 #endif //RAOP_NTP_H
diff --git a/lib/raop_rtp.c b/lib/raop_rtp.c
index 62543f7..0947e6c 100644
--- a/lib/raop_rtp.c
+++ b/lib/raop_rtp.c
@@ -36,10 +36,9 @@
 #define NO_FLUSH (-42)
 
 #define SECOND_IN_NSECS 1000000000
-#define RAOP_RTP_SYNC_DATA_COUNT 8
 #define SEC SECOND_IN_NSECS
 
-#define DELAY_AAC  0.275  //empirical, matches audio latency of about -0.25 sec after first clock sync event
+#define DELAY_AAC  0.20 //empirical, matches audio latency of about -0.25 sec after first clock sync event
 
 /* note: it is unclear what will happen in the unlikely event that this code is running at the time of the unix-time 
  * epoch event on 2038-01-19 at 3:14:08 UTC ! (but Apple will surely have removed AirPlay "legacy pairing" by then!) */
@@ -56,14 +55,16 @@ struct raop_rtp_s {
     // Time and sync
     raop_ntp_t *ntp;
     double rtp_clock_rate;
-    int64_t rtp_sync_offset;
-    raop_rtp_sync_data_t sync_data[RAOP_RTP_SYNC_DATA_COUNT];
-    int sync_data_index;
+
     uint64_t ntp_start_time;
     uint64_t rtp_start_time;
     uint64_t rtp_time;
     bool rtp_clock_started;
 
+    uint32_t rtp_sync;
+    uint64_t client_ntp_sync;
+    bool initial_sync;
+
     // Transmission Stats, could be used if a playout buffer is needed
     // float interarrival_jitter; // As defined by RTP RFC 3550, Section 6.4.1
     // unsigned int last_packet_transit_time;
@@ -161,12 +162,10 @@ raop_rtp_init(logger_t *logger, raop_callbacks_t *callbacks, raop_ntp_t *ntp, co
     raop_rtp->logger = logger;
     raop_rtp->ntp = ntp;
 
-    raop_rtp->rtp_sync_offset = 0;
-    raop_rtp->sync_data_index = 0;
-    for (int i = 0; i < RAOP_RTP_SYNC_DATA_COUNT; ++i) {
-        raop_rtp->sync_data[i].ntp_time = 0;
-        raop_rtp->sync_data[i].rtp_time = 0;
-    }
+    raop_rtp->rtp_sync = 0;
+    raop_rtp->client_ntp_sync = 0;
+    raop_rtp->initial_sync = false;
+    
     raop_rtp->ntp_start_time = 0;
     raop_rtp->rtp_start_time = 0;
     raop_rtp->rtp_clock_started = false;
@@ -386,59 +385,22 @@ raop_rtp_process_events(raop_rtp_t *raop_rtp, void *cb_data)
     return 0;
 }
 
-void raop_rtp_sync_clock(raop_rtp_t *raop_rtp, uint64_t *ntp_time, uint64_t *rtp_time) {
-    /* ntp_time = (uint64_t)(((int64_t)(raop_rtp->rtp_clock_rate * rtp_time)) + raop_rtp->rtp_sync_offset)  */
-    int latest, valid_data_count = 0;
-    uint64_t ntp_sum = 0, rtp_sum = 0;
-    double offset = ((double) *ntp_time) - raop_rtp->rtp_clock_rate * *rtp_time;
-    int64_t correction = 0;
-
-    raop_rtp->sync_data_index = (raop_rtp->sync_data_index + 1) % RAOP_RTP_SYNC_DATA_COUNT;
-    latest = raop_rtp->sync_data_index;
-    raop_rtp->sync_data[latest].rtp_time = *rtp_time;
-    raop_rtp->sync_data[latest].ntp_time = *ntp_time;
-
-    for (int i = 0; i < RAOP_RTP_SYNC_DATA_COUNT; i++) {
-        if (raop_rtp->sync_data[i].ntp_time == 0) continue;
-        valid_data_count++;
-        if (i == latest) continue;
-        ntp_sum += *ntp_time - raop_rtp->sync_data[i].ntp_time;
-        rtp_sum += *rtp_time - raop_rtp->sync_data[i].rtp_time;
+static uint64_t rtp_time_to_client_ntp(raop_rtp_t *raop_rtp,  uint32_t *rtp32) {
+    if (!raop_rtp->initial_sync) {
+        return 0;
     }
-
-    if (valid_data_count > 1) {
-        correction -= raop_rtp->rtp_sync_offset;
-        offset += (((double) ntp_sum) - raop_rtp->rtp_clock_rate * rtp_sum) / valid_data_count;
-    }
-    raop_rtp->rtp_sync_offset = (int64_t) offset;
-    correction += raop_rtp->rtp_sync_offset;
-
-    logger_log(raop_rtp->logger, LOGGER_DEBUG, "dataset %d raop_rtp sync correction=%lld, rtp_sync_offset = %lld ",
-               valid_data_count, correction, raop_rtp->rtp_sync_offset);
-}
-
-uint64_t rtp64_time (raop_rtp_t *raop_rtp, const uint32_t *rtp32) {
-    /* convert from 32-bit to 64-bit rtp time:
-     * the rtp_time 32-bit epoch at 44.1kHz has length of about 27 hours
-     * using 64-bit rtp time avoids any epoch issues.
-     * initial call sets epoch to 1; subsequent calls maintain consistent epoch.
-     * (assumes successive calls are close in time) */
-
-    if (raop_rtp->rtp_clock_started) {
-        uint32_t diff1 = *rtp32 -  ((uint32_t) raop_rtp->rtp_time);
-        uint32_t diff2 = ((uint32_t) raop_rtp->rtp_time) - *rtp32;
-        if (diff1 <= diff2) {
-            raop_rtp->rtp_time += (uint64_t) diff1;
-        } else {
-            raop_rtp->rtp_time -= (uint64_t) diff2;
-        }
+    uint64_t client_ntp = raop_rtp->client_ntp_sync;
+    if (*rtp32 >= raop_rtp->rtp_sync) {
+        client_ntp += (uint64_t) raop_rtp->rtp_clock_rate * (*rtp32 - raop_rtp->rtp_sync);
     } else {
-        raop_rtp->rtp_time = (0x01ULL << 32 ) + (uint64_t) *rtp32;
-        raop_rtp->rtp_start_time = raop_rtp->rtp_time;
-        raop_rtp->rtp_clock_started = true;
+        uint64_t ntp_shift = (uint64_t) raop_rtp->rtp_clock_rate * (raop_rtp->rtp_sync - *rtp32);
+        if (client_ntp > ntp_shift) {
+            client_ntp -= ntp_shift;
+        } else {
+            client_ntp = 0;
+        }
     }
-    //assert(*rtp32 == (uint32_t) raop_rtp->rtp_time);
-    return  raop_rtp->rtp_time;
+    return client_ntp; 
 }
 
 static THREAD_RETVAL
@@ -450,22 +412,15 @@ raop_rtp_thread_udp(void *arg)
     struct sockaddr_storage saddr;
     socklen_t saddrlen;
     bool got_remote_control_saddr = false;
+    uint64_t video_arrival_offset = 0;
 
-    /* for initial rtp to ntp conversions */    
-    bool have_synced = false;
-    bool no_data_yet = true;
+    /* initial audio stream has no data */    
     unsigned char no_data_marker[] = {0x00, 0x68, 0x34, 0x00 };
-    int rtp_count = 0;
-    double sync_adjustment = 0;
-    unsigned short seqnum1 = 0, seqnum2 = 0;
 
     assert(raop_rtp);
     bool logger_debug = (logger_get_level(raop_rtp->logger) >= LOGGER_DEBUG);
-    raop_rtp->ntp_start_time = raop_ntp_get_local_time(raop_rtp->ntp);
+    raop_rtp->ntp_start_time = raop_ntp_get_local_time();
     raop_rtp->rtp_clock_started = false;
-    for (int i = 0; i < RAOP_RTP_SYNC_DATA_COUNT; i++) {
-        raop_rtp->sync_data[i].ntp_time = 0;
-    }
 
     int no_resend = (raop_rtp->control_rport == 0); /* true when control_rport is not set */
 
@@ -526,14 +481,8 @@ raop_rtp_thread_udp(void *arg)
                 unsigned int resent_packetlen = packetlen - 4;
                 unsigned short seqnum = byteutils_get_short_be(resent_packet, 2);
                 if (resent_packetlen >= 12) {
-                    uint32_t timestamp = byteutils_get_int_be(resent_packet, 4);
-                    uint64_t rtp_time = rtp64_time(raop_rtp, &timestamp);
-		    uint64_t ntp_time = 0;
-		    if (have_synced) {
-                        ntp_time = (uint64_t) (raop_rtp->rtp_sync_offset + (int64_t) (raop_rtp->rtp_clock_rate * rtp_time));
-		    }
                     logger_log(raop_rtp->logger, LOGGER_DEBUG, "raop_rtp resent audio packet: seqnum=%u", seqnum);
-                    int result = raop_buffer_enqueue(raop_rtp->buffer, resent_packet, resent_packetlen, &ntp_time, &rtp_time, 1);
+                    int result = raop_buffer_enqueue(raop_rtp->buffer, resent_packet, resent_packetlen, 1);
                     assert(result >= 0);
                 } else if (logger_debug) {
                     /* type_c = 0x56 packets  with length 8 have been reported */
@@ -553,24 +502,30 @@ raop_rtp_thread_udp(void *arg)
                  * next_rtp = sync_rtp + 77175  = 441 * 175 (1.75 sec) for ALAC */
 
                 // The unit for the rtp clock is 1 / sample rate = 1 / 44100
-                uint32_t sync_rtp = byteutils_get_int_be(packet, 4);
-                uint64_t sync_rtp64 = rtp64_time(raop_rtp, &sync_rtp);
-                if (have_synced == false) {
+                uint64_t client_ntp_sync_prev = 0;
+                uint64_t rtp_sync_prev = 0;
+                if (!raop_rtp->initial_sync) {
                     logger_log(raop_rtp->logger, LOGGER_DEBUG, "first audio rtp sync");
-                    have_synced = true;
-                }
+                    raop_rtp->initial_sync = true;
+                } else {
+                   client_ntp_sync_prev = raop_rtp->client_ntp_sync;
+                   rtp_sync_prev = raop_rtp->rtp_sync;
+		}
+                raop_rtp->rtp_sync = byteutils_get_int_be(packet, 4);
                 uint64_t sync_ntp_raw = byteutils_get_long_be(packet, 8);
-                uint64_t sync_ntp_remote = raop_remote_timestamp_to_nano_seconds(raop_rtp->ntp, sync_ntp_raw);
+                raop_rtp->client_ntp_sync = raop_remote_timestamp_to_nano_seconds(raop_rtp->ntp, sync_ntp_raw);
+ 
                 if (logger_debug) {
-                    uint64_t sync_ntp_local = raop_ntp_convert_remote_time(raop_rtp->ntp, sync_ntp_remote);
+                    double offset_change = ((double) raop_rtp->client_ntp_sync) - raop_rtp->rtp_clock_rate * raop_rtp->rtp_sync;
+                    offset_change -= ((double) client_ntp_sync_prev) - raop_rtp->rtp_clock_rate * rtp_sync_prev;
+                    uint64_t sync_ntp_local = raop_ntp_convert_remote_time(raop_rtp->ntp,  raop_rtp->rtp_sync);
                     char *str = utils_data_to_string(packet, packetlen, 20);
                     logger_log(raop_rtp->logger, LOGGER_DEBUG,
-                               "raop_rtp sync: client ntp=%8.6f, ntp = %8.6f, ntp_start_time %8.6f\nts_client = %8.6f sync_rtp=%u\n%s",
-                               (double) sync_ntp_remote / SEC, (double) sync_ntp_local / SEC,
-                               (double) raop_rtp->ntp_start_time / SEC, (double) sync_ntp_remote / SEC, sync_rtp, str);
+                               "raop_rtp sync: ntp = %8.6f, ntp_start_time %8.6f\nts_client = %8.6f sync_rtp=%u offset change = %8.6f\n%s",
+                               (double) sync_ntp_local / SEC, (double) raop_rtp->ntp_start_time / SEC,
+                               (double) raop_rtp->client_ntp_sync / SEC, raop_rtp->rtp_sync, offset_change / SEC, str);
                     free(str);
                 }
-                raop_rtp_sync_clock(raop_rtp, &sync_ntp_remote, &sync_rtp64);		
             } else if (logger_debug) {
                 char *str = utils_data_to_string(packet, packetlen, 16);
                 logger_log(raop_rtp->logger, LOGGER_DEBUG, "raop_rtp unknown udp control packet\n%s", str);
@@ -615,6 +570,9 @@ raop_rtp_thread_udp(void *arg)
 
 
 	if (FD_ISSET(raop_rtp->dsock, &rfds)) {
+	    if (!raop_rtp->initial_sync && !video_arrival_offset) {
+                video_arrival_offset = raop_ntp_get_video_arrival_offset(raop_rtp->ntp);
+	    }
             //logger_log(raop_rtp->logger, LOGGER_INFO, "Would have data packet in queue");
             // Receiving audio data here
             saddrlen = sizeof(saddr);
@@ -633,83 +591,58 @@ raop_rtp_thread_udp(void *arg)
                 continue;
 	    }
 
-            uint32_t rtp_timestamp =  byteutils_get_int_be(packet, 4);
-            uint64_t rtp_time = rtp64_time(raop_rtp, &rtp_timestamp);
-	    uint64_t ntp_time = 0;
+	    if (!raop_rtp->initial_sync &&  raop_rtp->ct == 8 && video_arrival_offset) {
+                /* estimate a fake initial remote timestamp for video  synchronization  with AAC audio before the first rtp sync */
+ 	         uint64_t ts = raop_ntp_get_local_time() - video_arrival_offset;
+	         double delay = DELAY_AAC;
+		 ts += (uint64_t) (delay * SEC);
+		 raop_rtp->client_ntp_sync = ts;
+		 raop_rtp->rtp_sync = byteutils_get_int_be(packet, 4);
+		 raop_rtp->initial_sync = true;
+	    }	    
 
+            if (packetlen == 16 && memcmp(packet + 12, no_data_marker, 4) == 0) {
+                /* this is a "no data" packet */
+	        /* the first such packet could be used to provide the initial rtptime and seqnum formerly given in the RECORD request */
+                continue;
+            }
+	    
 	    if (raop_rtp->ct == 2 && packetlen == 44)  continue;   /* ignore the ALAC packets with format information only. */
 
-	    if (have_synced) {
-                ntp_time = (uint64_t) (raop_rtp->rtp_sync_offset + (int64_t) (raop_rtp->rtp_clock_rate * rtp_time));
-	    } else if (packetlen == 16 && memcmp(packet + 12, no_data_marker, 4) == 0) {
-	        /* use the special "no_data"  packet to help determine an initial offset before the first rtp sync. 
-                 * until the first rtp sync occurs, we don't know the exact client ntp timestamp that matches the client rtp timestamp */
-                if (no_data_yet) {
-	            int64_t sync_ntp =  ((int64_t) raop_ntp_get_local_time(raop_rtp->ntp)) - ((int64_t) raop_rtp->ntp_start_time) ;
-                    int64_t sync_rtp = ((int64_t) rtp_time) - ((int64_t) raop_rtp->rtp_start_time);
-                    unsigned short seqnum = byteutils_get_short_be(packet, 2);
-                    if  (rtp_count == 0) {
-                        sync_adjustment =  ((double) sync_ntp); 
-                        rtp_count = 1;
-                        seqnum1 = seqnum;
-                        seqnum2 = seqnum;
-                    }
-                    if (seqnum2 != seqnum) {  /* for AAC-ELD  only use copy 1 of the 3 copies of each  frame */
-                        rtp_count++;
-                        sync_adjustment += (((double) sync_ntp) - raop_rtp->rtp_clock_rate * sync_rtp - sync_adjustment) / rtp_count;
-                    }
-                    seqnum2 = seqnum1;
-                    seqnum1 = seqnum;
-                }
-                continue;
-	    } else {
-                no_data_yet = false;
-	    }
-            int result = raop_buffer_enqueue(raop_rtp->buffer, packet, packetlen, &ntp_time, &rtp_time, 1);
+            int result = raop_buffer_enqueue(raop_rtp->buffer, packet, packetlen, 1);
             assert(result >= 0);
 
-	    if (raop_rtp->ct == 2 && !have_synced) {
-                /* in ALAC Audio-only  mode wait until the first sync before dequeing */
+	    if (!raop_rtp->initial_sync) {
+                /* wait until the first sync before dequeing ALAC */
                 continue;
             } else {
             // Render continuous buffer entries
                 void *payload = NULL;
                 unsigned int payload_size;
                 unsigned short seqnum;
-                uint64_t rtp64_timestamp;
-                uint64_t ntp_timestamp;
+                uint32_t rtp_timestamp;
 
-                while ((payload = raop_buffer_dequeue(raop_rtp->buffer, &payload_size, &ntp_timestamp, &rtp64_timestamp, &seqnum, no_resend))) {
+                while ((payload = raop_buffer_dequeue(raop_rtp->buffer, &payload_size, &rtp_timestamp, &seqnum, no_resend))) {
                     audio_decode_struct audio_data; 
-                    audio_data.rtp_time = rtp64_timestamp;
+                    audio_data.rtp_time = rtp_timestamp;
                     audio_data.seqnum = seqnum;
                     audio_data.data_len = payload_size;
                     audio_data.data = payload;
                     audio_data.ct = raop_rtp->ct;
-                    if (have_synced) {
-                        if (ntp_timestamp == 0) {
-                            ntp_timestamp = (uint64_t) (raop_rtp->rtp_sync_offset + (int64_t) (raop_rtp->rtp_clock_rate * rtp64_timestamp));
-                        }
-                        audio_data.ntp_time_remote = ntp_timestamp;
-                        audio_data.ntp_time_local  = raop_ntp_convert_remote_time(raop_rtp->ntp, audio_data.ntp_time_remote);
-                        audio_data.sync_status = 1;
-                    } else {
-                        double elapsed_time =  raop_rtp->rtp_clock_rate * (rtp64_timestamp - raop_rtp->rtp_start_time) + sync_adjustment
-                            + DELAY_AAC * SECOND_IN_NSECS; 
-                        audio_data.ntp_time_local = raop_rtp->ntp_start_time + (uint64_t) elapsed_time;
-                        audio_data.ntp_time_remote = raop_ntp_convert_local_time(raop_rtp->ntp, audio_data.ntp_time_local);
-                        audio_data.sync_status = 0;
+                    audio_data.ntp_time_remote = rtp_time_to_client_ntp(raop_rtp, &rtp_timestamp);
+                    audio_data.ntp_time_local  = raop_ntp_convert_remote_time(raop_rtp->ntp, audio_data.ntp_time_remote);
+
+                    if (logger_debug) {
+                        uint64_t ntp_now = raop_ntp_get_local_time();
+                        int64_t latency = (audio_data.ntp_time_local ? ((int64_t) ntp_now) - ((int64_t) audio_data.ntp_time_local) : 0); 
+                        logger_log(raop_rtp->logger, LOGGER_DEBUG,
+                                   "raop_rtp audio: now = %8.6f, ntp = %8.6f, latency = %9.6f, ts = %8.6f, rtp_time=%u seqnum = %u",
+                                   (double) ntp_now / SEC, (double) audio_data.ntp_time_local / SEC, (double) latency / SEC,
+                                   (double) audio_data.ntp_time_remote /SEC, rtp_timestamp, seqnum);
                     }
+
                     raop_rtp->callbacks.audio_process(raop_rtp->callbacks.cls, raop_rtp->ntp, &audio_data);
                     free(payload);
-                    if (logger_debug) {
-                        uint64_t ntp_now = raop_ntp_get_local_time(raop_rtp->ntp);
-                        int64_t latency = ((int64_t) ntp_now) - ((int64_t) audio_data.ntp_time_local); 
-                        logger_log(raop_rtp->logger, LOGGER_DEBUG,
-                                   "raop_rtp audio: now = %8.6f, ntp = %8.6f, latency = %8.6f, rtp_time=%u seqnum = %u",
-                                   (double) ntp_now / SEC, (double) audio_data.ntp_time_local / SEC, (double) latency / SEC,
-                                   (uint32_t) rtp64_timestamp, seqnum);
-                    }
                 }
 
                 /* Handle possible resend requests */
diff --git a/lib/raop_rtp_mirror.c b/lib/raop_rtp_mirror.c
index 5b66194..6eb7bd3 100644
--- a/lib/raop_rtp_mirror.c
+++ b/lib/raop_rtp_mirror.c
@@ -201,6 +201,7 @@ raop_rtp_mirror_thread(void *arg)
     const char h265[] = "h265";
     bool unsupported_codec = false;
     bool video_stream_suspended = false;
+    bool first_packet = true;
     
     while (1) {
         fd_set rfds;
@@ -327,6 +328,11 @@ raop_rtp_mirror_thread(void *arg)
 	    }
             ntp_timestamp_raw = byteutils_get_long(packet, 8);
             ntp_timestamp_remote = raop_ntp_timestamp_to_nano_seconds(ntp_timestamp_raw, false);
+            if (first_packet) {
+	        uint64_t offset  = raop_ntp_get_local_time() - ntp_timestamp_remote;
+                raop_ntp_set_video_arrival_offset(raop_rtp_mirror->ntp, &offset);
+                first_packet = false;
+            }
 
 	    /* packet[4] + packet[5] identify the payload type:   values seen are:               *
              * 0x00 0x00: encrypted packet containing a non-IDR  type 1 VCL NAL unit             *
@@ -389,10 +395,10 @@ raop_rtp_mirror_thread(void *arg)
 
                 ntp_timestamp_local = raop_ntp_convert_remote_time(raop_rtp_mirror->ntp, ntp_timestamp_remote);
                 if (logger_debug) {
-                    uint64_t ntp_now = raop_ntp_get_local_time(raop_rtp_mirror->ntp);
-                    int64_t latency = ((int64_t) ntp_now) - ((int64_t) ntp_timestamp_local);
+                    uint64_t ntp_now = raop_ntp_get_local_time();
+                    int64_t latency = (ntp_timestamp_local ? ((int64_t) ntp_now) - ((int64_t) ntp_timestamp_local) : 0);
                     logger_log(raop_rtp_mirror->logger, LOGGER_DEBUG,
-                               "raop_rtp video: now = %8.6f, ntp = %8.6f, latency = %8.6f, ts = %8.6f, %s %s",
+                               "raop_rtp video: now = %8.6f, ntp = %8.6f, latency = %9.6f, ts = %8.6f, %s %s",
                                (double) ntp_now / SEC, (double) ntp_timestamp_local / SEC, (double) latency / SEC,
                                (double) ntp_timestamp_remote / SEC, packet_description, h265_video ? h265 : h264);
                 }
diff --git a/uxplay.cpp b/uxplay.cpp
index 3322ffb..a8f556f 100644
--- a/uxplay.cpp
+++ b/uxplay.cpp
@@ -1658,7 +1658,8 @@ extern "C" void audio_process (void *cls, raop_ntp_t *ntp, audio_decode_struct *
     }
     if (use_audio) {
         if (!remote_clock_offset) {
-            remote_clock_offset = data->ntp_time_local - data->ntp_time_remote;
+            uint64_t local_time = (data->ntp_time_local ? data->ntp_time_local : get_local_time());
+            remote_clock_offset = local_time - data->ntp_time_remote;
         }
         data->ntp_time_remote = data->ntp_time_remote + remote_clock_offset;
         switch (data->ct) {
@@ -1686,7 +1687,8 @@ extern "C" void video_process (void *cls, raop_ntp_t *ntp, video_decode_struct *
     }
     if (use_video) {
         if (!remote_clock_offset) {
-            remote_clock_offset = data->ntp_time_local - data->ntp_time_remote;
+            uint64_t local_time = (data->ntp_time_local ? data->ntp_time_local : get_local_time());
+            remote_clock_offset = local_time - data->ntp_time_remote;
         }
         data->ntp_time_remote = data->ntp_time_remote + remote_clock_offset;
         video_renderer_render_buffer(data->data, &(data->data_len), &(data->nal_count), &(data->ntp_time_remote));