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update packet reception statistics to use nanosecond timing

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This commit is contained in:
Mike Brady
2020-02-24 19:58:35 +00:00
parent 67e9b1b6cd
commit 32427423af
1 changed files with 14 additions and 14 deletions
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rtp.c
+14 -14
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@@ -108,7 +108,7 @@ void *rtp_audio_receiver(void *arg) {
int32_t last_seqno = -1;
uint8_t packet[2048], *pktp;
uint64_t time_of_previous_packet_fp = 0;
uint64_t time_of_previous_packet_ns = 0;
float longest_packet_time_interval_us = 0.0;
// mean and variance calculations from "online_variance" algorithm at
@@ -125,11 +125,11 @@ void *rtp_audio_receiver(void *arg) {
frame_count++;
uint64_t local_time_now_fp = get_absolute_time_in_fp();
if (time_of_previous_packet_fp) {
uint64_t local_time_now_ns = get_absolute_time_in_ns();
if (time_of_previous_packet_ns) {
float time_interval_us =
(((local_time_now_fp - time_of_previous_packet_fp) * 1000000) >> 32) * 1.0;
time_of_previous_packet_fp = local_time_now_fp;
(local_time_now_ns - time_of_previous_packet_ns) * 0.001;
time_of_previous_packet_ns = local_time_now_ns;
if (time_interval_us > longest_packet_time_interval_us)
longest_packet_time_interval_us = time_interval_us;
stat_n += 1;
@@ -143,11 +143,11 @@ void *rtp_audio_receiver(void *arg) {
stat_n = 0;
stat_mean = 0.0;
stat_M2 = 0.0;
time_of_previous_packet_fp = 0;
time_of_previous_packet_ns = 0;
longest_packet_time_interval_us = 0.0;
}
} else {
time_of_previous_packet_fp = local_time_now_fp;
time_of_previous_packet_ns = local_time_now_ns;
}
if (nread >= 0) {
@@ -270,8 +270,8 @@ void *rtp_control_receiver(void *arg) {
obfp += 2;
};
*obfp = 0;
// get raw timestamp information
// I think that a good way to understand these timestamps is that
// (1) the rtlt below is the timestamp of the frame that should be playing at the
@@ -282,19 +282,19 @@ void *rtp_control_receiver(void *arg) {
// Thus, (3) the latency can be calculated by subtracting the second from the
// first.
// There must be more to it -- there something missing.
// In addition, it seems that if the value of the short represented by the second
// pair of bytes in the packet is 7
// then an extra time lag is expected to be added, presumably by
// the AirPort Express.
// Best guess is that this delay is 11,025 frames.
uint32_t rtlt = nctohl(&packet[4]); // raw timestamp less latency
uint32_t rt = nctohl(&packet[16]); // raw timestamp
uint32_t fl = nctohs(&packet[2]); //
debug(1,"Sync Packet of %d bytes received: \"%s\", flags: %d, timestamps %u and %u,
giving a latency of %d frames.",plen,obf,fl,rt,rtlt,rt-rtlt);
//debug(1,"Monotonic timestamps are: %" PRId64 " and %" PRId64 "