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clean up initial timestamp of audio stream, before first sync event

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This commit is contained in:
fduncanh
2022-04-29 19:22:45 -04:00
parent 2f6cf2e8f2
commit f0fcba8fac
1 changed files with 13 additions and 11 deletions
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24
lib/raop_rtp.c
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@@ -35,6 +35,8 @@
#define RAOP_RTP_SAMPLE_RATE (44100.0 / 1000000.0)
#define RAOP_RTP_SYNC_DATA_COUNT 8
#define DELAY 500000 //this is empirical, there is about a 0.5 sec delay in initial audio timing before a clock sync event
typedef struct raop_rtp_sync_data_s {
uint64_t ntp_time; // The local wall clock time at the time of rtp_time
uint32_t rtp_time; // The remote rtp clock time corresponding to ntp_time
@@ -402,7 +404,7 @@ raop_rtp_thread_udp(void *arg)
uint64_t ntp_start_time = 0;
bool first_packet = true;
assert(raop_rtp);
int no_resend = (raop_rtp->control_rport == 0); /* true when control_rport is not set; resend code is present in initial Shairplay code, but appears to have been never used */
while(1) {
fd_set rfds;
struct timeval tv;
@@ -507,19 +509,18 @@ raop_rtp_thread_udp(void *arg)
//logger_log(raop_rtp->logger, LOGGER_DEBUG, "raop_rtp_thread_udp type_d 0x%02x, packetlen = %d", type_d, packetlen);
// Len = 16 appears if there is no time
if (packetlen >= 16) {
int no_resend = (raop_rtp->control_rport == 0);// false
if ( packetlen >= 12) {
uint32_t rtp_timestamp = byteutils_get_int_be(packet, 4) - rtp_start_time;
if (first_packet) {
rtp_start_time = rtp_timestamp;
rtp_timestamp = 0;
ntp_start_time = raop_ntp_get_local_time(raop_rtp->ntp);
first_packet = false;
}
if (packetlen == 16 && packet[12] == 0x00 && packet[13] == 0x68 && packet[14] == 0x34 && packet[15] == 0x00) {
unsigned short seqnum = byteutils_get_short_be(packet,2);
logger_log(raop_rtp->logger, LOGGER_DEBUG, "raop_rtp timing packet, seqnum=%u rtp=%u", seqnum, rtp_timestamp);
/* skip packet */
} else {
if (first_packet) {
ntp_start_time = raop_ntp_get_local_time(raop_rtp->ntp) + DELAY; /* DELAY = 500000 (0.5 sec) is empirical choice */
logger_log(raop_rtp->logger, LOGGER_DEBUG, "first audio packet, using DELAY= %d", DELAY);
rtp_start_time = rtp_timestamp;
rtp_timestamp = 0;
first_packet = false;
}
int result = raop_buffer_enqueue(raop_rtp->buffer, packet, packetlen, rtp_timestamp, 1);
assert(result >= 0);
}
@@ -528,6 +529,7 @@ raop_rtp_thread_udp(void *arg)
unsigned int payload_size;
uint32_t timestamp;
while ((payload = raop_buffer_dequeue(raop_rtp->buffer, &payload_size, &timestamp, no_resend))) {
/* rpt_timestamp wraps around to zero after about 27 hours */
if (timestamp < rtp_prev) {
const uint64_t shift = 0x100000000UL;
ntp_start_time += (uint64_t) (((double) (shift))/raop_rtp->rtp_sync_scale);