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fix(rtp): improve timestamp accuracy for video #3883

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Merged
ReenigneArcher merged 1 commit into from
May 21, 2025
Merged

fix(rtp): improve timestamp accuracy for video #3883

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29 changes: 18 additions & 11 deletions src/stream.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1263,7 +1263,7 @@ namespace stream {
void videoBroadcastThread(udp::socket &sock) {
auto shutdown_event = mail::man->event<bool>(mail::broadcast_shutdown);
auto packets = mail::man->queue<video::packet_t>(mail::video_packets);
auto timebase = boost::posix_time::microsec_clock::universal_time();
auto video_epoch = std::chrono::steady_clock::now();

// Video traffic is sent on this thread
platf::adjust_thread_priority(platf::thread_priority_e::high);
Expand Down Expand Up @@ -1459,14 +1459,20 @@ namespace stream {

size_t next_shard_to_send = 0;

// RTP video timestamps use a 90 KHz clock and the frame_timestamp from when the frame was captured
// When a timestamp isn't available (duplicate frames), the timestamp from rate control is used instead.
bool frame_is_dupe = false;
if (!packet->frame_timestamp) {
packet->frame_timestamp = ratecontrol_next_frame_start;
frame_is_dupe = true;
}
using rtp_tick = std::chrono::duration<uint32_t, std::ratio<1, 90000>>;
uint32_t timestamp = std::chrono::round<rtp_tick>(*packet->frame_timestamp - video_epoch).count();

// set FEC info now that we know for sure what our percentage will be for this frame
for (auto x = 0; x < shards.size(); ++x) {
auto *inspect = (video_packet_raw_t *) shards.data(x);

// RTP video timestamps use a 90 KHz clock
auto now = boost::posix_time::microsec_clock::universal_time();
auto timestamp = (now - timebase).total_microseconds() / (1000 / 90);

inspect->packet.fecInfo =
(x << 12 |
shards.data_shards << 22 |
Expand Down Expand Up @@ -1558,11 +1564,11 @@ namespace stream {

frame_network_latency_logger.second_point_now_and_log();

if (packet->is_idr()) {
BOOST_LOG(verbose) << "Key Frame ["sv << packet->frame_index() << "] :: send ["sv << shards.size() << "] shards..."sv;
} else {
BOOST_LOG(verbose) << "Frame ["sv << packet->frame_index() << "] :: send ["sv << shards.size() << "] shards..."sv << std::endl;
}
BOOST_LOG(verbose) << "Sent Frame seq ["sv << packet->frame_index() << "] pts ["sv << timestamp
<< "] shards ["sv << shards.size() << "/"sv << shards.percentage << "%]"sv
<< (frame_is_dupe ? " Dupe" : "")
<< (packet->is_idr() ? " Key" : "")
<< (packet->after_ref_frame_invalidation ? " RFI" : "");

++blockIndex;
lowseq += shards.size();
Expand Down Expand Up @@ -1622,6 +1628,8 @@ namespace stream {
break;
}

BOOST_LOG(verbose) << "Audio [seq "sv << sequenceNumber << ", pts "sv << timestamp << "] :: send..."sv;

audio_packet.rtp.sequenceNumber = util::endian::big(sequenceNumber);
audio_packet.rtp.timestamp = util::endian::big(timestamp);

Expand All @@ -1641,7 +1649,6 @@ namespace stream {
session->localAddress,
};
platf::send(send_info);
BOOST_LOG(verbose) << "Audio ["sv << sequenceNumber << "] :: send..."sv;

auto &fec_packet = session->audio.fec_packet;
// initialize the FEC header at the beginning of the FEC block
Expand Down
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