blob: e8f0ea5c8de07180acbf1930c652a28aa1db8635 [file] [log] [blame]
/*
* Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "modules/rtp_rtcp/source/rtp_sender_video.h"
#include <stdlib.h>
#include <string.h>
#include <limits>
#include <memory>
#include <utility>
#include <vector>
#include "absl/memory/memory.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "modules/rtp_rtcp/source/byte_io.h"
#include "modules/rtp_rtcp/source/rtp_format_video_generic.h"
#include "modules/rtp_rtcp/source/rtp_format_vp8.h"
#include "modules/rtp_rtcp/source/rtp_format_vp9.h"
#include "modules/rtp_rtcp/source/rtp_generic_frame_descriptor_extension.h"
#include "modules/rtp_rtcp/source/rtp_header_extensions.h"
#include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/trace_event.h"
namespace webrtc {
namespace {
constexpr size_t kRedForFecHeaderLength = 1;
constexpr int64_t kMaxUnretransmittableFrameIntervalMs = 33 * 4;
void BuildRedPayload(const RtpPacketToSend& media_packet,
RtpPacketToSend* red_packet) {
uint8_t* red_payload = red_packet->AllocatePayload(
kRedForFecHeaderLength + media_packet.payload_size());
RTC_DCHECK(red_payload);
red_payload[0] = media_packet.PayloadType();
auto media_payload = media_packet.payload();
memcpy(&red_payload[kRedForFecHeaderLength], media_payload.data(),
media_payload.size());
}
void AddRtpHeaderExtensions(const RTPVideoHeader& video_header,
FrameType frame_type,
bool set_video_rotation,
bool first_packet,
bool last_packet,
RtpPacketToSend* packet) {
if (last_packet && set_video_rotation)
packet->SetExtension<VideoOrientation>(video_header.rotation);
// Report content type only for key frames.
if (last_packet && frame_type == kVideoFrameKey &&
video_header.content_type != VideoContentType::UNSPECIFIED)
packet->SetExtension<VideoContentTypeExtension>(video_header.content_type);
if (last_packet &&
video_header.video_timing.flags != VideoSendTiming::kInvalid)
packet->SetExtension<VideoTimingExtension>(video_header.video_timing);
if (video_header.generic) {
RtpGenericFrameDescriptor generic_descriptor;
generic_descriptor.SetFirstPacketInSubFrame(first_packet);
generic_descriptor.SetLastPacketInSubFrame(last_packet);
generic_descriptor.SetFirstSubFrameInFrame(true);
generic_descriptor.SetLastSubFrameInFrame(true);
if (first_packet) {
generic_descriptor.SetFrameId(
static_cast<uint16_t>(video_header.generic->frame_id));
for (int64_t dep : video_header.generic->dependencies) {
generic_descriptor.AddFrameDependencyDiff(
video_header.generic->frame_id - dep);
}
uint8_t spatial_bimask = 1 << video_header.generic->spatial_index;
for (int layer : video_header.generic->higher_spatial_layers) {
RTC_DCHECK_GT(layer, video_header.generic->spatial_index);
RTC_DCHECK_LT(layer, 8);
spatial_bimask |= 1 << layer;
}
generic_descriptor.SetSpatialLayersBitmask(spatial_bimask);
generic_descriptor.SetTemporalLayer(video_header.generic->temporal_index);
}
packet->SetExtension<RtpGenericFrameDescriptorExtension>(
generic_descriptor);
}
}
bool MinimizeDescriptor(const RTPVideoHeader& full, RTPVideoHeader* minimized) {
if (full.codec == VideoCodecType::kVideoCodecVP8) {
minimized->codec = VideoCodecType::kVideoCodecVP8;
const auto& vp8 = absl::get<RTPVideoHeaderVP8>(full.video_type_header);
// Set minimum fields the RtpPacketizer is using to create vp8 packets.
auto& min_vp8 = minimized->video_type_header.emplace<RTPVideoHeaderVP8>();
min_vp8.InitRTPVideoHeaderVP8();
min_vp8.nonReference = vp8.nonReference;
return true;
}
// TODO(danilchap): Reduce vp9 codec specific descriptor too.
return false;
}
} // namespace
RTPSenderVideo::RTPSenderVideo(Clock* clock,
RTPSender* rtp_sender,
FlexfecSender* flexfec_sender)
: rtp_sender_(rtp_sender),
clock_(clock),
video_type_(kVideoCodecGeneric),
retransmission_settings_(kRetransmitBaseLayer |
kConditionallyRetransmitHigherLayers),
last_rotation_(kVideoRotation_0),
red_payload_type_(-1),
ulpfec_payload_type_(-1),
flexfec_sender_(flexfec_sender),
delta_fec_params_{0, 1, kFecMaskRandom},
key_fec_params_{0, 1, kFecMaskRandom},
fec_bitrate_(1000, RateStatistics::kBpsScale),
video_bitrate_(1000, RateStatistics::kBpsScale) {}
RTPSenderVideo::~RTPSenderVideo() {}
void RTPSenderVideo::SetVideoCodecType(enum VideoCodecType video_type) {
video_type_ = video_type;
}
VideoCodecType RTPSenderVideo::VideoCodecType() const {
return video_type_;
}
// Static.
RtpUtility::Payload* RTPSenderVideo::CreateVideoPayload(
const char payload_name[RTP_PAYLOAD_NAME_SIZE],
int8_t payload_type) {
enum VideoCodecType video_type = kVideoCodecGeneric;
if (RtpUtility::StringCompare(payload_name, "VP8", 3)) {
video_type = kVideoCodecVP8;
} else if (RtpUtility::StringCompare(payload_name, "VP9", 3)) {
video_type = kVideoCodecVP9;
} else if (RtpUtility::StringCompare(payload_name, "H264", 4)) {
video_type = kVideoCodecH264;
} else if (RtpUtility::StringCompare(payload_name, "I420", 4)) {
video_type = kVideoCodecGeneric;
} else if (RtpUtility::StringCompare(payload_name, "stereo", 6)) {
video_type = kVideoCodecGeneric;
} else {
video_type = kVideoCodecGeneric;
}
VideoPayload vp;
vp.videoCodecType = video_type;
return new RtpUtility::Payload(payload_name, PayloadUnion(vp));
}
void RTPSenderVideo::SendVideoPacket(std::unique_ptr<RtpPacketToSend> packet,
StorageType storage) {
// Remember some values about the packet before sending it away.
size_t packet_size = packet->size();
uint16_t seq_num = packet->SequenceNumber();
if (!rtp_sender_->SendToNetwork(std::move(packet), storage,
RtpPacketSender::kLowPriority)) {
RTC_LOG(LS_WARNING) << "Failed to send video packet " << seq_num;
return;
}
rtc::CritScope cs(&stats_crit_);
video_bitrate_.Update(packet_size, clock_->TimeInMilliseconds());
}
void RTPSenderVideo::SendVideoPacketAsRedMaybeWithUlpfec(
std::unique_ptr<RtpPacketToSend> media_packet,
StorageType media_packet_storage,
bool protect_media_packet) {
uint16_t media_seq_num = media_packet->SequenceNumber();
std::unique_ptr<RtpPacketToSend> red_packet(
new RtpPacketToSend(*media_packet));
BuildRedPayload(*media_packet, red_packet.get());
std::vector<std::unique_ptr<RedPacket>> fec_packets;
StorageType fec_storage = kDontRetransmit;
{
// Only protect while creating RED and FEC packets, not when sending.
rtc::CritScope cs(&crit_);
red_packet->SetPayloadType(red_payload_type_);
if (ulpfec_enabled()) {
if (protect_media_packet) {
ulpfec_generator_.AddRtpPacketAndGenerateFec(
media_packet->data(), media_packet->payload_size(),
media_packet->headers_size());
}
uint16_t num_fec_packets = ulpfec_generator_.NumAvailableFecPackets();
if (num_fec_packets > 0) {
uint16_t first_fec_sequence_number =
rtp_sender_->AllocateSequenceNumber(num_fec_packets);
fec_packets = ulpfec_generator_.GetUlpfecPacketsAsRed(
red_payload_type_, ulpfec_payload_type_, first_fec_sequence_number);
RTC_DCHECK_EQ(num_fec_packets, fec_packets.size());
if (retransmission_settings_ & kRetransmitFECPackets)
fec_storage = kAllowRetransmission;
}
}
}
// Send |red_packet| instead of |packet| for allocated sequence number.
size_t red_packet_size = red_packet->size();
if (rtp_sender_->SendToNetwork(std::move(red_packet), media_packet_storage,
RtpPacketSender::kLowPriority)) {
rtc::CritScope cs(&stats_crit_);
video_bitrate_.Update(red_packet_size, clock_->TimeInMilliseconds());
} else {
RTC_LOG(LS_WARNING) << "Failed to send RED packet " << media_seq_num;
}
for (const auto& fec_packet : fec_packets) {
// TODO(danilchap): Make ulpfec_generator_ generate RtpPacketToSend to avoid
// reparsing them.
std::unique_ptr<RtpPacketToSend> rtp_packet(
new RtpPacketToSend(*media_packet));
RTC_CHECK(rtp_packet->Parse(fec_packet->data(), fec_packet->length()));
rtp_packet->set_capture_time_ms(media_packet->capture_time_ms());
uint16_t fec_sequence_number = rtp_packet->SequenceNumber();
if (rtp_sender_->SendToNetwork(std::move(rtp_packet), fec_storage,
RtpPacketSender::kLowPriority)) {
rtc::CritScope cs(&stats_crit_);
fec_bitrate_.Update(fec_packet->length(), clock_->TimeInMilliseconds());
} else {
RTC_LOG(LS_WARNING) << "Failed to send ULPFEC packet "
<< fec_sequence_number;
}
}
}
void RTPSenderVideo::SendVideoPacketWithFlexfec(
std::unique_ptr<RtpPacketToSend> media_packet,
StorageType media_packet_storage,
bool protect_media_packet) {
RTC_DCHECK(flexfec_sender_);
if (protect_media_packet)
flexfec_sender_->AddRtpPacketAndGenerateFec(*media_packet);
SendVideoPacket(std::move(media_packet), media_packet_storage);
if (flexfec_sender_->FecAvailable()) {
std::vector<std::unique_ptr<RtpPacketToSend>> fec_packets =
flexfec_sender_->GetFecPackets();
for (auto& fec_packet : fec_packets) {
size_t packet_length = fec_packet->size();
uint16_t seq_num = fec_packet->SequenceNumber();
if (rtp_sender_->SendToNetwork(std::move(fec_packet), kDontRetransmit,
RtpPacketSender::kLowPriority)) {
rtc::CritScope cs(&stats_crit_);
fec_bitrate_.Update(packet_length, clock_->TimeInMilliseconds());
} else {
RTC_LOG(LS_WARNING) << "Failed to send FlexFEC packet " << seq_num;
}
}
}
}
void RTPSenderVideo::SetUlpfecConfig(int red_payload_type,
int ulpfec_payload_type) {
// Sanity check. Per the definition of UlpfecConfig (see config.h),
// a payload type of -1 means that the corresponding feature is
// turned off.
RTC_DCHECK_GE(red_payload_type, -1);
RTC_DCHECK_LE(red_payload_type, 127);
RTC_DCHECK_GE(ulpfec_payload_type, -1);
RTC_DCHECK_LE(ulpfec_payload_type, 127);
rtc::CritScope cs(&crit_);
red_payload_type_ = red_payload_type;
ulpfec_payload_type_ = ulpfec_payload_type;
// Must not enable ULPFEC without RED.
RTC_DCHECK(!(red_enabled() ^ ulpfec_enabled()));
// Reset FEC parameters.
delta_fec_params_ = FecProtectionParams{0, 1, kFecMaskRandom};
key_fec_params_ = FecProtectionParams{0, 1, kFecMaskRandom};
}
void RTPSenderVideo::GetUlpfecConfig(int* red_payload_type,
int* ulpfec_payload_type) const {
rtc::CritScope cs(&crit_);
*red_payload_type = red_payload_type_;
*ulpfec_payload_type = ulpfec_payload_type_;
}
size_t RTPSenderVideo::CalculateFecPacketOverhead() const {
if (flexfec_enabled())
return flexfec_sender_->MaxPacketOverhead();
size_t overhead = 0;
if (red_enabled()) {
// The RED overhead is due to a small header.
overhead += kRedForFecHeaderLength;
}
if (ulpfec_enabled()) {
// For ULPFEC, the overhead is the FEC headers plus RED for FEC header
// (see above) plus anything in RTP header beyond the 12 bytes base header
// (CSRC list, extensions...)
// This reason for the header extensions to be included here is that
// from an FEC viewpoint, they are part of the payload to be protected.
// (The base RTP header is already protected by the FEC header.)
overhead += ulpfec_generator_.MaxPacketOverhead() +
(rtp_sender_->RtpHeaderLength() - kRtpHeaderSize);
}
return overhead;
}
void RTPSenderVideo::SetFecParameters(const FecProtectionParams& delta_params,
const FecProtectionParams& key_params) {
rtc::CritScope cs(&crit_);
delta_fec_params_ = delta_params;
key_fec_params_ = key_params;
}
absl::optional<uint32_t> RTPSenderVideo::FlexfecSsrc() const {
if (flexfec_sender_) {
return flexfec_sender_->ssrc();
}
return absl::nullopt;
}
bool RTPSenderVideo::SendVideo(enum VideoCodecType video_type,
FrameType frame_type,
int8_t payload_type,
uint32_t rtp_timestamp,
int64_t capture_time_ms,
const uint8_t* payload_data,
size_t payload_size,
const RTPFragmentationHeader* fragmentation,
const RTPVideoHeader* video_header,
int64_t expected_retransmission_time_ms) {
if (payload_size == 0)
return false;
RTC_CHECK(video_header);
size_t fec_packet_overhead;
bool red_enabled;
int32_t retransmission_settings;
bool set_video_rotation;
{
rtc::CritScope cs(&crit_);
// According to
// http://www.etsi.org/deliver/etsi_ts/126100_126199/126114/12.07.00_60/
// ts_126114v120700p.pdf Section 7.4.5:
// The MTSI client shall add the payload bytes as defined in this clause
// onto the last RTP packet in each group of packets which make up a key
// frame (I-frame or IDR frame in H.264 (AVC), or an IRAP picture in H.265
// (HEVC)). The MTSI client may also add the payload bytes onto the last RTP
// packet in each group of packets which make up another type of frame
// (e.g. a P-Frame) only if the current value is different from the previous
// value sent.
// Set rotation when key frame or when changed (to follow standard).
// Or when different from 0 (to follow current receiver implementation).
set_video_rotation = frame_type == kVideoFrameKey ||
video_header->rotation != last_rotation_ ||
video_header->rotation != kVideoRotation_0;
last_rotation_ = video_header->rotation;
// FEC settings.
const FecProtectionParams& fec_params =
frame_type == kVideoFrameKey ? key_fec_params_ : delta_fec_params_;
if (flexfec_enabled())
flexfec_sender_->SetFecParameters(fec_params);
if (ulpfec_enabled())
ulpfec_generator_.SetFecParameters(fec_params);
fec_packet_overhead = CalculateFecPacketOverhead();
red_enabled = this->red_enabled();
retransmission_settings = retransmission_settings_;
}
// Maximum size of packet including rtp headers.
// Extra space left in case packet will be resent using fec or rtx.
int packet_capacity = rtp_sender_->MaxRtpPacketSize() - fec_packet_overhead -
(rtp_sender_->RtxStatus() ? kRtxHeaderSize : 0);
auto create_packet = [&] {
std::unique_ptr<RtpPacketToSend> rtp_packet = rtp_sender_->AllocatePacket();
RTC_DCHECK_LE(packet_capacity, rtp_packet->capacity());
rtp_packet->SetPayloadType(payload_type);
rtp_packet->SetTimestamp(rtp_timestamp);
rtp_packet->set_capture_time_ms(capture_time_ms);
return rtp_packet;
};
auto first_packet = create_packet();
auto middle_packet = absl::make_unique<RtpPacketToSend>(*first_packet);
auto last_packet = absl::make_unique<RtpPacketToSend>(*first_packet);
// Simplest way to estimate how much extensions would occupy is to set them.
AddRtpHeaderExtensions(*video_header, frame_type, set_video_rotation,
/*first=*/true, /*last=*/false, first_packet.get());
AddRtpHeaderExtensions(*video_header, frame_type, set_video_rotation,
/*first=*/false, /*last=*/false, middle_packet.get());
AddRtpHeaderExtensions(*video_header, frame_type, set_video_rotation,
/*first=*/false, /*last=*/true, last_packet.get());
RTC_DCHECK_GT(packet_capacity, first_packet->headers_size());
RTC_DCHECK_GT(packet_capacity, middle_packet->headers_size());
RTC_DCHECK_GT(packet_capacity, last_packet->headers_size());
RtpPacketizer::PayloadSizeLimits limits;
limits.max_payload_len = packet_capacity - middle_packet->headers_size();
RTC_DCHECK_GE(first_packet->headers_size(), middle_packet->headers_size());
limits.first_packet_reduction_len =
first_packet->headers_size() - middle_packet->headers_size();
RTC_DCHECK_GE(last_packet->headers_size(), middle_packet->headers_size());
limits.last_packet_reduction_len =
last_packet->headers_size() - middle_packet->headers_size();
RTPVideoHeader minimized_video_header;
const RTPVideoHeader* packetize_video_header = video_header;
if (first_packet->HasExtension<RtpGenericFrameDescriptorExtension>() &&
MinimizeDescriptor(*video_header, &minimized_video_header)) {
packetize_video_header = &minimized_video_header;
}
std::unique_ptr<RtpPacketizer> packetizer = RtpPacketizer::Create(
video_type, rtc::MakeArrayView(payload_data, payload_size), limits,
*packetize_video_header, frame_type, fragmentation);
const uint8_t temporal_id = GetTemporalId(*video_header);
StorageType storage = GetStorageType(temporal_id, retransmission_settings,
expected_retransmission_time_ms);
size_t num_packets = packetizer->NumPackets();
if (num_packets == 0)
return false;
bool first_frame = first_frame_sent_();
for (size_t i = 0; i < num_packets; ++i) {
std::unique_ptr<RtpPacketToSend> packet;
int expected_payload_capacity;
// Choose right packet template:
if (num_packets == 1) {
// No prepared template, create a new packet.
packet = create_packet();
AddRtpHeaderExtensions(*video_header, frame_type, set_video_rotation,
/*first=*/true, /*last=*/true, packet.get());
// TODO(bugs.webrtc.org/7990): Revisit this case when two byte header
// extension are implemented because then single packet might need more
// space for extensions than sum of first and last packet reductions.
expected_payload_capacity = limits.max_payload_len -
limits.first_packet_reduction_len -
limits.last_packet_reduction_len;
} else if (i == 0) {
packet = std::move(first_packet);
expected_payload_capacity =
limits.max_payload_len - limits.first_packet_reduction_len;
} else if (i == num_packets - 1) {
packet = std::move(last_packet);
expected_payload_capacity =
limits.max_payload_len - limits.last_packet_reduction_len;
} else {
packet = absl::make_unique<RtpPacketToSend>(*middle_packet);
expected_payload_capacity = limits.max_payload_len;
}
if (!packetizer->NextPacket(packet.get()))
return false;
RTC_DCHECK_LE(packet->payload_size(), expected_payload_capacity);
if (!rtp_sender_->AssignSequenceNumber(packet.get()))
return false;
// No FEC protection for upper temporal layers, if used.
bool protect_packet = temporal_id == 0 || temporal_id == kNoTemporalIdx;
// Put packetization finish timestamp into extension.
if (packet->HasExtension<VideoTimingExtension>()) {
packet->set_packetization_finish_time_ms(clock_->TimeInMilliseconds());
// TODO(ilnik): Due to webrtc:7859, packets with timing extensions are not
// protected by FEC. It reduces FEC efficiency a bit. When FEC is moved
// below the pacer, it can be re-enabled for these packets.
// NOTE: Any RTP stream processor in the network, modifying 'network'
// timestamps in the timing frames extension have to be an end-point for
// FEC, otherwise recovered by FEC packets will be corrupted.
protect_packet = false;
}
if (flexfec_enabled()) {
// TODO(brandtr): Remove the FlexFEC code path when FlexfecSender
// is wired up to PacedSender instead.
SendVideoPacketWithFlexfec(std::move(packet), storage, protect_packet);
} else if (red_enabled) {
SendVideoPacketAsRedMaybeWithUlpfec(std::move(packet), storage,
protect_packet);
} else {
SendVideoPacket(std::move(packet), storage);
}
if (first_frame) {
if (i == 0) {
RTC_LOG(LS_INFO)
<< "Sent first RTP packet of the first video frame (pre-pacer)";
}
if (i == num_packets - 1) {
RTC_LOG(LS_INFO)
<< "Sent last RTP packet of the first video frame (pre-pacer)";
}
}
}
TRACE_EVENT_ASYNC_END1("webrtc", "Video", capture_time_ms, "timestamp",
rtp_timestamp);
return true;
}
uint32_t RTPSenderVideo::VideoBitrateSent() const {
rtc::CritScope cs(&stats_crit_);
return video_bitrate_.Rate(clock_->TimeInMilliseconds()).value_or(0);
}
uint32_t RTPSenderVideo::FecOverheadRate() const {
rtc::CritScope cs(&stats_crit_);
return fec_bitrate_.Rate(clock_->TimeInMilliseconds()).value_or(0);
}
int RTPSenderVideo::SelectiveRetransmissions() const {
rtc::CritScope cs(&crit_);
return retransmission_settings_;
}
void RTPSenderVideo::SetSelectiveRetransmissions(uint8_t settings) {
rtc::CritScope cs(&crit_);
retransmission_settings_ = settings;
}
StorageType RTPSenderVideo::GetStorageType(
uint8_t temporal_id,
int32_t retransmission_settings,
int64_t expected_retransmission_time_ms) {
if (retransmission_settings == kRetransmitOff)
return StorageType::kDontRetransmit;
if (retransmission_settings == kRetransmitAllPackets)
return StorageType::kAllowRetransmission;
rtc::CritScope cs(&stats_crit_);
// Media packet storage.
if ((retransmission_settings & kConditionallyRetransmitHigherLayers) &&
UpdateConditionalRetransmit(temporal_id,
expected_retransmission_time_ms)) {
retransmission_settings |= kRetransmitHigherLayers;
}
if (temporal_id == kNoTemporalIdx)
return kAllowRetransmission;
if ((retransmission_settings & kRetransmitBaseLayer) && temporal_id == 0)
return kAllowRetransmission;
if ((retransmission_settings & kRetransmitHigherLayers) && temporal_id > 0)
return kAllowRetransmission;
return kDontRetransmit;
}
uint8_t RTPSenderVideo::GetTemporalId(const RTPVideoHeader& header) {
struct TemporalIdGetter {
uint8_t operator()(const RTPVideoHeaderVP8& vp8) { return vp8.temporalIdx; }
uint8_t operator()(const RTPVideoHeaderVP9& vp9) {
return vp9.temporal_idx;
}
uint8_t operator()(const RTPVideoHeaderH264&) { return kNoTemporalIdx; }
uint8_t operator()(const absl::monostate&) { return kNoTemporalIdx; }
};
return absl::visit(TemporalIdGetter(), header.video_type_header);
}
bool RTPSenderVideo::UpdateConditionalRetransmit(
uint8_t temporal_id,
int64_t expected_retransmission_time_ms) {
int64_t now_ms = clock_->TimeInMilliseconds();
// Update stats for any temporal layer.
TemporalLayerStats* current_layer_stats =
&frame_stats_by_temporal_layer_[temporal_id];
current_layer_stats->frame_rate_fp1000s.Update(1, now_ms);
int64_t tl_frame_interval = now_ms - current_layer_stats->last_frame_time_ms;
current_layer_stats->last_frame_time_ms = now_ms;
// Conditional retransmit only applies to upper layers.
if (temporal_id != kNoTemporalIdx && temporal_id > 0) {
if (tl_frame_interval >= kMaxUnretransmittableFrameIntervalMs) {
// Too long since a retransmittable frame in this layer, enable NACK
// protection.
return true;
} else {
// Estimate when the next frame of any lower layer will be sent.
const int64_t kUndefined = std::numeric_limits<int64_t>::max();
int64_t expected_next_frame_time = kUndefined;
for (int i = temporal_id - 1; i >= 0; --i) {
TemporalLayerStats* stats = &frame_stats_by_temporal_layer_[i];
absl::optional<uint32_t> rate = stats->frame_rate_fp1000s.Rate(now_ms);
if (rate) {
int64_t tl_next = stats->last_frame_time_ms + 1000000 / *rate;
if (tl_next - now_ms > -expected_retransmission_time_ms &&
tl_next < expected_next_frame_time) {
expected_next_frame_time = tl_next;
}
}
}
if (expected_next_frame_time == kUndefined ||
expected_next_frame_time - now_ms > expected_retransmission_time_ms) {
// The next frame in a lower layer is expected at a later time (or
// unable to tell due to lack of data) than a retransmission is
// estimated to be able to arrive, so allow this packet to be nacked.
return true;
}
}
}
return false;
}
} // namespace webrtc