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Cleanup of video packet overhead calculation.

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This CL updates the video packet overhead calculation to make it more
clear. This prepares for future work on improving the accuracy of the
calculation.

Bug: webrtc:9883
Change-Id: I1d623a3e0de45be7b6e4a1f9e3cbe54fd2b8a45a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/138077
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28040}
This commit is contained in:
Sebastian Jansson 2019-05-23 16:44:37 +02:00 committed by Commit Bot
parent e9a2ee2631
commit 890bc3069c
1 changed files with 26 additions and 33 deletions
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59
call/rtp_video_sender.cc
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@ -188,19 +188,13 @@ std::unique_ptr<FlexfecSender> MaybeCreateFlexfecSender(
RTPSender::FecExtensionSizes(), rtp_state, clock);
}
uint32_t CalculateOverheadRateBps(int packets_per_second,
size_t overhead_bytes_per_packet,
uint32_t max_overhead_bps) {
uint32_t overhead_bps =
static_cast<uint32_t>(8 * overhead_bytes_per_packet * packets_per_second);
return std::min(overhead_bps, max_overhead_bps);
}
int CalculatePacketRate(uint32_t bitrate_bps, size_t packet_size_bytes) {
size_t packet_size_bits = 8 * packet_size_bytes;
// Ceil for int value of bitrate_bps / packet_size_bits.
return static_cast<int>((bitrate_bps + packet_size_bits - 1) /
packet_size_bits);
DataRate CalculateMinOverheadRate(DataRate bitrate,
DataSize overhead_per_packet,
DataSize max_packet_size) {
TimeDelta packet_interval = max_packet_size / bitrate;
int packets_per_second =
rtc::dchecked_cast<int>(std::ceil(1 / packet_interval.seconds<double>()));
return packets_per_second * overhead_per_packet / TimeDelta::Seconds<1>();
}
} // namespace
@ -686,16 +680,17 @@ void RtpVideoSender::OnBitrateUpdated(uint32_t bitrate_bps,
int framerate) {
// Substract overhead from bitrate.
rtc::CritScope lock(&crit_);
DataSize packet_overhead = DataSize::bytes(
overhead_bytes_per_packet_ + transport_overhead_bytes_per_packet_);
DataSize max_total_packet_size = DataSize::bytes(
rtp_config_.max_packet_size + transport_overhead_bytes_per_packet_);
uint32_t payload_bitrate_bps = bitrate_bps;
if (send_side_bwe_with_overhead_) {
uint32_t overhead_bps = CalculateOverheadRateBps(
CalculatePacketRate(
bitrate_bps,
rtp_config_.max_packet_size + transport_overhead_bytes_per_packet_),
overhead_bytes_per_packet_ + transport_overhead_bytes_per_packet_,
bitrate_bps);
RTC_DCHECK_LE(overhead_bps, bitrate_bps);
payload_bitrate_bps = bitrate_bps - overhead_bps;
DataRate overhead_rate = CalculateMinOverheadRate(
DataRate::bps(bitrate_bps), packet_overhead, max_total_packet_size);
// TODO(srte): We probably should not accept 0 payload bitrate here.
payload_bitrate_bps =
rtc::saturated_cast<uint32_t>(bitrate_bps - overhead_rate.bps());
}
// Get the encoder target rate. It is the estimated network rate -
@ -716,18 +711,16 @@ void RtpVideoSender::OnBitrateUpdated(uint32_t bitrate_bps,
loss_mask_vector_.clear();
uint32_t encoder_overhead_rate_bps =
send_side_bwe_with_overhead_
? CalculateOverheadRateBps(
CalculatePacketRate(encoder_target_rate_bps_,
rtp_config_.max_packet_size +
transport_overhead_bytes_per_packet_ -
overhead_bytes_per_packet_),
overhead_bytes_per_packet_ +
transport_overhead_bytes_per_packet_,
bitrate_bps - encoder_target_rate_bps_)
: 0;
uint32_t encoder_overhead_rate_bps = 0;
if (send_side_bwe_with_overhead_) {
// TODO(srte): The packet size should probably match the one used above.
DataRate encoder_overhead_rate = CalculateMinOverheadRate(
DataRate::bps(encoder_target_rate_bps_), packet_overhead,
max_total_packet_size - DataSize::bytes(overhead_bytes_per_packet_));
encoder_overhead_rate_bps =
std::min(encoder_overhead_rate.bps<uint32_t>(),
bitrate_bps - encoder_target_rate_bps_);
}
// When the field trial "WebRTC-SendSideBwe-WithOverhead" is enabled
// protection_bitrate includes overhead.
const uint32_t media_rate = encoder_target_rate_bps_ +