f88aa97c52
The video encoder should be informed of incoming LossNotification RTCP messages. Since it is unaware of RTP sequence numbers, or anything else RTP-related, the sequence numbers mentioned in the RTCP message must first be mapped to timestamps, since those are meaningful to the encoder. This CL introduces RtpSequenceNumberMap, which maps RTP sequence numbers to timestamps, while providing: 1. Capping the number of entries. 2. Wrap-around handling. RtpSequenceNumberMap also remembers which packets were first and/or last in the frame. Later CLs will wire this up. Bug: webrtc:10501 Change-Id: Ie0662cdb5706a3bcf63aa2934816a9df88439357 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/130497 Commit-Queue: Elad Alon <eladalon@webrtc.org> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#27448}
115 lines
4.3 KiB
C++
115 lines
4.3 KiB
C++
/*
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* Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "modules/rtp_rtcp/source/rtp_sequence_number_map.h"
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#include <algorithm>
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#include <iterator>
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#include "absl/algorithm/container.h"
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#include "rtc_base/checks.h"
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#include "rtc_base/logging.h"
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#include "rtc_base/numerics/sequence_number_util.h"
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namespace webrtc {
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RtpSequenceNumberMap::RtpSequenceNumberMap(size_t max_entries)
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: max_entries_(max_entries) {
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RTC_DCHECK_GT(max_entries_, 4); // See code paring down to |max_entries_|.
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RTC_DCHECK_LE(max_entries_, 1 << 15);
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}
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RtpSequenceNumberMap::~RtpSequenceNumberMap() = default;
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void RtpSequenceNumberMap::Insert(uint16_t sequence_number, Info info) {
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RTC_DCHECK(associations_.size() < 2 ||
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AheadOf(associations_.back().sequence_number,
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associations_.front().sequence_number));
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if (associations_.empty()) {
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associations_.emplace_back(sequence_number, info);
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return;
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}
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if (AheadOrAt(sequence_number, associations_.front().sequence_number) &&
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AheadOrAt(associations_.back().sequence_number, sequence_number)) {
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// The sequence number has wrapped around and is within the range
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// currently held by |associations_| - we should invalidate all entries.
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RTC_LOG(LS_WARNING) << "Sequence number wrapped-around unexpectedly.";
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associations_.clear();
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associations_.emplace_back(sequence_number, info);
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return;
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}
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std::deque<Association>::iterator erase_to = associations_.begin();
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RTC_DCHECK_LE(associations_.size(), max_entries_);
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if (associations_.size() == max_entries_) {
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// Pare down the container so that inserting some additional elements
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// would not exceed the maximum size.
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const size_t new_size = 3 * max_entries_ / 4;
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erase_to = std::next(erase_to, max_entries_ - new_size);
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}
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// It is guaranteed that |associations_| can be split into two partitions,
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// either partition possibly empty, such that:
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// * In the first partition, all elements are AheadOf the new element.
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// This is the partition of the obsolete elements.
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// * In the second partition, the new element is AheadOf all the elements.
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// The elements of this partition may stay.
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auto cmp = [](const Association& a, uint16_t sequence_number) {
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return AheadOf(a.sequence_number, sequence_number);
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};
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RTC_DCHECK(erase_to != associations_.end());
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erase_to =
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std::lower_bound(erase_to, associations_.end(), sequence_number, cmp);
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associations_.erase(associations_.begin(), erase_to);
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associations_.emplace_back(sequence_number, info);
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RTC_DCHECK(associations_.size() == 1 ||
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AheadOf(associations_.back().sequence_number,
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associations_.front().sequence_number));
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}
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absl::optional<RtpSequenceNumberMap::Info> RtpSequenceNumberMap::Get(
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uint16_t sequence_number) const {
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// To make the binary search easier to understand, we use the fact that
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// adding a constant offset to all elements, as well as to the searched
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// element, does not change the relative ordering. This way, we can find
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// an offset that would make all of the elements strictly ascending according
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// to normal integer comparison.
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// Finding such an offset is easy - the offset that would map the oldest
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// element to 0 would serve this purpose.
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if (associations_.empty()) {
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return absl::nullopt;
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}
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const uint16_t offset =
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static_cast<uint16_t>(0) - associations_.front().sequence_number;
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auto cmp = [offset](const Association& a, uint16_t sequence_number) {
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return static_cast<uint16_t>(a.sequence_number + offset) <
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static_cast<uint16_t>(sequence_number + offset);
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};
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const auto elem = absl::c_lower_bound(associations_, sequence_number, cmp);
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return elem != associations_.end() && elem->sequence_number == sequence_number
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? absl::optional<Info>(elem->info)
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: absl::nullopt;
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}
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size_t RtpSequenceNumberMap::AssociationCountForTesting() const {
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return associations_.size();
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}
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} // namespace webrtc
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