blob: e58e2c00238c2c2ec0b9bb133f33be7d3a9d1dfb [file] [log] [blame]
// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <lib/zx/time.h>
#include <map>
#include <optional>
#include <ostream>
#include <variant>
// `TimestampExtrapolator` extrapolates timestamp-like values for a given
// timebase for forward offsets in a stream of data.
class TimestampExtrapolator {
// Creates a `TimestampExtrapolator` where `timebase` is the number of
// ticks per second of real time and `byte_duration` is the amount of real
// time consumed by a single byte of the uncompressed input.
// For example, with PCM audio at 48000Hz, the bytes per second is
// `48000 * number_of_channels * bytes_per_sample`
TimestampExtrapolator(uint64_t timebase, uint64_t bytes_per_second);
TimestampExtrapolator(TimestampExtrapolator&&) = default;
TimestampExtrapolator(TimestampExtrapolator&) = delete;
TimestampExtrapolator& operator=(TimestampExtrapolator&&) = delete;
// Creates a TimestampExtrapolator that can only carry over timestamps it has
// been informed of.
// Informs the extrapolator with an input `timestamp`, where `offset` is the
// index of the byte in the uncompressed stream to which the `timestamp`
// corresponds. This replaces any previously informed timestamp.
void Inform(size_t offset, uint64_t timestamp);
// Given a novel `offset` >= the the offset of the last informed timestamp,
// extrapolate a timestamp value. This consumes the most recently informed
// timestamp, leaving the extrapolator without a timestamp until another is
// provided by `Inform()`.
// Returns std::nullopt if there is no informed timestamp or no timebase for
// extrapolation. Asserts that `offset` >= the offset of the last informed
// timestamp.
std::optional<uint64_t> Extrapolate(size_t offset);
bool has_information() const { return last_information_.has_value(); };
struct IndexedTimestamp {
size_t offset;
uint64_t timestamp;
std::optional<uint64_t> timebase_;
uint64_t bytes_per_second_ = 0;
std::optional<IndexedTimestamp> last_information_;