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Cleanup RtpToNtpEstimator

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- Use NtpTime instead of pair of uint32_t to represent ntp time
- Increase precision estimate with NtpTime precision instead of ms precision
- Hide helper structs as private types
- Modernize interface to prefer return values over output parameters
- embed LinearRegression helper into the only user: UpdateParameters

Bug: webrtc:13757
Change-Id: I0a62a03e2869b2ae1eacaa15253accc43ba0a598
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/254780
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36232}
This commit is contained in:
Danil Chapovalov
2022-03-14 12:31:46 +01:00
committed by WebRTC LUCI CQ
parent 340cb5e46a
commit ae4fb618d7
7 changed files with 266 additions and 410 deletions
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67
system_wrappers/include/rtp_to_ntp_estimator.h
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@ -18,60 +18,51 @@
#include "absl/types/optional.h"
#include "modules/include/module_common_types_public.h"
#include "rtc_base/checks.h"
#include "rtc_base/numerics/moving_median_filter.h"
#include "system_wrappers/include/ntp_time.h"
namespace webrtc {
// Class for converting an RTP timestamp to the NTP domain in milliseconds.
// Converts an RTP timestamp to the NTP domain.
// The class needs to be trained with (at least 2) RTP/NTP timestamp pairs from
// RTCP sender reports before the convertion can be done.
class RtpToNtpEstimator {
public:
RtpToNtpEstimator();
~RtpToNtpEstimator();
static constexpr int kMaxInvalidSamples = 3;
RtpToNtpEstimator() = default;
RtpToNtpEstimator(const RtpToNtpEstimator&) = delete;
RtpToNtpEstimator& operator=(const RtpToNtpEstimator&) = delete;
~RtpToNtpEstimator() = default;
enum UpdateResult { kInvalidMeasurement, kSameMeasurement, kNewMeasurement };
// Updates measurements with RTP/NTP timestamp pair from a RTCP sender report.
UpdateResult UpdateMeasurements(NtpTime ntp, uint32_t rtp_timestamp);
// Converts an RTP timestamp to the NTP domain.
// Returns invalid NtpTime (i.e. NtpTime(0)) on failure.
NtpTime Estimate(uint32_t rtp_timestamp) const;
// Returns estimated rtp_timestamp frequency, or 0 on failure.
double EstimatedFrequencyKhz() const;
private:
// Estimated parameters from RTP and NTP timestamp pairs in `measurements_`.
// Defines linear estimation: NtpTime (in units of 1s/2^32) =
// `Parameters::slope` * rtp_timestamp + `Parameters::offset`.
struct Parameters {
double slope;
double offset;
};
// RTP and NTP timestamp pair from a RTCP SR report.
struct RtcpMeasurement {
RtcpMeasurement(uint32_t ntp_secs,
uint32_t ntp_frac,
int64_t unwrapped_timestamp);
bool IsEqual(const RtcpMeasurement& other) const;
NtpTime ntp_time;
int64_t unwrapped_rtp_timestamp;
};
// Estimated parameters from RTP and NTP timestamp pairs in `measurements_`.
struct Parameters {
Parameters() : frequency_khz(0.0), offset_ms(0.0) {}
Parameters(double frequency_khz, double offset_ms)
: frequency_khz(frequency_khz), offset_ms(offset_ms) {}
double frequency_khz;
double offset_ms;
};
// Updates measurements with RTP/NTP timestamp pair from a RTCP sender report.
// `new_rtcp_sr` is set to true if a new report is added.
bool UpdateMeasurements(uint32_t ntp_secs,
uint32_t ntp_frac,
uint32_t rtp_timestamp,
bool* new_rtcp_sr);
// Converts an RTP timestamp to the NTP domain in milliseconds.
// Returns true on success, false otherwise.
bool Estimate(int64_t rtp_timestamp, int64_t* ntp_timestamp_ms) const;
// Returns estimated rtp to ntp linear transform parameters.
const absl::optional<Parameters> params() const;
static const int kMaxInvalidSamples = 3;
private:
void UpdateParameters();
int consecutive_invalid_samples_;
int consecutive_invalid_samples_ = 0;
std::list<RtcpMeasurement> measurements_;
absl::optional<Parameters> params_;
mutable TimestampUnwrapper unwrapper_;