#include "input_state.h"
#include "libusb.h"
#include "pbo_frame_allocator.h"
+#include "queue_length_policy.h"
#include "ref_counted_frame.h"
#include "shared/ref_counted_gl_sync.h"
#include "theme.h"
class YCbCrInput;
} // namespace movit
-// A class to estimate the future jitter. Used in QueueLengthPolicy (see below).
-//
-// There are many ways to estimate jitter; I've tested a few ones (and also
-// some algorithms that don't explicitly model jitter) with different
-// parameters on some real-life data in experiments/queue_drop_policy.cpp.
-// This is one based on simple order statistics where I've added some margin in
-// the number of starvation events; I believe that about one every hour would
-// probably be acceptable, but this one typically goes lower than that, at the
-// cost of 2–3 ms extra latency. (If the queue is hard-limited to one frame, it's
-// possible to get ~10 ms further down, but this would mean framedrops every
-// second or so.) The general strategy is: Take the 99.9-percentile jitter over
-// last 5000 frames, multiply by two, and that's our worst-case jitter
-// estimate. The fact that we're not using the max value means that we could
-// actually even throw away very late frames immediately, which means we only
-// get one user-visible event instead of seeing something both when the frame
-// arrives late (duplicate frame) and then again when we drop.
-class JitterHistory {
-private:
- static constexpr size_t history_length = 5000;
- static constexpr double percentile = 0.999;
- static constexpr double multiplier = 2.0;
-
-public:
- void register_metrics(const std::vector<std::pair<std::string, std::string>> &labels);
- void unregister_metrics(const std::vector<std::pair<std::string, std::string>> &labels);
-
- void clear() {
- history.clear();
- orders.clear();
- }
- void frame_arrived(std::chrono::steady_clock::time_point now, int64_t frame_duration, size_t dropped_frames);
- std::chrono::steady_clock::time_point get_expected_next_frame() const { return expected_timestamp; }
- double estimate_max_jitter() const;
-
-private:
- // A simple O(k) based algorithm for getting the k-th largest or
- // smallest element from our window; we simply keep the multiset
- // ordered (insertions and deletions are O(n) as always) and then
- // iterate from one of the sides. If we had larger values of k,
- // we could go for a more complicated setup with two sets or heaps
- // (one increasing and one decreasing) that we keep balanced around
- // the point, or it is possible to reimplement std::set with
- // counts in each node. However, since k=5, we don't need this.
- std::multiset<double> orders;
- std::deque<std::multiset<double>::iterator> history;
-
- std::chrono::steady_clock::time_point expected_timestamp = std::chrono::steady_clock::time_point::min();
-
- // Metrics. There are no direct summaries for jitter, since we already have latency summaries.
- std::atomic<int64_t> metric_input_underestimated_jitter_frames{0};
- std::atomic<double> metric_input_estimated_max_jitter_seconds{0.0 / 0.0};
-};
-
-// For any card that's not the master (where we pick out the frames as they
-// come, as fast as we can process), there's going to be a queue. The question
-// is when we should drop frames from that queue (apart from the obvious
-// dropping if the 16-frame queue should become full), especially given that
-// the frame rate could be lower or higher than the master (either subtly or
-// dramatically). We have two (conflicting) demands:
-//
-// 1. We want to avoid starving the queue.
-// 2. We don't want to add more delay than is needed.
-//
-// Our general strategy is to drop as many frames as we can (helping for #2)
-// that we think is safe for #1 given jitter. To this end, we measure the
-// deviation from the expected arrival time for all cards, and use that for
-// continuous jitter estimation.
-//
-// We then drop everything from the queue that we're sure we won't need to
-// serve the output in the time before the next frame arrives. Typically,
-// this means the queue will contain 0 or 1 frames, although more is also
-// possible if the jitter is very high.
-class QueueLengthPolicy {
-public:
- QueueLengthPolicy() {}
-
- void register_metrics(const std::vector<std::pair<std::string, std::string>> &labels);
- void unregister_metrics(const std::vector<std::pair<std::string, std::string>> &labels);
-
- // Call after picking out a frame, so 0 means starvation.
- // Note that the policy has no memory; everything is given in as parameters.
- void update_policy(std::chrono::steady_clock::time_point now,
- std::chrono::steady_clock::time_point expected_next_frame,
- int64_t input_frame_duration,
- int64_t master_frame_duration,
- double max_input_card_jitter_seconds,
- double max_master_card_jitter_seconds);
- unsigned get_safe_queue_length() const { return safe_queue_length; }
-
-private:
- unsigned safe_queue_length = 0; // Can never go below zero.
-
- // Metrics.
- std::atomic<int64_t> metric_input_queue_safe_length_frames{1};
-};
-
class Mixer {
public:
// The surface format is used for offscreen destinations for OpenGL contexts we need.
--- /dev/null
+#ifndef _QUEUE_LENGTH_POLICY_H
+#define _QUEUE_LENGTH_POLICY_H 1
+
+#include <atomic>
+#include <string>
+#include <utility>
+#include <vector>
+
+// A class to estimate the future jitter. Used in QueueLengthPolicy (see below).
+//
+// There are many ways to estimate jitter; I've tested a few ones (and also
+// some algorithms that don't explicitly model jitter) with different
+// parameters on some real-life data in experiments/queue_drop_policy.cpp.
+// This is one based on simple order statistics where I've added some margin in
+// the number of starvation events; I believe that about one every hour would
+// probably be acceptable, but this one typically goes lower than that, at the
+// cost of 2–3 ms extra latency. (If the queue is hard-limited to one frame, it's
+// possible to get ~10 ms further down, but this would mean framedrops every
+// second or so.) The general strategy is: Take the 99.9-percentile jitter over
+// last 5000 frames, multiply by two, and that's our worst-case jitter
+// estimate. The fact that we're not using the max value means that we could
+// actually even throw away very late frames immediately, which means we only
+// get one user-visible event instead of seeing something both when the frame
+// arrives late (duplicate frame) and then again when we drop.
+class JitterHistory {
+private:
+ static constexpr size_t history_length = 5000;
+ static constexpr double percentile = 0.999;
+ static constexpr double multiplier = 2.0;
+
+public:
+ void register_metrics(const std::vector<std::pair<std::string, std::string>> &labels);
+ void unregister_metrics(const std::vector<std::pair<std::string, std::string>> &labels);
+
+ void clear() {
+ history.clear();
+ orders.clear();
+ }
+ void frame_arrived(std::chrono::steady_clock::time_point now, int64_t frame_duration, size_t dropped_frames);
+ std::chrono::steady_clock::time_point get_expected_next_frame() const { return expected_timestamp; }
+ double estimate_max_jitter() const;
+
+private:
+ // A simple O(k) based algorithm for getting the k-th largest or
+ // smallest element from our window; we simply keep the multiset
+ // ordered (insertions and deletions are O(n) as always) and then
+ // iterate from one of the sides. If we had larger values of k,
+ // we could go for a more complicated setup with two sets or heaps
+ // (one increasing and one decreasing) that we keep balanced around
+ // the point, or it is possible to reimplement std::set with
+ // counts in each node. However, since k=5, we don't need this.
+ std::multiset<double> orders;
+ std::deque<std::multiset<double>::iterator> history;
+
+ std::chrono::steady_clock::time_point expected_timestamp = std::chrono::steady_clock::time_point::min();
+
+ // Metrics. There are no direct summaries for jitter, since we already have latency summaries.
+ std::atomic<int64_t> metric_input_underestimated_jitter_frames{0};
+ std::atomic<double> metric_input_estimated_max_jitter_seconds{0.0 / 0.0};
+};
+
+// For any card that's not the master (where we pick out the frames as they
+// come, as fast as we can process), there's going to be a queue. The question
+// is when we should drop frames from that queue (apart from the obvious
+// dropping if the 16-frame queue should become full), especially given that
+// the frame rate could be lower or higher than the master (either subtly or
+// dramatically). We have two (conflicting) demands:
+//
+// 1. We want to avoid starving the queue.
+// 2. We don't want to add more delay than is needed.
+//
+// Our general strategy is to drop as many frames as we can (helping for #2)
+// that we think is safe for #1 given jitter. To this end, we measure the
+// deviation from the expected arrival time for all cards, and use that for
+// continuous jitter estimation.
+//
+// We then drop everything from the queue that we're sure we won't need to
+// serve the output in the time before the next frame arrives. Typically,
+// this means the queue will contain 0 or 1 frames, although more is also
+// possible if the jitter is very high.
+class QueueLengthPolicy {
+public:
+ QueueLengthPolicy() {}
+
+ void register_metrics(const std::vector<std::pair<std::string, std::string>> &labels);
+ void unregister_metrics(const std::vector<std::pair<std::string, std::string>> &labels);
+
+ // Call after picking out a frame, so 0 means starvation.
+ // Note that the policy has no memory; everything is given in as parameters.
+ void update_policy(std::chrono::steady_clock::time_point now,
+ std::chrono::steady_clock::time_point expected_next_frame,
+ int64_t input_frame_duration,
+ int64_t master_frame_duration,
+ double max_input_card_jitter_seconds,
+ double max_master_card_jitter_seconds);
+ unsigned get_safe_queue_length() const { return safe_queue_length; }
+
+private:
+ unsigned safe_queue_length = 0; // Can never go below zero.
+
+ // Metrics.
+ std::atomic<int64_t> metric_input_queue_safe_length_frames{1};
+};
+
+#endif // !defined(_QUEUE_LENGTH_POLICY_H)
projects / nageru / commitdiff