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Don't accumulate errors in capture frame pacing

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This commit is contained in:
ns6089
2023-08-27 19:13:21 +03:00
committed by Cameron Gutman
parent b494d06f89
commit 7662fe8616
1 changed files with 37 additions and 29 deletions
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66
src/platform/windows/display_base.cpp
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@@ -120,29 +120,30 @@ namespace platf::dxgi {
capture_e capture_e
display_base_t::capture(const push_captured_image_cb_t &push_captured_image_cb, const pull_free_image_cb_t &pull_free_image_cb, bool *cursor) { display_base_t::capture(const push_captured_image_cb_t &push_captured_image_cb, const pull_free_image_cb_t &pull_free_image_cb, bool *cursor) {
auto calculate_client_frame_interval = [&]() -> std::chrono::nanoseconds { auto adjust_client_frame_rate = [&]() -> DXGI_RATIONAL {
double display_frame_rate = (double) display_refresh_rate.Numerator / display_refresh_rate.Denominator;
double client_frame_rate_adjusted;
if (client_frame_rate >= display_frame_rate) {
client_frame_rate_adjusted = display_frame_rate * std::round(client_frame_rate / display_frame_rate);
}
else {
client_frame_rate_adjusted = display_frame_rate / std::round(display_frame_rate / client_frame_rate);
}
// Adjust capture frame interval when display refresh rate is not integral but very close to requested fps. // Adjust capture frame interval when display refresh rate is not integral but very close to requested fps.
// Can only decrease requested fps, otherwise client may start accumulating frames and suffer increased latency. if (display_refresh_rate.Denominator > 1) {
if (client_frame_rate > client_frame_rate_adjusted && client_frame_rate_adjusted / client_frame_rate > 0.99) { DXGI_RATIONAL candidate = display_refresh_rate;
BOOST_LOG(info) << "Adjusted capture rate to " << client_frame_rate_adjusted << "fps to better match display"; if (client_frame_rate % display_refresh_rate_rounded == 0) {
return std::chrono::nanoseconds(std::llround(std::nano::den / client_frame_rate_adjusted)); candidate.Numerator *= client_frame_rate / display_refresh_rate_rounded;
}
else if (display_refresh_rate_rounded % client_frame_rate == 0) {
candidate.Denominator *= display_refresh_rate_rounded / client_frame_rate;
}
double candidate_rate = (double) candidate.Numerator / candidate.Denominator;
// Can only decrease requested fps, otherwise client may start accumulating frames and suffer increased latency.
if (client_frame_rate > candidate_rate && candidate_rate / client_frame_rate > 0.99) {
BOOST_LOG(info) << "Adjusted capture rate to " << candidate_rate << "fps to better match display";
return candidate;
}
} }
return std::chrono::nanoseconds(1s) / client_frame_rate; return { (uint32_t) client_frame_rate, 1 };
}; };
const auto client_frame_interval = calculate_client_frame_interval(); DXGI_RATIONAL client_frame_rate_adjusted = adjust_client_frame_rate();
std::optional<std::chrono::steady_clock::time_point> next_frame_time; std::optional<std::chrono::steady_clock::time_point> frame_pacing_group_start;
uint32_t frame_pacing_group_frames = 0;
// Keep the display awake during capture. If the display goes to sleep during // Keep the display awake during capture. If the display goes to sleep during
// capture, best case is that capture stops until it powers back on. However, // capture, best case is that capture stops until it powers back on. However,
@@ -167,12 +168,18 @@ namespace platf::dxgi {
std::shared_ptr<img_t> img_out; std::shared_ptr<img_t> img_out;
// Try to continue frame pacing group, snapshot() is called with zero timeout after waiting for client frame interval // Try to continue frame pacing group, snapshot() is called with zero timeout after waiting for client frame interval
if (next_frame_time) { if (frame_pacing_group_start) {
const auto sleep_period = *next_frame_time - std::chrono::steady_clock::now(); const uint32_t seconds = (uint64_t) frame_pacing_group_frames * client_frame_rate_adjusted.Denominator / client_frame_rate_adjusted.Numerator;
const uint32_t remainder = (uint64_t) frame_pacing_group_frames * client_frame_rate_adjusted.Denominator % client_frame_rate_adjusted.Numerator;
const auto sleep_target = *frame_pacing_group_start +
std::chrono::nanoseconds(1s) * seconds +
std::chrono::nanoseconds(1s) * remainder / client_frame_rate_adjusted.Numerator;
const auto sleep_period = sleep_target - std::chrono::steady_clock::now();
if (sleep_period <= 0ns) { if (sleep_period <= 0ns) {
// We missed next frame time, invalidating current frame pacing group // We missed next frame time, invalidating current frame pacing group
next_frame_time = std::nullopt; frame_pacing_group_start = std::nullopt;
frame_pacing_group_frames = 0;
status = capture_e::timeout; status = capture_e::timeout;
} }
else { else {
@@ -184,34 +191,35 @@ namespace platf::dxgi {
auto f = stat_trackers::one_digit_after_decimal(); auto f = stat_trackers::one_digit_after_decimal();
BOOST_LOG(debug) << "Sleep overshoot (min/max/avg): " << f % min_overshoot << "ms/" << f % max_overshoot << "ms/" << f % avg_overshoot << "ms"; BOOST_LOG(debug) << "Sleep overshoot (min/max/avg): " << f % min_overshoot << "ms/" << f % max_overshoot << "ms/" << f % avg_overshoot << "ms";
}; };
std::chrono::nanoseconds overshoot_ns = std::chrono::steady_clock::now() - *next_frame_time; std::chrono::nanoseconds overshoot_ns = std::chrono::steady_clock::now() - sleep_target;
sleep_overshoot_tracker.collect_and_callback_on_interval(overshoot_ns.count() / 1000000., print_info, 20s); sleep_overshoot_tracker.collect_and_callback_on_interval(overshoot_ns.count() / 1000000., print_info, 20s);
} }
status = snapshot(pull_free_image_cb, img_out, 0ms, *cursor); status = snapshot(pull_free_image_cb, img_out, 0ms, *cursor);
if (status == capture_e::ok && img_out) { if (status == capture_e::ok && img_out) {
*next_frame_time += client_frame_interval; frame_pacing_group_frames += 1;
} }
else { else {
next_frame_time = std::nullopt; frame_pacing_group_start = std::nullopt;
frame_pacing_group_frames = 0;
} }
} }
} }
// Start new frame pacing group if necessary, snapshot() is called with non-zero timeout // Start new frame pacing group if necessary, snapshot() is called with non-zero timeout
if (status == capture_e::timeout || (status == capture_e::ok && !next_frame_time)) { if (status == capture_e::timeout || (status == capture_e::ok && !frame_pacing_group_start)) {
status = snapshot(pull_free_image_cb, img_out, 1000ms, *cursor); status = snapshot(pull_free_image_cb, img_out, 1000ms, *cursor);
if (status == capture_e::ok && img_out) { if (status == capture_e::ok && img_out) {
next_frame_time = img_out->frame_timestamp; frame_pacing_group_start = img_out->frame_timestamp;
if (!next_frame_time) { if (!frame_pacing_group_start) {
BOOST_LOG(warning) << "snapshot() provided image without timestamp"; BOOST_LOG(warning) << "snapshot() provided image without timestamp";
next_frame_time = std::chrono::steady_clock::now(); frame_pacing_group_start = std::chrono::steady_clock::now();
} }
*next_frame_time += client_frame_interval; frame_pacing_group_frames = 1;
} }
} }