Add fieldtrial to enable minimum pacing of video frames
If the RTP header extension playout-delay is used and set
to min=0, max>=0, frames are scheduled to be decoded as
soon as possible. There's a risk that too many frames are
sent to the decoder at once, which may cause problems
further down in the video pipeline.
This CL adds the fieldtrial WebRTC-ZeroPlayoutDelay with
the parameter min_pacing that determines the minimum
pacing interval between two frames scheduled for
decoding.
Bug: None
Change-Id: I471f7718761cfce9789b3aa8adea3e8a16ecb2fd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/223742
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Johannes Kron <kron@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34387}
diff --git a/modules/video_coding/timing_unittest.cc b/modules/video_coding/timing_unittest.cc
index ee86605..be6ac52 100644
--- a/modules/video_coding/timing_unittest.cc
+++ b/modules/video_coding/timing_unittest.cc
@@ -11,6 +11,7 @@
#include "modules/video_coding/timing.h"
#include "system_wrappers/include/clock.h"
+#include "test/field_trial.h"
#include "test/gtest.h"
namespace webrtc {
@@ -18,7 +19,7 @@
const int kFps = 25;
} // namespace
-TEST(ReceiverTiming, Tests) {
+TEST(ReceiverTimingTest, JitterDelay) {
SimulatedClock clock(0);
VCMTiming timing(&clock);
timing.Reset();
@@ -110,7 +111,7 @@
timing.UpdateCurrentDelay(timestamp);
}
-TEST(ReceiverTiming, WrapAround) {
+TEST(ReceiverTimingTest, TimestampWrapAround) {
SimulatedClock clock(0);
VCMTiming timing(&clock);
// Provoke a wrap-around. The fifth frame will have wrapped at 25 fps.
@@ -127,4 +128,89 @@
}
}
+TEST(ReceiverTimingTest, MaxWaitingTimeIsZeroForZeroRenderTime) {
+ // This is the default path when the RTP playout delay header extension is set
+ // to min==0.
+ constexpr int64_t kStartTimeUs = 3.15e13; // About one year in us.
+ constexpr int64_t kTimeDeltaMs = 1000.0 / 60.0;
+ constexpr int64_t kZeroRenderTimeMs = 0;
+ SimulatedClock clock(kStartTimeUs);
+ VCMTiming timing(&clock);
+ timing.Reset();
+ for (int i = 0; i < 10; ++i) {
+ clock.AdvanceTimeMilliseconds(kTimeDeltaMs);
+ int64_t now_ms = clock.TimeInMilliseconds();
+ EXPECT_LT(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), 0);
+ }
+ // Another frame submitted at the same time also returns a negative max
+ // waiting time.
+ int64_t now_ms = clock.TimeInMilliseconds();
+ EXPECT_LT(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), 0);
+ // MaxWaitingTime should be less than zero even if there's a burst of frames.
+ EXPECT_LT(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), 0);
+ EXPECT_LT(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), 0);
+ EXPECT_LT(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), 0);
+}
+
+TEST(ReceiverTimingTest, MaxWaitingTimeZeroDelayPacingExperiment) {
+ // The minimum pacing is enabled by a field trial and active if the RTP
+ // playout delay header extension is set to min==0.
+ constexpr int64_t kMinPacingMs = 3;
+ test::ScopedFieldTrials override_field_trials(
+ "WebRTC-ZeroPlayoutDelay/min_pacing:3ms/");
+ constexpr int64_t kStartTimeUs = 3.15e13; // About one year in us.
+ constexpr int64_t kTimeDeltaMs = 1000.0 / 60.0;
+ constexpr int64_t kZeroRenderTimeMs = 0;
+ SimulatedClock clock(kStartTimeUs);
+ VCMTiming timing(&clock);
+ timing.Reset();
+ // MaxWaitingTime() returns zero for evenly spaced video frames.
+ for (int i = 0; i < 10; ++i) {
+ clock.AdvanceTimeMilliseconds(kTimeDeltaMs);
+ int64_t now_ms = clock.TimeInMilliseconds();
+ EXPECT_EQ(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), 0);
+ }
+ // Another frame submitted at the same time is paced according to the field
+ // trial setting.
+ int64_t now_ms = clock.TimeInMilliseconds();
+ EXPECT_EQ(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), kMinPacingMs);
+ // If there's a burst of frames, the min pacing interval is summed.
+ EXPECT_EQ(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), 2 * kMinPacingMs);
+ EXPECT_EQ(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), 3 * kMinPacingMs);
+ EXPECT_EQ(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms), 4 * kMinPacingMs);
+ // Allow a few ms to pass, this should be subtracted from the MaxWaitingTime.
+ constexpr int64_t kTwoMs = 2;
+ clock.AdvanceTimeMilliseconds(kTwoMs);
+ now_ms = clock.TimeInMilliseconds();
+ EXPECT_EQ(timing.MaxWaitingTime(kZeroRenderTimeMs, now_ms),
+ 5 * kMinPacingMs - kTwoMs);
+}
+
+TEST(ReceiverTimingTest, DefaultMaxWaitingTimeUnaffectedByPacingExperiment) {
+ // The minimum pacing is enabled by a field trial but should not have any
+ // effect if render_time_ms is greater than 0;
+ test::ScopedFieldTrials override_field_trials(
+ "WebRTC-ZeroPlayoutDelay/min_pacing:3ms/");
+ constexpr int64_t kStartTimeUs = 3.15e13; // About one year in us.
+ constexpr int64_t kTimeDeltaMs = 1000.0 / 60.0;
+ SimulatedClock clock(kStartTimeUs);
+ VCMTiming timing(&clock);
+ timing.Reset();
+ clock.AdvanceTimeMilliseconds(kTimeDeltaMs);
+ int64_t now_ms = clock.TimeInMilliseconds();
+ int64_t render_time_ms = now_ms + 30;
+ // Estimate the internal processing delay from the first frame.
+ int64_t estimated_processing_delay =
+ (render_time_ms - now_ms) - timing.MaxWaitingTime(render_time_ms, now_ms);
+ EXPECT_GT(estimated_processing_delay, 0);
+
+ // Any other frame submitted at the same time should be scheduled according to
+ // its render time.
+ for (int i = 0; i < 5; ++i) {
+ render_time_ms += kTimeDeltaMs;
+ EXPECT_EQ(timing.MaxWaitingTime(render_time_ms, now_ms),
+ render_time_ms - now_ms - estimated_processing_delay);
+ }
+}
+
} // namespace webrtc