Remove WebRTC-LowLatencyRenderer field trial

There is no active use of it, and the fields are enabled by default in
the uses of it.

Change-Id: Ibfdb3f1befca886cb4b2f4b2ae4d6235aafafe3d
Fixed: webrtc:13998
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/256262
Reviewed-by: Johannes Kron <kron@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Evan Shrubsole <eshr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36655}

modules/video_coding/generic_decoder.cc

@@ -33,18 +33,12 @@ VCMDecodedFrameCallback::VCMDecodedFrameCallback(
     : _clock(clock),
       _timing(timing),
       _timestampMap(kDecoderFrameMemoryLength),
-      _extra_decode_time("t", absl::nullopt),
+      _extra_decode_time("t", absl::nullopt) {
-      low_latency_renderer_enabled_("enabled", true),
-      low_latency_renderer_include_predecode_buffer_("include_predecode_buffer",
-                                                     true) {
   ntp_offset_ =
       _clock->CurrentNtpInMilliseconds() - _clock->TimeInMilliseconds();
 
   ParseFieldTrial({&_extra_decode_time},
                   field_trials.Lookup("WebRTC-SlowDownDecoder"));
-  ParseFieldTrial({&low_latency_renderer_enabled_,
-                   &low_latency_renderer_include_predecode_buffer_},
-                  field_trials.Lookup("WebRTC-LowLatencyRenderer"));
 }
 
 VCMDecodedFrameCallback::~VCMDecodedFrameCallback() {}
@@ -123,20 +117,16 @@ void VCMDecodedFrameCallback::Decoded(VideoFrame& decodedImage,
   decodedImage.set_packet_infos(frameInfo->packet_infos);
   decodedImage.set_rotation(frameInfo->rotation);
 
-  if (low_latency_renderer_enabled_) {
   absl::optional<int> max_composition_delay_in_frames =
       _timing->MaxCompositionDelayInFrames();
   if (max_composition_delay_in_frames) {
     // Subtract frames that are in flight.
-      if (low_latency_renderer_include_predecode_buffer_) {
     *max_composition_delay_in_frames -= timestamp_map_size;
     *max_composition_delay_in_frames =
         std::max(0, *max_composition_delay_in_frames);
-      }
     decodedImage.set_max_composition_delay_in_frames(
         max_composition_delay_in_frames);
   }
-  }
 
   RTC_DCHECK(frameInfo->decodeStart);
   const Timestamp now = _clock->CurrentTime();

modules/video_coding/generic_decoder.h

@@ -66,16 +66,6 @@ class VCMDecodedFrameCallback : public DecodedImageCallback {
   int64_t ntp_offset_;
   // Set by the field trial WebRTC-SlowDownDecoder to simulate a slow decoder.
   FieldTrialOptional<TimeDelta> _extra_decode_time;
-
-  // Set by the field trial WebRTC-LowLatencyRenderer. The parameter `enabled`
-  // determines if the low-latency renderer algorithm should be used for the
-  // case min playout delay=0 and max playout delay>0.
-  FieldTrialParameter<bool> low_latency_renderer_enabled_;
-  // Set by the field trial WebRTC-LowLatencyRenderer. The parameter
-  // `include_predecode_buffer` determines if the predecode buffer should be
-  // taken into account when calculating maximum number of frames in composition
-  // queue.
-  FieldTrialParameter<bool> low_latency_renderer_include_predecode_buffer_;
 };
 
 class VCMGenericDecoder {

modules/video_coding/timing.cc

@@ -22,6 +22,8 @@ namespace {
 
 // Default pacing that is used for the low-latency renderer path.
 constexpr TimeDelta kZeroPlayoutDelayDefaultMinPacing = TimeDelta::Millis(8);
+constexpr TimeDelta kLowLatencyRendererMaxPlayoutDelay = TimeDelta::Millis(500);
+
 }  // namespace
 
 VCMTiming::VCMTiming(Clock* clock, const FieldTrialsView& field_trials)
@@ -36,12 +38,9 @@ VCMTiming::VCMTiming(Clock* clock, const FieldTrialsView& field_trials)
       current_delay_(TimeDelta::Zero()),
       prev_frame_timestamp_(0),
       num_decoded_frames_(0),
-      low_latency_renderer_enabled_("enabled", true),
       zero_playout_delay_min_pacing_("min_pacing",
                                      kZeroPlayoutDelayDefaultMinPacing),
       last_decode_scheduled_(Timestamp::Zero()) {
-  ParseFieldTrial({&low_latency_renderer_enabled_},
-                  field_trials.Lookup("WebRTC-LowLatencyRenderer"));
   ParseFieldTrial({&zero_playout_delay_min_pacing_},
                   field_trials.Lookup("WebRTC-ZeroPlayoutDelay"));
 }
@@ -165,12 +164,9 @@ void VCMTiming::SetLastDecodeScheduledTimestamp(
 
 Timestamp VCMTiming::RenderTimeInternal(uint32_t frame_timestamp,
                                         Timestamp now) const {
-  constexpr TimeDelta kLowLatencyRendererMaxPlayoutDelay =
-      TimeDelta::Millis(500);
   if (min_playout_delay_.IsZero() &&
       (max_playout_delay_.IsZero() ||
-       (low_latency_renderer_enabled_ &&
+       max_playout_delay_ <= kLowLatencyRendererMaxPlayoutDelay)) {
-        max_playout_delay_ <= kLowLatencyRendererMaxPlayoutDelay))) {
     // Render as soon as possible or with low-latency renderer algorithm.
     return Timestamp::Zero();
   }

modules/video_coding/timing.h

@@ -141,11 +141,6 @@ class VCMTiming {
   uint32_t prev_frame_timestamp_ RTC_GUARDED_BY(mutex_);
   absl::optional<TimingFrameInfo> timing_frame_info_ RTC_GUARDED_BY(mutex_);
   size_t num_decoded_frames_ RTC_GUARDED_BY(mutex_);
-  // Set by the field trial WebRTC-LowLatencyRenderer. The parameter enabled
-  // determines if the low-latency renderer algorithm should be used for the
-  // case min playout delay=0 and max playout delay>0.
-  FieldTrialParameter<bool> low_latency_renderer_enabled_
-      RTC_GUARDED_BY(mutex_);
   absl::optional<int> max_composition_delay_in_frames_ RTC_GUARDED_BY(mutex_);
   // Set by the field trial WebRTC-ZeroPlayoutDelay. The parameter min_pacing
   // determines the minimum delay between frames scheduled for decoding that is

video/video_receive_stream2.cc

@@ -244,9 +244,6 @@ VideoReceiveStream2::VideoReceiveStream2(
       rtp_stream_sync_(call->worker_thread(), this),
       max_wait_for_keyframe_ms_(DetermineMaxWaitForFrame(config_, true)),
       max_wait_for_frame_ms_(DetermineMaxWaitForFrame(config_, false)),
-      low_latency_renderer_enabled_("enabled", true),
-      low_latency_renderer_include_predecode_buffer_("include_predecode_buffer",
-                                                     true),
       maximum_pre_stream_decoders_("max", kDefaultMaximumPreStreamDecoders),
       decode_sync_(decode_sync),
       decode_queue_(task_queue_factory_->CreateTaskQueue(
@@ -286,9 +283,6 @@ VideoReceiveStream2::VideoReceiveStream2(
                                                        true);
   }
 
-  ParseFieldTrial({&low_latency_renderer_enabled_,
-                   &low_latency_renderer_include_predecode_buffer_},
-                  call_->trials().Lookup("WebRTC-LowLatencyRenderer"));
   ParseFieldTrial(
       {
           &maximum_pre_stream_decoders_,
@@ -975,18 +969,16 @@ void VideoReceiveStream2::UpdatePlayoutDelays() const {
   if (minimum_delay_ms >= 0) {
     timing_->set_min_playout_delay(TimeDelta::Millis(minimum_delay_ms));
     if (frame_minimum_playout_delay_ms_ == 0 &&
-        frame_maximum_playout_delay_ms_ > 0 && low_latency_renderer_enabled_) {
+        frame_maximum_playout_delay_ms_ > 0) {
       // TODO(kron): Estimate frame rate from video stream.
       constexpr double kFrameRate = 60.0;
       // Convert playout delay in ms to number of frames.
       int max_composition_delay_in_frames = std::lrint(
           static_cast<double>(frame_maximum_playout_delay_ms_ * kFrameRate) /
           rtc::kNumMillisecsPerSec);
-      if (low_latency_renderer_include_predecode_buffer_) {
       // Subtract frames in buffer.
       max_composition_delay_in_frames = std::max<int16_t>(
           max_composition_delay_in_frames - frame_buffer_->Size(), 0);
-      }
       timing_->SetMaxCompositionDelayInFrames(
           absl::make_optional(max_composition_delay_in_frames));
     }

video/video_receive_stream2.h

@@ -309,16 +309,6 @@ class VideoReceiveStream2
   std::vector<std::unique_ptr<EncodedFrame>> buffered_encoded_frames_
       RTC_GUARDED_BY(decode_queue_);
 
-  // Set by the field trial WebRTC-LowLatencyRenderer. The parameter `enabled`
-  // determines if the low-latency renderer algorithm should be used for the
-  // case min playout delay=0 and max playout delay>0.
-  FieldTrialParameter<bool> low_latency_renderer_enabled_;
-  // Set by the field trial WebRTC-LowLatencyRenderer. The parameter
-  // `include_predecode_buffer` determines if the predecode buffer should be
-  // taken into account when calculating maximum number of frames in composition
-  // queue.
-  FieldTrialParameter<bool> low_latency_renderer_include_predecode_buffer_;
-
   // Set by the field trial WebRTC-PreStreamDecoders. The parameter `max`
   // determines the maximum number of decoders that are created up front before
   // any video frame has been received.