Make Frame buffer not drop frames unnecessary

Now VCMTiming::MaxWaitingTime will not clip negative values. Thus frame
buffer will be able to distinguish between late frames and when waiting
cycle was simply interrupted by a new inserted frame right before the
waiting timer would expire.

Bug: webrtc:8917
Change-Id: I6b253f459fcb3a346064a103cc92ee332b074e1b
Reviewed-on: https://webrtc-review.googlesource.com/57741
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22210}

modules/video_coding/frame_buffer2.cc

@@ -34,6 +34,10 @@ constexpr int kMaxFramesBuffered = 600;
 // Max number of decoded frame info that will be saved.
 constexpr int kMaxFramesHistory = 50;
 
+// The time it's allowed for a frame to be late to its rendering prediction and
+// still be rendered.
+constexpr int kMaxAllowedFrameDalayMs = 5;
+
 constexpr int64_t kLogNonDecodedIntervalMs = 5000;
 }  // namespace
 
@@ -119,7 +123,9 @@ FrameBuffer::ReturnReason FrameBuffer::NextFrame(
         // This will cause the frame buffer to prefer high framerate rather
         // than high resolution in the case of the decoder not decoding fast
         // enough and the stream has multiple spatial and temporal layers.
-        if (wait_ms == 0)
+        // For multiple temporal layers it may cause non-base layer frames to be
+        // skipped if they are late.
+        if (wait_ms < -kMaxAllowedFrameDalayMs)
           continue;
 
         break;

modules/video_coding/frame_buffer2_unittest.cc

@@ -52,9 +52,9 @@ class VCMTimingFake : public VCMTiming {
     return last_ms_;
   }
 
-  uint32_t MaxWaitingTime(int64_t render_time_ms,
-                          int64_t now_ms) const override {
-    return std::max<int>(0, render_time_ms - now_ms - kDecodeTime);
+  int64_t MaxWaitingTime(int64_t render_time_ms,
+                         int64_t now_ms) const override {
+    return render_time_ms - now_ms - kDecodeTime;
   }
 
   bool GetTimings(int* decode_ms,
@@ -359,7 +359,7 @@ TEST_F(TestFrameBuffer2, DropTemporalLayerSlowDecoder) {
 
   for (int i = 0; i < 10; ++i) {
     ExtractFrame();
-    clock_.AdvanceTimeMilliseconds(60);
+    clock_.AdvanceTimeMilliseconds(70);
   }
 
   CheckFrame(0, pid, 0);
@@ -388,10 +388,10 @@ TEST_F(TestFrameBuffer2, DropSpatialLayerSlowDecoder) {
 
   ExtractFrame();
   ExtractFrame();
-  clock_.AdvanceTimeMilliseconds(55);
+  clock_.AdvanceTimeMilliseconds(57);
   for (int i = 2; i < 12; ++i) {
     ExtractFrame();
-    clock_.AdvanceTimeMilliseconds(55);
+    clock_.AdvanceTimeMilliseconds(57);
   }
 
   CheckFrame(0, pid, 0);

modules/video_coding/receiver.cc

@@ -20,6 +20,7 @@
 #include "modules/video_coding/internal_defines.h"
 #include "modules/video_coding/media_opt_util.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/trace_event.h"
 #include "system_wrappers/include/clock.h"
 
@@ -192,8 +193,8 @@ VCMEncodedFrame* VCMReceiver::FrameForDecoding(uint16_t max_wait_time_ms,
         static_cast<int32_t>(clock_->TimeInMilliseconds() - start_time_ms);
     uint16_t new_max_wait_time =
         static_cast<uint16_t>(VCM_MAX(available_wait_time, 0));
-    uint32_t wait_time_ms =
-        timing_->MaxWaitingTime(render_time_ms, clock_->TimeInMilliseconds());
+    uint32_t wait_time_ms = rtc::saturated_cast<uint32_t>(
+        timing_->MaxWaitingTime(render_time_ms, clock_->TimeInMilliseconds()));
     if (new_max_wait_time < wait_time_ms) {
       // We're not allowed to wait until the frame is supposed to be rendered,
       // waiting as long as we're allowed to avoid busy looping, and then return

modules/video_coding/timing.cc

@@ -234,17 +234,14 @@ int VCMTiming::RequiredDecodeTimeMs() const {
   return decode_time_ms;
 }
 
-uint32_t VCMTiming::MaxWaitingTime(int64_t render_time_ms,
-                                   int64_t now_ms) const {
+int64_t VCMTiming::MaxWaitingTime(int64_t render_time_ms,
+                                  int64_t now_ms) const {
   rtc::CritScope cs(&crit_sect_);
 
   const int64_t max_wait_time_ms =
       render_time_ms - now_ms - RequiredDecodeTimeMs() - render_delay_ms_;
 
-  if (max_wait_time_ms < 0) {
-    return 0;
-  }
-  return static_cast<uint32_t>(max_wait_time_ms);
+  return max_wait_time_ms;
 }
 
 int VCMTiming::TargetVideoDelay() const {

modules/video_coding/timing.h

@@ -78,7 +78,7 @@ class VCMTiming {
 
   // Returns the maximum time in ms that we can wait for a frame to become
   // complete before we must pass it to the decoder.
-  virtual uint32_t MaxWaitingTime(int64_t render_time_ms, int64_t now_ms) const;
+  virtual int64_t MaxWaitingTime(int64_t render_time_ms, int64_t now_ms) const;
 
   // Returns the current target delay which is required delay + decode time +
   // render delay.