Periodically update codec bit/frame rate settings.

webrtc/test/fake_encoder.cc

Index: webrtc/test/fake_encoder.cc
diff --git a/webrtc/test/fake_encoder.cc b/webrtc/test/fake_encoder.cc
index fce12c61a804c8af841435b001779374b912066c..8de59a1d0b8ec57b9aa52a46f8cedf70f233aeae 100644
--- a/webrtc/test/fake_encoder.cc
+++ b/webrtc/test/fake_encoder.cc
@@ -27,8 +27,9 @@ namespace test {
 FakeEncoder::FakeEncoder(Clock* clock)
     : clock_(clock),
       callback_(nullptr),
+      configured_input_framerate_(-1),
       max_target_bitrate_kbps_(-1),
-      last_encode_time_ms_(0) {
+      pending_keyframe_(true) {
   // Generate some arbitrary not-all-zero data
   for (size_t i = 0; i < sizeof(encoded_buffer_); ++i) {
     encoded_buffer_[i] = static_cast<uint8_t>(i);
@@ -47,6 +48,8 @@ int32_t FakeEncoder::InitEncode(const VideoCodec* config,
   rtc::CritScope cs(&crit_sect_);
   config_ = *config;
   target_bitrate_.SetBitrate(0, 0, config_.startBitrate * 1000);
+  configured_input_framerate_ = config_.maxFramerate;
+  pending_keyframe_ = true;
   return 0;
 }
 
@@ -59,9 +62,10 @@ int32_t FakeEncoder::Encode(const VideoFrame& input_image,
   EncodedImageCallback* callback;
   uint32_t target_bitrate_sum_kbps;
   int max_target_bitrate_kbps;
-  int64_t last_encode_time_ms;
   size_t num_encoded_bytes;
+  int framerate;
   VideoCodecMode mode;
+  bool keyframe;
   {
     rtc::CritScope cs(&crit_sect_);
     max_framerate = config_.maxFramerate;
@@ -72,42 +76,33 @@ int32_t FakeEncoder::Encode(const VideoFrame& input_image,
     callback = callback_;
     target_bitrate_sum_kbps = target_bitrate_.get_sum_kbps();
     max_target_bitrate_kbps = max_target_bitrate_kbps_;
-    last_encode_time_ms = last_encode_time_ms_;
     num_encoded_bytes = sizeof(encoded_buffer_);
     mode = config_.mode;
+    if (configured_input_framerate_ > 0) {
+      framerate = configured_input_framerate_;
+    } else {
+      framerate = max_framerate;
+    }
+    keyframe = pending_keyframe_;
+    pending_keyframe_ = false;
   }
 
-  int64_t time_now_ms = clock_->TimeInMilliseconds();
-  const bool first_encode = (last_encode_time_ms == 0);
-  RTC_DCHECK_GT(max_framerate, 0);
-  int64_t time_since_last_encode_ms = 1000 / max_framerate;
-  if (!first_encode) {
-    // For all frames but the first we can estimate the display time by looking
-    // at the display time of the previous frame.
-    time_since_last_encode_ms = time_now_ms - last_encode_time_ms;
-  }
-  if (time_since_last_encode_ms > 3 * 1000 / max_framerate) {
-    // Rudimentary check to make sure we don't widely overshoot bitrate target
-    // when resuming encoding after a suspension.
-    time_since_last_encode_ms = 3 * 1000 / max_framerate;
+  for (FrameType frame_type : *frame_types) {
+    if (frame_type == kVideoFrameKey) {
+      keyframe = true;
+      break;
+    }
   }
 
-  size_t bits_available =
-      static_cast<size_t>(target_bitrate_sum_kbps * time_since_last_encode_ms);
-  size_t min_bits = static_cast<size_t>(simulcast_streams[0].minBitrate *
-                                        time_since_last_encode_ms);
+  RTC_DCHECK_GT(max_framerate, 0);
 
-  if (bits_available < min_bits)
-    bits_available = min_bits;
-  size_t max_bits =
-      static_cast<size_t>(max_target_bitrate_kbps * time_since_last_encode_ms);
-  if (max_bits > 0 && max_bits < bits_available)
-    bits_available = max_bits;
+  size_t bitrate = target_bitrate_sum_kbps;
+  bitrate =
+      std::max(bitrate, static_cast<size_t>(simulcast_streams[0].minBitrate));
+  if (max_target_bitrate_kbps > 0)
+    bitrate = std::min(bitrate, static_cast<size_t>(max_target_bitrate_kbps));
 
-  {
-    rtc::CritScope cs(&crit_sect_);
-    last_encode_time_ms_ = time_now_ms;
-  }
+  size_t bits_available = target_bitrate_sum_kbps * 1000 / framerate;
 
   RTC_DCHECK_GT(num_simulcast_streams, 0);
   for (unsigned char i = 0; i < num_simulcast_streams; ++i) {
@@ -116,18 +111,38 @@ int32_t FakeEncoder::Encode(const VideoFrame& input_image,
     specifics.codecType = kVideoCodecGeneric;
     specifics.codecSpecific.generic.simulcast_idx = i;
     size_t min_stream_bits = static_cast<size_t>(
-        simulcast_streams[i].minBitrate * time_since_last_encode_ms);
+        (simulcast_streams[i].minBitrate * 1000) / framerate);
     size_t max_stream_bits = static_cast<size_t>(
-        simulcast_streams[i].maxBitrate * time_since_last_encode_ms);
+        (simulcast_streams[i].maxBitrate * 1000) / framerate);
     size_t stream_bits = (bits_available > max_stream_bits) ? max_stream_bits :
         bits_available;
     size_t stream_bytes = (stream_bits + 7) / 8;
-    if (first_encode) {
+    if (keyframe) {
       // The first frame is a key frame and should be larger.
-      // TODO(holmer): The FakeEncoder should store the bits_available between
-      // encodes so that it can compensate for oversized frames.
-      stream_bytes *= 10;
+      // Store the overshoot bytes and distribute them over the coming frames,
+      // so that we on average meet the bitrate target.
+      const int kKeyframeSizeFactor = 10;
+      // Pay 1/2 of a frame debt factor every frame.
+      const int kNumDebtPayments = (kKeyframeSizeFactor - 1) * 2;
+      debt_bytes_.resize(kNumDebtPayments);
+      size_t total_debt_bytes = (kKeyframeSizeFactor - 1) * stream_bytes;
+      for (int i = 0; i < kNumDebtPayments; ++i)
+        debt_bytes_[i] += total_debt_bytes / kNumDebtPayments;

[stefan-webrtc, 2017/05/23 17:03:20]

An option is to just keep track of a total debt and pay X% of it every frame?
That seems simpler than keeping a vector of debts.

[sprang_webrtc, 2017/05/24 09:07:07]

Maybe, but then paying of the whole debt will take some time, and the frame
dropper only has a certain time it allows overshoot, right?

[holmer, 2017/06/02 11:38:05]

You could have a total_debt and a payed_debt and try to reach total_debt =
payed_debt, or something like that. But maybe it's too complicated.

+      stream_bytes *= kKeyframeSizeFactor;
+    } else {
+      if (!debt_bytes_.empty()) {
+        size_t debt_bytes = std::min(stream_bytes, debt_bytes_[0]);
+        debt_bytes_.pop_front();
+        if (debt_bytes >= stream_bytes) {

[stefan-webrtc, 2017/05/23 17:03:20]

This can only be true if == right? What is it that we want to do within this if
clause? Maybe useful with a comment, or I'm just tired. :)

[sprang_webrtc, 2017/05/24 09:07:07]

Oops, the std::min above shouldn't be there.
I'll add a comment.

+          if (debt_bytes_.empty())
+            debt_bytes_.resize(1);
+          debt_bytes_[0] += debt_bytes - stream_bytes + 1;
+          debt_bytes = stream_bytes - 1;
+        }
+        stream_bytes -= debt_bytes;
+      }
     }
+
     if (stream_bytes > num_encoded_bytes)
       stream_bytes = num_encoded_bytes;
 
@@ -175,6 +190,7 @@ int32_t FakeEncoder::SetRateAllocation(const BitrateAllocation& rate_allocation,
                                        uint32_t framerate) {
   rtc::CritScope cs(&crit_sect_);
   target_bitrate_ = rate_allocation;
+  configured_input_framerate_ = framerate;
   return 0;
 }
 
@@ -183,6 +199,11 @@ const char* FakeEncoder::ImplementationName() const {
   return kImplementationName;
 }
 
+int FakeEncoder::GetConfiguredInputFramerate() {
+  rtc::CritScope cs(&crit_sect_);
+  return configured_input_framerate_;
+}
+
 FakeH264Encoder::FakeH264Encoder(Clock* clock)
     : FakeEncoder(clock), callback_(nullptr), idr_counter_(0) {
   FakeEncoder::RegisterEncodeCompleteCallback(this);