Add frame_helpers

A number of utility functions to be shared between frame buffer 2
and the new frame scheduling implementation based on frame buffer 3.

Change-Id: Icc932c6c76fddeeedc8aa64ec27c7e0c955abfd0
Bug: webrtc:13343
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/241604
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Evan Shrubsole <eshr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35743}
diff --git a/modules/video_coding/frame_helpers.cc b/modules/video_coding/frame_helpers.cc
new file mode 100644
index 0000000..870f198
--- /dev/null
+++ b/modules/video_coding/frame_helpers.cc
@@ -0,0 +1,90 @@
+/*
+ *  Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "modules/video_coding/frame_helpers.h"
+
+#include <utility>
+
+#include "rtc_base/logging.h"
+
+namespace webrtc {
+
+bool FrameHasBadRenderTiming(int64_t render_time_ms,
+                             int64_t now_ms,
+                             int target_video_delay) {
+  // Zero render time means render immediately.
+  if (render_time_ms == 0) {
+    return false;
+  }
+  if (render_time_ms < 0) {
+    return true;
+  }
+  const int64_t kMaxVideoDelayMs = 10000;
+  if (std::abs(render_time_ms - now_ms) > kMaxVideoDelayMs) {
+    int frame_delay = static_cast<int>(std::abs(render_time_ms - now_ms));
+    RTC_LOG(LS_WARNING)
+        << "A frame about to be decoded is out of the configured "
+           "delay bounds ("
+        << frame_delay << " > " << kMaxVideoDelayMs
+        << "). Resetting the video jitter buffer.";
+    return true;
+  }
+  if (target_video_delay > kMaxVideoDelayMs) {
+    RTC_LOG(LS_WARNING) << "The video target delay has grown larger than "
+                        << kMaxVideoDelayMs << " ms.";
+    return true;
+  }
+  return false;
+}
+
+std::unique_ptr<EncodedFrame> CombineAndDeleteFrames(
+    absl::InlinedVector<std::unique_ptr<EncodedFrame>, 4> frames) {
+  RTC_DCHECK(!frames.empty());
+
+  if (frames.size() == 1) {
+    return std::move(frames[0]);
+  }
+
+  size_t total_length = 0;
+  for (const auto& frame : frames) {
+    total_length += frame->size();
+  }
+  const EncodedFrame& last_frame = *frames.back();
+  std::unique_ptr<EncodedFrame> first_frame = std::move(frames[0]);
+  auto encoded_image_buffer = EncodedImageBuffer::Create(total_length);
+  uint8_t* buffer = encoded_image_buffer->data();
+  first_frame->SetSpatialLayerFrameSize(first_frame->SpatialIndex().value_or(0),
+                                        first_frame->size());
+  memcpy(buffer, first_frame->data(), first_frame->size());
+  buffer += first_frame->size();
+
+  // Spatial index of combined frame is set equal to spatial index of its top
+  // spatial layer.
+  first_frame->SetSpatialIndex(last_frame.SpatialIndex().value_or(0));
+
+  first_frame->video_timing_mutable()->network2_timestamp_ms =
+      last_frame.video_timing().network2_timestamp_ms;
+  first_frame->video_timing_mutable()->receive_finish_ms =
+      last_frame.video_timing().receive_finish_ms;
+
+  // Append all remaining frames to the first one.
+  for (size_t i = 1; i < frames.size(); ++i) {
+    // Let |next_frame| fall out of scope so it is deleted after copying.
+    std::unique_ptr<EncodedFrame> next_frame = std::move(frames[i]);
+    first_frame->SetSpatialLayerFrameSize(
+        next_frame->SpatialIndex().value_or(0), next_frame->size());
+    memcpy(buffer, next_frame->data(), next_frame->size());
+    buffer += next_frame->size();
+  }
+  first_frame->SetEncodedData(encoded_image_buffer);
+  return first_frame;
+}
+
+}  // namespace webrtc