New class AdaptedVideoTrackSource.

webrtc/media/base/adaptedvideotracksource.cc

+/*
+ *  Copyright (c) 2016 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 "webrtc/media/base/adaptedvideotracksource.h"
+
+namespace rtc {
+
+AdaptedVideoTrackSource::AdaptedVideoTrackSource() {
+  thread_checker_.DetachFromThread();
+}
+
+bool AdaptedVideoTrackSource::GetStats(Stats* stats) {
+  rtc::CritScope lock(&stats_crit_);
+
+  if (!stats_) {
+    return false;
+  }
+
+  *stats = *stats_;
+  return true;
+}
+
+void AdaptedVideoTrackSource::OnFrame(const cricket::VideoFrame& frame) {
+  rtc::CritScope lock(&apply_rotation_crit_);

[perkj_webrtc, 2016/09/20 12:26:09]

I would avoid holding a lock when you call the broadcaster.  Everything here is
thread safe if you use apply_rotation() instead.

[nisse-webrtc, 2016/09/20 13:17:47]

The lock is needed to ensure that a sink that sets wants.rotation_applied = true
never receives a frame with pending rotation.

We could get rid of this lock if we relax the requirements a bit and say that a
sink can get frames with any rotation. And for a sink which sets
wants.rotation_applied == true, it is expected to check for pending rotation and
discard such frames.

Hmm, and the only place I can find within webrtc where rotation_applied can be
set to true is WebRtcVideoChannel2::WebRtcVideoSendStream, and it should be easy
to add that logic to WebRtcVideoChannel2::WebRtcVideoSendStream::OnFrame. Does
that make sense? Not sure what other applications might be affected.

+  if (apply_rotation_ && frame.rotation() != webrtc::kVideoRotation_0) {
+    rtc::scoped_refptr<webrtc::VideoFrameBuffer> buffer(
+        frame.video_frame_buffer());
+    if (buffer->native_handle()) {
+      // Sources producing native frames must handle apply_rotation
+      // themselves. But even if they do, we may occasionally end up
+      // in this case, for frames in flight at the time
+      // applied_rotation is set to true. In that case, we just drop
+      // the frame.
+      LOG(LS_WARNING) << "Native frame requiring rotation. Discarding.";
+      return;
+    }
+    broadcaster_.OnFrame(cricket::WebRtcVideoFrame(
+        webrtc::I420Buffer::Rotate(buffer, frame.rotation()),
+        webrtc::kVideoRotation_0, frame.timestamp_us()));
+  } else {
+    broadcaster_.OnFrame(frame);
+  }
+}
+
+void AdaptedVideoTrackSource::AddOrUpdateSink(
+    rtc::VideoSinkInterface<cricket::VideoFrame>* sink,
+    const rtc::VideoSinkWants& wants) {
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
+
+  broadcaster_.AddOrUpdateSink(sink, wants);
+  OnSinkWantsChanged(broadcaster_.wants());
+}
+
+void AdaptedVideoTrackSource::RemoveSink(
+    rtc::VideoSinkInterface<cricket::VideoFrame>* sink) {
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
+
+  broadcaster_.RemoveSink(sink);
+  OnSinkWantsChanged(broadcaster_.wants());
+}
+
+bool AdaptedVideoTrackSource::apply_rotation() {
+  rtc::CritScope lock(&apply_rotation_crit_);
+  return apply_rotation_;
+}
+
+void AdaptedVideoTrackSource::OnSinkWantsChanged(
+    const rtc::VideoSinkWants& wants) {

[perkj_webrtc, 2016/09/20 12:26:09]

add thread checker. Should be called on same thread as AddOrUpdateSink.

[nisse-webrtc, 2016/09/20 13:17:47]

Done. Even if it seems a bit overkill to me: method is now private, there are
only two call sites, and both already use a thread checker.

+  {
+    rtc::CritScope lock(&apply_rotation_crit_);
+    apply_rotation_ = wants.rotation_applied;
+  }
+
+  video_adapter_.OnResolutionRequest(wants.max_pixel_count,
+                                     wants.max_pixel_count_step_up);
+}
+
+bool AdaptedVideoTrackSource::AdaptFrame(int width,
+                                         int height,
+                                         int64_t time_us,
+                                         int* out_width,
+                                         int* out_height,
+                                         int* crop_width,
+                                         int* crop_height,
+                                         int* crop_x,
+                                         int* crop_y) {
+  {
+    rtc::CritScope lock(&stats_crit_);
+    stats_ = rtc::Optional<Stats>({width, height});
+  }
+
+  if (!broadcaster_.frame_wanted()) {
+    return false;
+  }
+
+  if (!video_adapter_.AdaptFrameResolution(
+          width, height, time_us * rtc::kNumNanosecsPerMicrosec,
+          crop_width, crop_height, out_width, out_height)) {
+    // VideoAdapter dropped the frame.
+    return false;
+  }
+
+  *crop_x = (width - *crop_width) / 2;
+  *crop_y = (height - *crop_height) / 2;
+  return true;
+}
+
+}  // namespace rtc