AecDump interface

webrtc/modules/audio_processing/include/audio_processing.h

Index: webrtc/modules/audio_processing/include/audio_processing.h
diff --git a/webrtc/modules/audio_processing/include/audio_processing.h b/webrtc/modules/audio_processing/include/audio_processing.h
index 99e4b690ff52680a8226ed872c825d207f9d2901..3761da4f45cc523772ac2a29cbc46c3941b5f91a 100644
--- a/webrtc/modules/audio_processing/include/audio_processing.h
+++ b/webrtc/modules/audio_processing/include/audio_processing.h
@@ -29,6 +29,7 @@ namespace webrtc {
 
 struct AecCore;
 
+class AecDump;
 class AudioFrame;
 
 class NonlinearBeamformer;
@@ -447,6 +448,15 @@ class AudioProcessing {
   virtual void set_delay_offset_ms(int offset) = 0;
   virtual int delay_offset_ms() const = 0;
 
+  // Starts recording debugging information through the provided
+  // webrtc::AecDump. Log file and maximum file size logic is supposed
+  // to be handled by implementing instance of AecDump. Calling this
+  // method when logging is active resets the active AecDump with a
+  // new one. This causes the d-tor of the earlier AecDump to be
+  // called. The d-tor call may block until all pending logging tasks

[peah-webrtc, 2017/04/07 12:57:16]

Is the blocking needed because the taskqueue must be destroyed as well?

[aleloi, 2017/04/12 11:05:30]

The destructor of the AecDump impl uses this pattern:

rtc::Event thread_sync_event(false /* manual_reset */, false);
worker_queue_->PostTask([&thread_sync_event] { thread_sync_event.Set(); });
thread_sync_event.Wait(rtc::Event::kForever);

The 3rd line blocks the task in the 2nd line has been run. The queue is FIFO, so
all pending tasks must be done first. 

This pattern is used in other places, e.g. AudioSendStream::Stop(),
VideoSendStream(). It simplifies resource handling with task queues: the member
variables of AecDump may only be deallocated when there are no queued tasks with
pointers to them.

The task queue itself is not destroyed.

+  // are completed.
+  virtual void StartDebugRecording(std::unique_ptr<AecDump> aec_dump) = 0;
+
   // Starts recording debugging information to a file specified by |filename|,
   // a NULL-terminated string. If there is an ongoing recording, the old file
   // will be closed, and recording will continue in the newly specified file.