Add LoudestFilter in ConferenceTransport

webrtc/voice_engine/test/auto_test/fakes/loudest_filter.cc

Index: webrtc/voice_engine/test/auto_test/fakes/loudest_filter.cc
diff --git a/webrtc/voice_engine/test/auto_test/fakes/loudest_filter.cc b/webrtc/voice_engine/test/auto_test/fakes/loudest_filter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1eb0b83801ab97f1408d04b5127c02f2fea737fd
--- /dev/null
+++ b/webrtc/voice_engine/test/auto_test/fakes/loudest_filter.cc
@@ -0,0 +1,76 @@
+/*
+ *  Copyright (c) 2015 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/voice_engine/test/auto_test/fakes/loudest_filter.h"
+
+#include "webrtc/base/checks.h"
+
+namespace voetest {
+
+void LoudestFilter::RemoveTimeoutStreams(uint32 time_ms) {
+  auto it = stream_levels_.begin();
+  while (it != stream_levels_.end()) {

[hlundin-webrtc, 2015/08/10 10:50:17]

I suggest you make this a for loop instead
for (auto stream : stream_levels_) {
...
But maybe you cannot call erase on the stream variable.

If that doesn't work, you should still be able to use
for (auto it = stream_levels_.begin(); it != c.end(); ) {
...

There's an example at http://en.cppreference.com/w/cpp/container/map/erase.
Note also how in that example they do not ++ the iterator when erase is called,
but rather update it with the output from the erase method.

[minyue-webrtc, 2015/08/12 14:53:23]

I do not think for (auto stream : stream_levels_) can work.

The "while" vs. "for" in the example you provided is a tie. I agree that it is
better to use the C++11 std::map feature "it = erase(it)"

+    if (rtc::TimeDiff(time_ms, it->second.last_time_ms_) >

[hlundin-webrtc, 2015/08/10 10:50:17]

Oh, is that why you kept using uint32_t for the time variables? You may
disregard from my earlier comments about this.

[minyue-webrtc, 2015/08/12 14:53:23]

Acknowledged.

+        kStreamTimeOutMs) {
+      stream_levels_.erase(it++);

[hlundin-webrtc, 2015/08/10 10:50:17]

I'm not sure it is valid after you called erase. "References and iterators to
the erased elements are invalidated."

[minyue-webrtc, 2015/08/12 14:53:23]

I saw many examples of this on the net. It should be valid. but better to use
C++11 feature of it = erase(it). I thought that I tried it and the compiler did
not work. But now it does, which is nice. 

+    } else {
+      ++it;
+    }
+  }
+}
+
+unsigned int LoudestFilter::FindQuietestStream() {
+  int quietest_level = kInvalidAudioLevel;
+  unsigned int quietest_ssrc = 0;
+  for (auto stream : stream_levels_) {
+    if (quietest_level == kInvalidAudioLevel ||
+        stream.second.audio_level_ > quietest_level) {

[hlundin-webrtc, 2015/08/10 10:50:17]

Comment about the fact that a quiet stream has a high audio level.

[minyue-webrtc, 2015/08/12 14:53:23]

Done.

+      quietest_level = stream.second.audio_level_;
+      quietest_ssrc = stream.first;
+    }
+  }
+  return quietest_ssrc;
+}
+
+bool LoudestFilter::DecideForward(unsigned int source_ssrc, int audio_level) {
+  uint32 time_now_ms = rtc::Time();
+  RemoveTimeoutStreams(time_now_ms);
+
+  if (audio_level == kInvalidAudioLevel) {
+    // Always forward streams with unknown audio level, and don't keep their
+    // states.
+    return true;
+  }
+
+  auto it = stream_levels_.find(source_ssrc);
+  if (it != stream_levels_.end()) {
+    // Stream has been forwarded. Update and continue to forward.
+    it->second.audio_level_ = audio_level;
+    it->second.last_time_ms_ = time_now_ms;
+    return true;
+  }
+
+  if (stream_levels_.size() < kMaxMixSize) {
+    stream_levels_[source_ssrc].Set(audio_level, time_now_ms);
+    return true;
+  }
+
+  unsigned int quietest_ssrc = FindQuietestStream();
+  CHECK_NE(0u, quietest_ssrc);
+  if (audio_level < stream_levels_[quietest_ssrc].audio_level_) {

[hlundin-webrtc, 2015/08/10 10:50:17]

Again, explain that "up is down, and down is up".

[minyue-webrtc, 2015/08/12 14:53:23]

Done.

+    stream_levels_.erase(quietest_ssrc);
+    stream_levels_[source_ssrc].Set(audio_level, time_now_ms);
+    return true;
+  }
+  return false;
+}
+
+}  // namespace voetest
+