From 051f678808d03fb2e68fe2a084b1deeb326c71bf Mon Sep 17 00:00:00 2001
From: aleloi <aleloi@webrtc.org>
Date: Mon, 31 Oct 2016 03:26:40 -0700
Subject: [PATCH] Add a NeededFrequency() method to the AudioMixer::Source
 interface.

This change will allow for a audio source to report its sampling rate
to the audio mixer. It is needed in order to mix at a lower sampling
rate. Mixing at a lower sampling rate can in many cases lead to big
efficiency improvements, as reported by experiments.

The code affected is all implementations of the Source interface:
AudioReceiveStream and a mock class. The AudioReceiveStream now
queries its underlying voe::Channel object for the needed frequency.

Note that the changes to the mixing algorithm are done in a later CL.

BUG=webrtc:6346
NOTRY=True
TBR=solenberg@webrtc.org

Review-Url: https://codereview.webrtc.org/2448113009
Cr-Commit-Position: refs/heads/master@{#14839}
---
 webrtc/api/audio/audio_mixer.h                          | 6 +++++-
 webrtc/audio/audio_receive_stream.cc                    | 6 +++++-
 webrtc/audio/audio_receive_stream.h                     | 3 ++-
 webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc | 3 ++-
 webrtc/voice_engine/channel_proxy.cc                    | 4 ++++
 webrtc/voice_engine/channel_proxy.h                     | 2 ++
 6 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/webrtc/api/audio/audio_mixer.h b/webrtc/api/audio/audio_mixer.h
index ee39daaf10..f786d6c99b 100644
--- a/webrtc/api/audio/audio_mixer.h
+++ b/webrtc/api/audio/audio_mixer.h
@@ -42,7 +42,11 @@ class AudioMixer : public rtc::RefCountInterface {
                                                  AudioFrame* audio_frame) = 0;
 
     // A way for a mixer implementation to distinguish participants.
-    virtual int Ssrc() = 0;
+    virtual int Ssrc() const = 0;
+
+    // A way for this source to say that GetAudioFrameWithInfo called
+    // with this sample rate or higher will not cause quality loss.
+    virtual int PreferredSampleRate() const = 0;
 
     virtual ~Source() {}
   };
diff --git a/webrtc/audio/audio_receive_stream.cc b/webrtc/audio/audio_receive_stream.cc
index 12b8b3f7ad..657a7608ec 100644
--- a/webrtc/audio/audio_receive_stream.cc
+++ b/webrtc/audio/audio_receive_stream.cc
@@ -278,7 +278,11 @@ AudioMixer::Source::AudioFrameInfo AudioReceiveStream::GetAudioFrameWithInfo(
   return channel_proxy_->GetAudioFrameWithInfo(sample_rate_hz, audio_frame);
 }
 
-int AudioReceiveStream::Ssrc() {
+int AudioReceiveStream::PreferredSampleRate() const {
+  return channel_proxy_->NeededFrequency();
+}
+
+int AudioReceiveStream::Ssrc() const {
   return config_.rtp.local_ssrc;
 }
 
diff --git a/webrtc/audio/audio_receive_stream.h b/webrtc/audio/audio_receive_stream.h
index e6416cd9a3..906ddb626d 100644
--- a/webrtc/audio/audio_receive_stream.h
+++ b/webrtc/audio/audio_receive_stream.h
@@ -57,7 +57,8 @@ class AudioReceiveStream final : public webrtc::AudioReceiveStream,
   // AudioMixer::Source
   AudioFrameInfo GetAudioFrameWithInfo(int sample_rate_hz,
                                        AudioFrame* audio_frame) override;
-  int Ssrc() override;
+  int PreferredSampleRate() const override;
+  int Ssrc() const override;
 
  private:
   VoiceEngine* voice_engine() const;
diff --git a/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc b/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc
index 28976fae88..e743192d02 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc
@@ -61,7 +61,8 @@ class MockMixerAudioSource : public AudioMixer::Source {
   MOCK_METHOD2(GetAudioFrameWithInfo,
                AudioFrameInfo(int sample_rate_hz, AudioFrame* audio_frame));
 
-  MOCK_METHOD0(Ssrc, int());
+  MOCK_CONST_METHOD0(PreferredSampleRate, int());
+  MOCK_CONST_METHOD0(Ssrc, int());
 
   AudioFrame* fake_frame() { return &fake_frame_; }
   AudioFrameInfo fake_info() { return fake_audio_frame_info_; }
diff --git a/webrtc/voice_engine/channel_proxy.cc b/webrtc/voice_engine/channel_proxy.cc
index ba58502e95..982cf1db7f 100644
--- a/webrtc/voice_engine/channel_proxy.cc
+++ b/webrtc/voice_engine/channel_proxy.cc
@@ -221,6 +221,10 @@ AudioMixer::Source::AudioFrameInfo ChannelProxy::GetAudioFrameWithInfo(
   return channel()->GetAudioFrameWithInfo(sample_rate_hz, audio_frame);
 }
 
+int ChannelProxy::NeededFrequency() const {
+  return static_cast<int>(channel()->NeededFrequency(-1));
+}
+
 Channel* ChannelProxy::channel() const {
   RTC_DCHECK(channel_owner_.channel());
   return channel_owner_.channel();
diff --git a/webrtc/voice_engine/channel_proxy.h b/webrtc/voice_engine/channel_proxy.h
index d19c0092a7..a9ec8604ab 100644
--- a/webrtc/voice_engine/channel_proxy.h
+++ b/webrtc/voice_engine/channel_proxy.h
@@ -97,6 +97,8 @@ class ChannelProxy {
       int sample_rate_hz,
       AudioFrame* audio_frame);
 
+  virtual int NeededFrequency() const;
+
  private:
   Channel* channel() const;