[Chromoting] Implement down mixing in AudioPump

remoting/protocol/audio_pump_unittest.cc

Index: remoting/protocol/audio_pump_unittest.cc
diff --git a/remoting/protocol/audio_pump_unittest.cc b/remoting/protocol/audio_pump_unittest.cc
index 806cd0a7ece8e36fabfd5cf353487952526ef0d1..b6f0c1eab9a2e1e4312b24c12a890886dd8b7ffd 100644
--- a/remoting/protocol/audio_pump_unittest.cc
+++ b/remoting/protocol/audio_pump_unittest.cc
@@ -27,9 +27,13 @@ namespace protocol {
 namespace {
 
 // Creates a dummy packet with 1k data
-std::unique_ptr<AudioPacket> MakeAudioPacket() {
+std::unique_ptr<AudioPacket> MakeAudioPacket(int channel_count = 2) {
   std::unique_ptr<AudioPacket> packet(new AudioPacket);
-  packet->add_data()->resize(1000);
+  packet->add_data()->resize(1024);
+  packet->set_encoding(AudioPacket::ENCODING_RAW);
+  packet->set_sampling_rate(AudioPacket::SAMPLING_RATE_44100);
+  packet->set_bytes_per_sample(AudioPacket::BYTES_PER_SAMPLE_2);
+  packet->set_channels(static_cast<AudioPacket::Channels>(channel_count));
   return packet;
 }
 
@@ -42,6 +46,8 @@ class FakeAudioEncoder : public AudioEncoder {
 
   std::unique_ptr<AudioPacket> Encode(
       std::unique_ptr<AudioPacket> packet) override {
+    EXPECT_TRUE(!!packet);
+    EXPECT_LE(packet->channels(), 2);
     return packet;
   }
   int GetBitrate() override { return 160000; }
@@ -127,5 +133,24 @@ TEST_F(AudioPumpTest, BufferSizeLimit) {
   EXPECT_EQ(num_sent_packets + 1, sent_packets_.size());
 }
 
+TEST_F(AudioPumpTest, DownmixAudioPacket) {
+  base::RunLoop().RunUntilIdle();

[joedow, 2017/05/26 16:01:51]

Please add a comment here to note why this is needed.  I had to look at another
test to figure out what this is for (comment from test above: '// Run message
loop to let the pump start the capturer.').

[Hzj_jie, 2017/05/26 20:08:04]

Done.

+  ASSERT_TRUE(source_->callback());
+
+  // Randomly generate several audio packets with different channel counts.

[joedow, 2017/05/26 16:01:51]

nit: This isn't random if you define a static list of channel numbers.  Please
fix the comment.

[Hzj_jie, 2017/05/26 20:08:03]

Done.

+  static const int kChannels[] = {
+    8, 6, 2, 1, 8, 8, 8, 8, 6, 6, 6, 6, 2,
+  };

[joedow, 2017/05/26 16:01:51]

Would it make sense to use the enum names here instead?  I suppose it makes
sense that 8 == 7.1 audio, but if I saw 'AUDIO_7_1' I think it would be easier
to scan.

[Hzj_jie, 2017/05/26 20:08:04]

Done.

+
+  for (size_t i = 0; i < arraysize(kChannels); i++) {
+    source_->callback().Run(MakeAudioPacket(kChannels[i]));
+    base::RunLoop().RunUntilIdle();

[joedow, 2017/05/26 16:01:51]

Please add comments (as in the test above) to explain why you are running the
run loops.

[Hzj_jie, 2017/05/26 20:08:04]

Done.

+    done_closures_.front().Run();
+    base::RunLoop().RunUntilIdle();
+  }
+
+  EXPECT_EQ(sent_packets_.size(), arraysize(kChannels));
+}
+
 }  // namespace protocol
 }  // namespace remoting