AudioConverter: Express delay in frames rather than msec.

media/base/audio_converter_unittest.cc

Index: media/base/audio_converter_unittest.cc
diff --git a/media/base/audio_converter_unittest.cc b/media/base/audio_converter_unittest.cc
index 3aebc54d323e9e554a7583128819fed1513d071c..9d73dd32e68d6e00b15b45f0496d61515a2aa37a 100644
--- a/media/base/audio_converter_unittest.cc
+++ b/media/base/audio_converter_unittest.cc
@@ -216,21 +216,20 @@ TEST(AudioConverterTest, AudioDelayAndDiscreteChannelCount) {
   converter.AddInput(&callback);
   converter.Convert(audio_bus.get());
 
-  // Calculate the expected buffer delay for given AudioParameters.
-  double input_sample_rate = input_parameters.sample_rate();
-  int fill_count =
-      (output_parameters.frames_per_buffer() * input_sample_rate /
-       output_parameters.sample_rate()) / input_parameters.frames_per_buffer();
-
-  base::TimeDelta input_frame_duration = base::TimeDelta::FromMicroseconds(
-      base::Time::kMicrosecondsPerSecond / input_sample_rate);
-
-  int expected_last_delay_milliseconds =
-      fill_count * input_parameters.frames_per_buffer() *
-      input_frame_duration.InMillisecondsF();
-
-  EXPECT_EQ(expected_last_delay_milliseconds,

[chcunningham, 2016/05/24 01:34:38]

This old method for building an expectation is busted. It relied heavily on
external factors, the imprecision of using milliseconds, and rounding done in
the FakeAudioRenderCallback. I'm not sure its worth it to check the delay as I'm
doing now, but this at least serves to document the details of building an
expectation. 

-            callback.last_audio_delay_milliseconds());
+  // double input_sample_rate = input_parameters.sample_rate();
+  // int fill_count =
+  //     (output_parameters.frames_per_buffer() * input_sample_rate /
+  //      output_parameters.sample_rate()) /
+  //      input_parameters.frames_per_buffer();
+  //
+  // This magic number is the accumulated MultiChannelResampler delay after
+  // |fill_count| (4) callbacks to provide input. The number of frames delayed
+  // is an implementation detail of the SincResampler chunk size (480 for the
+  // first two callbacks, 512 for the last two callbacks). See
+  // SincResampler.ChunkSize().
+  int kExpectedDelay = 992;
+
+  EXPECT_EQ(kExpectedDelay, callback.last_frames_delayed());
   EXPECT_EQ(input_parameters.channels(), callback.last_channel_count());
 }