AudioConverter: Express delay in frames rather than msec.

media/base/audio_converter.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // AudioConverter is a complete mixing, resampling, buffering, and channel
 // mixing solution for converting data from one set of AudioParameters to
 // another.
 //
 // For efficiency, pieces are only invoked when necessary; i.e.,
 //    - The resampler is only used if sample rates differ.
@@ skipping 38 matching lines @@
   // Interface for inputs into the converter.  Each InputCallback is added or
   // removed from Convert() processing via AddInput() and RemoveInput().
   class MEDIA_EXPORT InputCallback {
    public:
     // Method for providing more data into the converter.  Expects |audio_bus|
     // to be completely filled with data upon return; zero padded if not enough
     // frames are available to satisfy the request.  The return value is the
     // volume level of the provided audio data.  If a volume level of zero is
     // returned no further processing will be done on the provided data, else
     // the volume level will be used to scale the provided audio data.
+    // |frames_delayed| is given in terms of the input sample rate.
     virtual double ProvideInput(AudioBus* audio_bus,
-                                base::TimeDelta buffer_delay) = 0;
+                                uint32_t frames_delayed) = 0;
 
    protected:
     virtual ~InputCallback() {}
   };
 
   // Constructs an AudioConverter for converting between the given input and
   // output parameters.  Specifying |disable_fifo| means all InputCallbacks are
   // capable of handling arbitrary buffer size requests; i.e. one call might ask
   // for 10 frames of data (indicated by the size of AudioBus provided) and the
   // next might ask for 20.  In synthetic testing, disabling the FIFO yields a
   // ~20% speed up for common cases.
   AudioConverter(const AudioParameters& input_params,
                  const AudioParameters& output_params,
                  bool disable_fifo);
   ~AudioConverter();
 
-  // Converts audio from all inputs into the |dest|. If an |initial_delay| is
-  // specified, it will be propagated to each input.
+  // Converts audio from all inputs into the |dest|. If |initial_frames_delayed|

[Henrik Grunell, 2016/05/25 14:48:38]

initial_frames_delayed or frames_delayed?

[chcunningham, 2016/05/25 18:21:15]

Fixed - frames_delayed.

+  // is specified, it will be propagated to each input. Count of frames must be
+  // given in terms of the output sample rate.

[Henrik Grunell, 2016/05/25 14:48:38]

Nit: last sentence is implicit, you could skip it.

[chcunningham, 2016/05/25 18:21:15]

Ha, I know you're right, but I always have to pause and ponder a bit before I
remember what the expectation is. If you don't mind, I'd like to leave this to
help me quickly remember. 

   void Convert(AudioBus* dest);
-  void ConvertWithDelay(const base::TimeDelta& initial_delay, AudioBus* dest);
+  void ConvertWithDelay(uint32_t frames_dealyed, AudioBus* dest);

[Henrik Grunell, 2016/05/25 14:48:38]

Spelling.

[chcunningham, 2016/05/25 18:21:15]

Done.

 
   // Adds or removes an input from the converter.  RemoveInput() will call
   // Reset() if no inputs remain after the specified input is removed.
   void AddInput(InputCallback* input);
   void RemoveInput(InputCallback* input);
 
   // Flushes all buffered data.
   void Reset();
 
   // The maximum size in frames that guarantees we will only make a single call
@@ skipping 35 matching lines @@
   std::unique_ptr<AudioBus> unmixed_audio_;
 
   // Temporary AudioBus destination for mixing inputs.
   std::unique_ptr<AudioBus> mixer_input_audio_bus_;
 
   // Since resampling is expensive, figure out if we should downmix channels
   // before resampling.
   bool downmix_early_;
 
   // Used to calculate buffer delay information for InputCallbacks.
-  base::TimeDelta input_frame_duration_;
-  base::TimeDelta output_frame_duration_;
-  base::TimeDelta initial_delay_;
-  int resampler_frame_delay_;
+  uint32_t initial_frames_delayed_;
+  uint32_t resampler_frames_delayed_;
+  const double io_sample_rate_ratio_;
 
   // Number of channels of input audio data.  Set during construction via the
   // value from the input AudioParameters class.  Preserved to recreate internal
   // AudioBus structures on demand in response to varying frame size requests.
   const int input_channel_count_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioConverter);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_CONVERTER_H_