third_party/WebKit/Source/modules/webaudio/GainNode.cpp

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    notice, this list of conditions and the following disclaimer in the
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 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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#include "modules/webaudio/GainNode.h"
#include "modules/webaudio/AudioNodeInput.h"
#include "modules/webaudio/AudioNodeOutput.h"
#include "modules/webaudio/GainOptions.h"
#include "platform/audio/AudioBus.h"
#include "platform/audio/AudioUtilities.h"

namespace blink {

GainHandler::GainHandler(AudioNode& node,
                         float sample_rate,
                         AudioParamHandler& gain)
    : AudioHandler(kNodeTypeGain, node, sample_rate),
      gain_(&gain),
      sample_accurate_gain_values_(
          AudioUtilities::kRenderQuantumFrames)  // FIXME: can probably
                                                 // share temp buffer
                                                 // in context
{
  AddInput();
  AddOutput(1);

  Initialize();
}

scoped_refptr<GainHandler> GainHandler::Create(AudioNode& node,
                                               float sample_rate,
                                               AudioParamHandler& gain) {
  return base::AdoptRef(new GainHandler(node, sample_rate, gain));
}

void GainHandler::Process(size_t frames_to_process) {
  // FIXME: for some cases there is a nice optimization to avoid processing
  // here, and let the gain change happen in the summing junction input of the
  // AudioNode we're connected to.  Then we can avoid all of the following:

  AudioBus* output_bus = Output(0).Bus();
  DCHECK(output_bus);

  if (!IsInitialized() || !Input(0).IsConnected()) {
    output_bus->Zero();
  } else {
    AudioBus* input_bus = Input(0).Bus();

    if (gain_->HasSampleAccurateValues()) {
      // Apply sample-accurate gain scaling for precise envelopes, grain
      // windows, etc.
      DCHECK_LE(frames_to_process, sample_accurate_gain_values_.size());
      if (frames_to_process <= sample_accurate_gain_values_.size()) {
        float* gain_values = sample_accurate_gain_values_.Data();
        gain_->CalculateSampleAccurateValues(gain_values, frames_to_process);
        output_bus->CopyWithSampleAccurateGainValuesFrom(
            *input_bus, gain_values, frames_to_process);
      }
    } else {
      // Apply the gain.
      if (gain_->Value() == 0) {
        // If the gain is 0, just zero the bus and set the silence hint.
        output_bus->Zero();
      } else {
        output_bus->CopyWithGainFrom(*input_bus, gain_->Value());
      }
    }
  }
}

void GainHandler::ProcessOnlyAudioParams(size_t frames_to_process) {
  DCHECK(Context()->IsAudioThread());
  DCHECK_LE(frames_to_process, AudioUtilities::kRenderQuantumFrames);

  float values[AudioUtilities::kRenderQuantumFrames];

  gain_->CalculateSampleAccurateValues(values, frames_to_process);
}

// FIXME: this can go away when we do mixing with gain directly in summing
// junction of AudioNodeInput
//
// As soon as we know the channel count of our input, we can lazily initialize.
// Sometimes this may be called more than once with different channel counts, in
// which case we must safely uninitialize and then re-initialize with the new
// channel count.
void GainHandler::CheckNumberOfChannelsForInput(AudioNodeInput* input) {
  DCHECK(Context()->IsAudioThread());
  DCHECK(Context()->IsGraphOwner());

  DCHECK(input);
  DCHECK_EQ(input, &this->Input(0));
  if (input != &this->Input(0))
    return;

  unsigned number_of_channels = input->NumberOfChannels();

  if (IsInitialized() && number_of_channels != Output(0).NumberOfChannels()) {
    // We're already initialized but the channel count has changed.
    Uninitialize();
  }

  if (!IsInitialized()) {
    // This will propagate the channel count to any nodes connected further
    // downstream in the graph.
    Output(0).SetNumberOfChannels(number_of_channels);
    Initialize();
  }

  AudioHandler::CheckNumberOfChannelsForInput(input);
}

// ----------------------------------------------------------------

GainNode::GainNode(BaseAudioContext& context)
    : AudioNode(context),
      gain_(AudioParam::Create(context, kParamTypeGainGain, "Gain.gain", 1.0)) {
  SetHandler(
      GainHandler::Create(*this, context.sampleRate(), gain_->Handler()));
}

GainNode* GainNode::Create(BaseAudioContext& context,
                           ExceptionState& exception_state) {
  DCHECK(IsMainThread());

  if (context.IsContextClosed()) {
    context.ThrowExceptionForClosedState(exception_state);
    return nullptr;
  }

  return new GainNode(context);
}

GainNode* GainNode::Create(BaseAudioContext* context,
                           const GainOptions& options,
                           ExceptionState& exception_state) {
  GainNode* node = Create(*context, exception_state);

  if (!node)
    return nullptr;

  node->HandleChannelOptions(options, exception_state);

  node->gain()->setValue(options.gain());

  return node;
}

AudioParam* GainNode::gain() const {
  return gain_;
}

void GainNode::Trace(blink::Visitor* visitor) {
  visitor->Trace(gain_);
  AudioNode::Trace(visitor);
}

}  // namespace blink