DownmixStage Class Reference

Combines multiple audio graph sources into a single source. More...

#include <DownmixStage.h>

Inheritance diagram for DownmixStage:

Collaboration diagram for DownmixStage:

Public Types
enum class	ApplyVolume { Discard , MapChannels , Mixdown }
Public Types inherited from AudioGraph::Source
using	Buffers = AudioGraph::Buffers

Public Member Functions
	DownmixStage (std::vector< std::unique_ptr< DownmixSource > > downmixSources, size_t numChannels, size_t bufferSize, ApplyVolume applyGain)
	~DownmixStage () override
bool	AcceptsBuffers (const Buffers &buffers) const override
bool	AcceptsBlockSize (size_t blockSize) const override
std::optional< size_t >	Acquire (Buffers &data, size_t maxToProcess) override
	Occupy vacant space in Buffers with some data. More...
sampleCount	Remaining () const override
	Result includes any amount Acquired and not yet Released. More...
bool	Release () override
	Caller is done examining last Acquire()d positions. More...
Public Member Functions inherited from AudioGraph::Source
virtual	~Source ()
virtual bool	AcceptsBuffers (const Buffers &buffers) const =0
virtual bool	AcceptsBlockSize (size_t blockSize) const =0
virtual std::optional< size_t >	Acquire (Buffers &data, size_t bound)=0
	Occupy vacant space in Buffers with some data. More...
virtual sampleCount	Remaining () const =0
	Result includes any amount Acquired and not yet Released. More...
virtual bool	Release ()=0
	Caller is done examining last Acquire()d positions. More...
virtual bool	Terminates () const
	Needed only to make some postconditions assertable; defaults true. More...

Private Attributes
std::vector< std::unique_ptr< DownmixSource > >	mDownmixSources
AudioGraph::Buffers	mFloatBuffers
size_t	mNumChannels
ApplyVolume	mApplyVolume

Detailed Description

Combines multiple audio graph sources into a single source.

Definition at line 20 of file DownmixStage.h.

Member Enumeration Documentation

ApplyVolume

enum class DownmixStage::ApplyVolume

strong

Enumerator
Discard
MapChannels
Mixdown

Definition at line 23 of file DownmixStage.h.

   {
      Discard,//< No source volume is applied
      MapChannels, //< Apply volume per source's channel
      Mixdown, //< Average volume from all channels in the source, numOutChannels should be 1
   };

Constructor & Destructor Documentation

DownmixStage()

DownmixStage::DownmixStage	(	std::vector< std::unique_ptr< DownmixSource > >	downmixSources,
		size_t	numChannels,
		size_t	bufferSize,
		ApplyVolume	applyGain
	)

Definition at line 42 of file DownmixStage.cpp.

   : mDownmixSources(std::move(downmixSources))
 // PRL:  Bug2536: see other comments below for the last, padding argument
 // TODO: more-than-two-channels
 // Issue 3565 workaround:  allocate one extra buffer when applying a
 // GVerb effect stage.  It is simply discarded
 // See also issue 3854, when the number of out channels expected by the
 // plug-in is yet larger
   , mFloatBuffers { 3, bufferSize, 1, 1 }
   , mNumChannels(numChannels)
   , mApplyVolume(applyGain)
{
   
}

~DownmixStage()

DownmixStage::~DownmixStage ( )

overridedefault

Member Function Documentation

AcceptsBlockSize()

bool DownmixStage::AcceptsBlockSize ( size_t  blockSize ) const

overridevirtual

Implements AudioGraph::Source.

Definition at line 68 of file DownmixStage.cpp.

{
   return blockSize <= mFloatBuffers.BufferSize();
}

References AudioGraph::Buffers::BufferSize(), and mFloatBuffers.

Referenced by AcceptsBuffers().

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AcceptsBuffers()

bool DownmixStage::AcceptsBuffers ( const Buffers &  buffers ) const

overridevirtual

Implements AudioGraph::Source.

Definition at line 62 of file DownmixStage.cpp.

{
   return buffers.Channels() == mNumChannels &&
      AcceptsBlockSize(buffers.BlockSize());  
}

References AcceptsBlockSize(), AudioGraph::Buffers::BlockSize(), AudioGraph::Buffers::Channels(), and mNumChannels.

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Acquire()

std::optional< size_t > DownmixStage::Acquire ( Buffers &  data, size_t  bound  )

overridevirtual

Occupy vacant space in Buffers with some data.

May exceeed a single block of production Can assume same buffer is passed each time, while the caller advances it over the previous production, or discards it, or rotates the buffer. May rewind or rotate the buffer.

Returns

number of positions available to read from data or nullopt to fail

Precondition

AcceptsBuffers(data)

AcceptsBlockSize(data.BlockSize())

bound <= data.BlockSize()

data.BlockSize() <= data.Remaining()

Postcondition

result: !result || *result <= bound

result: !result || *result <= data.Remaining()

result: !result || *result <= Remaining()

data.Remaining() > 0

result: !result || bound == 0 || Remaining() == 0 || *result > 0 (progress guarantee)

!Terminates() or Remaining() was not previously defined, or is unchanged

Implements AudioGraph::Source.

Definition at line 73 of file DownmixStage.cpp.

{
   // TODO: more-than-two-channels
   auto maxChannels = std::max(2u, mFloatBuffers.Channels());
   const auto channelFlags = stackAllocate(unsigned char, mNumChannels);
   const auto volumes = stackAllocate(float, mNumChannels);
   if (mApplyVolume == ApplyVolume::Discard)
      std::fill(volumes, volumes + mNumChannels, 1.0f);
 
   size_t maxOut = 0;
   for (auto c = 0;c < data.Channels(); ++c)
      data.ClearBuffer(c, maxToProcess);
 
   for (auto& downmixSource : mDownmixSources)
   {
      auto oResult = downmixSource->GetDownstream().Acquire(mFloatBuffers, maxToProcess);
      // One of MixVariableRates or MixSameRate assigns into mTemp[*][*]
      // which are the sources for the CopySamples calls, and they copy into
      // mBuffer[*][*]
      if (!oResult)
         return 0;
      const auto result = *oResult;
      maxOut = std::max(maxOut, result);
 
      // Insert effect stages here!  Passing them all channels of the track
 
      const auto limit = std::min<size_t>(downmixSource->NChannels(), maxChannels);
      for (size_t j = 0; j < limit; ++j)
      {
         const auto pFloat = (const float*)mFloatBuffers.GetReadPosition(j);
         if (mApplyVolume != ApplyVolume::Discard)
         {
            for (size_t c = 0; c < mNumChannels; ++c)
            {
               if (mNumChannels > 1)
                  volumes[c] = downmixSource->GetChannelGain(c);
               else
                  volumes[c] = downmixSource->GetChannelGain(j);
            }
            if (mApplyVolume == ApplyVolume::Mixdown &&
                mNumChannels == 1 &&
                downmixSource->CanMakeMono())
            {
               volumes[0] /= static_cast<float>(limit);
            }
         }
 
         downmixSource->FindChannelFlags(channelFlags, mNumChannels, j);
         MixBuffers(mNumChannels, channelFlags, volumes, *pFloat, data, result);
      }
 
      downmixSource->GetDownstream().Release();
      mFloatBuffers.Advance(result);
      mFloatBuffers.Rotate();
   }
 
   // MB: this doesn't take warping into account, replaced with code based on mSamplePos
   //mT += (maxOut / mRate);
 
   assert(maxOut <= maxToProcess);
   return maxOut;
}

References AudioGraph::Buffers::Advance(), AudioGraph::Buffers::Channels(), AudioGraph::Buffers::ClearBuffer(), Discard, AudioGraph::Buffers::GetReadPosition(), mApplyVolume, mDownmixSources, mFloatBuffers, anonymous_namespace{DownmixStage.cpp}::MixBuffers(), Mixdown, mNumChannels, AudioGraph::Buffers::Rotate(), and stackAllocate.

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Release()

bool DownmixStage::Release ( )

overridevirtual

Caller is done examining last Acquire()d positions.

May be called only after at least one successful call to Acquire()

Returns

success

Postcondition

!Terminates() or Remaining() reduced by what was last returned by Acquire()

Implements AudioGraph::Source.

Definition at line 144 of file DownmixStage.cpp.

{
   return true;
}

Remaining()

sampleCount DownmixStage::Remaining ( ) const

overridevirtual

Result includes any amount Acquired and not yet Released.

May be undefined before the first successful call to Acquire()

Postcondition

result: result >= 0

Implements AudioGraph::Source.

Definition at line 135 of file DownmixStage.cpp.

{
   return std::accumulate(
      mDownmixSources.begin(), mDownmixSources.end(), sampleCount { 0 },
      [](sampleCount sum, const auto& source) {
         return std::max(sum, source->GetDownstream().Remaining());
      });
}

References mDownmixSources.

Member Data Documentation

mApplyVolume

ApplyVolume DownmixStage::mApplyVolume

private

Definition at line 35 of file DownmixStage.h.

Referenced by Acquire().

mDownmixSources

std::vector<std::unique_ptr<DownmixSource> > DownmixStage::mDownmixSources

private

Definition at line 31 of file DownmixStage.h.

Referenced by Acquire(), and Remaining().

mFloatBuffers

AudioGraph::Buffers DownmixStage::mFloatBuffers

private

Definition at line 33 of file DownmixStage.h.

Referenced by AcceptsBlockSize(), and Acquire().

mNumChannels

size_t DownmixStage::mNumChannels

private

Definition at line 34 of file DownmixStage.h.

Referenced by AcceptsBuffers(), and Acquire().

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The documentation for this class was generated from the following files:

• DownmixStage.h
• DownmixStage.cpp