Resample Class Reference

Interface to libsoxr. More...

#include <Resample.h>

Collaboration diagram for Resample:

Public Member Functions
	Resample (const bool useBestMethod, const double dMinFactor, const double dMaxFactor)
	~Resample ()
	Resample (Resample &&) noexcept=default
Resample &	operator= (Resample &&) noexcept=default
	Resample (const Resample &)=delete
Resample &	operator= (const Resample &)=delete
std::pair< size_t, size_t >	Process (double factor, const float *inBuffer, size_t inBufferLen, bool lastFlag, float *outBuffer, size_t outBufferLen)
	Main processing function. Resamples from the input buffer to the output buffer. More...

Static Public Attributes
static EnumSetting< int >	FastMethodSetting
static EnumSetting< int >	BestMethodSetting

Protected Member Functions
void	SetMethod (const bool useBestMethod)

Protected Attributes
int	mMethod
soxrHandle	mHandle
bool	mbWantConstRateResampling

Detailed Description

Interface to libsoxr.

This class abstracts the interface to different resampling libraries:

libsoxr, written by Rob Sykes. LGPL.

Since Audacity always does resampling on mono streams that are contiguous in memory, this class doesn't support multiple channels or some of the other optional features of some of these resamplers.

Definition at line 26 of file Resample.h.

Constructor & Destructor Documentation

Resample() [1/3]

Resample::Resample	(	const bool	useBestMethod,
		const double	dMinFactor,
		const double	dMaxFactor
	)

Resamplers may have more than one method, offering a tradeoff between speed and quality. Audacity identifies two methods out of all of the choices: a Fast method intended for real-time audio I/O, and a Best method intended for mixing and exporting. The first parameter lets you select either the best method or the fast method.

Definition at line 32 of file Resample.cpp.

{
   this->SetMethod(useBestMethod);
   soxr_quality_spec_t q_spec;
   if (dMinFactor == dMaxFactor)
   {
      mbWantConstRateResampling = true; // constant rate resampling
      q_spec = soxr_quality_spec("\0\1\4\6"[mMethod], 0);
   }
   else
   {
      mbWantConstRateResampling = false; // variable rate resampling
      q_spec = soxr_quality_spec(SOXR_HQ, SOXR_VR);
   }
   mHandle.reset(soxr_create(1, dMinFactor, 1, 0, 0, &q_spec, 0));
}

References mbWantConstRateResampling, mHandle, mMethod, and SetMethod().

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~Resample()

Resample::~Resample

(

)

Definition at line 49 of file Resample.cpp.

{
}

Resample() [2/3]

Resample::Resample ( Resample &&  )

defaultnoexcept

Resample() [3/3]

Resample::Resample ( const Resample &  )

delete

Member Function Documentation

operator=() [1/2]

Resample & Resample::operator= ( const Resample &  )

delete

operator=() [2/2]

Resample & Resample::operator= ( Resample &&  )

defaultnoexcept

Process()

std::pair< size_t, size_t > Resample::Process	(	double	factor,
		const float *	inBuffer,
		size_t	inBufferLen,
		bool	lastFlag,
		float *	outBuffer,
		size_t	outBufferLen
	)

Main processing function. Resamples from the input buffer to the output buffer.

Reads samples from the input buffer, and writes samples to the output buffer. Stops when either is exhausted, or we reach a convenient block end, unless lastFlag is set to force emptying the input buffer. The number of input samples used is returned in inBufferUsed, and the number of output samples generated is the return value of the function. This function may do nothing if you don't pass a large enough output buffer (i.e. there is no where to put a full block of output data)

Parameters

factor	The scaling factor to resample by.
inBuffer	Buffer of input samples to be processed (mono)
inBufferLen	Length of the input buffer, in samples.
lastFlag	Flag to indicate this is the last lot of input samples and the buffer needs to be emptied out into the rate converter. (unless lastFlag is true, we don't guarantee to process all the samples in the input this time, we may leave some for next time)
outBuffer	Buffer to write output (converted) samples to.
outBufferLen	How big outBuffer is.

Returns

Number of input samples consumed, and number of output samples created by this call

Definition at line 88 of file Resample.cpp.

{
   size_t idone, odone;
   if (mbWantConstRateResampling)
   {
      soxr_process(mHandle.get(),
            inBuffer , (lastFlag? ~inBufferLen : inBufferLen), &idone,
            outBuffer,                           outBufferLen, &odone);
   }
   else
   {
      soxr_set_io_ratio(mHandle.get(), 1/factor, 0);
 
      inBufferLen = lastFlag? ~inBufferLen : inBufferLen;
      soxr_process(mHandle.get(),
            inBuffer , inBufferLen , &idone,
            outBuffer, outBufferLen, &odone);
   }
   return { idone, odone };
}

References mbWantConstRateResampling, and mHandle.

Referenced by ChangeSpeedBase::ProcessOne().

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SetMethod()

void Resample::SetMethod ( const bool  useBestMethod )

protected

Definition at line 114 of file Resample.cpp.

{
   if (useBestMethod)
      mMethod = BestMethodSetting.ReadEnum();
   else
      mMethod = FastMethodSetting.ReadEnum();
}

References BestMethodSetting, FastMethodSetting, mMethod, and EnumSetting< Enum >::ReadEnum().

Referenced by Resample().

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Member Data Documentation

BestMethodSetting

EnumSetting< int > Resample::BestMethodSetting

static

Initial value:

{
   wxT("/Quality/LibsoxrHQSampleRateConverterChoice"),
   methodNames,
   3, 
 
   
   intChoicesMethod,
   wxT("/Quality/LibsoxrHQSampleRateConverter")
}

Definition at line 49 of file Resample.h.

Referenced by QualityPrefs::PopulateOrExchange(), and SetMethod().

FastMethodSetting

EnumSetting< int > Resample::FastMethodSetting

static

Initial value:

{
   wxT("/Quality/LibsoxrSampleRateConverterChoice"),
   methodNames,
   1,  
 
   
   intChoicesMethod,
   wxT("/Quality/LibsoxrSampleRateConverter")
}

Definition at line 48 of file Resample.h.

Referenced by QualityPrefs::PopulateOrExchange(), and SetMethod().

mbWantConstRateResampling

bool Resample::mbWantConstRateResampling

protected

Definition at line 87 of file Resample.h.

Referenced by Process(), and Resample().

mHandle

soxrHandle Resample::mHandle

protected

Definition at line 86 of file Resample.h.

Referenced by Process(), and Resample().

mMethod

int Resample::mMethod

protected

Definition at line 85 of file Resample.h.

Referenced by Resample(), and SetMethod().

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

• Resample.h
• Resample.cpp