//$ nocpp

/**
 * @file CDSPResampler.h
 *
 * @brief The master sample rate converter (resampler) class.
 *
 * This file includes the master sample rate converter (resampler) class that
 * combines all elements of this library into a single front-end class.
 *
 * r8brain-free-src Copyright (c) 2013-2014 Aleksey Vaneev
 * See the "License.txt" file for license.
 */

#ifndef R8B_CDSPRESAMPLER_INCLUDED
#define R8B_CDSPRESAMPLER_INCLUDED

#include "CDSPBlockConvolver.h"
#include "CDSPFracInterpolator.h"

namespace r8b
{

	/**
	 * @brief The master sample rate converter (resampler) class.
	 *
	 * This class can be considered the "master" sample rate converter (resampler)
	 * class since it combines all functionality of this library into a single
	 * front-end class to perform sample rate conversion to/from any sample rate,
	 * including non-integer sample rates.
	 *
	 * Note that objects of this class can be constructed on the stack as it has a
	 * small member data size. The default template parameters of this class are
	 * suited for 27-bit fixed point resampling.
	 *
	 * Use the CDSPResampler16 class for 16-bit resampling.
	 *
	 * Use the CDSPResampler16IR class for 16-bit impulse response resampling.
	 *
	 * Use the CDSPResampler24 class for 24-bit resampling (including 32-bit
	 * floating point resampling).
	 *
	 * @param CInterpClass Interpolator class that should be used by the
	 * resampler. The desired interpolation quality can be defined via the
	 * template parameters of the interpolator class. See
	 * r8b::CDSPFracInterpolator and r8b::CDSPFracDelayFilterBank for description
	 * of the template parameters.
	 */

	template <class CInterpClass =
		CDSPFracInterpolator<R8B_FLTLEN, R8B_FLTFRACS>>
	class CDSPResampler : public CDSPProcessor
	{
	public:
		/**
		 * Constructor initalizes the resampler object.
		 *
		 * Note that increasing the transition band and decreasing attenuation
		 * reduces the filter length, this in turn reduces the "input before
		 * output" delay. However, the filter length has only a minor influence on
		 * the overall resampling speed.
		 *
		 * It should be noted that the ReqAtten specifies the minimal difference
		 * between the loudest input signal component and the produced aliasing
		 * artifacts during resampling. For example, if ReqAtten=100 was specified
		 * when performing 2x upsampling, the analysis of the resulting signal may
		 * display high-frequency components which are quieter than the loudest
		 * part of the input signal by only 100 decibel meaning the high-frequency
		 * part did not become "magically" completely silent after resampling. You
		 * have to specify a higher ReqAtten value if you need a totally clean
		 * high-frequency content. On the other hand, it may not be reasonable to
		 * have a high-frequency content cleaner than the input signal itself: if
		 * the input signal is 16-bit, setting ReqAtten to 150 will make its
		 * high-frequency content 24-bit, but the original part of the signal will
		 * remain 16-bit.
		 *
		 * @param SrcSampleRate Source signal sample rate. Both sample rates can
		 * be specified as a ratio, e.g. SrcSampleRate = 1.0, DstSampleRate = 2.0.
		 * @param DstSampleRate Destination signal sample rate. The "power of 2"
		 * ratios between the source and destination sample rates force resampler
		 * to use several fast "power of 2" resampling steps, without using
		 * fractional interpolation at all. Note that the "power of 2" upsampling
		 * (but not downsampling) requires a lot of buffer memory: e.g. upsampling
		 * by a factor of 16 requires an intermediate buffer MaxInLen*(16+8)
		 * samples long. So, when doing the "power of 2" upsampling it is highly
		 * recommended to do it in small steps, e.g. no more than 256 samples at
		 * once (also set the MaxInLen to 256).
		 * @param MaxInLen The maximal planned length of the input buffer (in
		 * samples) that will be passed to the resampler. The resampler relies on
		 * this value as it allocates intermediate buffers. Input buffers longer
		 * than this value should never be supplied to the resampler. Note that
		 * the resampler may use the input buffer itself for intermediate sample
		 * data storage.
		 * @param ReqTransBand Required transition band, in percent of the
		 * spectral space of the input signal (or the output signal if
		 * downsampling is performed) between filter's -3 dB point and the Nyquist
		 * frequency. The range is from CDSPFIRFilter::getLPMinTransBand() to
		 * CDSPFIRFilter::getLPMaxTransBand(), inclusive. When upsampling 88200 or
		 * 96000 audio to a higher sample rates the ReqTransBand can be
		 * considerably increased, up to 30. The selection of ReqTransBand depends
		 * on the level of desire to preserve the high-frequency content. While
		 * values 0.5 to 2 are extremely "greedy" settings, not necessary in most
		 * cases, values 2 to 3 can be used in most cases. Values 3 to 4 are
		 * relaxed settings, but they still offer a flat frequency response up to
		 * 21kHz with 44.1k source or destination sample rate.
		 * @param ReqAtten Required stop-band attenuation in decibel, in the range
		 * CDSPFIRFilter::getLPMinAtten() to CDSPFIRFilter::getLPMaxAtten(),
		 * inclusive. The actual attenuation may be 0.40-4.46 dB higher. The
		 * general formula for selecting the ReqAtten is 6.02 * Bits + 40, where
		 * "Bits" is the bit resolution (e.g. 16, 24), "40" is an added resolution
		 * for stationary signals, this value can be decreased to 20 to 10 if the
		 * signal being resampled is mostly non-stationary (e.g. impulse
		 * response).
		 * @param ReqPhase Required filter's phase response. Note that this
		 * setting does not affect interpolator's phase response which is always
		 * linear-phase. Also note that if the "power of 2" resampling was engaged
		 * by the resampler together with the minimum-phase response, the audio
		 * stream may become fractionally delayed by up to 1 sample, depending on
		 * the minimum-phase filter's actual fractional delay. If the output
		 * stream should always start at "time zero" offset with minimum-phase
		 * filters the UsePower2 should be set to "false". Linear-phase filters
		 * do not have fractional delay.
		 * @param UsePower2 "True" if the "power of 2" resampling optimization
		 * should be used when possible. This value should be set to "false" if
		 * the access to interpolator is needed in any case (also the source and
		 * destination sample rates should not be equal).
		 * @see CDSPFIRFilterCache::getLPFilter()
		 */

		CDSPResampler(const double SrcSampleRate, const double DstSampleRate,
					  const int MaxInLen, const double ReqTransBand = 2.0,
					  const double ReqAtten                         = 206.91,
					  const EDSPFilterPhaseResponse ReqPhase        = fprLinearPhase,
					  const bool UsePower2                          = true)
		{
			R8BASSERT(SrcSampleRate > 0.0);
			R8BASSERT(DstSampleRate > 0.0);
			R8BASSERT(MaxInLen > 0);

			if (SrcSampleRate == DstSampleRate)
			{
				ConvCount = 0;
				return;
			}

			int SrcSRMult;
			int SrcSRDiv  = 1;
			int MaxOutLen = MaxInLen;
			int ConvBufCapacities[ 2 ];
			double PrevLatencyFrac = 0.0;

			if (DstSampleRate * 2 > SrcSampleRate)
			{
				// Only a single convolver with 2X upsampling is required.

				SrcSRMult             = 2;
				const double NormFreq = (DstSampleRate > SrcSampleRate ? 0.5 : 0.5 * DstSampleRate / SrcSampleRate);

				Convs[0] = new CDSPBlockConvolver(CDSPFIRFilterCache::getLPFilter(NormFreq, ReqTransBand, ReqAtten, ReqPhase, 2.0), 2, 1, 0.0);

				ConvCount            = 1;
				MaxOutLen            = Convs[0]->getMaxOutLen(MaxOutLen);
				ConvBufCapacities[0] = MaxOutLen;
				PrevLatencyFrac      = Convs[0]->getLatencyFrac();

				// Find if the destination to source sample rate ratio is
				// a "power of 2" value.

				int UseConvCount = 1;

				while (true)
				{
					const double TestSR = SrcSampleRate * (1 << UseConvCount);

					if (TestSR > DstSampleRate)
					{
						UseConvCount = 0; // Power of 2 not found.
						break;
					}

					if (TestSR == DstSampleRate)
					{
						break; // Power of 2 found.
					}

					UseConvCount++;
				}

				if (UsePower2 && UseConvCount > 0)
				{
					R8BASSERT(UseConvCount <= ConvCountMax);

					ConvBufCapacities[1] = 0;
					ConvCount            = UseConvCount;

					for (int i = 1; i < UseConvCount; ++i)
					{
						const double tb = (i >= 2 ? 45.0 : 34.0);

						Convs[i] = new CDSPBlockConvolver(CDSPFIRFilterCache::getLPFilter(0.5, tb, ReqAtten, ReqPhase, 2.0), 2, 1, PrevLatencyFrac);

						MaxOutLen                = Convs[i]->getMaxOutLen(MaxOutLen);
						ConvBufCapacities[i & 1] = MaxOutLen;
						PrevLatencyFrac          = Convs[i]->getLatencyFrac();
					}

					ConvBufs[0].alloc(ConvBufCapacities[0]);

					if (ConvBufCapacities[1] > 0) { ConvBufs[1].alloc(ConvBufCapacities[1]); }

					return; // No interpolator is needed.
				}

				ConvBufs[0].alloc(ConvBufCapacities[0]);
			}
			else
			{
				SrcSRMult            = 1;
				ConvBufCapacities[0] = 0;
				ConvCount            = 0;
				const double CheckSR = DstSampleRate * 4;

				while (CheckSR * SrcSRDiv <= SrcSampleRate)
				{
					SrcSRDiv *= 2;

					// If downsampling is even deeper, use a less steep filter at
					// this step.

					const double tb =
							(CheckSR * SrcSRDiv <= SrcSampleRate ? 45.0 : 34.0);

					Convs[ConvCount] = new CDSPBlockConvolver(CDSPFIRFilterCache::getLPFilter(0.5, tb, ReqAtten, ReqPhase, 1.0), 1, 2, PrevLatencyFrac);

					MaxOutLen       = Convs[ConvCount]->getMaxOutLen(MaxOutLen);
					PrevLatencyFrac = Convs[ConvCount]->getLatencyFrac();
					ConvCount++;

					R8BASSERT(ConvCount < ConvCountMax);
				}

				const double NormFreq = DstSampleRate * SrcSRDiv / SrcSampleRate;
				const int downf       = (UsePower2 && NormFreq == 0.5 ? 2 : 1);

				Convs[ConvCount] = new CDSPBlockConvolver(CDSPFIRFilterCache::getLPFilter(NormFreq, ReqTransBand, ReqAtten, ReqPhase, 1.0), 1, downf,
														  PrevLatencyFrac);

				MaxOutLen       = Convs[ConvCount]->getMaxOutLen(MaxOutLen);
				PrevLatencyFrac = Convs[ConvCount]->getLatencyFrac();
				ConvCount++;

				if (downf > 1)
				{
					return; // No interpolator is needed.
				}
			}

			Interp = new CInterpClass(SrcSampleRate * SrcSRMult / SrcSRDiv, DstSampleRate, PrevLatencyFrac);

			MaxOutLen = Interp->getMaxOutLen(MaxOutLen);

			if (MaxOutLen <= ConvBufCapacities[0]) { InterpBuf = ConvBufs[0]; }
			else if (MaxOutLen <= MaxInLen) { InterpBuf = nullptr; }
			else
			{
				TmpBuf.alloc(MaxOutLen);
				InterpBuf = TmpBuf;
			}
		}

		int getLatency() const override { return (0); }

		double getLatencyFrac() const override { return (0.0); }

		int getInLenBeforeOutStart(const int NextInLen) const override
		{
			int l = (Interp == nullptr ? 0 : Interp->getInLenBeforeOutStart(NextInLen));

			for (int i = ConvCount - 1; i >= 0; i--) { l = Convs[i]->getInLenBeforeOutStart(l); }

			return (l);
		}

		int getMaxOutLen(const int/* MaxInLen */) const override { return (0); }

		/**
		 * Function clears (resets) the state of *this object and returns it to
		 * the state after construction. All input data accumulated in the
		 * internal buffer so far will be discarded.
		 *
		 * This function makes it possible to use *this object for converting
		 * separate streams from the same source sample rate to the same
		 * destination sample rate without reconstructing the object. It is more
		 * efficient to clear the state of the resampler object than to destroy it
		 * and create a new object.
		 */
		void clear() override
		{
			for (int i = 0; i < ConvCount; ++i) { Convs[i]->clear(); }

			if (Interp != nullptr) { Interp->clear(); }
		}

		/**
		 * Function performs sample rate conversion.
		 *
		 * If the source and destination sample rates are equal, the resampler
		 * will do nothing and will simply return the input buffer unchanged.
		 *
		 * You do not need to allocate an intermediate output buffer for use with
		 * this function. If required, the resampler will allocate a suitable
		 * intermediate output buffer itself.
		 *
		 * @param ip0 Input buffer. This buffer may be used as output buffer by
		 * this function.
		 * @param l The number of samples available in the input buffer. Should
		 * not exceed the MaxInLen supplied to the constructor.
		 * @param[out] op0 This variable receives the pointer to the resampled
		 * data. On function's return, this pointer may point to the address
		 * within the "ip0" input buffer, or to *this object's internal buffer. In
		 * real-time applications it is suggested to pass this pointer to the next
		 * output audio block and consume any data left from the previous output
		 * audio block first before calling the process() function again. The
		 * buffer pointed to by the "op0" on return may be owned by the resampler,
		 * so it should not be freed by the caller.
		 * @return The number of samples available in the "op0" output buffer. If
		 * the data from the output buffer "op0" is going to be written to a
		 * bigger output buffer, it is suggested to check the returned number of
		 * samples so that no overflow of the bigger output buffer happens.
		 */
		int process(double* ip0, int l, double*& op0) override
		{
			R8BASSERT(l >= 0);

			if (ConvCount == 0)
			{
				op0 = ip0;
				return (l);
			}

			double* ip = ip0;
			double* op = nullptr;

			for (int i = 0; i < ConvCount; ++i)
			{
				op = (ConvBufs[i & 1] == nullptr ? ip0 : ConvBufs[i & 1]);
				l  = Convs[i]->process(ip, l, op);
				ip = op;
			}

			if (Interp == nullptr)
			{
				op0 = op;
				return (l);
			}

			op  = (InterpBuf == nullptr ? ip0 : InterpBuf);
			op0 = op;

			return (Interp->process(ip, l, op));
		}

		/**
		 * Function performs resampling of an input sample buffer of the specified
		 * length in the "one-shot" mode. This function can be useful when impulse
		 * response resampling is required.
		 *
		 * @param MaxInLen The max input length value which was previously passed
		 * to the constructor.
		 * @param ip Input buffer pointer.
		 * @param iplen Length of the input buffer in samples.
		 * @param op Output buffer pointer.
		 * @param oplen Length of the output buffer in samples.
		 */

		void oneshot(const int MaxInLen, const double* ip, int iplen,
					 double* op, int oplen)
		{
			const CFixedBuffer<double> ZeroBuf(MaxInLen);
			memset(&ZeroBuf[0], 0, MaxInLen * sizeof(double));

			while (oplen > 0)
			{
				int rc;
				double* p;

				if (iplen == 0)
				{
					rc = MaxInLen;
					p  = static_cast<double*>(&ZeroBuf[0]);
				}
				else
				{
					rc = min(iplen, MaxInLen);
					p  = const_cast<double*>(ip);
					ip += rc;
					iplen -= rc;
				}

				double* op0;
				int wc = process(p, rc, op0);

				wc = min(oplen, wc);
				memcpy(op, op0, wc * sizeof(double));
				op += wc;
				oplen -= wc;
			}

			clear();
		}

	private:
		static const int ConvCountMax = 8; ///< 8 convolvers with the
		///< built-in 2x up- or downsampling is enough for 256x up- or
		///< downsampling.
		///<
		CPtrKeeper<CDSPBlockConvolver*> Convs[ ConvCountMax ]; ///< Convolvers.
		///<
		int ConvCount = 0; ///< The number of objects defined in the Convs[] array.
		///< Equals to 0 if sample rate conversion is not needed.
		///<
		CPtrKeeper<CInterpClass*> Interp; ///< Fractional interpolator object.
		///< Equals NULL if no fractional interpolation is required meaning
		///< the "power of 2" resampling is performed or no resampling is
		///< performed at all.
		///<
		CFixedBuffer<double> ConvBufs[ 2 ]; ///< Intermediate convolution
		///< buffers to use, used only when at least 2x upsampling is
		///< performed. These buffers are used in flip-flop manner. If NULL
		///< then the input buffer will be used instead.
		///<
		CFixedBuffer<double> TmpBuf; ///< Additional output buffer, can be
		///< addressed by the InterpBuf pointer.
		///<
		double* InterpBuf = nullptr; ///< Final output interpolation buffer to use. If NULL
		///< then the input buffer will be used instead. Otherwise this
		///< pointer points to either ConvBufs or TmpBuf.
		///<
	};

	/**
	 * @brief The resampler class for 16-bit resampling.
	 *
	 * This class defines resampling parameters suitable for 16-bit resampling,
	 * using linear-phase low-pass filter. See the r8b::CDSPResampler class for
	 * details.
	 */

	class CDSPResampler16 final : public CDSPResampler<CDSPFracInterpolator<18, 137>>
	{
	public:
		/**
		 * Constructor initializes the 16-bit resampler. See the
		 * r8b::CDSPResampler class for details.
		 *
		 * @param SrcSampleRate Source signal sample rate.
		 * @param DstSampleRate Destination signal sample rate.
		 * @param MaxInLen The maximal planned length of the input buffer (in
		 * samples) that will be passed to the resampler.
		 * @param ReqTransBand Required transition band, in percent.
		 */

		CDSPResampler16(const double SrcSampleRate, const double DstSampleRate, const int MaxInLen, const double ReqTransBand = 2.0)
			: CDSPResampler<CDSPFracInterpolator<18, 137>>(SrcSampleRate, DstSampleRate, MaxInLen, ReqTransBand, 136.45, fprLinearPhase, true) { }
	};

	/**
	 * @brief The resampler class for 16-bit impulse response resampling.
	 *
	 * This class defines resampling parameters suitable for 16-bit impulse
	 * response resampling, using linear-phase low-pass filter. Impulse responses
	 * usually do not feature stationary signal components and thus need resampler
	 * with a less SNR. See the r8b::CDSPResampler class for details.
	 */

	class CDSPResampler16IR final : public CDSPResampler<CDSPFracInterpolator<14, 67>>
	{
	public:
		/**
		 * Constructor initializes the 16-bit impulse response resampler. See the
		 * r8b::CDSPResampler class for details.
		 *
		 * @param SrcSampleRate Source signal sample rate.
		 * @param DstSampleRate Destination signal sample rate.
		 * @param MaxInLen The maximal planned length of the input buffer (in
		 * samples) that will be passed to the resampler.
		 * @param ReqTransBand Required transition band, in percent.
		 */

		CDSPResampler16IR(const double SrcSampleRate, const double DstSampleRate, const int MaxInLen, const double ReqTransBand = 2.0)
			: CDSPResampler<CDSPFracInterpolator<14, 67>>(SrcSampleRate, DstSampleRate, MaxInLen, ReqTransBand, 109.56, fprLinearPhase, true) { }
	};

	/**
	 * @brief The resampler class for 24-bit resampling.
	 *
	 * This class defines resampling parameters suitable for 24-bit resampling
	 * (including 32-bit floating point resampling), using linear-phase low-pass
	 * filter. See the r8b::CDSPResampler class for details.
	 */

	class CDSPResampler24 final : public CDSPResampler<CDSPFracInterpolator<24, 673>>
	{
	public:
		/**
		 * Constructor initializes the 24-bit resampler (including 32-bit floating
		 * point). See the r8b::CDSPResampler class for details.
		 *
		 * @param SrcSampleRate Source signal sample rate.
		 * @param DstSampleRate Destination signal sample rate.
		 * @param MaxInLen The maximal planned length of the input buffer (in
		 * samples) that will be passed to the resampler.
		 * @param ReqTransBand Required transition band, in percent.
		 */

		CDSPResampler24(const double SrcSampleRate, const double DstSampleRate, const int MaxInLen, const double ReqTransBand = 2.0)
			: CDSPResampler<CDSPFracInterpolator<24, 673>>(SrcSampleRate, DstSampleRate, MaxInLen, ReqTransBand, 180.15, fprLinearPhase, true) { }
	};
} // namespace r8b

#endif // R8B_CDSPRESAMPLER_INCLUDED