hart_dsp.hpp

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#pragma once
 
#include <algorithm>  // fill()
#include <memory>
#include <ostream>
#include <string>
#include <unordered_map>
 
#include "hart_audio_buffer.hpp"
#include "hart_channel_flags.hpp"
#include "envelopes/hart_envelope.hpp"
#include "hart_utils.hpp"                  // make_unique()
 
namespace hart
{
 
/// @defgroup DSP DSP
/// @brief Process signals
 
/// @brief Hash table of automation envelope sequences mapped to param ids.
/// @details Keys: Param IDs (int enums like GainDb::gainDb)
///          Values: Sequence of automation envelope values for this Param ID, one value per frame
/// @ingroup DataStructures
using EnvelopeBuffers = std::unordered_map<int, std::vector<double>>;
 
/// @brief Polymorphic base for all DSP
/// @warning This class exists only for type erasure and polymorphism.
/// Do NOT inherit custom DSP from this class directly.
/// Inherit from @ref hart::DSP instead.
/// @ingroup DSP
template <typename SampleType>
class DSPBase
{
public:
    /// @brief Prepare for processing
    /// @details In real-time DSP, such methods are usually used for allocating memory and other non-realtime-safe and heavyweight
    /// operations. But keep in mind that that HART does not do real-time processing, so this merely follows common real-time
    /// DSP design conventions, where non-realtime operations are done in a separate callback like this one.
    /// This method is guaranteed to be called after @ref supportsChannelLayout() and @ref supportsSampleRate(), but before @ref process().
    /// It is guaranteed that the number of input and output channels obeys supportsChannelLayout() and supportsSampleRate() preferences.
    /// It is guaranteed that all subsequent process() calls will be in line with the arguments received in this callback.
    /// @param sampleRateHz sample rate at which the audio should be interpreted and processed
    /// @param numInputChannels Number of input channels
    /// @param numOutputChannels Number of output channels
    /// @param maxBlockSizeFrames Maximum block size in frames (samples)
    virtual void prepare (double sampleRateHz, size_t numInputChannels, size_t numOutputChannels, size_t maxBlockSizeFrames) = 0;
 
    /// @brief Processes the audio
    /// @details Depending on circumstances, this callback will either be called once to process an entire piece of audio from
    /// start to finish, or called repeatedly, one block at a time (see @ref AudioTestBuilder::withBlockSize()).
    /// All audio blocks except the last one are guaranteed to be equal to ```maxBlockSizeFrames``` set in @ref prepare() callback.
    /// It is guaranteed that input and output buffers are equal in length in frames (samples) to each,
    /// but they might have different number of channels. Use @ref supportsChannelLayout() to indicate
    /// whether the effect supports a specific i/o configuration or not, as it will be called before @ref prepare().
    /// It is guaranteed that ```envelopeBuffers``` will only contain the values for all attached envelopes for this instance of DSP
    /// effect, and will not contain any data (including key with empty item) if there's no envelope attached to a specific parameter
    /// ID in this effects's instance. It will never contain envelopes for IDs that get rejected by @ref supportsEnvelopeFor().
    /// Each vector in the `envelopeBuffers` map is guaranteed to be at least as large as input (and output) block. For partial blocks,
    /// only the first `input.getNumFrames()` elements contain valid data for the current block; the rest may be stale or uninitialized.
    /// DSP implementations are expected to ignore values beyond that index range.
    /// @note This method may be called in a replacing manner, i. e. ```input``` and ```output``` may be references to the same object.
    /// @warning Remember that the very last block of audio is almost always smaller than the block size set in @ref prepare(), so be
    /// careful with buffer bounds.
    /// @note Note that this method does not have to be real-time safe, as all rendering always happens offline.
    /// Also note that, unlike real-time audio applications, this method is called on the same thread as all others like @ref prepare().
    /// @param input Input audio block
    /// @param output Output audio block
    /// @param envelopeBuffers Envelope values for this block, see @ref EnvelopeBuffers
    /// @param channelsToProcess Channels that need processing. Process channels that are marked `true`, bypass ones marked `false`.
    virtual void process (const AudioBuffer<SampleType>& input, AudioBuffer<SampleType>& output, const EnvelopeBuffers& envelopeBuffers, ChannelFlags channelsToProcess) = 0;
 
    /// @brief Resets to initial state
    /// @details Ideally should be implemented in a way that audio produced after resetting is identical to audio produced after instantiation
    virtual void reset() {}
 
    /// @brief Sets DSP value
    /// @param paramId Some ID that your subclass understands;
    /// use of enums is encouraged for readability
    /// @param value Value of the param in an appropriate unit;
    /// use of SI units is encouraged (i.e. s instead of ms. Hz instead of kHz) to make better use of unit literals (see @ref Units)
    /// @warning This method is only called to set a fixed value before processing, and is not called to do automation (via @ref hart::Envelope)
    /// If you want your class to support automation for a specific parameter, override @ref supportsEnvelopeFor(), and then
    /// use @c envelopeBuffers provided in @ref process() callback.
    virtual void setValue (int paramId, double value) = 0;
 
    /// @brief Retrieves DSP value
    /// @details Among other things, it can be used to retrieve various readings like Gain Reduction measurements from your effect for further inspection
    /// @param paramId Some ID that your subclass understands
    /// @return The value of requested parameter in a unit that your subclass understands
    /// @note This method is only intended for parameters that don't have an automation envelope attached to this specific instance.
    /// To get values for automated parameters, use @c envelopeBuffers provided in @ref process() callback.
    virtual double getValue (int /* paramId */) const
    {
        return 0.0;
    }
 
    /// @brief Tells the runner (host) whether this effect supports a specific i/o configuration.
    /// @details It is guaranteed that the effect will not receive unsupported number of channels in @ref process().
    /// However, it is not always possible to handle gracefully channel layout being unsupported, so in some circumstances
    /// it can cause an exception or a test failure. This method is guaranteed to be called at least once before @ref prepare()
    virtual bool supportsChannelLayout (size_t numInputChannels, size_t numOutputChannels) const = 0;
 
    /// @brief Makes a text representation of this DSP effect for test failure outputs.
    /// @details It is strongly encouraged to follow python's
    /// <a href="https://docs.python.org/3/reference/datamodel.html#object.__repr__" target="_blank">repr()</a>
    /// conventions for returned text - basically, put something like "MyClass(value1, value2)" (with no quotes)
    /// into the stream whenever possible, or "<Readable info in angled brackets>" otherwise.
    /// Also, use built-in stream manipulators like @ref dbPrecision wherever applicable.
    /// Use @ref HART_DEFINE_GENERIC_REPRESENT() to get a basic implementation for this method.
    /// @param[out] stream Output stream to write to
    virtual void represent (std::ostream& stream) const = 0;
 
    /// @brief Tells whether this effect accepts automation envelopes for a particular parameter
    /// @param paramId Some ID that your subclass understands
    /// @return true if your subclass can process automation for this parameter, false otherwise
    virtual bool supportsEnvelopeFor (int /* paramId */) const { return false; }
 
    /// @brief Tells whether this effect supports given sample rate
    /// @details It is guaranteed to be called before @ref prepare()
    /// @param sampleRateHz Sample rate in question
    /// @return true if effect is capable of interpreting and processing in a given sample rate, false otherwise
    virtual bool supportsSampleRate (double /* sampleRateHz */) const { return true; }
 
    /// @brief Returns a smart pointer with a copy of this object
    virtual std::unique_ptr<DSPBase<SampleType>> copy() const { return nullptr; }
 
    /// @brief Returns a smart pointer with a moved instance of this object
    virtual std::unique_ptr<DSPBase<SampleType>> move() = 0;
 
    /// @brief Destructor
    virtual ~DSPBase() = default;
 
    /// @brief Default constructor
    DSPBase() = default;
 
    /// @brief Copies from another DSP effect instance
    /// @details Attached automation envelopes are deep-copied
    DSPBase (const DSPBase& other):
        m_channelsToProcess (other.m_channelsToProcess)
    {
        for (auto& pair : other.m_envelopes)
            m_envelopes.emplace (pair.first, pair.second->copy());
    }
 
    /// @brief Move constructor
    /// @details Attached automation envelopes are moved as well
    DSPBase (DSPBase&& other) noexcept:
        m_envelopes (std::move (other.m_envelopes)),
        m_channelsToProcess (other.m_channelsToProcess)
    {
    }
 
    /// @brief Copies from another DSP effect instance
    /// @details Attached automation envelopes are deep-copied
    DSPBase& operator= (const DSPBase& other)
    {
        if (this == &other)
            return *this;
 
        for (auto& pair : other.m_envelopes)
            m_envelopes.emplace (pair.first, pair.second->copy());
 
        m_channelsToProcess = other.m_channelsToProcess;
        return *this;
    }
 
    /// @brief Move assignment
    /// @details Attached automation envelopes are moved as well
    DSPBase& operator= (DSPBase&& other) noexcept
    {
        if (this != &other)
            m_envelopes = std::move (other.m_envelopes);
 
        m_channelsToProcess = other.m_channelsToProcess;
        return *this;
    }
 
    /// @brief Checks if there's an automation envelope attached to a specific parameter
    /// @details The envelopes are guaranteed to be attached strictly before @ref prepare()
    /// callback, so by the time of the first @ref process() call consider the presence or
    /// absence of envelope permanent.
    /// @return Reference to itself for chaining
    bool hasEnvelopeFor (int paramId)
    {
        return m_envelopes.find (paramId) != m_envelopes.end();
    }
 
    /// @brief Prepares all the attached envelopes and the effect itself for processing
    /// @details This method is intended to be called by DSP hosts like @ref hart::AudioTestBuilder or @ref hart::Signal.
    /// If you're making something that owns an instance of a DSP and needs it to generate audio,
    /// you must call this method before calling @ref processWithEnvelopes().
    /// You must also call @ref supportsChannelLayout() and @ref supportsSampleRate() before calling this method.
    /// @attention If you're not making a custom host, you probably don't need to call this method.
    void prepareWithEnvelopes (double sampleRateHz, size_t numInputChannels, size_t numOutputChannels, size_t maxBlockSizeFrames)
    {
        m_envelopeBuffers.clear();  // TODO: Remove only unused buffers
 
        for (auto& item : m_envelopes)
        {
            const int paramId = item.first;
            m_envelopeBuffers.emplace (paramId, std::vector<double> (maxBlockSizeFrames));
        }
 
        hassert (m_envelopes.size() == m_envelopeBuffers.size());
 
        for (auto& item : m_envelopeBuffers)
        {
            const int paramId = item.first;
            auto& envelopeBuffer = item.second;
 
            // Sanity checks
            hassert (supportsEnvelopeFor (paramId) && "Envelope for this id is unsupported, yet there's an envelope buffer allocated for it");
            hassert (hasEnvelopeFor (paramId) && "Envelope for this param id is not attached, yet there's an envelope buffer allocated for it");
 
            if (envelopeBuffer.size() != maxBlockSizeFrames)
                envelopeBuffer.resize (maxBlockSizeFrames);
        }
 
        m_channelsToProcess.resize (numInputChannels);
        prepare (sampleRateHz, numInputChannels, numOutputChannels, maxBlockSizeFrames);
    }
 
    /// @brief Resets the DSP instance, and all associated Envelopes
    /// @attention If you're not making a custom host, you probably don't need to call this method.
    void resetWithEnvelopes()
    {
        for (auto& item : m_envelopes)
        {
            std::unique_ptr<Envelope>& envelope = item.second;
            envelope->reset();
        }
 
        reset();
    }
 
    /// @brief Returns a structure indicating which channels should be processed by this DSP
    /// @details See `hart::DSP::atChannels()`, `hart::DSP::atChannel()`, `hart::DSP::atAllChannels()`
    /// @return Set of flags for each channel, see `hart::ChannelFlags`.
    /// `true` for channels that need processing, `false` for channels that need bypassing.
    ChannelFlags getChannelsToProcess()
    {
        return m_channelsToProcess;
    }
 
    /// @brief Renders all the automation envelopes and processes the audio
    /// @details This method is intended to be called by DSP hosts like @ref hart::AudioTestBuilder @ref hart::Signal.
    /// If you're making something that owns an instance of a Signal and needs it to generate audio,
    /// you must call it after calling @ref prepareWithEnvelopes().
    /// @attention If you're not making a custom host, you probably don't need to call this method.
    /// @param input Input audio block
    /// @param output Output audio block
    void processWithEnvelopes (const AudioBuffer<SampleType>& input, AudioBuffer<SampleType>& output)
    {
        for (auto& item : m_envelopeBuffers)
        {
            const int paramId = item.first;
            auto& envelopeBuffer = item.second;
 
            // Sanity checks
            hassert (supportsEnvelopeFor (paramId) && "Envelope for this id is unsupported, yet there's an envelope buffer allocated for it");
            hassert (hasEnvelopeFor (paramId) && "Envelope for this param id is not attached, yet there's an envelope buffer allocated for it");
            hassert (input.getNumFrames() <= envelopeBuffer.size() && "Envelope Buffers were not allocated properly for this buffer size");
 
            // Render envelope values
            getValues (paramId, input.getNumFrames(), envelopeBuffer);
        }
 
        process (input, output, m_envelopeBuffers, m_channelsToProcess);
    }
 
    /// @brief Makes a text representation of this DSP with optional "atChannels" appendix
    /// @details For internal use by hosts
    void representWithActiveChannels (std::ostream& stream) const
    {
        this->represent (stream);
 
        if (m_channelsToProcess.allTrue())
            return;
 
        stream << ".atChannels (";
        m_channelsToProcess.representAsInitializerList (stream);
        stream << ')';
    }
 
    /// @brief Helper for template resolution
    /// @private
    using SampleTypePublicAlias = SampleType;
 
protected:
    std::unordered_map<int, std::unique_ptr<Envelope>> m_envelopes;
    ChannelFlags m_channelsToProcess {true};
 
private:
    EnvelopeBuffers m_envelopeBuffers;
 
    /// @brief Gets sample-accurate automation envelope values for a specific parameter
    /// @param[in] paramId Some ID that your subclass understands
    /// @param[in] blockSize Buffer size in frames, should be the same as ```input```/```output```'s size in @ref process()
    /// @param[out] valuesOutput Container to get filled with the rendered automation values
    void getValues (int paramId, size_t blockSize, std::vector<double>& valuesOutput)
    {
        if (valuesOutput.size() < blockSize)
        {
            HART_WARNING ("Make sure to configure your envelope container size before processing audio");
            valuesOutput.resize (blockSize);
        }
 
        if (! hasEnvelopeFor (paramId))
        {
            const double value = getValue (paramId);
            std::fill (valuesOutput.begin(), valuesOutput.end(), value);
        }
        else
        {
            m_envelopes[paramId]->renderNextBlock (blockSize, valuesOutput);
        }
    }
};
 
/// @brief Base for DSP effects
/// @details This class is used both for adapting your DSP classes that you wish to test,
/// and for using in DSP chains of @ref Signals, so you can use stock effects like @ref GainDb
/// as tested processors, and you can use your tested DSP subclasses in Signals' DSP chains with
/// other effects. You can even chain multiple of your own DSP classes together this way.
/// All the callbacks of this class are guaranteed to be called from the same thread.
/// To make your custom DSP wrapper, inherit from it like so
/// (note the <a href="https://en.cppreference.com/w/cpp/language/crtp.html">CRTP</a>
/// in the template args here, it's important!):
/// @code{.cpp}
/// template<typename SampleType>
/// class MyCustomDSP: public DSP<SampleType, MyCustomDSP<SampleType>>
/// {
///     // ...
/// };
/// @endcode
/// @tparam SampleType Type of values that will be processed, typically ```float``` or ```double```
/// @tparam Derived Subclass for CRTP
/// @ingroup DSP
template<typename SampleType, typename Derived>
class DSP:
    public DSPBase<SampleType>
{
public:
    /// @brief Adds envelope to a specific parameter by moving it
    /// @details Guaranteed to be called strictly after the @ref supportsEnvelopeFor() callback,
    /// and only if it has returned ```true``` for this specific ```paramId```.
    /// Can be chained together like ```myEffect.withEnvelope (someId, someEnvelope).withEnvelope (otherId, otherEnvelope)```.
    /// If called multiple times for the same paramId, only last envelope for this ID will be used, all previous ones will be descarded.
    /// @param paramId Some ID that your subclass understands
    /// @param envelope Envelope to be attached
    /// @return Reference to itself for chaining
    Derived& withEnvelope (int paramId, Envelope&& envelope) &
    {
        _withEnvelope (paramId, envelope);
        return static_cast<Derived&> (*this);
    }
 
    /// @brief Adds envelope to a specific parameter by moving it
    /// @details Guaranteed to be called strictly after the @ref supportsEnvelopeFor() callback,
    /// and only if it has returned ```true``` for this specific ```paramId```.
    /// Can be chained together like ```myEffect.withEnvelope (someId, someEnvelope).withEnvelope (otherId, otherEnvelope)```.
    /// If called multiple times for the same paramId, only last envelope for this ID will be used, all previous ones will be descarded.
    /// @param paramId Some ID that your subclass understands
    /// @param envelope Envelope to be attached
    /// @return Reference to itself for chaining
    Derived&& withEnvelope (int paramId, Envelope&& envelope) &&
    {
        _withEnvelope (paramId, envelope);
        return static_cast<Derived&&> (*this);
    }
 
    /// @brief Adds envelope to a specific parameter by copying it
    /// @details Guaranteed to be called strictly after the @ref supportsEnvelopeFor() callback,
    /// and only if it has returned ```true``` for this specific ```paramId```.
    /// Can be chained together like ```myEffect.withEnvelope (someId, someEnvelope).withEnvelope (otherId, otherEnvelope)```.
    /// If called multiple times for the same paramId, only last envelope for this ID will be used, all previous ones will be descarded.
    /// @param paramId Some ID that your subclass understands
    /// @param envelope Envelope to be attached
    /// @return Reference to itself for chaining
    Derived& withEnvelope (int paramId, const Envelope& envelope) &
    {
        _withEnvelope (paramId, envelope);
        return static_cast<Derived&> (*this);
    }
 
    /// @brief Adds envelope to a specific parameter by copying it
    /// @details Guaranteed to be called strictly after the @ref supportsEnvelopeFor() callback,
    /// and only if it has returned ```true``` for this specific ```paramId```.
    /// Can be chained together like ```myEffect.withEnvelope (someId, someEnvelope).withEnvelope (otherId, otherEnvelope)```.
    /// If called multiple times for the same paramId, only last envelope for this ID will be used, all previous ones will be descarded.
    /// @param paramId Some ID that your subclass understands
    /// @param envelope Envelope to be attached
    /// @return Reference to itself for chaining
    Derived&& withEnvelope (int paramId, const Envelope& envelope) &&
    {
        _withEnvelope (paramId, envelope);
        return static_cast<Derived&&> (*this);
    }
 
    // TODO: withEnvelope() that takes a unique_ptr to the envelope
 
    /// @brief Returns a smart pointer with a moved instance of this object
    virtual std::unique_ptr<DSPBase<SampleType>> move() override
    {
        return hart::make_unique<Derived> (std::move (static_cast<Derived&> (*this)));
    }
 
    /// @brief Makes this DSP process only specific channels, and ignore the rest
    /// @details If not set, the DSP applies to all channels by default.
    /// If you call this method multiple times, only the last one will be applied.
    /// To select only one channel, consider using @ref DSP::atChannel() instead.
    /// @param channelsToProcess List of channels this DSP should apply to,
    /// e.g. `{0, 1}` or `{Channel::left, Channel::right}` for left and right channels only.
    /// @see `hart::Channel`
    Derived& atChannels (std::initializer_list<size_t> channelsToProcess) &
    {
        _atChannels (channelsToProcess);
        return static_cast<Derived&> (*this);
    }
 
    /// @brief Makes this DSP process only specific channels, and ignore the rest
    /// @details If not set, the DSP applies to all channels by default.
    /// If you call this method multiple times, only the last one will be applied.
    /// To select only one channel, consider using @ref DSP::atChannel() instead.
    /// @param channelsToProcess List of channels this DSP should apply to,
    /// e.g. `{0, 1}` or `{Channel::left, Channel::right}` for left and right channels only.
    /// @see `hart::Channel`
    Derived&& atChannels (std::initializer_list<size_t> channelsToProcess) &&
    {
        _atChannels (channelsToProcess);
        return static_cast<Derived&&> (*this);
    }
 
    /// @brief Makes this DSP process only specific channels, and bypass the rest
    /// @details If not set, the DSP applies to all channels by default.
    /// If you call this method multiple times, only the last one will be applied.
    /// To select multiple channels, use @ref DSP::atChannels() or
    /// @ref atAllChannelsExcept() instead.
    /// @param channelToProcess Channel this DSP should apply to (zero-based),
    /// e.g. `0` or `Channel::left` for left channel.
    /// @note If not set, the DSP applies to all channels by default
    /// @see `hart::Channel`
    Derived& atChannel (size_t channelToProcess) &
    {
        _atChannel (channelToProcess);
        return static_cast<Derived&> (*this);
    }
 
    /// @brief Makes this DSP process only specific channels, and bypass the rest
    /// @details If not set, the DSP applies to all channels by default.
    /// If you call this method multiple times, only the last one will be applied.
    /// To select multiple channels, use @ref DSP::atChannels() or
    /// @ref atAllChannelsExcept() instead.
    /// @param channelToProcess Channel this DSP should apply to (zero-based),
    /// e.g. `0` or `Channel::left` for left channel.
    /// @note If not set, the DSP applies to all channels by default
    /// @see `hart::Channel`
    Derived&& atChannel (size_t channelToProcess) &&
    {
        _atChannel (channelToProcess);
        return static_cast<Derived&&> (*this);
    }
 
    /// @brief Makes this DSP apply to all channels
    /// @details This is the default setting anyway, so this method is only
    /// for cases when you need to override previous @ref atChannel(),
    /// @ref atChannels() or @ref atAllChannelsExcept() calls.
    Derived& atAllChannels() &
    {
        this->m_channelsToProcess.setAllTo (true);
        return static_cast<Derived&> (*this);
    }
 
    /// @brief Makes this DSP apply to all channels
    /// @details This is the default setting anyway, so this method is only
    /// for cases when you need to override previous @ref atChannel(),
    /// @ref atChannels() or @ref atAllChannelsExcept() calls.
    Derived&& atAllChannels() &&
    {
        this->m_channelsToProcess.setAllTo (true);
        return static_cast<Derived&&> (*this);
    }
 
    /// @brief Makes this DSP process only specific channels, and bypass the rest
    /// @details If not set, DSP applies to all channels by default.
    /// If you call this method multiple times, only the last one will be applied.
    /// @param channelsToSkip List of channels this DSP should NOT apply to,
    /// e.g. `{0, 1}` or `{Channel::left, Channel::right}` to bypass left and right
    /// channels, and process the rest
    /// @see `hart::Channel`
    Derived& atAllChannelsExcept (std::initializer_list<size_t> channelsToSkip) &
    {
        _atAllChannelsExcept (channelsToSkip);
        return static_cast<Derived&> (*this);
    }
 
    /// @brief Makes this DSP process only specific channels, and bypass the rest
    /// @details If not set, DSP applies to all channels by default.
    /// If you call this method multiple times, only the last one will be applied.
    /// @param channelsToSkip List of channels this DSP should NOT apply to,
    /// e.g. `{0, 1}` or `{Channel::left, Channel::right}` to bypass left and right
    /// channels, and process the rest
    /// @see `hart::Channel`
    Derived&& atAllChannelsExcept (std::initializer_list<size_t> channelsToSkip) &&
    {
        _atAllChannelsExcept (channelsToSkip);
        return static_cast<Derived&&> (*this);
    }
 
private:
    void _withEnvelope (int paramId, Envelope&& envelope)
    {
        if (! this->supportsEnvelopeFor (paramId))
            HART_THROW_OR_RETURN (hart::UnsupportedError, std::string ("DSP doesn't support envelopes for param ID: ") + std::to_string (paramId), *this);
 
        this->m_envelopes.emplace (paramId, hart::make_unique<Envelope> (std::move (envelope)));
    }
 
    void _withEnvelope (int paramId, const Envelope& envelope)
    {
        if (! this->supportsEnvelopeFor(paramId))
            HART_THROW_OR_RETURN (hart::UnsupportedError, std::string ("DSP doesn't support envelopes for param ID: ") + std::to_string (paramId), *this);
 
        this->m_envelopes.emplace (paramId, envelope.copy());
    }
 
    void _atChannels (std::initializer_list<size_t> channelsToProcess)
    {
        this->m_channelsToProcess.setAllTo (false);
 
        for (size_t channel : channelsToProcess)
        {
            if (channel >= this->m_channelsToProcess.size())
                HART_THROW_OR_RETURN_VOID (hart::ValueError, "Channel exceeds max number of channels");
 
            this->m_channelsToProcess[channel] = true;
        }
    }
 
    void _atChannel (size_t channelToProcess)
    {
        if (channelToProcess >= this->m_channelsToProcess.size())
            HART_THROW_OR_RETURN_VOID (hart::ValueError, "Channel exceeds max number of channels");
 
        this->m_channelsToProcess.setAllTo (false);
        this->m_channelsToProcess[channelToProcess] = true;
    }
 
    void _atAllChannelsExcept (std::initializer_list<size_t> channelsToSkip)
    {
        this->m_channelsToProcess.setAllTo (true);
 
        for (size_t channel : channelsToSkip)
        {
            if (channel >= this->m_channelsToProcess.size())
                HART_THROW_OR_RETURN_VOID (hart::ValueError, "Channel exceeds max number of channels");
 
            this->m_channelsToProcess[channel] = false;
        }
    }
};
 
/// @brief Prints readable text representation of the DSP object into the I/O stream
/// @relates DSP
/// @ingroup DSP
template <typename SampleType>
inline std::ostream& operator<< (std::ostream& stream, const DSPBase<SampleType>& dsp)
{
    // TODO: Represent with the envelopes
    dsp.representWithActiveChannels (stream);
    return stream;
}
 
/// @brief Forbids @ref hart::DSP::copy() method
/// @details Put this into your class body's ```public``` section if either is true:
///  - Your class is not trivially copyable
///  - You don't want to trouble yourself with implementing copy semantics for your class
/// @ingroup DSP
#define HART_DSP_NON_COPYABLE
    std::unique_ptr<DSP<SampleType>> copy() const override { return nullptr; }
 
/// @brief Forbids @ref hart::DSP::move() method
/// @details Put this into your class body's ```public``` section if either is true:
///  - Your class is not trivially movable
///  - You don't want to trouble yourself with implementing move semantics for your class
///
/// Obviously, you won't be able to pass your class to the host
/// by rvalue or explicit move, but you still can pass
/// it wrapped into a smart pointer like so:
/// ```cpp
/// processAudioWith (hart::make_unique<MyDspType>()).withThis().withThat().process();
/// ```
/// @ingroup DSP
#define HART_DSP_NON_MOVABLE
    std::unique_ptr<DSP<SampleType>> move() override { return nullptr; }
 
/// @brief Implements a generic @ref hart::DSP::copy() method
/// @ingroup DSP
#define HART_DSP_COPYABLE(ClassName) virtual
        std::unique_ptr<DSPBase<SampleType>> copy() const override \
{
    return hart::make_unique<ClassName> (static_cast<const ClassName&> (*this)); \
}
 
/// @brief Implements a generic @ref hart::DSP::move() method
/// @ingroup DSP
#define HART_DSP_MOVABLE(ClassName) virtual
        std::unique_ptr<DSPBase<SampleType>> move() override \
{
    return hart::make_unique<ClassName> (std::move (static_cast<ClassName&> (*this))); \
}
 
}  // namespace hart
 
/// @private
#define HART_DSP_DECLARE_ALIASES_FOR(ClassName)
    namespace aliases_float{
        using ClassName = hart::ClassName<float>;
    }
    namespace aliases_double{
        using ClassName = hart::ClassName<double>;
    }