Blip_Buffer.h

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// Band-limited sound synthesis buffer
 
// Blip_Buffer 0.4.1
#ifndef BLIP_BUFFER_H
#define BLIP_BUFFER_H
 
        // internal
        #include <limits.h>
        #if INT_MAX < 0x7FFFFFFF
                #error "int must be at least 32 bits"
        #endif
        
        typedef int blip_long;
        typedef unsigned blip_ulong;
 
// Time unit at source clock rate
typedef blip_long blip_time_t;
 
// Output samples are 16-bit signed, with a range of -32768 to 32767
typedef short blip_sample_t;
enum { blip_sample_max = 32767 };
 
class Blip_Buffer {
public:
        typedef const char* blargg_err_t;
        
        // Set output sample rate and buffer length in milliseconds (1/1000 sec, defaults
        // to 1/4 second), then clear buffer. Returns NULL on success, otherwise if there
        // isn't enough memory, returns error without affecting current buffer setup.
        blargg_err_t set_sample_rate( long samples_per_sec, int msec_length = 1000 / 4 );
        
        // Set number of source time units per second
        void clock_rate( long );
        
        // End current time frame of specified duration and make its samples available
        // (along with any still-unread samples) for reading with read_samples(). Begins
        // a new time frame at the end of the current frame.
        void end_frame( blip_time_t time );
        
        // Read at most 'max_samples' out of buffer into 'dest', removing them from from
        // the buffer. Returns number of samples actually read and removed. If stereo is
        // true, increments 'dest' one extra time after writing each sample, to allow
        // easy interleving of two channels into a stereo output buffer.
        long read_samples( blip_sample_t* dest, long max_samples, int stereo = 0 );
        
// Additional optional features
 
        // Current output sample rate
        long sample_rate() const;
        
        // Length of buffer, in milliseconds
        int length() const;
        
        // Number of source time units per second
        long clock_rate() const;
        
        // Set frequency high-pass filter frequency, where higher values reduce bass more
        void bass_freq( int frequency );
        
        // Number of samples delay from synthesis to samples read out
        int output_latency() const;
        
        // Remove all available samples and clear buffer to silence. If 'entire_buffer' is
        // false, just clears out any samples waiting rather than the entire buffer.
        void clear( int entire_buffer = 1 );
        
        // Number of samples available for reading with read_samples()
        long samples_avail() const;
        
        // Remove 'count' samples from those waiting to be read
        void remove_samples( long count );
        
// Experimental features
        
        // Count number of clocks needed until 'count' samples will be available.
        // If buffer can't even hold 'count' samples, returns number of clocks until
        // buffer becomes full.
        blip_time_t count_clocks( long count ) const;
        
        // Number of raw samples that can be mixed within frame of specified duration.
        long count_samples( blip_time_t duration ) const;
        
        // Mix 'count' samples from 'buf' into buffer.
        void mix_samples( blip_sample_t const* buf, long count );
        
        // not documented yet
        void set_modified() { modified_ = 1; }
        int clear_modified() { int b = modified_; modified_ = 0; return b; }
        typedef blip_ulong blip_resampled_time_t;
        void remove_silence( long count );
        blip_resampled_time_t resampled_duration( int t ) const     { return t * factor_; }
        blip_resampled_time_t resampled_time( blip_time_t t ) const { return t * factor_ + offset_; }
        blip_resampled_time_t clock_rate_factor( long clock_rate ) const;
public:
        Blip_Buffer();
        ~Blip_Buffer();
        
        Blip_Buffer(Blip_Buffer &&) = default;
 
        // Deprecated
        typedef blip_resampled_time_t resampled_time_t;
        blargg_err_t sample_rate( long r ) { return set_sample_rate( r ); }
        blargg_err_t sample_rate( long r, int msec ) { return set_sample_rate( r, msec ); }
private:
        // noncopyable
        Blip_Buffer( const Blip_Buffer& );
        Blip_Buffer& operator = ( const Blip_Buffer& );
public:
        typedef blip_time_t buf_t_;
        blip_ulong factor_;
        blip_resampled_time_t offset_;
        buf_t_* buffer_;
        blip_long buffer_size_;
        blip_long reader_accum_;
        int bass_shift_;
private:
        long sample_rate_;
        long clock_rate_;
        int bass_freq_;
        int length_;
        int modified_;
        friend class Blip_Reader;
};
 
#ifdef HAVE_CONFIG_H
        #include "config.h"
#endif
 
// Number of bits in resample ratio fraction. Higher values give a more accurate ratio
// but reduce maximum buffer size.
#ifndef BLIP_BUFFER_ACCURACY
        #define BLIP_BUFFER_ACCURACY 16
#endif
 
// Number bits in phase offset. Fewer than 6 bits (64 phase offsets) results in
// noticeable broadband noise when synthesizing high frequency square waves.
// Affects size of Blip_Synth objects since they store the waveform directly.
#ifndef BLIP_PHASE_BITS
        #if BLIP_BUFFER_FAST
                #define BLIP_PHASE_BITS 8
        #else
                #define BLIP_PHASE_BITS 6
        #endif
#endif
 
        // Internal
        typedef blip_ulong blip_resampled_time_t;
        int const blip_widest_impulse_ = 16;
        int const blip_buffer_extra_ = blip_widest_impulse_ + 2;
        int const blip_res = 1 << BLIP_PHASE_BITS;
        class blip_eq_t;
        
        class Blip_Synth_Fast_ {
        public:
                Blip_Buffer* buf;
                int last_amp;
                int delta_factor;
                
                void volume_unit( double );
                Blip_Synth_Fast_();
                void treble_eq( blip_eq_t const& ) { }
        };
        
        class Blip_Synth_ {
        public:
                Blip_Buffer* buf;
                int last_amp;
                int delta_factor;
                
                void volume_unit( double );
                Blip_Synth_( short* impulses, int width );
                void treble_eq( blip_eq_t const& );
        private:
                double volume_unit_;
                short* const impulses;
                int const width;
                blip_long kernel_unit;
                int impulses_size() const { return blip_res / 2 * width + 1; }
                void adjust_impulse();
        };
 
// Quality level. Start with blip_good_quality.
const int blip_med_quality  = 8;
const int blip_good_quality = 12;
const int blip_high_quality = 16;
 
// Range specifies the greatest expected change in amplitude. Calculate it
// by finding the difference between the maximum and minimum expected
// amplitudes (max - min).
template<int quality,int range>
class Blip_Synth {
public:
        // Set overall volume of waveform
        void volume( double v ) { impl.volume_unit( v * (1.0 / (range < 0 ? -range : range)) ); }
        
        // Configure low-pass filter (see blip_buffer.txt)
        void treble_eq( blip_eq_t const& eq )       { impl.treble_eq( eq ); }
        
        // Get/set Blip_Buffer used for output
        Blip_Buffer* output() const                 { return impl.buf; }
        void output( Blip_Buffer* b )               { impl.buf = b; impl.last_amp = 0; }
        
        // Update amplitude of waveform at given time. Using this requires a separate
        // Blip_Synth for each waveform.
        void update( blip_time_t time, int amplitude );
 
// Low-level interface
 
        // Add an amplitude transition of specified delta, optionally into specified buffer
        // rather than the one set with output(). Delta can be positive or negative.
        // The actual change in amplitude is delta * (volume / range)
        void offset( blip_time_t, int delta, Blip_Buffer* ) const;
        void offset( blip_time_t t, int delta ) const { offset( t, delta, impl.buf ); }
        
        // Works directly in terms of fractional output samples. Contact author for more info.
        void offset_resampled( blip_resampled_time_t, int delta, Blip_Buffer* ) const;
        
        // Same as offset(), except code is inlined for higher performance
        void offset_inline( blip_time_t t, int delta, Blip_Buffer* buf ) const {
                offset_resampled( t * buf->factor_ + buf->offset_, delta, buf );
        }
        void offset_inline( blip_time_t t, int delta ) const {
                offset_resampled( t * impl.buf->factor_ + impl.buf->offset_, delta, impl.buf );
        }
        
private:
#if BLIP_BUFFER_FAST
        Blip_Synth_Fast_ impl;
#else
        Blip_Synth_ impl;
        typedef short imp_t;
        imp_t impulses [blip_res * (quality / 2) + 1];
public:
        Blip_Synth() : impl( impulses, quality ) { }
#endif
};
 
// Low-pass equalization parameters
class blip_eq_t {
public:
        // Logarithmic rolloff to treble dB at half sampling rate. Negative values reduce
        // treble, small positive values (0 to 5.0) increase treble.
        blip_eq_t( double treble_db = 0 );
        
        // See blip_buffer.txt
        blip_eq_t( double treble, long rolloff_freq, long sample_rate, long cutoff_freq = 0 );
        
private:
        double treble;
        long rolloff_freq;
        long sample_rate;
        long cutoff_freq;
        void generate( float* out, int count ) const;
        friend class Blip_Synth_;
};
 
int const blip_sample_bits = 30;
 
// Dummy Blip_Buffer to direct sound output to, for easy muting without
// having to stop sound code.
class Silent_Blip_Buffer : public Blip_Buffer {
        buf_t_ buf [blip_buffer_extra_ + 1];
public:
        // The following cannot be used (an assertion will fail if attempted):
        blargg_err_t set_sample_rate( long samples_per_sec, int msec_length );
        blip_time_t count_clocks( long count ) const;
        void mix_samples( blip_sample_t const* buf, long count );
        
        Silent_Blip_Buffer();
};
 
        #if defined (__GNUC__) || _MSC_VER >= 1100
                #define BLIP_RESTRICT __restrict
        #else
                #define BLIP_RESTRICT
        #endif
 
// Optimized reading from Blip_Buffer, for use in custom sample output
 
// Begin reading from buffer. Name should be unique to the current block.
#define BLIP_READER_BEGIN( name, blip_buffer ) \
        const Blip_Buffer::buf_t_* BLIP_RESTRICT name##_reader_buf = (blip_buffer).buffer_;\
        blip_long name##_reader_accum = (blip_buffer).reader_accum_
 
// Get value to pass to BLIP_READER_NEXT()
#define BLIP_READER_BASS( blip_buffer ) ((blip_buffer).bass_shift_)
 
// Constant value to use instead of BLIP_READER_BASS(), for slightly more optimal
// code at the cost of having no bass control
int const blip_reader_default_bass = 9;
 
// Current sample
#define BLIP_READER_READ( name )        (name##_reader_accum >> (blip_sample_bits - 16))
 
// Current raw sample in full internal resolution
#define BLIP_READER_READ_RAW( name )    (name##_reader_accum)
 
// Advance to next sample
#define BLIP_READER_NEXT( name, bass ) \
        (void) (name##_reader_accum += *name##_reader_buf++ - (name##_reader_accum >> (bass)))
 
// End reading samples from buffer. The number of samples read must now be removed
// using Blip_Buffer::remove_samples().
#define BLIP_READER_END( name, blip_buffer ) \
        (void) ((blip_buffer).reader_accum_ = name##_reader_accum)
 
 
// Compatibility with older version
const long blip_unscaled = 65535;
const int blip_low_quality  = blip_med_quality;
const int blip_best_quality = blip_high_quality;
 
// Deprecated; use BLIP_READER macros as follows:
// Blip_Reader r; r.begin( buf ); -> BLIP_READER_BEGIN( r, buf );
// int bass = r.begin( buf )      -> BLIP_READER_BEGIN( r, buf ); int bass = BLIP_READER_BASS( buf );
// r.read()                       -> BLIP_READER_READ( r )
// r.read_raw()                   -> BLIP_READER_READ_RAW( r )
// r.next( bass )                 -> BLIP_READER_NEXT( r, bass )
// r.next()                       -> BLIP_READER_NEXT( r, blip_reader_default_bass )
// r.end( buf )                   -> BLIP_READER_END( r, buf )
class Blip_Reader {
public:
        int begin( Blip_Buffer& );
        blip_long read() const          { return accum >> (blip_sample_bits - 16); }
        blip_long read_raw() const      { return accum; }
        void next( int bass_shift = 9 )         { accum += *buf++ - (accum >> bass_shift); }
        void end( Blip_Buffer& b )              { b.reader_accum_ = accum; }
        
private:
        const Blip_Buffer::buf_t_* buf;
        blip_long accum;
};
 
// End of public interface
 
#include <assert.h>
 
template<int quality,int range>
inline void Blip_Synth<quality,range>::offset_resampled( blip_resampled_time_t time,
                int delta, Blip_Buffer* blip_buf ) const
{
        // Fails if time is beyond end of Blip_Buffer, due to a bug in caller code or the
        // need for a longer buffer as set by set_sample_rate().
        assert( (blip_long) (time >> BLIP_BUFFER_ACCURACY) < blip_buf->buffer_size_ );
        delta *= impl.delta_factor;
        blip_long* BLIP_RESTRICT buf = blip_buf->buffer_ + (time >> BLIP_BUFFER_ACCURACY);
        int phase = (int) (time >> (BLIP_BUFFER_ACCURACY - BLIP_PHASE_BITS) & (blip_res - 1));
 
#if BLIP_BUFFER_FAST
        blip_long left = buf [0] + delta;
        
        // Kind of crappy, but doing shift after multiply results in overflow.
        // Alternate way of delaying multiply by delta_factor results in worse
        // sub-sample resolution.
        blip_long right = (delta >> BLIP_PHASE_BITS) * phase;
        left  -= right;
        right += buf [1];
        
        buf [0] = left;
        buf [1] = right;
#else
 
        int const fwd = (blip_widest_impulse_ - quality) / 2;
        int const rev = fwd + quality - 2;
        int const mid = quality / 2 - 1;
        
        imp_t const* BLIP_RESTRICT imp = impulses + blip_res - phase;
        
        #if defined (_M_IX86) || defined (_M_IA64) || defined (__i486__) || \
                        defined (__x86_64__) || defined (__ia64__) || defined (__i386__)
        
        // straight forward implementation resulted in better code on GCC for x86
        
        #define ADD_IMP( out, in ) \
                buf [out] += (blip_long) imp [blip_res * (in)] * delta
        
        #define BLIP_FWD( i ) {\
                ADD_IMP( fwd     + i, i     );\
                ADD_IMP( fwd + 1 + i, i + 1 );\
        }
        #define BLIP_REV( r ) {\
                ADD_IMP( rev     - r, r + 1 );\
                ADD_IMP( rev + 1 - r, r     );\
        }
 
                BLIP_FWD( 0 )
                if ( quality > 8  ) BLIP_FWD( 2 )
                if ( quality > 12 ) BLIP_FWD( 4 )
                {
                        ADD_IMP( fwd + mid - 1, mid - 1 );
                        ADD_IMP( fwd + mid    , mid     );
                        imp = impulses + phase;
                }
                if ( quality > 12 ) BLIP_REV( 6 )
                if ( quality > 8  ) BLIP_REV( 4 )
                BLIP_REV( 2 )
                
                ADD_IMP( rev    , 1 );
                ADD_IMP( rev + 1, 0 );
                
        #else
        
        // for RISC processors, help compiler by reading ahead of writes
        
        #define BLIP_FWD( i ) {\
                blip_long t0 =                       i0 * delta + buf [fwd     + i];\
                blip_long t1 = imp [blip_res * (i + 1)] * delta + buf [fwd + 1 + i];\
                i0 =           imp [blip_res * (i + 2)];\
                buf [fwd     + i] = t0;\
                buf [fwd + 1 + i] = t1;\
        }
        #define BLIP_REV( r ) {\
                blip_long t0 =                 i0 * delta + buf [rev     - r];\
                blip_long t1 = imp [blip_res * r] * delta + buf [rev + 1 - r];\
                i0 =           imp [blip_res * (r - 1)];\
                buf [rev     - r] = t0;\
                buf [rev + 1 - r] = t1;\
        }
                
                blip_long i0 = *imp;
                BLIP_FWD( 0 )
                if ( quality > 8  ) BLIP_FWD( 2 )
                if ( quality > 12 ) BLIP_FWD( 4 )
                {
                        blip_long t0 =                   i0 * delta + buf [fwd + mid - 1];
                        blip_long t1 = imp [blip_res * mid] * delta + buf [fwd + mid    ];
                        imp = impulses + phase;
                        i0 = imp [blip_res * mid];
                        buf [fwd + mid - 1] = t0;
                        buf [fwd + mid    ] = t1;
                }
                if ( quality > 12 ) BLIP_REV( 6 )
                if ( quality > 8  ) BLIP_REV( 4 )
                BLIP_REV( 2 )
                
                blip_long t0 =   i0 * delta + buf [rev    ];
                blip_long t1 = *imp * delta + buf [rev + 1];
                buf [rev    ] = t0;
                buf [rev + 1] = t1;
        #endif
        
#endif
}
 
#undef BLIP_FWD
#undef BLIP_REV
 
template<int quality,int range>
#if BLIP_BUFFER_FAST
        inline
#endif
void Blip_Synth<quality,range>::offset( blip_time_t t, int delta, Blip_Buffer* buf ) const
{
        offset_resampled( t * buf->factor_ + buf->offset_, delta, buf );
}
 
template<int quality,int range>
#if BLIP_BUFFER_FAST
        inline
#endif
void Blip_Synth<quality,range>::update( blip_time_t t, int amp )
{
        int delta = amp - impl.last_amp;
        impl.last_amp = amp;
        offset_resampled( t * impl.buf->factor_ + impl.buf->offset_, delta, impl.buf );
}
 
inline blip_eq_t::blip_eq_t( double t ) :
                treble( t ), rolloff_freq( 0 ), sample_rate( 44100 ), cutoff_freq( 0 ) { }
inline blip_eq_t::blip_eq_t( double t, long rf, long sr, long cf ) :
                treble( t ), rolloff_freq( rf ), sample_rate( sr ), cutoff_freq( cf ) { }
 
inline int  Blip_Buffer::length() const         { return length_; }
inline long Blip_Buffer::samples_avail() const  { return (long) (offset_ >> BLIP_BUFFER_ACCURACY); }
inline long Blip_Buffer::sample_rate() const    { return sample_rate_; }
inline int  Blip_Buffer::output_latency() const { return blip_widest_impulse_ / 2; }
inline long Blip_Buffer::clock_rate() const     { return clock_rate_; }
inline void Blip_Buffer::clock_rate( long cps ) { factor_ = clock_rate_factor( clock_rate_ = cps ); }
 
inline int Blip_Reader::begin( Blip_Buffer& blip_buf )
{
        buf = blip_buf.buffer_;
        accum = blip_buf.reader_accum_;
        return blip_buf.bass_shift_;
}
 
int const blip_max_length = 0;
int const blip_default_length = 250;
 
#endif