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Diffstat (limited to 'Alc/mastering.c')
| -rw-r--r-- | Alc/mastering.c | 543 |
1 files changed, 543 insertions, 0 deletions
diff --git a/Alc/mastering.c b/Alc/mastering.c new file mode 100644 index 00000000..6745c1c7 --- /dev/null +++ b/Alc/mastering.c @@ -0,0 +1,543 @@ +#include "config.h" + +#include <math.h> + +#include "mastering.h" +#include "alu.h" +#include "almalloc.h" +#include "static_assert.h" +#include "math_defs.h" + + +/* Early MSVC lacks round/roundf */ +#if defined(_MSC_VER) && _MSC_VER < 1800 +static double round(double val) +{ + if(val < 0.0) + return ceil(val-0.5); + return floor(val+0.5); +} +#define roundf(f) ((float)round((float)(f))) +#endif + + +/* These structures assume BUFFERSIZE is a power of 2. */ +static_assert((BUFFERSIZE & (BUFFERSIZE-1)) == 0, "BUFFERSIZE is not a power of 2"); + +typedef struct SlidingHold { + ALfloat Values[BUFFERSIZE]; + ALsizei Expiries[BUFFERSIZE]; + ALsizei LowerIndex; + ALsizei UpperIndex; + ALsizei Length; +} SlidingHold; + +/* General topology and basic automation was based on the following paper: + * + * D. Giannoulis, M. Massberg and J. D. Reiss, + * "Parameter Automation in a Dynamic Range Compressor," + * Journal of the Audio Engineering Society, v61 (10), Oct. 2013 + * + * Available (along with supplemental reading) at: + * + * http://c4dm.eecs.qmul.ac.uk/audioengineering/compressors/ + */ +typedef struct Compressor { + ALsizei NumChans; + ALuint SampleRate; + + struct { + ALuint Knee : 1; + ALuint Attack : 1; + ALuint Release : 1; + ALuint PostGain : 1; + ALuint Declip : 1; + } Auto; + + ALsizei LookAhead; + + ALfloat PreGain; + ALfloat PostGain; + + ALfloat Threshold; + ALfloat Slope; + ALfloat Knee; + + ALfloat Attack; + ALfloat Release; + + alignas(16) ALfloat SideChain[2*BUFFERSIZE]; + alignas(16) ALfloat CrestFactor[BUFFERSIZE]; + + SlidingHold *Hold; + ALfloat (*Delay)[BUFFERSIZE]; + ALsizei DelayIndex; + + ALfloat CrestCoeff; + ALfloat GainEstimate; + ALfloat AdaptCoeff; + + ALfloat LastPeakSq; + ALfloat LastRmsSq; + ALfloat LastRelease; + ALfloat LastAttack; + ALfloat LastGainDev; +} Compressor; + + +/* This sliding hold follows the input level with an instant attack and a + * fixed duration hold before an instant release to the next highest level. + * It is a sliding window maximum (descending maxima) implementation based on + * Richard Harter's ascending minima algorithm available at: + * + * http://www.richardhartersworld.com/cri/2001/slidingmin.html + */ +static ALfloat UpdateSlidingHold(SlidingHold *Hold, const ALsizei i, const ALfloat in) +{ + const ALsizei mask = BUFFERSIZE - 1; + const ALsizei length = Hold->Length; + ALfloat *restrict values = Hold->Values; + ALsizei *restrict expiries = Hold->Expiries; + ALsizei lowerIndex = Hold->LowerIndex; + ALsizei upperIndex = Hold->UpperIndex; + + if(i >= expiries[upperIndex]) + upperIndex = (upperIndex + 1) & mask; + + if(in >= values[upperIndex]) + { + values[upperIndex] = in; + expiries[upperIndex] = i + length; + lowerIndex = upperIndex; + } + else + { + do { + do { + if(!(in >= values[lowerIndex])) + goto found_place; + } while(lowerIndex--); + lowerIndex = mask; + } while(1); + found_place: + + lowerIndex = (lowerIndex + 1) & mask; + values[lowerIndex] = in; + expiries[lowerIndex] = i + length; + } + + Hold->LowerIndex = lowerIndex; + Hold->UpperIndex = upperIndex; + + return values[upperIndex]; +} + +static void ShiftSlidingHold(SlidingHold *Hold, const ALsizei n) +{ + const ALsizei lowerIndex = Hold->LowerIndex; + ALsizei *restrict expiries = Hold->Expiries; + ALsizei i = Hold->UpperIndex; + + if(lowerIndex < i) + { + for(;i < BUFFERSIZE;i++) + expiries[i] -= n; + i = 0; + } + for(;i < lowerIndex;i++) + expiries[i] -= n; + + expiries[i] -= n; +} + +/* Multichannel compression is linked via the absolute maximum of all + * channels. + */ +static void LinkChannels(Compressor *Comp, const ALsizei SamplesToDo, ALfloat (*restrict OutBuffer)[BUFFERSIZE]) +{ + const ALsizei index = Comp->LookAhead; + const ALsizei numChans = Comp->NumChans; + ALfloat *restrict sideChain = Comp->SideChain; + ALsizei c, i; + + ASSUME(SamplesToDo > 0); + ASSUME(numChans > 0); + + for(i = 0;i < SamplesToDo;i++) + sideChain[index + i] = 0.0f; + + for(c = 0;c < numChans;c++) + { + ALsizei offset = index; + for(i = 0;i < SamplesToDo;i++) + { + sideChain[offset] = maxf(sideChain[offset], fabsf(OutBuffer[c][i])); + ++offset; + } + } +} + +/* This calculates the squared crest factor of the control signal for the + * basic automation of the attack/release times. As suggested by the paper, + * it uses an instantaneous squared peak detector and a squared RMS detector + * both with 200ms release times. + */ +static void CrestDetector(Compressor *Comp, const ALsizei SamplesToDo) +{ + const ALfloat a_crest = Comp->CrestCoeff; + const ALsizei index = Comp->LookAhead; + const ALfloat *restrict sideChain = Comp->SideChain; + ALfloat *restrict crestFactor = Comp->CrestFactor; + ALfloat y2_peak = Comp->LastPeakSq; + ALfloat y2_rms = Comp->LastRmsSq; + ALsizei i; + + ASSUME(SamplesToDo > 0); + + for(i = 0;i < SamplesToDo;i++) + { + ALfloat x_abs = sideChain[index + i]; + ALfloat x2 = maxf(0.000001f, x_abs * x_abs); + + y2_peak = maxf(x2, lerp(x2, y2_peak, a_crest)); + y2_rms = lerp(x2, y2_rms, a_crest); + crestFactor[i] = y2_peak / y2_rms; + } + + Comp->LastPeakSq = y2_peak; + Comp->LastRmsSq = y2_rms; +} + +/* The side-chain starts with a simple peak detector (based on the absolute + * value of the incoming signal) and performs most of its operations in the + * log domain. + */ +static void PeakDetector(Compressor *Comp, const ALsizei SamplesToDo) +{ + const ALsizei index = Comp->LookAhead; + ALfloat *restrict sideChain = Comp->SideChain; + ALsizei i; + + ASSUME(SamplesToDo > 0); + + for(i = 0;i < SamplesToDo;i++) + { + const ALuint offset = index + i; + const ALfloat x_abs = sideChain[offset]; + + sideChain[offset] = logf(maxf(0.000001f, x_abs)); + } +} + +/* An optional hold can be used to extend the peak detector so it can more + * solidly detect fast transients. This is best used when operating as a + * limiter. + */ +static void PeakHoldDetector(Compressor *Comp, const ALsizei SamplesToDo) +{ + const ALsizei index = Comp->LookAhead; + ALfloat *restrict sideChain = Comp->SideChain; + SlidingHold *hold = Comp->Hold; + ALsizei i; + + ASSUME(SamplesToDo > 0); + + for(i = 0;i < SamplesToDo;i++) + { + const ALsizei offset = index + i; + const ALfloat x_abs = sideChain[offset]; + const ALfloat x_G = logf(maxf(0.000001f, x_abs)); + + sideChain[offset] = UpdateSlidingHold(hold, i, x_G); + } + + ShiftSlidingHold(hold, SamplesToDo); +} + +/* This is the heart of the feed-forward compressor. It operates in the log + * domain (to better match human hearing) and can apply some basic automation + * to knee width, attack/release times, make-up/post gain, and clipping + * reduction. + */ +static void GainCompressor(Compressor *Comp, const ALsizei SamplesToDo) +{ + const bool autoKnee = Comp->Auto.Knee; + const bool autoAttack = Comp->Auto.Attack; + const bool autoRelease = Comp->Auto.Release; + const bool autoPostGain = Comp->Auto.PostGain; + const bool autoDeclip = Comp->Auto.Declip; + const ALsizei lookAhead = Comp->LookAhead; + const ALfloat threshold = Comp->Threshold; + const ALfloat slope = Comp->Slope; + const ALfloat attack = Comp->Attack; + const ALfloat release = Comp->Release; + const ALfloat c_est = Comp->GainEstimate; + const ALfloat a_adp = Comp->AdaptCoeff; + const ALfloat *restrict crestFactor = Comp->CrestFactor; + ALfloat *restrict sideChain = Comp->SideChain; + ALfloat postGain = Comp->PostGain; + ALfloat knee = Comp->Knee; + ALfloat t_att = attack; + ALfloat t_rel = release - attack; + ALfloat a_att = expf(-1.0f / t_att); + ALfloat a_rel = expf(-1.0f / t_rel); + ALfloat y_1 = Comp->LastRelease; + ALfloat y_L = Comp->LastAttack; + ALfloat c_dev = Comp->LastGainDev; + ALsizei i; + + ASSUME(SamplesToDo > 0); + + for(i = 0;i < SamplesToDo;i++) + { + const ALfloat y2_crest = crestFactor[i]; + const ALfloat x_G = sideChain[lookAhead + i]; + const ALfloat x_over = x_G - threshold; + ALfloat knee_h; + ALfloat y_G; + ALfloat x_L; + + if(autoKnee) + knee = maxf(0.0f, 2.5f * (c_dev + c_est)); + knee_h = 0.5f * knee; + + /* This is the gain computer. It applies a static compression curve + * to the control signal. + */ + if(x_over <= -knee_h) + y_G = 0.0f; + else if(fabsf(x_over) < knee_h) + y_G = (x_over + knee_h) * (x_over + knee_h) / (2.0f * knee); + else + y_G = x_over; + + x_L = -slope * y_G; + + if(autoAttack) + { + t_att = 2.0f * attack / y2_crest; + a_att = expf(-1.0f / t_att); + } + + if(autoRelease) + { + t_rel = 2.0f * release / y2_crest - t_att; + a_rel = expf(-1.0f / t_rel); + } + + /* Gain smoothing (ballistics) is done via a smooth decoupled peak + * detector. The attack time is subtracted from the release time + * above to compensate for the chained operating mode. + */ + y_1 = maxf(x_L, lerp(x_L, y_1, a_rel)); + y_L = lerp(y_1, y_L, a_att); + + /* Knee width and make-up gain automation make use of a smoothed + * measurement of deviation between the control signal and estimate. + * The estimate is also used to bias the measurement to hot-start its + * average. + */ + c_dev = lerp(-y_L - c_est, c_dev, a_adp); + + if(autoPostGain) + { + /* Clipping reduction is only viable when make-up gain is being + * automated. It modifies the deviation to further attenuate the + * control signal when clipping is detected. The adaptation + * time is sufficiently long enough to suppress further clipping + * at the same output level. + */ + if(autoDeclip) + c_dev = maxf(c_dev, sideChain[i] - y_L - threshold - c_est); + + postGain = -(c_dev + c_est); + } + + sideChain[i] = expf(postGain - y_L); + } + + Comp->LastRelease = y_1; + Comp->LastAttack = y_L; + Comp->LastGainDev = c_dev; +} + +/* Combined with the hold time, a look-ahead delay can improve handling of + * fast transients by allowing the envelope time to converge prior to + * reaching the offending impulse. This is best used when operating as a + * limiter. + */ +static void SignalDelay(Compressor *Comp, const ALsizei SamplesToDo, ALfloat (*restrict OutBuffer)[BUFFERSIZE]) +{ + const ALsizei mask = BUFFERSIZE - 1; + const ALsizei numChans = Comp->NumChans; + const ALsizei indexIn = Comp->DelayIndex; + const ALsizei indexOut = Comp->DelayIndex - Comp->LookAhead; + ALfloat (*restrict delay)[BUFFERSIZE] = Comp->Delay; + ALsizei c, i; + + ASSUME(SamplesToDo > 0); + ASSUME(numChans > 0); + + for(c = 0;c < numChans;c++) + { + for(i = 0;i < SamplesToDo;i++) + { + ALfloat sig = OutBuffer[c][i]; + + OutBuffer[c][i] = delay[c][(indexOut + i) & mask]; + delay[c][(indexIn + i) & mask] = sig; + } + } + + Comp->DelayIndex = (indexIn + SamplesToDo) & mask; +} + +/* The compressor is initialized with the following settings: + * + * NumChans - Number of channels to process. + * SampleRate - Sample rate to process. + * AutoKnee - Whether to automate the knee width parameter. + * AutoAttack - Whether to automate the attack time parameter. + * AutoRelease - Whether to automate the release time parameter. + * AutoPostGain - Whether to automate the make-up (post) gain parameter. + * AutoDeclip - Whether to automate clipping reduction. Ignored when + * not automating make-up gain. + * LookAheadTime - Look-ahead time (in seconds). + * HoldTime - Peak hold-time (in seconds). + * PreGainDb - Gain applied before detection (in dB). + * PostGainDb - Make-up gain applied after compression (in dB). + * ThresholdDb - Triggering threshold (in dB). + * Ratio - Compression ratio (x:1). Set to INFINITY for true + * limiting. Ignored when automating knee width. + * KneeDb - Knee width (in dB). Ignored when automating knee + * width. + * AttackTimeMin - Attack time (in seconds). Acts as a maximum when + * automating attack time. + * ReleaseTimeMin - Release time (in seconds). Acts as a maximum when + * automating release time. + */ +Compressor* CompressorInit(const ALsizei NumChans, const ALuint SampleRate, + const ALboolean AutoKnee, const ALboolean AutoAttack, + const ALboolean AutoRelease, const ALboolean AutoPostGain, + const ALboolean AutoDeclip, const ALfloat LookAheadTime, + const ALfloat HoldTime, const ALfloat PreGainDb, + const ALfloat PostGainDb, const ALfloat ThresholdDb, + const ALfloat Ratio, const ALfloat KneeDb, + const ALfloat AttackTime, const ALfloat ReleaseTime) +{ + Compressor *Comp; + ALsizei lookAhead; + ALsizei hold; + size_t size; + + lookAhead = (ALsizei)clampf(roundf(LookAheadTime*SampleRate), 0.0f, BUFFERSIZE-1); + hold = (ALsizei)clampf(roundf(HoldTime*SampleRate), 0.0f, BUFFERSIZE-1); + /* The sliding hold implementation doesn't handle a length of 1. A 1-sample + * hold is useless anyway, it would only ever give back what was just given + * to it. + */ + if(hold == 1) + hold = 0; + + size = sizeof(*Comp); + if(lookAhead > 0) + { + size += sizeof(*Comp->Delay) * NumChans; + if(hold > 0) + size += sizeof(*Comp->Hold); + } + + Comp = al_calloc(16, size); + Comp->NumChans = NumChans; + Comp->SampleRate = SampleRate; + Comp->Auto.Knee = AutoKnee; + Comp->Auto.Attack = AutoAttack; + Comp->Auto.Release = AutoRelease; + Comp->Auto.PostGain = AutoPostGain; + Comp->Auto.Declip = AutoPostGain && AutoDeclip; + Comp->LookAhead = lookAhead; + Comp->PreGain = powf(10.0f, PreGainDb / 20.0f); + Comp->PostGain = PostGainDb * logf(10.0f) / 20.0f; + Comp->Threshold = ThresholdDb * logf(10.0f) / 20.0f; + Comp->Slope = 1.0f / maxf(1.0f, Ratio) - 1.0f; + Comp->Knee = maxf(0.0f, KneeDb * logf(10.0f) / 20.0f); + Comp->Attack = maxf(1.0f, AttackTime * SampleRate); + Comp->Release = maxf(1.0f, ReleaseTime * SampleRate); + + /* Knee width automation actually treats the compressor as a limiter. By + * varying the knee width, it can effectively be seen as applying + * compression over a wide range of ratios. + */ + if(AutoKnee) + Comp->Slope = -1.0f; + + if(lookAhead > 0) + { + if(hold > 0) + { + Comp->Hold = (SlidingHold*)(Comp + 1); + Comp->Hold->Values[0] = -HUGE_VALF; + Comp->Hold->Expiries[0] = hold; + Comp->Hold->Length = hold; + Comp->Delay = (ALfloat(*)[BUFFERSIZE])(Comp->Hold + 1); + } + else + { + Comp->Delay = (ALfloat(*)[BUFFERSIZE])(Comp + 1); + } + } + + Comp->CrestCoeff = expf(-1.0f / (0.200f * SampleRate)); // 200ms + Comp->GainEstimate = Comp->Threshold * -0.5f * Comp->Slope; + Comp->AdaptCoeff = expf(-1.0f / (2.0f * SampleRate)); // 2s + + return Comp; +} + +void ApplyCompression(Compressor *Comp, const ALsizei SamplesToDo, ALfloat (*restrict OutBuffer)[BUFFERSIZE]) +{ + const ALsizei numChans = Comp->NumChans; + const ALfloat preGain = Comp->PreGain; + ALfloat *restrict sideChain; + ALsizei c, i; + + ASSUME(SamplesToDo > 0); + ASSUME(numChans > 0); + + if(preGain != 1.0f) + { + for(c = 0;c < numChans;c++) + { + for(i = 0;i < SamplesToDo;i++) + OutBuffer[c][i] *= preGain; + } + } + + LinkChannels(Comp, SamplesToDo, OutBuffer); + + if(Comp->Auto.Attack || Comp->Auto.Release) + CrestDetector(Comp, SamplesToDo); + + if(Comp->Hold) + PeakHoldDetector(Comp, SamplesToDo); + else + PeakDetector(Comp, SamplesToDo); + + GainCompressor(Comp, SamplesToDo); + + if(Comp->Delay) + SignalDelay(Comp, SamplesToDo, OutBuffer); + + sideChain = Comp->SideChain; + for(c = 0;c < numChans;c++) + { + for(i = 0;i < SamplesToDo;i++) + OutBuffer[c][i] *= sideChain[i]; + } + + memmove(sideChain, sideChain+SamplesToDo, Comp->LookAhead*sizeof(ALfloat)); +} + + +ALsizei GetCompressorLookAhead(const Compressor *Comp) +{ return Comp->LookAhead; } |