Add distance compensation to the HQ decoder

This only compensates for timing and gain differences caused by differences in
the physical speaker distances. It's not near-field compensation. This also
relies on having proper distance values defined in the ambdec definition file.

1 files changed, 107 insertions, 4 deletions

diff --git a/Alc/bformatdec.c b/Alc/bformatdec.c
index 3a07ac36..7c202228 100644
--- a/Alc/bformatdec.c
+++ b/Alc/bformatdec.c
@@ -161,6 +161,8 @@ static void init_encoder(void)
 }
 
 
+#define MAX_DELAY_LENGTH 128
+
 /* NOTE: Low-frequency (LF) fields and BandSplitter filters are unused with
  * single-band decoding
  */
@@ -181,6 +183,14 @@ typedef struct BFormatDec {
         ALuint NumChannels;
     } UpSampler;
 
+    struct {
+        alignas(16) ALfloat Buffer[MAX_DELAY_LENGTH];
+        ALfloat Gain;
+        ALuint Length; /* Valid range is [0...MAX_DELAY_LENGTH). */
+    } Delay[MAX_OUTPUT_CHANNELS];
+
+    ALfloat ChannelMix[BUFFERSIZE];
+
     ALuint NumChannels;
     ALboolean DualBand;
     ALboolean Periphonic;
@@ -229,7 +239,7 @@ void bformatdec_reset(BFormatDec *dec, const AmbDecConf *conf, ALuint chancount,
         0,  1, 3,  4, 8,  9, 15
     };
     const ALfloat *coeff_scale = UnitScale;
-    ALfloat ratio;
+    ALfloat maxdist, ratio;
     ALuint i;
 
     al_free(dec->Samples);
@@ -345,6 +355,45 @@ void bformatdec_reset(BFormatDec *dec, const AmbDecConf *conf, ALuint chancount,
             }
         }
     }
+
+
+    maxdist = 0.0f;
+    for(i = 0;i < conf->NumSpeakers;i++)
+        maxdist = maxf(maxdist, conf->Speakers[i].Distance);
+
+    memset(dec->Delay, 0, sizeof(dec->Delay));
+    if(maxdist > 0.0f)
+    {
+        for(i = 0;i < conf->NumSpeakers;i++)
+        {
+            ALuint chan = chanmap[i];
+            ALfloat delay;
+
+            /* Distance compensation only delays in steps of the sample rate.
+             * This is a bit less accurate since the delay time falls to the
+             * nearest sample time, but it's far simpler as it doesn't have to
+             * deal with phase offsets. This means at 48khz, for instance, the
+             * distance delay will be in steps of about 7 millimeters.
+             */
+            delay = floorf((maxdist-conf->Speakers[i].Distance) / SPEEDOFSOUNDMETRESPERSEC *
+                           (ALfloat)srate + 0.5f);
+            if(delay >= (ALfloat)MAX_DELAY_LENGTH)
+                ERR("Delay for speaker \"%s\" exceeds buffer length (%f >= %u)\n",
+                    al_string_get_cstr(conf->Speakers[i].Name), delay, MAX_DELAY_LENGTH);
+
+            dec->Delay[chan].Length = (ALuint)clampf(delay, 0.0f, (ALfloat)(MAX_DELAY_LENGTH-1));
+            dec->Delay[chan].Gain = conf->Speakers[i].Distance / maxdist;
+            TRACE("Channel %u \"%s\" distance compensation: %u samples, %f gain\n", chan,
+                al_string_get_cstr(conf->Speakers[i].Name), dec->Delay[chan].Length,
+                dec->Delay[chan].Gain
+            );
+        }
+    }
+    else
+    {
+        for(i = 0;i < conf->NumSpeakers;i++)
+            dec->Delay[chanmap[i]].Gain = 1.0f;
+    }
 }
 
 
@@ -374,17 +423,71 @@ void bformatdec_process(struct BFormatDec *dec, ALfloat (*restrict OutBuffer)[BU
 
         for(chan = 0;chan < OutChannels;chan++)
         {
-            apply_row(OutBuffer[chan], dec->MatrixHF[chan], dec->SamplesHF,
+            memset(dec->ChannelMix, 0, SamplesToDo*sizeof(ALfloat));
+            apply_row(dec->ChannelMix, dec->MatrixHF[chan], dec->SamplesHF,
                       dec->NumChannels, SamplesToDo);
-            apply_row(OutBuffer[chan], dec->MatrixLF[chan], dec->SamplesLF,
+            apply_row(dec->ChannelMix, dec->MatrixLF[chan], dec->SamplesLF,
                       dec->NumChannels, SamplesToDo);
+
+            if(dec->Delay[chan].Length > 0)
+            {
+                const ALuint base = dec->Delay[chan].Length;
+                if(SamplesToDo >= base)
+                {
+                    for(i = 0;i < base;i++)
+                        OutBuffer[chan][i] += dec->Delay[chan].Buffer[i] * dec->Delay[chan].Gain;
+                    for(;i < SamplesToDo;i++)
+                        OutBuffer[chan][i] += dec->ChannelMix[i-base] * dec->Delay[chan].Gain;
+                    memcpy(dec->Delay[chan].Buffer, &dec->ChannelMix[SamplesToDo-base],
+                        base*sizeof(ALfloat));
+                }
+                else
+                {
+                    for(i = 0;i < SamplesToDo;i++)
+                        OutBuffer[chan][i] += dec->Delay[chan].Buffer[i] * dec->Delay[chan].Gain;
+                    memmove(dec->Delay[chan].Buffer, dec->Delay[chan].Buffer+SamplesToDo,
+                            base - SamplesToDo);
+                    memcpy(dec->Delay[chan].Buffer+base-SamplesToDo, dec->ChannelMix,
+                        SamplesToDo*sizeof(ALfloat));
+                }
+            }
+            else for(i = 0;i < SamplesToDo;i++)
+                OutBuffer[chan][i] += dec->ChannelMix[i] * dec->Delay[chan].Gain;
         }
     }
     else
     {
         for(chan = 0;chan < OutChannels;chan++)
-            apply_row(OutBuffer[chan], dec->MatrixHF[chan], InSamples,
+        {
+            memset(dec->ChannelMix, 0, SamplesToDo*sizeof(ALfloat));
+            apply_row(dec->ChannelMix, dec->MatrixHF[chan], InSamples,
                       dec->NumChannels, SamplesToDo);
+
+            if(dec->Delay[chan].Length > 0)
+            {
+                const ALuint base = dec->Delay[chan].Length;
+                if(SamplesToDo >= base)
+                {
+                    for(i = 0;i < base;i++)
+                        OutBuffer[chan][i] += dec->Delay[chan].Buffer[i] * dec->Delay[chan].Gain;
+                    for(;i < SamplesToDo;i++)
+                        OutBuffer[chan][i] += dec->ChannelMix[i-base] * dec->Delay[chan].Gain;
+                    memcpy(dec->Delay[chan].Buffer, &dec->ChannelMix[SamplesToDo-base],
+                        base*sizeof(ALfloat));
+                }
+                else
+                {
+                    for(i = 0;i < SamplesToDo;i++)
+                        OutBuffer[chan][i] += dec->Delay[chan].Buffer[i] * dec->Delay[chan].Gain;
+                    memmove(dec->Delay[chan].Buffer, dec->Delay[chan].Buffer+SamplesToDo,
+                            base - SamplesToDo);
+                    memcpy(dec->Delay[chan].Buffer+base-SamplesToDo, dec->ChannelMix,
+                        SamplesToDo*sizeof(ALfloat));
+                }
+            }
+            else for(i = 0;i < SamplesToDo;i++)
+                OutBuffer[chan][i] += dec->ChannelMix[i] * dec->Delay[chan].Gain;
+        }
     }
 }