Fade in sounds to prevent clicking (#1220)

* Fade in sounds to prevent clicking

* Fix range check

* Use absolute value

* Add `FADETIME`

* Remove redundant check

src/dogs.h

@@ -3564,8 +3564,8 @@ static const unsigned char dsdgact[] = {
 // http://creativecommons.org/publicdomain/zero/1.0/
 
 static const unsigned char dsdgatk[] = {
-  3,0,34,86,213,30,0,0,120,112,113,110,109,106,105,103,102,102,102,102,104,106,
+  3,0,34,86,213,30,0,0,128,127,126,125,124,123,121,120,118,117,116,115,114,115,
-  110,113,117,122,127,132,137,141,144,147,149,150,151,152,152,152,151,150,148,
+  116,117,120,123,127,131,136,140,144,147,149,150,151,152,152,152,151,150,148,
   145,142,138,135,131,128,125,123,121,121,120,121,121,121,121,121,121,121,121,
   120,120,119,119,118,118,117,116,116,116,116,117,119,120,122,125,127,130,133,
   136,139,141,144,146,147,148,149,149,148,146,144,142,139,136,134,131,128,125,

src/i_oalsound.c

@@ -546,6 +546,22 @@ static boolean IsPaddedSound(const byte *data, int size)
     return true;
 }
 
+static void FadeInMono8(byte *data, ALsizei size, ALsizei freq)
+{
+    const int fadelen = freq * FADETIME / 1000000;
+    int i;
+
+    if (data[0] == 128 || size < fadelen)
+    {
+        return;
+    }
+
+    for (i = 0; i < fadelen; i++)
+    {
+        data[i] = (data[i] - 128) * i / fadelen + 128;
+    }
+}
+
 boolean I_OAL_CacheSound(sfxinfo_t *sfx)
 {
     int lumpnum;
@@ -604,6 +620,9 @@ boolean I_OAL_CacheSound(sfxinfo_t *sfx)
 
             // All Doom sounds are 8-bit
             format = AL_FORMAT_MONO8;
+
+            // Fade in sounds that start at a non-zero amplitude to prevent clicking.
+            FadeInMono8(sampledata, size, freq);
         }
         else
         {

src/i_sndfile.c

@@ -23,6 +23,7 @@
 #include <sndfile.h>
 #include <stdlib.h>
 #include <string.h>
+#include <math.h>
 
 #include "i_oalstream.h"
 #include "m_swap.h"
@@ -483,6 +484,38 @@ static boolean OpenFile(sndfile_t *file, void *data, sf_count_t size)
     return true;
 }
 
+static void FadeInMono16(short *data, ALsizei size, ALsizei freq)
+{
+    const int fadelen = freq * FADETIME / 1000000;
+    int i;
+
+    if (!data[0] || size / sizeof(short) < fadelen)
+    {
+        return;
+    }
+
+    for (i = 0; i < fadelen; i++)
+    {
+        data[i] = data[i] * i / fadelen;
+    }
+}
+
+static void FadeInMonoFloat32(float *data, ALsizei size, ALsizei freq)
+{
+    const int fadelen = freq * FADETIME / 1000000;
+    int i;
+
+    if (fabsf(data[0]) < 0.000001f || size / sizeof(float) < fadelen)
+    {
+        return;
+    }
+
+    for (i = 0; i < fadelen; i++)
+    {
+        data[i] = data[i] * i / fadelen;
+    }
+}
+
 boolean I_SND_LoadFile(void *data, ALenum *format, byte **wavdata,
                        ALsizei *size, ALsizei *freq)
 {
@@ -519,10 +552,21 @@ boolean I_SND_LoadFile(void *data, ALenum *format, byte **wavdata,
         return false;
     }
 
-    *wavdata = local_wavdata;
     *size = num_frames * file.frame_size / file.sfinfo.channels;
     *freq = file.sfinfo.samplerate;
 
+    // Fade in sounds that start at a non-zero amplitude to prevent clicking.
+    if (*format == AL_FORMAT_MONO16)
+    {
+        FadeInMono16(local_wavdata, *size, *freq);
+    }
+    else if (*format == AL_FORMAT_MONO_FLOAT32)
+    {
+        FadeInMonoFloat32(local_wavdata, *size, *freq);
+    }
+
+    *wavdata = local_wavdata;
+
     CloseFile(&file);
 
     return true;

src/i_sndfile.h

@@ -22,6 +22,8 @@
 #include "al.h"
 #include "doomtype.h"
 
+#define FADETIME 1000 // microseconds
+
 boolean I_SND_LoadFile(void *data, ALenum *format, byte **wavdata,
                        ALsizei *size, ALsizei *freq);