sound: Add config variable to control buffer size.

Add snd_maxslicetime_ms variable to control the size of the output
sound buffer, and reduce the default from 70ms to 28ms to match Doom's
35fps timer. Thanks to Holering for reporting this (fixes #345).

4 files changed, 18 insertions, 3 deletions

diff --git a/src/i_sdlsound.c b/src/i_sdlsound.c
index c8ec6853..e60e18e3 100644
--- a/src/i_sdlsound.c
+++ b/src/i_sdlsound.c
@@ -50,7 +50,6 @@
 
 #define LOW_PASS_FILTER
 //#define DEBUG_DUMP_WAVS
-#define MAX_SOUND_SLICE_TIME 70 /* ms */
 #define NUM_CHANNELS 16
 
 typedef struct allocated_sound_s allocated_sound_t;
@@ -961,7 +960,7 @@ static void I_SDL_ShutdownSound(void)
     sound_initialized = false;
 }
 
-// Calculate slice size, based on MAX_SOUND_SLICE_TIME.
+// Calculate slice size, based on snd_maxslicetime_ms.
 // The result must be a power of two.
 
 static int GetSliceSize(void)
@@ -969,7 +968,7 @@ static int GetSliceSize(void)
     int limit;
     int n;
 
-    limit = (snd_samplerate * MAX_SOUND_SLICE_TIME) / 1000;
+    limit = (snd_samplerate * snd_maxslicetime_ms) / 1000;
 
     // Try all powers of two, not exceeding the limit.
 
diff --git a/src/i_sound.c b/src/i_sound.c
index f12c8204..7aa3a31b 100644
--- a/src/i_sound.c
+++ b/src/i_sound.c
@@ -47,6 +47,11 @@ int snd_samplerate = 44100;
 
 int snd_cachesize = 64 * 1024 * 1024;
 
+// Config variable that controls the sound buffer size.
+// We default to 28ms (1000 / 35fps = 1 buffer per tic).
+
+int snd_maxslicetime_ms = 28;
+
 // Low-level sound and music modules we are using
 
 static sound_module_t *sound_module;
@@ -434,6 +439,7 @@ void I_BindSoundVariables(void)
     M_BindVariable("snd_sbirq",         &snd_sbirq);
     M_BindVariable("snd_sbdma",         &snd_sbdma);
     M_BindVariable("snd_mport",         &snd_mport);
+    M_BindVariable("snd_maxslicetime_ms", &snd_maxslicetime_ms);
     M_BindVariable("snd_samplerate",    &snd_samplerate);
     M_BindVariable("snd_cachesize",     &snd_cachesize);
     M_BindVariable("opl_io_port",       &opl_io_port);
diff --git a/src/i_sound.h b/src/i_sound.h
index e4062959..db00ab5c 100644
--- a/src/i_sound.h
+++ b/src/i_sound.h
@@ -233,6 +233,7 @@ extern int snd_sfxdevice;
 extern int snd_musicdevice;
 extern int snd_samplerate;
 extern int snd_cachesize;
+extern int snd_maxslicetime_ms;
 
 void I_BindSoundVariables(void);
 
diff --git a/src/m_config.c b/src/m_config.c
index 3f0c24cf..edc0a174 100644
--- a/src/m_config.c
+++ b/src/m_config.c
@@ -798,6 +798,15 @@ static default_t extra_defaults_list[] =
     CONFIG_VARIABLE_INT(snd_cachesize),
 
     //!
+    // Maximum size of the output sound buffer size in milliseconds.
+    // Sound output is generated periodically in slices. Higher values
+    // might be more efficient but will introduce latency to the
+    // sound output. The default is 28ms (one slice per tic with the
+    // 35fps timer).
+
+    CONFIG_VARIABLE_INT(snd_maxslicetime_ms),
+
+    //!
     // The I/O port to use to access the OPL chip.  Only relevant when
     // using native OPL music playback.
     //