snd: make SDL buffer length configurable

Makes it (approximately) independent of sample rate (snd_speed).

Changes the default (at 48khz) from 2048 to 1024, still not as
aggressive as some other engines.

Signed-off-by: bones_was_here <bones_was_here@xonotic.au>

diff --git a/snd_main.c b/snd_main.c
index 4c9467307d493e6fdc82a4bf91073d6e77d02214..9ac20114b941d85b3a8d2b87b1c7df7e79fafe45 100644 (file)
--- a/snd_main.c
+++ b/snd_main.c
@@ -245,6 +245,7 @@ static cvar_t snd_show = {CF_CLIENT, "snd_show", "0", "shows some statistics abo
 static cvar_t snd_speed = {CF_CLIENT | CF_ARCHIVE, "snd_speed", "48000", "sound output frequency, in hertz"};
 static cvar_t snd_width = {CF_CLIENT | CF_ARCHIVE, "snd_width", "4", "sound output precision, in bytes - 1 = 8bit, 2 = 16bit, 4 = 32bit float"};
 static cvar_t snd_channels = {CF_CLIENT | CF_ARCHIVE, "snd_channels", "2", "number of channels for the sound output (2 for stereo; up to 8 supported for 3D sound)"};
+cvar_t snd_bufferlength = {CF_CLIENT | CF_ARCHIVE, "snd_bufferlength", "20", "Desired length of the SDL2 audio buffer in milliseconds, smaller values reduce latency but can lead to underflow if the system is heavily loaded. Affects only how many sample frames are requested (which will be a power of 2 between 512 and 8192 inclusive)"};
 
 static cvar_t snd_startloopingsounds = {CF_CLIENT, "snd_startloopingsounds", "1", "whether to start sounds that would loop (you want this to be 1); existing sounds are not affected"};
 static cvar_t snd_startnonloopingsounds = {CF_CLIENT, "snd_startnonloopingsounds", "1", "whether to start sounds that would not loop (you want this to be 1); existing sounds are not affected"};
@@ -765,6 +766,7 @@ void S_Init(void)
        Cvar_RegisterVariable(&snd_speed);
        Cvar_RegisterVariable(&snd_width);
        Cvar_RegisterVariable(&snd_channels);
+       Cvar_RegisterVariable(&snd_bufferlength);
        Cvar_RegisterVariable(&snd_mutewhenidle);
        Cvar_RegisterVariable(&snd_maxchannelvolume);
        Cvar_RegisterVariable(&snd_softclip);

diff --git a/snd_main.h b/snd_main.h
index 6eb7b8ea8eff3372960e19fe203e23b8ff6830da..681fc32f45083adccad75c8aa7ee7d1e19f222d8 100644 (file)
--- a/snd_main.h
+++ b/snd_main.h
@@ -146,6 +146,7 @@ extern struct mempool_s *snd_mempool;
 /// Used for isolating performance in the renderer.
 extern qbool simsound;
 
+extern cvar_t snd_bufferlength;
 
 #define STREAM_BUFFERSIZE 16384 ///< in sampleframes
 

diff --git a/snd_sdl.c b/snd_sdl.c
index 3752dcdee49c47f726f93071afc923eeb04ccd87..e34a46e8506fb00db4ebde4c7c603d7edb237bd8 100644 (file)
--- a/snd_sdl.c
+++ b/snd_sdl.c
@@ -114,7 +114,8 @@ qbool SndSys_Init (snd_format_t* fmt)
                return false;
        }
 
-       buffersize = (unsigned int)ceil((double)fmt->speed / 25.0); // 2048 bytes on 24kHz to 48kHz
+       // SDL2 wiki recommends this range
+       buffersize = bound(512, ceil((double)fmt->speed * snd_bufferlength.value / 1000.0), 8192);
 
        // Init the SDL Audio subsystem
        memset(&wantspec, 0, sizeof(wantspec));