ref: 15ee1e9730b7731039d8ccec07d940a543165e94
dir: /src/i_sdlsound.c/
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
// Copyright(C) 2008 David Flater
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// DESCRIPTION:
// System interface for sound.
//
#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "SDL.h"
#include "SDL_mixer.h"
#ifdef HAVE_LIBSAMPLERATE
#include <samplerate.h>
#endif
#include "deh_str.h"
#include "i_sound.h"
#include "i_system.h"
#include "i_swap.h"
#include "m_argv.h"
#include "m_misc.h"
#include "w_wad.h"
#include "z_zone.h"
#include "doomtype.h"
#define LOW_PASS_FILTER
//#define DEBUG_DUMP_WAVS
#define NUM_CHANNELS 16
typedef struct allocated_sound_s allocated_sound_t;
struct allocated_sound_s
{
sfxinfo_t *sfxinfo;
Mix_Chunk chunk;
int use_count;
int pitch;
allocated_sound_t *prev, *next;
};
static boolean sound_initialized = false;
static allocated_sound_t *channels_playing[NUM_CHANNELS];
static int mixer_freq;
static Uint16 mixer_format;
static int mixer_channels;
static boolean use_sfx_prefix;
static boolean (*ExpandSoundData)(sfxinfo_t *sfxinfo,
byte *data,
int samplerate,
int length) = NULL;
// Doubly-linked list of allocated sounds.
// When a sound is played, it is moved to the head, so that the oldest
// sounds not used recently are at the tail.
static allocated_sound_t *allocated_sounds_head = NULL;
static allocated_sound_t *allocated_sounds_tail = NULL;
static int allocated_sounds_size = 0;
int use_libsamplerate = 0;
// Scale factor used when converting libsamplerate floating point numbers
// to integers. Too high means the sounds can clip; too low means they
// will be too quiet. This is an amount that should avoid clipping most
// of the time: with all the Doom IWAD sound effects, at least. If a PWAD
// is used, clipping might occur.
float libsamplerate_scale = 0.65f;
// Hook a sound into the linked list at the head.
static void AllocatedSoundLink(allocated_sound_t *snd)
{
snd->prev = NULL;
snd->next = allocated_sounds_head;
allocated_sounds_head = snd;
if (allocated_sounds_tail == NULL)
{
allocated_sounds_tail = snd;
}
else
{
snd->next->prev = snd;
}
}
// Unlink a sound from the linked list.
static void AllocatedSoundUnlink(allocated_sound_t *snd)
{
if (snd->prev == NULL)
{
allocated_sounds_head = snd->next;
}
else
{
snd->prev->next = snd->next;
}
if (snd->next == NULL)
{
allocated_sounds_tail = snd->prev;
}
else
{
snd->next->prev = snd->prev;
}
}
static void FreeAllocatedSound(allocated_sound_t *snd)
{
// Unlink from linked list.
AllocatedSoundUnlink(snd);
// Keep track of the amount of allocated sound data:
allocated_sounds_size -= snd->chunk.alen;
free(snd);
}
// Search from the tail backwards along the allocated sounds list, find
// and free a sound that is not in use, to free up memory. Return true
// for success.
static boolean FindAndFreeSound(void)
{
allocated_sound_t *snd;
snd = allocated_sounds_tail;
while (snd != NULL)
{
if (snd->use_count == 0)
{
FreeAllocatedSound(snd);
return true;
}
snd = snd->prev;
}
// No available sounds to free...
return false;
}
// Enforce SFX cache size limit. We are just about to allocate "len"
// bytes on the heap for a new sound effect, so free up some space
// so that we keep allocated_sounds_size < snd_cachesize
static void ReserveCacheSpace(size_t len)
{
if (snd_cachesize <= 0)
{
return;
}
// Keep freeing sound effects that aren't currently being played,
// until there is enough space for the new sound.
while (allocated_sounds_size + len > snd_cachesize)
{
// Free a sound. If there is nothing more to free, stop.
if (!FindAndFreeSound())
{
break;
}
}
}
// Allocate a block for a new sound effect.
static allocated_sound_t *AllocateSound(sfxinfo_t *sfxinfo, size_t len)
{
allocated_sound_t *snd;
// Keep allocated sounds within the cache size.
ReserveCacheSpace(len);
// Allocate the sound structure and data. The data will immediately
// follow the structure, which acts as a header.
do
{
snd = malloc(sizeof(allocated_sound_t) + len);
// Out of memory? Try to free an old sound, then loop round
// and try again.
if (snd == NULL && !FindAndFreeSound())
{
return NULL;
}
} while (snd == NULL);
// Skip past the chunk structure for the audio buffer
snd->chunk.abuf = (byte *) (snd + 1);
snd->chunk.alen = len;
snd->chunk.allocated = 1;
snd->chunk.volume = MIX_MAX_VOLUME;
snd->pitch = NORM_PITCH;
snd->sfxinfo = sfxinfo;
snd->use_count = 0;
// Keep track of how much memory all these cached sounds are using...
allocated_sounds_size += len;
AllocatedSoundLink(snd);
return snd;
}
// Lock a sound, to indicate that it may not be freed.
static void LockAllocatedSound(allocated_sound_t *snd)
{
// Increase use count, to stop the sound being freed.
++snd->use_count;
//printf("++ %s: Use count=%i\n", snd->sfxinfo->name, snd->use_count);
// When we use a sound, re-link it into the list at the head, so
// that the oldest sounds fall to the end of the list for freeing.
AllocatedSoundUnlink(snd);
AllocatedSoundLink(snd);
}
// Unlock a sound to indicate that it may now be freed.
static void UnlockAllocatedSound(allocated_sound_t *snd)
{
if (snd->use_count <= 0)
{
I_Error("Sound effect released more times than it was locked...");
}
--snd->use_count;
//printf("-- %s: Use count=%i\n", snd->sfxinfo->name, snd->use_count);
}
// Search through the list of allocated sounds and return the one that matches
// the supplied sfxinfo entry and pitch level.
static allocated_sound_t * GetAllocatedSoundBySfxInfoAndPitch(sfxinfo_t *sfxinfo, int pitch)
{
allocated_sound_t * p = allocated_sounds_head;
while (p != NULL)
{
if (p->sfxinfo == sfxinfo && p->pitch == pitch)
{
return p;
}
p = p->next;
}
return NULL;
}
// Allocate a new sound chunk and pitch-shift an existing sound up-or-down
// into it.
static allocated_sound_t * PitchShift(allocated_sound_t *insnd, int pitch)
{
allocated_sound_t * outsnd;
Sint16 *inp, *outp;
Sint16 *srcbuf, *dstbuf;
Uint32 srclen, dstlen;
srcbuf = (Sint16 *)insnd->chunk.abuf;
srclen = insnd->chunk.alen;
// determine ratio pitch:NORM_PITCH and apply to srclen, then invert.
// This is an approximation of vanilla behaviour based on measurements
dstlen = (int)((1 + (1 - (float)pitch / NORM_PITCH)) * srclen);
// ensure that the new buffer is an even length
if ((dstlen % 2) == 0)
{
dstlen++;
}
outsnd = AllocateSound(insnd->sfxinfo, dstlen);
if (!outsnd)
{
return NULL;
}
outsnd->pitch = pitch;
dstbuf = (Sint16 *)outsnd->chunk.abuf;
// loop over output buffer. find corresponding input cell, copy over
for (outp = dstbuf; outp < dstbuf + dstlen/2; ++outp)
{
inp = srcbuf + (int)((float)(outp - dstbuf) / dstlen * srclen);
*outp = *inp;
}
return outsnd;
}
// When a sound stops, check if it is still playing. If it is not,
// we can mark the sound data as CACHE to be freed back for other
// means.
static void ReleaseSoundOnChannel(int channel)
{
allocated_sound_t *snd = channels_playing[channel];
Mix_HaltChannel(channel);
if (snd == NULL)
{
return;
}
channels_playing[channel] = NULL;
UnlockAllocatedSound(snd);
// if the sound is a pitch-shift and it's not in use, immediately
// free it
if (snd->pitch != NORM_PITCH && snd->use_count <= 0)
{
FreeAllocatedSound(snd);
}
}
#ifdef HAVE_LIBSAMPLERATE
// Returns the conversion mode for libsamplerate to use.
static int SRC_ConversionMode(void)
{
switch (use_libsamplerate)
{
// 0 = disabled
default:
case 0:
return -1;
// Ascending numbers give higher quality
case 1:
return SRC_LINEAR;
case 2:
return SRC_ZERO_ORDER_HOLD;
case 3:
return SRC_SINC_FASTEST;
case 4:
return SRC_SINC_MEDIUM_QUALITY;
case 5:
return SRC_SINC_BEST_QUALITY;
}
}
// libsamplerate-based generic sound expansion function for any sample rate
// unsigned 8 bits --> signed 16 bits
// mono --> stereo
// samplerate --> mixer_freq
// Returns number of clipped samples.
// DWF 2008-02-10 with cleanups by Simon Howard.
static boolean ExpandSoundData_SRC(sfxinfo_t *sfxinfo,
byte *data,
int samplerate,
int length)
{
SRC_DATA src_data;
float *data_in;
uint32_t i, abuf_index=0, clipped=0;
// uint32_t alen;
int retn;
int16_t *expanded;
allocated_sound_t *snd;
Mix_Chunk *chunk;
src_data.input_frames = length;
data_in = malloc(length * sizeof(float));
src_data.data_in = data_in;
src_data.src_ratio = (double)mixer_freq / samplerate;
// We include some extra space here in case of rounding-up.
src_data.output_frames = src_data.src_ratio * length + (mixer_freq / 4);
src_data.data_out = malloc(src_data.output_frames * sizeof(float));
assert(src_data.data_in != NULL && src_data.data_out != NULL);
// Convert input data to floats
for (i=0; i<length; ++i)
{
// Unclear whether 128 should be interpreted as "zero" or whether a
// symmetrical range should be assumed. The following assumes a
// symmetrical range.
data_in[i] = data[i] / 127.5 - 1;
}
// Do the sound conversion
retn = src_simple(&src_data, SRC_ConversionMode(), 1);
assert(retn == 0);
// Allocate the new chunk.
// alen = src_data.output_frames_gen * 4;
snd = AllocateSound(sfxinfo, src_data.output_frames_gen * 4);
if (snd == NULL)
{
return false;
}
chunk = &snd->chunk;
expanded = (int16_t *) chunk->abuf;
// Convert the result back into 16-bit integers.
for (i=0; i<src_data.output_frames_gen; ++i)
{
// libsamplerate does not limit itself to the -1.0 .. 1.0 range on
// output, so a multiplier less than INT16_MAX (32767) is required
// to avoid overflows or clipping. However, the smaller the
// multiplier, the quieter the sound effects get, and the more you
// have to turn down the music to keep it in balance.
// 22265 is the largest multiplier that can be used to resample all
// of the Vanilla DOOM sound effects to 48 kHz without clipping
// using SRC_SINC_BEST_QUALITY. It is close enough (only slightly
// too conservative) for SRC_SINC_MEDIUM_QUALITY and
// SRC_SINC_FASTEST. PWADs with interestingly different sound
// effects or target rates other than 48 kHz might still result in
// clipping--I don't know if there's a limit to it.
// As the number of clipped samples increases, the signal is
// gradually overtaken by noise, with the loudest parts going first.
// However, a moderate amount of clipping is often tolerated in the
// quest for the loudest possible sound overall. The results of
// using INT16_MAX as the multiplier are not all that bad, but
// artifacts are noticeable during the loudest parts.
float cvtval_f =
src_data.data_out[i] * libsamplerate_scale * INT16_MAX;
int32_t cvtval_i = cvtval_f + (cvtval_f < 0 ? -0.5 : 0.5);
// Asymmetrical sound worries me, so we won't use -32768.
if (cvtval_i < -INT16_MAX)
{
cvtval_i = -INT16_MAX;
++clipped;
}
else if (cvtval_i > INT16_MAX)
{
cvtval_i = INT16_MAX;
++clipped;
}
// Left and right channels
expanded[abuf_index++] = cvtval_i;
expanded[abuf_index++] = cvtval_i;
}
free(data_in);
free(src_data.data_out);
if (clipped > 0)
{
fprintf(stderr, "Sound '%s': clipped %u samples (%0.2f %%)\n",
sfxinfo->name, clipped,
400.0 * clipped / chunk->alen);
}
return true;
}
#endif
static boolean ConvertibleRatio(int freq1, int freq2)
{
int ratio;
if (freq1 > freq2)
{
return ConvertibleRatio(freq2, freq1);
}
else if ((freq2 % freq1) != 0)
{
// Not in a direct ratio
return false;
}
else
{
// Check the ratio is a power of 2
ratio = freq2 / freq1;
while ((ratio & 1) == 0)
{
ratio = ratio >> 1;
}
return ratio == 1;
}
}
#ifdef DEBUG_DUMP_WAVS
// Debug code to dump resampled sound effects to WAV files for analysis.
static void WriteWAV(char *filename, byte *data,
uint32_t length, int samplerate)
{
FILE *wav;
unsigned int i;
unsigned short s;
wav = fopen(filename, "wb");
// Header
fwrite("RIFF", 1, 4, wav);
i = LONG(36 + samplerate);
fwrite(&i, 4, 1, wav);
fwrite("WAVE", 1, 4, wav);
// Subchunk 1
fwrite("fmt ", 1, 4, wav);
i = LONG(16);
fwrite(&i, 4, 1, wav); // Length
s = SHORT(1);
fwrite(&s, 2, 1, wav); // Format (PCM)
s = SHORT(2);
fwrite(&s, 2, 1, wav); // Channels (2=stereo)
i = LONG(samplerate);
fwrite(&i, 4, 1, wav); // Sample rate
i = LONG(samplerate * 2 * 2);
fwrite(&i, 4, 1, wav); // Byte rate (samplerate * stereo * 16 bit)
s = SHORT(2 * 2);
fwrite(&s, 2, 1, wav); // Block align (stereo * 16 bit)
s = SHORT(16);
fwrite(&s, 2, 1, wav); // Bits per sample (16 bit)
// Data subchunk
fwrite("data", 1, 4, wav);
i = LONG(length);
fwrite(&i, 4, 1, wav); // Data length
fwrite(data, 1, length, wav); // Data
fclose(wav);
}
#endif
// Generic sound expansion function for any sample rate.
// Returns number of clipped samples (always 0).
static boolean ExpandSoundData_SDL(sfxinfo_t *sfxinfo,
byte *data,
int samplerate,
int length)
{
SDL_AudioCVT convertor;
allocated_sound_t *snd;
Mix_Chunk *chunk;
uint32_t expanded_length;
// Calculate the length of the expanded version of the sample.
expanded_length = (uint32_t) ((((uint64_t) length) * mixer_freq) / samplerate);
// Double up twice: 8 -> 16 bit and mono -> stereo
expanded_length *= 4;
// Allocate a chunk in which to expand the sound
snd = AllocateSound(sfxinfo, expanded_length);
if (snd == NULL)
{
return false;
}
chunk = &snd->chunk;
// If we can, use the standard / optimized SDL conversion routines.
if (samplerate <= mixer_freq
&& ConvertibleRatio(samplerate, mixer_freq)
&& SDL_BuildAudioCVT(&convertor,
AUDIO_U8, 1, samplerate,
mixer_format, mixer_channels, mixer_freq))
{
convertor.len = length;
convertor.buf = malloc(convertor.len * convertor.len_mult);
assert(convertor.buf != NULL);
memcpy(convertor.buf, data, length);
SDL_ConvertAudio(&convertor);
memcpy(chunk->abuf, convertor.buf, chunk->alen);
free(convertor.buf);
}
else
{
Sint16 *expanded = (Sint16 *) chunk->abuf;
int expanded_length;
int expand_ratio;
int i;
// Generic expansion if conversion does not work:
//
// SDL's audio conversion only works for rate conversions that are
// powers of 2; if the two formats are not in a direct power of 2
// ratio, do this naive conversion instead.
// number of samples in the converted sound
expanded_length = ((uint64_t) length * mixer_freq) / samplerate;
expand_ratio = (length << 8) / expanded_length;
for (i=0; i<expanded_length; ++i)
{
Sint16 sample;
int src;
src = (i * expand_ratio) >> 8;
sample = data[src] | (data[src] << 8);
sample -= 32768;
// expand 8->16 bits, mono->stereo
expanded[i * 2] = expanded[i * 2 + 1] = sample;
}
#ifdef LOW_PASS_FILTER
// Perform a low-pass filter on the upscaled sound to filter
// out high-frequency noise from the conversion process.
{
float rc, dt, alpha;
// Low-pass filter for cutoff frequency f:
//
// For sampling rate r, dt = 1 / r
// rc = 1 / 2*pi*f
// alpha = dt / (rc + dt)
// Filter to the half sample rate of the original sound effect
// (maximum frequency, by nyquist)
dt = 1.0f / mixer_freq;
rc = 1.0f / (3.14f * samplerate);
alpha = dt / (rc + dt);
// Both channels are processed in parallel, hence [i-2]:
for (i=2; i<expanded_length * 2; ++i)
{
expanded[i] = (Sint16) (alpha * expanded[i]
+ (1 - alpha) * expanded[i-2]);
}
}
#endif /* #ifdef LOW_PASS_FILTER */
}
return true;
}
// Load and convert a sound effect
// Returns true if successful
static boolean CacheSFX(sfxinfo_t *sfxinfo)
{
int lumpnum;
unsigned int lumplen;
int samplerate;
unsigned int length;
byte *data;
// need to load the sound
lumpnum = sfxinfo->lumpnum;
data = W_CacheLumpNum(lumpnum, PU_STATIC);
lumplen = W_LumpLength(lumpnum);
// Check the header, and ensure this is a valid sound
if (lumplen < 8
|| data[0] != 0x03 || data[1] != 0x00)
{
// Invalid sound
return false;
}
// 16 bit sample rate field, 32 bit length field
samplerate = (data[3] << 8) | data[2];
length = (data[7] << 24) | (data[6] << 16) | (data[5] << 8) | data[4];
// If the header specifies that the length of the sound is greater than
// the length of the lump itself, this is an invalid sound lump
// We also discard sound lumps that are less than 49 samples long,
// as this is how DMX behaves - although the actual cut-off length
// seems to vary slightly depending on the sample rate. This needs
// further investigation to better understand the correct
// behavior.
if (length > lumplen - 8 || length <= 48)
{
return false;
}
// The DMX sound library seems to skip the first 16 and last 16
// bytes of the lump - reason unknown.
data += 16;
length -= 32;
// Sample rate conversion
if (!ExpandSoundData(sfxinfo, data + 8, samplerate, length))
{
return false;
}
#ifdef DEBUG_DUMP_WAVS
{
char filename[16];
allocated_sound_t * snd;
M_snprintf(filename, sizeof(filename), "%s.wav",
DEH_String(sfxinfo->name));
snd = GetAllocatedSoundBySfxInfoAndPitch(sfxinfo, NORM_PITCH);
WriteWAV(filename, snd->chunk.abuf, snd->chunk.alen,mixer_freq);
}
#endif
// don't need the original lump any more
W_ReleaseLumpNum(lumpnum);
return true;
}
static void GetSfxLumpName(sfxinfo_t *sfx, char *buf, size_t buf_len)
{
// Linked sfx lumps? Get the lump number for the sound linked to.
if (sfx->link != NULL)
{
sfx = sfx->link;
}
// Doom adds a DS* prefix to sound lumps; Heretic and Hexen don't
// do this.
if (use_sfx_prefix)
{
M_snprintf(buf, buf_len, "ds%s", DEH_String(sfx->name));
}
else
{
M_StringCopy(buf, DEH_String(sfx->name), buf_len);
}
}
// Preload all the sound effects - stops nasty ingame freezes
static void I_SDL_PrecacheSounds(sfxinfo_t *sounds, int num_sounds)
{
char namebuf[9];
int i;
printf("I_SDL_PrecacheSounds: Precaching all sound effects..");
for (i=0; i<num_sounds; ++i)
{
if ((i % 6) == 0)
{
printf(".");
fflush(stdout);
}
GetSfxLumpName(&sounds[i], namebuf, sizeof(namebuf));
sounds[i].lumpnum = W_CheckNumForName(namebuf);
if (sounds[i].lumpnum != -1)
{
CacheSFX(&sounds[i]);
}
}
printf("\n");
}
// Load a SFX chunk into memory and ensure that it is locked.
static boolean LockSound(sfxinfo_t *sfxinfo)
{
// If the sound isn't loaded, load it now
if (GetAllocatedSoundBySfxInfoAndPitch(sfxinfo, NORM_PITCH) == NULL)
{
if (!CacheSFX(sfxinfo))
{
return false;
}
}
LockAllocatedSound(GetAllocatedSoundBySfxInfoAndPitch(sfxinfo, NORM_PITCH));
return true;
}
//
// Retrieve the raw data lump index
// for a given SFX name.
//
static int I_SDL_GetSfxLumpNum(sfxinfo_t *sfx)
{
char namebuf[9];
GetSfxLumpName(sfx, namebuf, sizeof(namebuf));
return W_GetNumForName(namebuf);
}
static void I_SDL_UpdateSoundParams(int handle, int vol, int sep)
{
int left, right;
if (!sound_initialized || handle < 0 || handle >= NUM_CHANNELS)
{
return;
}
left = ((254 - sep) * vol) / 127;
right = ((sep) * vol) / 127;
if (left < 0) left = 0;
else if ( left > 255) left = 255;
if (right < 0) right = 0;
else if (right > 255) right = 255;
Mix_SetPanning(handle, left, right);
}
//
// Starting a sound means adding it
// to the current list of active sounds
// in the internal channels.
// As the SFX info struct contains
// e.g. a pointer to the raw data,
// it is ignored.
// As our sound handling does not handle
// priority, it is ignored.
// Pitching (that is, increased speed of playback)
// is set, but currently not used by mixing.
//
static int I_SDL_StartSound(sfxinfo_t *sfxinfo, int channel, int vol, int sep, int pitch)
{
allocated_sound_t *snd;
if (!sound_initialized || channel < 0 || channel >= NUM_CHANNELS)
{
return -1;
}
// Release a sound effect if there is already one playing
// on this channel
ReleaseSoundOnChannel(channel);
// Get the sound data
if (!LockSound(sfxinfo))
{
return -1;
}
snd = GetAllocatedSoundBySfxInfoAndPitch(sfxinfo, pitch);
if (snd == NULL)
{
allocated_sound_t *newsnd;
// fetch the base sound effect, un-pitch-shifted
snd = GetAllocatedSoundBySfxInfoAndPitch(sfxinfo, NORM_PITCH);
if (snd == NULL)
{
return -1;
}
if (snd_pitchshift)
{
newsnd = PitchShift(snd, pitch);
if (newsnd)
{
LockAllocatedSound(newsnd);
UnlockAllocatedSound(snd);
snd = newsnd;
}
}
}
else
{
LockAllocatedSound(snd);
}
// play sound
Mix_PlayChannel(channel, &snd->chunk, 0);
channels_playing[channel] = snd;
// set separation, etc.
I_SDL_UpdateSoundParams(channel, vol, sep);
return channel;
}
static void I_SDL_StopSound(int handle)
{
if (!sound_initialized || handle < 0 || handle >= NUM_CHANNELS)
{
return;
}
// Sound data is no longer needed; release the
// sound data being used for this channel
ReleaseSoundOnChannel(handle);
}
static boolean I_SDL_SoundIsPlaying(int handle)
{
if (!sound_initialized || handle < 0 || handle >= NUM_CHANNELS)
{
return false;
}
return Mix_Playing(handle);
}
//
// Periodically called to update the sound system
//
static void I_SDL_UpdateSound(void)
{
int i;
// Check all channels to see if a sound has finished
for (i=0; i<NUM_CHANNELS; ++i)
{
if (channels_playing[i] && !I_SDL_SoundIsPlaying(i))
{
// Sound has finished playing on this channel,
// but sound data has not been released to cache
ReleaseSoundOnChannel(i);
}
}
}
static void I_SDL_ShutdownSound(void)
{
if (!sound_initialized)
{
return;
}
Mix_CloseAudio();
SDL_QuitSubSystem(SDL_INIT_AUDIO);
sound_initialized = false;
}
// Calculate slice size, based on snd_maxslicetime_ms.
// The result must be a power of two.
static int GetSliceSize(void)
{
int limit;
int n;
limit = (snd_samplerate * snd_maxslicetime_ms) / 1000;
// Try all powers of two, not exceeding the limit.
for (n=0;; ++n)
{
// 2^n <= limit < 2^n+1 ?
if ((1 << (n + 1)) > limit)
{
return (1 << n);
}
}
// Should never happen?
return 1024;
}
static boolean I_SDL_InitSound(boolean _use_sfx_prefix)
{
int i;
use_sfx_prefix = _use_sfx_prefix;
// No sounds yet
for (i=0; i<NUM_CHANNELS; ++i)
{
channels_playing[i] = NULL;
}
if (SDL_Init(SDL_INIT_AUDIO) < 0)
{
fprintf(stderr, "Unable to set up sound.\n");
return false;
}
if (Mix_OpenAudioDevice(snd_samplerate, AUDIO_S16SYS, 2, GetSliceSize(), NULL, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE) < 0)
{
fprintf(stderr, "Error initialising SDL_mixer: %s\n", Mix_GetError());
return false;
}
ExpandSoundData = ExpandSoundData_SDL;
Mix_QuerySpec(&mixer_freq, &mixer_format, &mixer_channels);
#ifdef HAVE_LIBSAMPLERATE
if (use_libsamplerate != 0)
{
if (SRC_ConversionMode() < 0)
{
I_Error("I_SDL_InitSound: Invalid value for use_libsamplerate: %i",
use_libsamplerate);
}
ExpandSoundData = ExpandSoundData_SRC;
}
#else
if (use_libsamplerate != 0)
{
fprintf(stderr, "I_SDL_InitSound: use_libsamplerate=%i, but "
"libsamplerate support not compiled in.\n",
use_libsamplerate);
}
#endif
Mix_AllocateChannels(NUM_CHANNELS);
SDL_PauseAudio(0);
sound_initialized = true;
return true;
}
static snddevice_t sound_sdl_devices[] =
{
SNDDEVICE_SB,
SNDDEVICE_PAS,
SNDDEVICE_GUS,
SNDDEVICE_WAVEBLASTER,
SNDDEVICE_SOUNDCANVAS,
SNDDEVICE_AWE32,
};
sound_module_t sound_sdl_module =
{
sound_sdl_devices,
arrlen(sound_sdl_devices),
I_SDL_InitSound,
I_SDL_ShutdownSound,
I_SDL_GetSfxLumpNum,
I_SDL_UpdateSound,
I_SDL_UpdateSoundParams,
I_SDL_StartSound,
I_SDL_StopSound,
I_SDL_SoundIsPlaying,
I_SDL_PrecacheSounds,
};