jepler/fruitjam-doom
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

opl: Use SDL_mixer post-mix hook for OPL output.

Browse source 
Using Mix_HookMusic() to generate the OPL output stream works fine if
you only ever play OPL music and don't want to use the normal music
output functionality of SDL_mixer. However, now that it's possible to
use substitute music packs with any music output type, this is no longer
the case. Using Mix_HookMusic() disables normal output from eg. Ogg and
FLAC playback. As an alternative, use the post-mix hook and mix the
output from the OPL emulator there.

Cleanup fix as part of #440.
This commit is contained in:
Simon Howard 2018-10-24 20:03:34 -04:00
parent 00f6a3e75b
commit 3bde136c60
1 changed files with 22 additions and 25 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

47
opl/opl_sdl.c
View file

@ -75,7 +75,7 @@ static int opl_opl3mode;
// Temporary mixing buffer used by the mixing callback.
static int32_t *mix_buffer = NULL;
static uint8_t *mix_buffer = NULL;
// Register number that was written.
@ -155,36 +155,32 @@ static void AdvanceTime(unsigned int nsamples)
// Call the OPL emulator code to fill the specified buffer.
static void FillBuffer(int16_t *buffer, unsigned int nsamples)
static void FillBuffer(uint8_t *buffer, unsigned int nsamples)
{
// This seems like a reasonable assumption. mix_buffer is
// 1 second long, which should always be much longer than the
// SDL mix buffer.
assert(nsamples < mixing_freq);
OPL3_GenerateStream(&opl_chip, buffer, nsamples);
// OPL output is generated into temporary buffer and then mixed
// (to avoid overflows etc.)
OPL3_GenerateStream(&opl_chip, (Bit16s *) mix_buffer, nsamples);
SDL_MixAudioFormat(buffer, mix_buffer, AUDIO_S16SYS, nsamples * 4,
SDL_MIX_MAXVOLUME);
}
// Callback function to fill a new sound buffer:
static void OPL_Mix_Callback(void *udata,
Uint8 *byte_buffer,
int buffer_bytes)
static void OPL_Mix_Callback(void *udata, Uint8 *buffer, int len)
{
int16_t *buffer;
unsigned int buffer_len;
unsigned int filled = 0;
// Buffer length in samples (quadrupled, because of 16-bit and stereo)
buffer = (int16_t *) byte_buffer;
buffer_len = buffer_bytes / 4;
unsigned int filled, buffer_samples;
// Repeatedly call the OPL emulator update function until the buffer is
// full.
filled = 0;
buffer_samples = len / 4;
while (filled < buffer_len)
while (filled < buffer_samples)
{
uint64_t next_callback_time;
uint64_t nsamples;
@ -197,7 +193,7 @@ static void OPL_Mix_Callback(void *udata,
if (opl_sdl_paused || OPL_Queue_IsEmpty(callback_queue))
{
nsamples = buffer_len - filled;
nsamples = buffer_samples - filled;
}
else
{
@ -206,9 +202,9 @@ static void OPL_Mix_Callback(void *udata,
nsamples = (next_callback_time - current_time) * mixing_freq;
nsamples = (nsamples + OPL_SECOND - 1) / OPL_SECOND;
if (nsamples > buffer_len - filled)
if (nsamples > buffer_samples - filled)
{
nsamples = buffer_len - filled;
nsamples = buffer_samples - filled;
}
}
@ -216,7 +212,7 @@ static void OPL_Mix_Callback(void *udata,
// Add emulator output to buffer.
FillBuffer(buffer + filled * 2, nsamples);
FillBuffer(buffer + filled * 4, nsamples);
filled += nsamples;
// Invoke callbacks for this point in time.
@ -340,9 +336,8 @@ static int OPL_SDL_Init(unsigned int port_base)
return 0;
}
// Mix buffer:
mix_buffer = malloc(mixing_freq * sizeof(uint32_t) * 2);
// Mix buffer: four bytes per sample (16 bits * 2 channels):
mix_buffer = malloc(mixing_freq * 4);
// Create the emulator structure:
@ -352,8 +347,10 @@ static int OPL_SDL_Init(unsigned int port_base)
callback_mutex = SDL_CreateMutex();
callback_queue_mutex = SDL_CreateMutex();
// TODO: This should be music callback? or-?
Mix_HookMusic(OPL_Mix_Callback, NULL);
// Set postmix that adds the OPL music. This is deliberately done
// as a postmix and not using Mix_HookMusic() as the latter disables
// normal SDL_mixer music mixing.
Mix_SetPostMix(OPL_Mix_Callback, NULL);
return 1;
}