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https://github.com/ekeeke/Genesis-Plus-GX.git
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224 lines
7.3 KiB
C
224 lines
7.3 KiB
C
/****************************************************************************
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* gx_audio.c
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*
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* Genesis Plus GX audio support
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*
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* Copyright Eke-Eke (2007-2015), based on original work from Softdev (2006)
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*
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* Redistribution and use of this code or any derivative works are permitted
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* provided that the following conditions are met:
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*
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* - Redistributions may not be sold, nor may they be used in a commercial
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* product or activity.
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*
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* - Redistributions that are modified from the original source must include the
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* complete source code, including the source code for all components used by a
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* binary built from the modified sources. However, as a special exception, the
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* source code distributed need not include anything that is normally distributed
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* (in either source or binary form) with the major components (compiler, kernel,
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* and so on) of the operating system on which the executable runs, unless that
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* component itself accompanies the executable.
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*
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* - Redistributions must reproduce the above copyright notice, this list of
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* conditions and the following disclaimer in the documentation and/or other
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* materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************************/
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#include "shared.h"
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/* Length is dimensionned for at least one frame of emulation */
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#define SOUND_BUFFER_LEN 4096
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/* Number of sound buffers */
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#define SOUND_BUFFER_NUM 3
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/* DMA soundbuffers (required to be 32-bytes aligned) */
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static u8 soundbuffer[SOUND_BUFFER_NUM][SOUND_BUFFER_LEN] ATTRIBUTE_ALIGN(32);
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/* Current work soundbuffer */
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static int bufferIndex;
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static int bufferSize;
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/* Background music */
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static u8 *Bg_music_ogg = NULL;
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static u32 Bg_music_ogg_size = 0;
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/* Frame Sync */
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u32 audioSync;
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static u32 audioWait;
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/***************************************************************************************/
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/* Audio engine */
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/***************************************************************************************/
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/* Audio DMA callback */
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static void ai_callback(void)
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{
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audioWait = 0;
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}
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/* AUDIO engine initialization */
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void gx_audio_Init(void)
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{
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/* Initialize AUDIO processing library (ASNDLIB) */
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/* AUDIO & DSP hardware are initialized */
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/* Default samplerate is set to 48kHz */
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ASND_Init();
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/* Load background music from FAT device */
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char fname[MAXPATHLEN];
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sprintf(fname,"%s/Bg_music.ogg",DEFAULT_PATH);
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FILE *f = fopen(fname,"rb");
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if (f)
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{
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struct stat filestat;
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stat(fname, &filestat);
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Bg_music_ogg_size = filestat.st_size;
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Bg_music_ogg = memalign(32,Bg_music_ogg_size);
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if (Bg_music_ogg)
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{
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fread(Bg_music_ogg,1,Bg_music_ogg_size,f);
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}
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fclose(f);
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}
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}
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/* AUDIO engine shutdown */
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void gx_audio_Shutdown(void)
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{
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PauseOgg(1);
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StopOgg();
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ASND_Pause(1);
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ASND_End();
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if (Bg_music_ogg)
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{
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free(Bg_music_ogg);
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}
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}
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/***
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gx_audio_Update
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This function retrieves samples for the frame then set the next DMA parameters
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Parameters will be taken in account only when current DMA operation is over
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To keep audio & video synchronized, DMA from external memory to audio interface is
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started once by video update function when first frame is ready to be displayed,
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then anytime video mode is changed and emulation resynchronized to video hardware.
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Once started, audio DMA restarts automatically when all samples have been played.
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At that time:
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- if DMA settings have not been updated, previous sound buffer will be played again
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- if DMA settings are updated too fast, one sound buffer frame might be skipped
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Therefore, in order to maintain perfect audio playback without any sound skipping
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or lagging, we need to make sure frame emulation is completed and this function is
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called before previous DMA transfer is finished and after it has been started.
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This is done by synchronizing frame emulation with audio DMA interrupt (which happens
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anytime audio DMA restarts). When video sync is enabled, to keep emulation in sync
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with both video AND audio, an appropriate number of samples is rendered per frame by
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adjusting emulator output samplerate.
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***/
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int gx_audio_Update(int status)
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{
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/* Current available soundbuffer */
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s16 *sb = (s16 *)(soundbuffer[bufferIndex]);
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/* Make sure current audio frame has not already been updated */
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if (status & AUDIO_UPDATE)
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{
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/* Retrieve audio samples (size must be multiple of 32 bytes) */
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bufferSize = audio_update(sb) * 4;
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DCStoreRange((void *)sb, bufferSize);
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/* Mark current audio frame as being updated */
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status &= ~AUDIO_UPDATE;
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}
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/* Wait until previous audio frame is started before pushing current audio frame into DMA */
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if ((status & AUDIO_WAIT) && !audioWait)
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{
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/* Update audio DMA settings for current frame */
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AUDIO_InitDMA((u32)sb, bufferSize);
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/* Next soundbuffer */
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bufferIndex = (bufferIndex + 1) % SOUND_BUFFER_NUM;
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/* Set audio wait flag */
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audioWait = audioSync;
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/* Current audio frame is ready for upcoming DMA */
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status &= ~AUDIO_WAIT;
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}
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return status;
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}
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/***
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gx_audio_Start
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This function restarts the audio engine
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This is called when coming back from Main Menu
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***/
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void gx_audio_Start(void)
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{
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/* shutdown background music */
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PauseOgg(1);
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StopOgg();
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/* shutdown menu audio processing */
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ASND_Pause(1);
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ASND_End();
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AUDIO_StopDMA();
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AUDIO_RegisterDMACallback(NULL);
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DSP_Halt();
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/* DMA Interrupt callback */
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AUDIO_RegisterDMACallback(ai_callback);
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/* emulation is synchronized with audio hardware by default */
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audioSync = AUDIO_WAIT;
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/* reset emulation audio processing */
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memset(soundbuffer, 0, sizeof(soundbuffer));
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audioWait = 0;
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bufferSize = 0;
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bufferIndex = 0;
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}
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/***
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gx_audio_Stop
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This function stops current Audio DMA process
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This is called when going back to Main Menu
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***/
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void gx_audio_Stop(void)
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{
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/* restart menu audio processing */
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DSP_Unhalt();
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ASND_Init();
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ASND_Pause(0);
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/* play background music */
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if (Bg_music_ogg && !Shutdown)
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{
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PauseOgg(0);
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PlayOgg((char *)Bg_music_ogg, Bg_music_ogg_size, 0, OGG_INFINITE_TIME);
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SetVolumeOgg(((int)config.bgm_volume * MAX_VOLUME) / 100);
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}
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}
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