codec: sid: add cRSID-1.0 for 21st century SID playback

Plain import of the library parts first. Adaptions to Rockbox will
follow. A *lot* of kudos go to Mihaly Horvath for creating this library
from his already lightweight cSID-light, mainly for Rockbox. Besides a
lot of other things, he made his algorithms integer-only and
significantly improved the C64 emulation, so finally RSIDs could be
played as well as PSIDs. TinySID was nice for what it is, but this is a
quantum leap in SID playback quality for Rockbox. Check for example:

https://hvsc.csdb.dk/MUSICIANS/P/Page_Jason/Eighth.sid
https://hvsc.csdb.dk/MUSICIANS/J/Jeff/Blowing.sid

Change-Id: I353e12fbfd7cd8696b834616e55743e7b844a73e

1 files changed, 62 insertions, 0 deletions

diff --git a/lib/rbcodec/codecs/cRSID/host/audio.c b/lib/rbcodec/codecs/cRSID/host/audio.c
new file mode 100644
index 0000000000..2e06279113
--- /dev/null
+++ b/lib/rbcodec/codecs/cRSID/host/audio.c
@@ -0,0 +1,62 @@
+
+#ifdef CRSID_PLATFORM_PC
+
+#include <SDL/SDL.h>
+
+
+void cRSID_soundCallback(void* userdata, unsigned char *buf, int len) {
+ cRSID_generateSound( (cRSID_C64instance*)userdata, buf, len );
+}
+
+
+void* cRSID_initSound(cRSID_C64instance* C64, unsigned short samplerate, unsigned short buflen) {
+ static SDL_AudioSpec soundspec;
+ if ( SDL_Init(SDL_INIT_AUDIO) < 0 ) {
+  fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError()); return NULL;
+ }
+ soundspec.freq=samplerate; soundspec.channels=1; soundspec.format=AUDIO_S16;
+ soundspec.samples=buflen; soundspec.userdata=C64; soundspec.callback=cRSID_soundCallback;
+ if ( SDL_OpenAudio(&soundspec, NULL) < 0 ) {
+  fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError()); return NULL;
+ }
+ return (void*)&soundspec;
+}
+
+
+void cRSID_closeSound (void) {
+ SDL_PauseAudio(1); SDL_CloseAudio();
+}
+
+
+void cRSID_startSound (void) {
+ SDL_PauseAudio(0);
+}
+
+
+void cRSID_stopSound (void) {
+ SDL_PauseAudio(1);
+}
+
+
+void cRSID_generateSound(cRSID_C64instance* C64instance, unsigned char *buf, unsigned short len) {
+ static unsigned short i;
+ static int Output;
+ for(i=0;i<len;i+=2) {
+  Output=cRSID_generateSample(C64instance); //cRSID_emulateC64(C64instance);
+  //if (Output>=32767) Output=32767; else if (Output<=-32768) Output=-32768; //saturation logic on overflow
+  buf[i]=Output&0xFF; buf[i+1]=Output>>8;
+ }
+}
+
+
+#endif
+
+
+static inline signed short cRSID_generateSample (cRSID_C64instance* C64) { //call this from custom buffer-filler
+ static int Output;
+ Output=cRSID_emulateC64(C64);
+ if (C64->PSIDdigiMode) Output += cRSID_playPSIDdigi(C64);
+ if (Output>=32767) Output=32767; else if (Output<=-32768) Output=-32768; //saturation logic on overflow
+ return (signed short) Output;
+}
+