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

2 files changed, 122 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;
+}
+
diff --git a/lib/rbcodec/codecs/cRSID/host/file.c b/lib/rbcodec/codecs/cRSID/host/file.c
new file mode 100644
index 0000000000..c87f37ebb4
--- /dev/null
+++ b/lib/rbcodec/codecs/cRSID/host/file.c
@@ -0,0 +1,60 @@
+
+
+#ifdef CRSID_PLATFORM_PC
+
+int cRSID_loadSIDfile (unsigned char* SIDfileData, char* filename, int maxlen) {
+ static signed short Data;
+ static signed int SizeCnt;
+ static FILE *SIDfile;
+
+ if ( (SIDfile=fopen(filename,"rb")) == NULL ) return CRSID_ERROR_LOAD;
+
+ SizeCnt=0;
+
+ while ( (Data=fgetc(SIDfile)) != EOF ) {
+  if (SizeCnt >= maxlen) return CRSID_ERROR_LOAD;
+  SIDfileData[SizeCnt] = Data; SizeCnt++;
+ }
+
+ fclose(SIDfile);
+ return SizeCnt;
+}
+
+#endif
+
+
+cRSID_SIDheader* cRSID_processSIDfile(cRSID_C64instance* C64, unsigned char* filedata, int filesize) {
+ int i;
+ unsigned short SIDdataOffset;
+ cRSID_SIDheader* SIDheader;
+ static const char MagicStringPSID[]="PSID";
+ //static const char MagicStringRSID[]="RSID";
+
+ C64->SIDheader = SIDheader = (cRSID_SIDheader*) filedata;
+
+ for (i=0x0000; i < 0xA000; ++i) C64->RAMbank[i]=0; //fresh start (maybe some bugged SIDs want 0 at certain RAM-locations)
+ for (i=0xC000; i < 0xD000; ++i) C64->RAMbank[i]=0;
+
+ if ( SIDheader->MagicString[0] != 'P' && SIDheader->MagicString[0] != 'R' ) return NULL;
+ for (i=1; i < (int)(sizeof(MagicStringPSID)-1); ++i) { if (SIDheader->MagicString[i] != MagicStringPSID[i]) return NULL; }
+ C64->RealSIDmode = ( SIDheader->MagicString[0] == 'R' );
+
+ if (SIDheader->LoadAddressH==0 && SIDheader->LoadAddressH==0) { //load-address taken from first 2 bytes of the C64 PRG
+  C64->LoadAddress = (filedata[SIDheader->HeaderSize+1]<<8) + (filedata[SIDheader->HeaderSize+0]);
+  SIDdataOffset = SIDheader->HeaderSize+2;
+ }
+ else { //load-adress taken from SID-header
+  C64->LoadAddress = (SIDheader->LoadAddressH<<8) + (SIDheader->LoadAddressL);
+  SIDdataOffset = SIDheader->HeaderSize;
+ }
+
+ for (i=SIDdataOffset; i<filesize; ++i) C64->RAMbank [ C64->LoadAddress + (i-SIDdataOffset) ] = filedata[i];
+
+ i = C64->LoadAddress + (filesize-SIDdataOffset);
+ C64->EndAddress = (i<0x10000) ? i : 0xFFFF;
+
+ C64->PSIDdigiMode = ( !C64->RealSIDmode && (SIDheader->ModelFormatStandard & 2) );
+
+ return C64->SIDheader;
+}
+