Solved bug in border collision when enabling border mask (fixes #68 I…

README.md

@@ -21,8 +21,8 @@ FreeIntv requires two Intellivision BIOS files to be placed in the libretro 'sys
 
 * BIOS filenames are case-sensitive
 
-## Entertainment Computer System and Intellivoice
-FreeIntv does not currently support Entertainment Computer System (ECS) and Intellivoice functionality. Contributions to the code are welcome!
+## Entertainment Computer System
+FreeIntv does not currently support Entertainment Computer System (ECS) functionality. Contributions to the code are welcome!
 
 ## Controller overlays
 Mattel Intellivision games were often meant to be played with game-specific cards overlaid on the numeric keypad. These overlays convey information which can be very useful in gameplay. Images of a limited selection of Intellivision titles are available at: http://www.intellivisionlives.com/bluesky/games/instructions.shtml

src/libretro.c

@@ -156,7 +156,7 @@ void retro_unload_game(void)
 
 void retro_run(void)
 {
-	int i = 0;
+	int c, i, j, k, l;
 	int showKeypad0 = false;
 	int showKeypad1 = false;
 
@@ -291,13 +291,28 @@ void retro_run(void)
 		audioInc = 3733.5 / audioSamples;
         ivoiceInc = 1.0;
 
+        j = 0;
 		for(i=0; i<audioSamples; i++)
 		{
-            int c = (PSGBuffer[(int) audioBufferPos] + ivoiceBuffer[(int) ivoiceBufferPos]) / 2;
+            // Sound interpolator:
+            //   The PSG module generates audio at 224010 hz (3733.5 samples per frame)
+            //   Very high frequencies like 0x0001 would generate chirps on output
+            //   (For example, Lock&Chase) so this code interpolates audio, making
+            //   these silent as in real hardware.
+            audioBufferPos += audioInc;
+            k = audioBufferPos;
+            l = k - j;
+
+            c = 0;
+            while (j < k)
+                c += PSGBuffer[j++];
+            c = c / l;
+            // Finally it adds the Intellivoice output (properly generated at the
+            // same frequency as output)
+            c = (c + ivoiceBuffer[(int) ivoiceBufferPos]) / 2;
 
 			Audio(c, c); // Audio(left, right)
 
-			audioBufferPos += audioInc;
             ivoiceBufferPos += ivoiceInc;
 
             if (ivoiceBufferPos >= ivoiceBufferSize)

src/psg.c

@@ -15,6 +15,7 @@
 	along with FreeIntv.  If not, see http://www.gnu.org/licenses/
 */
 
+#include <stdio.h>
 #include <string.h>
 #include <stdint.h>
 #include "psg.h"
@@ -182,6 +183,11 @@ void PSGInit()
 void PSGFrame()
 {
 	PSGBufferPos = 0;
+ #if 0  // Debugging
+    {
+        fprintf(stderr, "%04x %04x %04x %02x %02x %02x\n", ChA, ChB, ChC, VolA, VolB, VolC);
+    }
+ #endif
 }
 
 int psg_masks[16] = {

src/stic.c

@@ -177,14 +177,14 @@ void drawBorder(int scanline)
 	int color = colors[Memory[0x2C] & 0x0f]; // border color
 
 	if(scanline>=112) { return; }
-    if (scanline == delayV - 1 || scanline == 104) {    // Collision border is 1 pixel thick
+    if (scanline == delayV - 1 || scanline == 104 || extendTop != 0 && scanline >= 7 && scanline < 16) {    // Collision border is 1 pixel thick, or 9 if extendTop is set
         for(i=1 * 2; i < (8 + 160) * 2; i += 2)         // It extends from column -7 to 159
         {
             collBuffer[i] |= cbit;
             collBuffer[i+384] |= cbit;
         }
     } else if (scanline > delayV - 1 && scanline < 104) {   // Left and right side collision border
-        for(i=1 * 2; i < 8 * 2; i += 2)                 // Left side from column -7 to -1
+        for(i=1 * 2; i < 16+(16*extendLeft); i += 2)                 // Left side from column -7 to -1 (or 7 if extendLeft is set)
         {
             collBuffer[i] |= cbit;
             collBuffer[i+384] |= cbit;
@@ -532,7 +532,7 @@ void drawSprites(int scanline) // MOBs
 void STICDrawFrame(int enabled)
 {
 	int row, offset;
-	int i, j;
+	int i;
 
     offset = 0;
     if (enabled == 0) {
@@ -587,11 +587,42 @@ void STICDrawFrame(int enabled)
             for (i = 1 * 2; i < 168 * 2; i += 2) {
                 if (collBuffer[i] == 0)
                     continue;
-                for (j = 0; j < 8; j++) {
-                    if (((collBuffer[i] >> j) & 1) != 0) {
-                        Memory[0x18 + j] |= collBuffer[i] & ~(1 << j);
-                    }
-                }
+                if (collBuffer[i] & 0x01)
+                    Memory[0x18] |= collBuffer[i];
+                if (collBuffer[i] & 0x02)
+                    Memory[0x19] |= collBuffer[i];
+                if (collBuffer[i] & 0x04)
+                    Memory[0x1a] |= collBuffer[i];
+                if (collBuffer[i] & 0x08)
+                    Memory[0x1b] |= collBuffer[i];
+                if (collBuffer[i] & 0x10)
+                    Memory[0x1c] |= collBuffer[i];
+                if (collBuffer[i] & 0x20)
+                    Memory[0x1d] |= collBuffer[i];
+                if (collBuffer[i] & 0x40)
+                    Memory[0x1e] |= collBuffer[i];
+                if (collBuffer[i] & 0x80)
+                    Memory[0x1f] |= collBuffer[i];
+            }
+            for (i = 1 * 2 + 384; i < 168 * 2 + 384; i += 2) {
+                if (collBuffer[i] == 0)
+                    continue;
+                if (collBuffer[i] & 0x01)
+                    Memory[0x18] |= collBuffer[i];
+                if (collBuffer[i] & 0x02)
+                    Memory[0x19] |= collBuffer[i];
+                if (collBuffer[i] & 0x04)
+                    Memory[0x1a] |= collBuffer[i];
+                if (collBuffer[i] & 0x08)
+                    Memory[0x1b] |= collBuffer[i];
+                if (collBuffer[i] & 0x10)
+                    Memory[0x1c] |= collBuffer[i];
+                if (collBuffer[i] & 0x20)
+                    Memory[0x1d] |= collBuffer[i];
+                if (collBuffer[i] & 0x40)
+                    Memory[0x1e] |= collBuffer[i];
+                if (collBuffer[i] & 0x80)
+                    Memory[0x1f] |= collBuffer[i];
             }
             memcpy(&frame[offset], &scanBuffer[0], 352 * sizeof(unsigned int));
             memcpy(&frame[offset + 352], &scanBuffer[384], 352 * sizeof(unsigned int));