Add back long sample optimization on sound mixer

1 files changed, 20 insertions, 13 deletions

diff --git a/src/apu.c b/src/apu.c
index d107e1e..d40b2fa 100644
--- a/src/apu.c
+++ b/src/apu.c
@@ -251,23 +251,30 @@ sound_mix(void) {
             }
         }
 
-        for(size_t i = 0; i < AUDIO_BUF_LEN; i++) {
-            // Remember we are using fixed point values.
-            mix_buffer[i] += (0x80 ^ (s8)ch->data[ch->pos >> 12]) * vol;
-            ch->pos += ch->inc;
+        if (ch->pos + ch->inc * AUDIO_BUF_LEN >= ch->length) {
+            for(size_t i = 0; i < AUDIO_BUF_LEN; i++) {
+                // Remember we are using fixed point values.
+                mix_buffer[i] += (0x80 ^ (s8)ch->data[ch->pos >> 12]) * vol;
+                ch->pos += ch->inc;
 
-            if (ch->pos >= ch->length) {
-                // If looping is not active disable the channel.
-                if (ch->loop_length == 0) {
-                    ch->data = NULL;
-                    break;
-                }
+                if (ch->pos >= ch->length) {
+                    // If looping is not active disable the channel.
+                    if (ch->loop_length == 0) {
+                        ch->data = NULL;
+                        break;
+                    }
 
-                // Loop the sample.
-                while (ch->pos >= ch->length) {
-                    ch->pos -= ch->loop_length;
+                    // Loop the sample.
+                    while (ch->pos >= ch->length) {
+                        ch->pos -= ch->loop_length;
+                    }
                 }
             }
+        } else {
+            for(size_t i = 0; i < AUDIO_BUF_LEN; i++) {
+                mix_buffer[i] += (0x80 ^ (s8)ch->data[ch->pos >> 12]) * vol;
+                ch->pos += ch->inc;
+            }
         }
     }