Suppress unnecessary "stop note" commands so the byestream file is smaller

miditones.c

@@ -253,8 +253,13 @@
 * 30 September 2016, Scott Allen, V1.13
 *     - Allow -c channel numbers to be specified as hex or octal
 *     - Add -r to end the file with "repeat" instead of "score end"
+* 30 September 2016, Len Shustek, V1.14
+*     - Prevent unnecessary "note off" commands from being generated by delaying
+*       them until we see if a "note on" is generated before the next wait.
+*       Thanks to Scott Allen for inspiring me to do this. In the best case we've
+*       seen, this makes the bytestream 21% smaller!
 */
-#define VERSION "1.13"
+#define VERSION "1.14"
 
 /*--------------------------------------------------------------------------------------------
 
@@ -381,6 +386,7 @@ unsigned long tempo;            /* current tempo in usec/qnote */
 
 struct tonegen_status {         /* current status of a tone generator */
    bool playing;                /* is it playing? */
+   bool stopnote_pending;       /* do we need to stop this generator before the next wait? */
    int track;                   /* if so, which track is the note from? */
    int note;                    /* what note is playing? */
    int instrument;              /* what instrument? */
@@ -398,7 +404,7 @@ struct track_status {           /* current processing point of a MIDI track */
    unsigned char cmd;           /* CMD_xxxx next to do */
    unsigned char note;          /* for which note */
    unsigned char chan;          /* from which channel it was */
-   unsigned char velocity;
+   unsigned char velocity;      /* the current volume */
    unsigned char last_event;    /* the last event, for MIDI's "running status" */
    bool tonegens[MAX_TONEGENS]; /* which tone generators our notes are playing on */
 } track[MAX_TRACKS] = {
@@ -1003,6 +1009,25 @@ void find_note (int tracknum) {
 }
 
 
+/*  generate "stop note" commands for any channels that have them pending */
+
+void gen_stopnotes(void) {
+    struct tonegen_status *tg;
+    for (int tgnum = 0; tgnum < num_tonegens; ++tgnum) {
+        tg = &tonegen[tgnum];
+        if (tg->stopnote_pending) {
+             if (binaryoutput) {
+                putc (CMD_STOPNOTE | tgnum, outfile);
+                outfile_bytecount += 1;
+             } else {
+                fprintf (outfile, "0x%02X, ", CMD_STOPNOTE | tgnum);
+                outfile_items (1);
+            }
+            tg->stopnote_pending = false;
+        }
+    }
+}
+
 /*********************  main  ****************************/
 
 int main (int argc, char *argv[]) {
@@ -1196,6 +1221,7 @@ This is not unlike multiway merging used for tape sorting algoritms in the 50's!
 
          delta_time = earliest_time - timenow;
          if (delta_time) {
+            gen_stopnotes(); /* first check if any tone generators have "stop note" commands pending */
             /* Convert ticks to milliseconds based on the current tempo */
             unsigned long long temp;
             temp = ((unsigned long long) delta_time * tempo) / ticks_per_beat;
@@ -1240,13 +1266,7 @@ This is not unlike multiway merging used for tape sorting algoritms in the 50's!
                            fprintf (logfile,
                                     "->Stop note %d, generator %d, track %d\n",
                                     tg->note, tgnum, tracknum);
-                        if (binaryoutput) {
+                        tg->stopnote_pending = true;  /* must stop the current note if another doesn't start first */
-                           putc (CMD_STOPNOTE | tgnum, outfile);
-                           outfile_bytecount += 1;
-                        } else {
-                           fprintf (outfile, "0x%02X, ", CMD_STOPNOTE | tgnum);
-                           outfile_items (1);
-                        }
                         tg->playing = false;
                         trk->tonegens[tgnum] = false;
                      }
@@ -1294,6 +1314,7 @@ This is not unlike multiway merging used for tape sorting algoritms in the 50's!
                   tg->playing = true;
                   tg->track = tracknum;
                   tg->note = trk->note;
+                  tg->stopnote_pending = false;
                   trk->tonegens[tgnum] = true;
                   trk->preferred_tonegen = tgnum;
                   ++note_on_commands;
@@ -1359,6 +1380,7 @@ This is not unlike multiway merging used for tape sorting algoritms in the 50's!
       while (tracks_done < num_tracks);
 
       // generate the end-of-score command and some commentary
+      gen_stopnotes(); /* flush out any pending "stop note" commands */
       outfile_bytecount++;
       if (binaryoutput)
          putc (gen_restart ? CMD_RESTART : CMD_STOP, outfile);