txtp: Allow single groups and loop_mode auto for layers

doc/TXTP.md

@@ -95,7 +95,19 @@ BIK_E1_6A_DialEnd_00000000.audio.multi.bik#3
 
 mode = layers
 ```
-Note that the number of channels is the sum of all layers so three 2ch layers play as a 6ch file (you can manually downmix using mixing commands, described later, since vgmstream can't guess if the result should be stereo or 5.1 audio). If all layers share loop points they are automatically kept.
+
+If all layers share loop points they are automatically kept.
+```
+BGM1a.adx  # loops from 10.0 to 90.0
+BGM1b.adx  # loops from 10.0 to 90.0
+mode = layers
+# resulting file loops from 10.0 to 90.0
+
+# if layers *don't* share loop points this sets a full loop (0..max)
+loop_mode = auto
+```
+
+Note that the number of channels is the sum of all layers so three 2ch layers play as a 6ch file (you can manually downmix using mixing commands, described later, since vgmstream can't guess if the result should be stereo or 5.1 audio).
 
 
 ### Mixed groups
@@ -158,7 +170,7 @@ Examples:
 - `S`: take all files as segments (equivalent to `mode = segments`)
 - `3L2`: layer 2 files starting from file 3
 - `2L3R`: group every 3 files from position 2 as layers
-- `1S1`: segment of one file (useless thus ignored)
+- `1S1`: segment of one file (mostly useless but allowed as internal file may have play config)
 - `1L1`: layer of one file (same)
 - `9999L`: absurd values are ignored
 

src/meta/txtp.c

@@ -266,14 +266,15 @@ static void update_vgmstream_list(VGMSTREAM* vgmstream, txtp_header* txtp, int p
     //;VGM_LOG("TXTP: compact vgmstreams=%i\n", txtp->vgmstream_count);
 }
 
-static int make_group_segment(txtp_header* txtp, int position, int count) {
+static int make_group_segment(txtp_header* txtp, int is_group, int position, int count) {
     VGMSTREAM* vgmstream = NULL;
     segmented_layout_data *data_s = NULL;
     int i, loop_flag = 0;
 
 
-    if (count == 1) { /* nothing to do */
+    /* allowed for actual groups (not final "mode"), otherwise skip to optimize */
-        //;VGM_LOG("TXTP: ignored segments of 1\n");
+    if (!is_group && count == 1) {
+        //;VGM_LOG("TXTP: ignored single group\n");
         return 1;
     }
 
@@ -349,14 +350,15 @@ fail:
     return 0;
 }
 
-static int make_group_layer(txtp_header* txtp, int position, int count) {
+static int make_group_layer(txtp_header* txtp, int is_group, int position, int count) {
     VGMSTREAM* vgmstream = NULL;
     layered_layout_data* data_l = NULL;
     int i;
 
 
-    if (count == 1) { /* nothing to do */
+    /* allowed for actual groups (not final mode), otherwise skip to optimize */
-        //;VGM_LOG("TXTP: ignored layer of 1\n");
+    if (!is_group && count == 1) {
+        //;VGM_LOG("TXTP: ignored single group\n");
         return 1;
     }
 
@@ -392,6 +394,12 @@ static int make_group_layer(txtp_header* txtp, int position, int count) {
         }
     }
 
+    /* loop settings only make sense if this group becomes final vgmstream */
+    if (position == 0 && txtp->vgmstream_count == count) {
+        if (txtp->is_loop_auto && !vgmstream->loop_flag) {
+            vgmstream_force_loop(vgmstream, 1, 0, vgmstream->num_samples);
+        }
+    }
 
     /* set new vgmstream and reorder positions */
     update_vgmstream_list(vgmstream, txtp, position, count);
@@ -404,12 +412,13 @@ fail:
     return 0;
 }
 
-static int make_group_random(txtp_header* txtp, int position, int count, int selected) {
+static int make_group_random(txtp_header* txtp, int is_group, int position, int count, int selected) {
     VGMSTREAM* vgmstream = NULL;
     int i;
 
-    if (count == 1) { /* nothing to do */
+    /* allowed for actual groups (not final mode), otherwise skip to optimize */
-        //;VGM_LOG("TXTP: ignored random of 1\n");
+    if (!is_group && count == 1) {
+        //;VGM_LOG("TXTP: ignored single group\n");
         return 1;
     }
 
@@ -484,15 +493,15 @@ static int parse_groups(txtp_header* txtp) {
             //;VGM_LOG("TXTP: group=%i, count=%i, groups=%i\n", pos, grp->count, groups);
             switch(grp->type) {
                 case TXTP_GROUP_MODE_LAYERED:
-                    if (!make_group_layer(txtp, pos, grp->count))
+                    if (!make_group_layer(txtp, 1, pos, grp->count))
                         goto fail;
                     break;
                 case TXTP_GROUP_MODE_SEGMENTED:
-                    if (!make_group_segment(txtp, pos, grp->count))
+                    if (!make_group_segment(txtp, 1, pos, grp->count))
                         goto fail;
                     break;
                 case TXTP_GROUP_MODE_RANDOM:
-                    if (!make_group_random(txtp, pos, grp->count, grp->selected))
+                    if (!make_group_random(txtp, 1, pos, grp->count, grp->selected))
                         goto fail;
                     break;
                 default:
@@ -506,11 +515,11 @@ static int parse_groups(txtp_header* txtp) {
 
     /* final tweaks (should be integrated with the above?) */
     if (txtp->is_layered) {
-        if (!make_group_layer(txtp, 0, txtp->vgmstream_count))
+        if (!make_group_layer(txtp, 0, 0, txtp->vgmstream_count))
             goto fail;
     }
     if (txtp->is_segmented) {
-        if (!make_group_segment(txtp, 0, txtp->vgmstream_count))
+        if (!make_group_segment(txtp, 0, 0, txtp->vgmstream_count))
             goto fail;
     }
     if (txtp->is_single) {