1 files changed, 210 insertions, 0 deletions
diff --git a/audio/chmap_sel.c b/audio/chmap_sel.c
new file mode 100644
index 0000000000..8e5be5c86e
--- /dev/null
+++ b/audio/chmap_sel.c
@@ -0,0 +1,210 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+#include <assert.h>
+
+#include "chmap_sel.h"
+
+// 5.1 and 5.1(side) are practically the same. It doesn't make much sense to
+// reject either of them.
+static const int replaceable_speakers[][2] = {
+    {MP_SPEAKER_ID_SL, MP_SPEAKER_ID_BL},
+    {MP_SPEAKER_ID_SR, MP_SPEAKER_ID_BR},
+    {-1},
+};
+
+// list[] contains a list of speaker pairs, with each pair indicating how
+// a speaker can be swapped for another speaker. Try to replace speakers from
+// the left of the list with the ones on the right, or the other way around.
+static bool replace_speakers(struct mp_chmap *map, const int list[][2])
+{
+    if (!mp_chmap_is_valid(map))
+        return false;
+    for (int dir = 0; dir < 2; dir++) {
+        int from = dir ? 0 : 1;
+        int to   = dir ? 1 : 0;
+        bool replaced = false;
+        struct mp_chmap t = *map;
+        for (int n = 0; n < t.num; n++) {
+            for (int i = 0; list[i][0] != -1; i++) {
+                if (t.speaker[n] == list[i][from]) {
+                    t.speaker[n] = list[i][to];
+                    replaced = true;
+                    break;
+                }
+            }
+        }
+        if (replaced && mp_chmap_is_valid(&t)) {
+            *map = t;
+            return true;
+        }
+    }
+    return false;
+}
+
+// Allow all channel layouts that can be expressed with mp_chmap.
+// (By default, all layouts are rejected.)
+void mp_chmap_sel_add_any(struct mp_chmap_sel *s)
+{
+    s->allow_any = true;
+}
+
+// Allow all waveext formats, and force waveext channel order.
+void mp_chmap_sel_add_waveext(struct mp_chmap_sel *s)
+{
+    s->allow_waveext = true;
+}
+
+void mp_chmap_sel_add_alsa_def(struct mp_chmap_sel *s)
+{
+    for (int n = 0; n < MP_NUM_CHANNELS; n++) {
+        struct mp_chmap t;
+        mp_chmap_from_channels_alsa(&t, n);
+        if (t.num)
+            mp_chmap_sel_add_map(s, &t);
+    }
+}
+
+#define ARRAY_LEN(x) (sizeof(x) / sizeof((x)[0]))
+
+// Add a channel map that should be allowed.
+void mp_chmap_sel_add_map(struct mp_chmap_sel *s, const struct mp_chmap *map)
+{
+    assert(s->num_chmaps < ARRAY_LEN(s->chmaps));
+    if (mp_chmap_is_valid(map))
+        s->chmaps[s->num_chmaps++] = *map;
+}
+
+// Allow all waveext formats in default order.
+void mp_chmap_sel_add_waveext_def(struct mp_chmap_sel *s)
+{
+    for (int n = 1; n < MP_NUM_CHANNELS; n++) {
+        struct mp_chmap map;
+        mp_chmap_from_channels(&map, n);
+        mp_chmap_sel_add_map(s, &map);
+    }
+}
+
+// Whitelist a speaker (MP_SPEAKER_ID_...). All layouts that contain whitelisted
+// speakers are allowed.
+void mp_chmap_sel_add_speaker(struct mp_chmap_sel *s, int id)
+{
+    assert(id >= 0 && id < MP_SPEAKER_ID_COUNT);
+    s->speakers[id] = true;
+}
+
+static bool test_speakers(const struct mp_chmap_sel *s, struct mp_chmap *map)
+{
+    for (int n = 0; n < map->num; n++) {
+        if (!s->speakers[map->speaker[n]])
+            return false;
+    }
+    return true;
+}
+
+static bool test_maps(const struct mp_chmap_sel *s, struct mp_chmap *map)
+{
+    for (int n = 0; n < s->num_chmaps; n++) {
+        if (mp_chmap_equals_reordered(&s->chmaps[n], map)) {
+            *map = s->chmaps[n];
+            return true;
+        }
+    }
+    return false;
+}
+
+static bool test_waveext(const struct mp_chmap_sel *s, struct mp_chmap *map)
+{
+    if (s->allow_waveext) {
+        struct mp_chmap t = *map;
+        mp_chmap_reorder_to_waveext(&t);
+        if (mp_chmap_is_waveext(&t)) {
+            *map = t;
+            return true;
+        }
+    }
+    return false;
+}
+
+static bool test_layout(const struct mp_chmap_sel *s, struct mp_chmap *map)
+{
+    if (!mp_chmap_is_valid(map))
+        return false;
+
+    return s->allow_any || test_waveext(s, map) || test_speakers(s, map) ||
+           test_maps(s, map);
+}
+
+// Determine which channel map to use given a source channel map, and various
+// parameters restricting possible choices. If the map doesn't match, select
+// a fallback and set it.
+// If no matching layout is found, a reordered layout may be returned.
+// If that is not possible, a fallback for up/downmixing may be returned.
+// If no choice is possible, set *map to empty.
+bool mp_chmap_sel_adjust(const struct mp_chmap_sel *s, struct mp_chmap *map)
+{
+    if (test_layout(s, map))
+        return true;
+    if (mp_chmap_is_unknown(map)) {
+        struct mp_chmap t = {0};
+        if (mp_chmap_sel_get_def(s, &t, map->num) && test_layout(s, &t)) {
+            *map = t;
+            return true;
+        }
+    }
+    // 5.1 <-> 5.1(side)
+    if (replace_speakers(map, replaceable_speakers) && test_layout(s, map))
+        return true;
+    // Fallback to mono/stereo as last resort
+    if (map->num == 1) {
+        *map = (struct mp_chmap) MP_CHMAP_INIT_MONO;
+    } else if (map->num >= 2) {
+        *map = (struct mp_chmap) MP_CHMAP_INIT_STEREO;
+    }
+    if (test_layout(s, map))
+        return true;
+    *map = (struct mp_chmap) {0};
+    return false;
+}
+
+// Set map to a default layout with num channels. Used for audio APIs that
+// return a channel count as part of format negotiation, but give no
+// information about the channel layout.
+// If the channel count is correct, do nothing and leave *map untouched.
+bool mp_chmap_sel_get_def(const struct mp_chmap_sel *s, struct mp_chmap *map,
+                          int num)
+{
+    if (map->num != num) {
+        *map = (struct mp_chmap) {0};
+        // Set of speakers or waveext might allow it.
+        struct mp_chmap t;
+        mp_chmap_from_channels(&t, num);
+        mp_chmap_reorder_to_waveext(&t);
+        if (test_layout(s, &t)) {
+            *map = t;
+        } else {
+            for (int n = 0; n < s->num_chmaps; n++) {
+                if (s->chmaps[n].num == num) {
+                    *map = s->chmaps[n];
+                    break;
+                }
+            }
+        }
+    }
+    return map->num > 0;
+}