audio: refactor mixer code and delete mixer.c

mixer.c didn't really deserve to be separate anymore, as half of its
contents were unnecessary glue code after recent changes. It also
created a weird split between audio.c and af.c due to the fact that
mixer.c could insert audio filters. With the code being in audio.c
directly, together with other code that unserts filters during runtime,
it will be possible to cleanup this code a bit and make it work like the
video filter code.

As part of this change, make the balance code work like the volume code,
and add an option to back the current balance value. Also, since the
balance semantics are unexpected for most users (panning between the
audio channels, instead of just changing the relative volume), and there
are some other volumes, formally deprecate both the old property and the
new option.

6 files changed, 88 insertions, 33 deletions

diff --git a/player/audio.c b/player/audio.c
index b61e464090..6c53bdf721 100644
--- a/player/audio.c
+++ b/player/audio.c
@@ -31,7 +31,6 @@
 #include "common/common.h"
 #include "osdep/timer.h"
 
-#include "audio/mixer.h"
 #include "audio/audio.h"
 #include "audio/audio_buffer.h"
 #include "audio/decode/dec_audio.h"
@@ -120,6 +119,69 @@ fail:
     mp_notify(mpctx, MP_EVENT_CHANGE_ALL, NULL);
 }
 
+// Called when opts->softvol_volume or opts->softvol_mute were changed.
+void audio_update_volume(struct MPContext *mpctx)
+{
+    struct MPOpts *opts = mpctx->opts;
+    struct ao_chain *ao_c = mpctx->ao_chain;
+    if (!ao_c || ao_c->af->initialized < 1)
+        return;
+
+    float gain = MPMAX(opts->softvol_volume / 100.0, 0);
+    if (opts->softvol_mute == 1)
+        gain = 0.0;
+
+    if (!af_control_any_rev(ao_c->af, AF_CONTROL_SET_VOLUME, &gain)) {
+        if (gain == 1.0)
+            return;
+        MP_VERBOSE(mpctx, "Inserting volume filter.\n");
+        if (!(af_add(ao_c->af, "volume", "softvol", NULL)
+              && af_control_any_rev(ao_c->af, AF_CONTROL_SET_VOLUME, &gain)))
+            MP_ERR(mpctx, "No volume control available.\n");
+    }
+}
+
+/* NOTE: Currently the balance code is seriously buggy: it always changes
+ * the af_pan mapping between the first two input channels and first two
+ * output channels to particular values. These values make sense for an
+ * af_pan instance that was automatically inserted for balance control
+ * only and is otherwise an identity transform, but if the filter was
+ * there for another reason, then ignoring and overriding the original
+ * values is completely wrong.
+ */
+void audio_update_balance(struct MPContext *mpctx)
+{
+    struct MPOpts *opts = mpctx->opts;
+    struct ao_chain *ao_c = mpctx->ao_chain;
+    if (!ao_c || ao_c->af->initialized < 1)
+        return;
+
+    float val = opts->balance;
+
+    if (af_control_any_rev(ao_c->af, AF_CONTROL_SET_PAN_BALANCE, &val))
+        return;
+
+    if (val == 0)
+        return;
+
+    struct af_instance *af_pan_balance;
+    if (!(af_pan_balance = af_add(ao_c->af, "pan", "autopan", NULL))) {
+        MP_ERR(mpctx, "No balance control available.\n");
+        return;
+    }
+
+    /* make all other channels pass through since by default pan blocks all */
+    for (int i = 2; i < AF_NCH; i++) {
+        float level[AF_NCH] = {0};
+        level[i] = 1.f;
+        af_control_ext_t arg_ext = { .ch = i, .arg = level };
+        af_pan_balance->control(af_pan_balance, AF_CONTROL_SET_PAN_LEVEL,
+                                &arg_ext);
+    }
+
+    af_pan_balance->control(af_pan_balance, AF_CONTROL_SET_PAN_BALANCE, &val);
+}
+
 static int recreate_audio_filters(struct MPContext *mpctx)
 {
     assert(mpctx->ao_chain);
@@ -132,7 +194,11 @@ static int recreate_audio_filters(struct MPContext *mpctx)
     if (afs->initialized < 1 && af_init(afs) < 0)
         goto fail;
 
-    mixer_reinit_audio(mpctx->mixer, afs);
+    if (mpctx->opts->softvol == SOFTVOL_NO)
+        MP_ERR(mpctx, "--softvol=no is not supported anymore.\n");
+
+    audio_update_volume(mpctx);
+    audio_update_balance(mpctx);
 
     mp_notify(mpctx, MPV_EVENT_AUDIO_RECONFIG, NULL);
 
@@ -210,7 +276,6 @@ void uninit_audio_out(struct MPContext *mpctx)
         // Note: with gapless_audio, stop_play is not correctly set
         if (mpctx->opts->gapless_audio || mpctx->stop_play == AT_END_OF_FILE)
             ao_drain(mpctx->ao);
-        mixer_uninit_audio(mpctx->mixer);
         ao_uninit(mpctx->ao);
 
         mp_notify(mpctx, MPV_EVENT_AUDIO_RECONFIG, NULL);
@@ -243,7 +308,6 @@ static void ao_chain_uninit(struct ao_chain *ao_c)
 void uninit_audio_chain(struct MPContext *mpctx)
 {
     if (mpctx->ao_chain) {
-        mixer_uninit_audio(mpctx->mixer);
         ao_chain_uninit(mpctx->ao_chain);
         mpctx->ao_chain = NULL;
 
diff --git a/player/command.c b/player/command.c
index a815ae8a1d..d8f4f83529 100644
--- a/player/command.c
+++ b/player/command.c
@@ -54,7 +54,6 @@
 #include "video/decode/vd.h"
 #include "video/out/vo.h"
 #include "video/csputils.h"
-#include "audio/mixer.h"
 #include "audio/audio_buffer.h"
 #include "audio/out/ao.h"
 #include "audio/filter/af.h"
@@ -1561,7 +1560,8 @@ static int mp_property_mixer_active(void *ctx, struct m_property *prop,
                                     int action, void *arg)
 {
     MPContext *mpctx = ctx;
-    return m_property_flag_ro(action, arg, mixer_audio_initialized(mpctx->mixer));
+    struct ao_chain *ao_c = mpctx->ao_chain;
+    return m_property_flag_ro(action, arg, ao_c && ao_c->af->initialized > 0);
 }
 
 /// Volume (RW)
@@ -1590,7 +1590,7 @@ static int mp_property_volume(void *ctx, struct m_property *prop,
 
     int r = mp_property_generic_option(mpctx, prop, action, arg);
     if (action == M_PROPERTY_SET)
-        mixer_update_volume(mpctx->mixer);
+        audio_update_volume(mpctx);
     return r;
 }
 
@@ -1607,7 +1607,7 @@ static int mp_property_mute(void *ctx, struct m_property *prop,
 
     int r = mp_property_generic_option(mpctx, prop, action, arg);
     if (action == M_PROPERTY_SET)
-        mixer_update_volume(mpctx->mixer);
+        audio_update_volume(mpctx);
     return r;
 }
 
@@ -1841,23 +1841,10 @@ static int mp_property_balance(void *ctx, struct m_property *prop,
                                int action, void *arg)
 {
     MPContext *mpctx = ctx;
-    float bal;
 
-    switch (action) {
-    case M_PROPERTY_GET:
-        mixer_getbalance(mpctx->mixer, arg);
-        return M_PROPERTY_OK;
-    case M_PROPERTY_GET_TYPE:
-        *(struct m_option *)arg = (struct m_option){
-            .type = CONF_TYPE_FLOAT,
-            .flags = M_OPT_RANGE,
-            .min = -1,
-            .max = 1,
-        };
-        return M_PROPERTY_OK;
-    case M_PROPERTY_PRINT: {
+    if (action == M_PROPERTY_PRINT) {
         char **str = arg;
-        mixer_getbalance(mpctx->mixer, &bal);
+        float bal = mpctx->opts->balance;
         if (bal == 0.f)
             *str = talloc_strdup(NULL, "center");
         else if (bal == -1.f)
@@ -1871,11 +1858,11 @@ static int mp_property_balance(void *ctx, struct m_property *prop,
         }
         return M_PROPERTY_OK;
     }
-    case M_PROPERTY_SET:
-        mixer_setbalance(mpctx->mixer, *(float *)arg);
-        return M_PROPERTY_OK;
-    }
-    return M_PROPERTY_NOT_IMPLEMENTED;
+
+    int r = mp_property_generic_option(mpctx, prop, action, arg);
+    if (action == M_PROPERTY_SET)
+        audio_update_balance(mpctx);
+    return r;
 }
 
 static struct track* track_next(struct MPContext *mpctx, enum stream_type type,
diff --git a/player/core.h b/player/core.h
index 8afcfbe64d..f2a9f191fa 100644
--- a/player/core.h
+++ b/player/core.h
@@ -287,7 +287,6 @@ typedef struct MPContext {
 
     struct lavfi *lavfi;
 
-    struct mixer *mixer;
     struct ao *ao;
     struct mp_audio *ao_decoder_fmt; // for weak gapless audio check
     struct ao_chain *ao_chain;
@@ -429,6 +428,8 @@ void uninit_audio_out(struct MPContext *mpctx);
 void uninit_audio_chain(struct MPContext *mpctx);
 int init_audio_decoder(struct MPContext *mpctx, struct track *track);
 void reinit_audio_chain_src(struct MPContext *mpctx, struct lavfi_pad *src);
+void audio_update_volume(struct MPContext *mpctx);
+void audio_update_balance(struct MPContext *mpctx);
 
 // configfiles.c
 void mp_parse_cfgfiles(struct MPContext *mpctx);
@@ -558,4 +559,11 @@ int init_video_decoder(struct MPContext *mpctx, struct track *track);
 int get_deinterlacing(struct MPContext *mpctx);
 void set_deinterlacing(struct MPContext *mpctx, bool enable);
 
+// Values of MPOpts.softvol
+enum {
+    SOFTVOL_NO = 0,
+    SOFTVOL_YES = 1,
+    SOFTVOL_AUTO = 2,
+};
+
 #endif /* MPLAYER_MP_CORE_H */
diff --git a/player/loadfile.c b/player/loadfile.c
index 2b88ecfeb0..94d0b2bd5d 100644
--- a/player/loadfile.c
+++ b/player/loadfile.c
@@ -42,7 +42,6 @@
 #include "common/encode.h"
 #include "input/input.h"
 
-#include "audio/mixer.h"
 #include "audio/audio.h"
 #include "audio/audio_buffer.h"
 #include "audio/decode/dec_audio.h"
diff --git a/player/main.c b/player/main.c
index 88b60e1937..78652fe562 100644
--- a/player/main.c
+++ b/player/main.c
@@ -52,7 +52,6 @@
 
 #include "audio/decode/dec_audio.h"
 #include "audio/out/ao.h"
-#include "audio/mixer.h"
 #include "demux/demux.h"
 #include "stream/stream.h"
 #include "sub/osd.h"
@@ -360,7 +359,6 @@ struct MPContext *mp_create(void)
 
     mpctx->input = mp_input_init(mpctx->global);
     screenshot_init(mpctx);
-    mpctx->mixer = mixer_init(mpctx, mpctx->global);
     command_init(mpctx);
     init_libav(mpctx->global);
     mp_clients_init(mpctx);
diff --git a/player/playloop.c b/player/playloop.c
index 0062a30888..fd16c78e68 100644
--- a/player/playloop.c
+++ b/player/playloop.c
@@ -36,7 +36,6 @@
 #include "osdep/terminal.h"
 #include "osdep/timer.h"
 
-#include "audio/mixer.h"
 #include "audio/decode/dec_audio.h"
 #include "audio/filter/af.h"
 #include "audio/out/ao.h"