audio: change how filters are inserted on playback speed changes

Use a pseudo-filter when changing speed with resampling, instead of
somehow changing a samplerate somewhere. This uses the same underlying
mechanism, but is a bit more structured and cleaner. It also makes some
of the following changes easier.

Since we now always use filters to change audio speed, move most of the
work set_playback_speed() does to recreate_audio_filters().

4 files changed, 72 insertions, 1 deletions

diff --git a/audio/decode/dec_audio.c b/audio/decode/dec_audio.c
index 29674f3e0e..8b38b71bc7 100644
--- a/audio/decode/dec_audio.c
+++ b/audio/decode/dec_audio.c
@@ -227,7 +227,6 @@ static int filter_n_bytes(struct dec_audio *da, struct mp_audio_buffer *outbuf,
     // Filter
     struct mp_audio filter_data;
     mp_audio_buffer_peek(da->decode_buffer, &filter_data);
-    filter_data.rate = da->afilter->input.rate; // due to playback speed change
     len = MPMIN(filter_data.samples, len);
     filter_data.samples = len;
     bool eof = error == AD_EOF && filter_data.samples == 0;
diff --git a/audio/filter/af.c b/audio/filter/af.c
index 6a3b4bf0d5..d396a73ce3 100644
--- a/audio/filter/af.c
+++ b/audio/filter/af.c
@@ -53,6 +53,7 @@ extern const struct af_info af_info_center;
 extern const struct af_info af_info_sinesuppress;
 extern const struct af_info af_info_karaoke;
 extern const struct af_info af_info_scaletempo;
+extern const struct af_info af_info_forcespeed;
 extern const struct af_info af_info_bs2b;
 extern const struct af_info af_info_lavfi;
 extern const struct af_info af_info_convert24;
@@ -83,6 +84,7 @@ static const struct af_info *const filter_list[] = {
     &af_info_center,
     &af_info_sinesuppress,
     &af_info_karaoke,
+    &af_info_forcespeed,
     &af_info_scaletempo,
 #if HAVE_LIBBS2B
     &af_info_bs2b,
diff --git a/audio/filter/af.h b/audio/filter/af.h
index b95039b4d0..5c7a6c0e7c 100644
--- a/audio/filter/af.h
+++ b/audio/filter/af.h
@@ -120,6 +120,7 @@ enum af_control {
     AF_CONTROL_SET_PAN_BALANCE,
     AF_CONTROL_GET_PAN_BALANCE,
     AF_CONTROL_SET_PLAYBACK_SPEED,
+    AF_CONTROL_SET_PLAYBACK_SPEED_RESAMPLE,
 };
 
 // Argument for AF_CONTROL_SET_PAN_LEVEL
diff --git a/audio/filter/af_forcespeed.c b/audio/filter/af_forcespeed.c
new file mode 100644
index 0000000000..d2d2f9abb7
--- /dev/null
+++ b/audio/filter/af_forcespeed.c
@@ -0,0 +1,69 @@
+/*
+ * 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 "af.h"
+
+struct priv {
+    double speed;
+};
+
+static int control(struct af_instance *af, int cmd, void *arg)
+{
+    struct priv *priv = af->priv;
+
+    switch (cmd) {
+    case AF_CONTROL_REINIT: {
+        struct mp_audio *in = arg;
+        struct mp_audio orig_in = *in;
+        struct mp_audio *out = af->data;
+
+        mp_audio_copy_config(out, in);
+        out->rate = in->rate * priv->speed;
+
+        return mp_audio_config_equals(in, &orig_in) ? AF_OK : AF_FALSE;
+    }
+    case AF_CONTROL_SET_PLAYBACK_SPEED_RESAMPLE: {
+        priv->speed = *(double *)arg;
+        return AF_OK;
+    }
+    }
+    return AF_UNKNOWN;
+}
+
+static int filter(struct af_instance *af, struct mp_audio *data, int flags)
+{
+    mp_audio_copy_config(data, af->data);
+    return 0;
+}
+
+static int af_open(struct af_instance *af)
+{
+    struct priv *priv = af->priv;
+    af->control = control;
+    af->filter = filter;
+    priv->speed = 1.0;
+    return AF_OK;
+}
+
+#define OPT_BASE_STRUCT struct priv
+
+const struct af_info af_info_forcespeed = {
+    .info = "Force audio speed",
+    .name = "forcespeed",
+    .open = af_open,
+    .priv_size = sizeof(struct priv),
+};