1 files changed, 114 insertions, 0 deletions
diff --git a/audio/filter/af_drop.c b/audio/filter/af_drop.c
new file mode 100644
index 0000000000..499389dd2b
--- /dev/null
+++ b/audio/filter/af_drop.c
@@ -0,0 +1,114 @@
+#include "audio/aframe.h"
+#include "audio/format.h"
+#include "common/common.h"
+#include "filters/f_autoconvert.h"
+#include "filters/filter_internal.h"
+#include "filters/user_filters.h"
+
+struct priv {
+    double speed;
+    double diff; // amount of too many additional samples in normal speed
+    struct mp_aframe *last; // for repeating
+};
+
+static void af_drop_process(struct mp_filter *f)
+{
+    struct priv *p = f->priv;
+
+    if (!mp_pin_in_needs_data(f->ppins[1]))
+        return;
+
+    struct mp_frame frame = {0};
+
+    double last_dur = p->last ? mp_aframe_duration(p->last) : 0;
+    if (p->last && p->diff < 0 && -p->diff > last_dur / 2) {
+        MP_VERBOSE(f, "repeat\n");
+        frame = MAKE_FRAME(MP_FRAME_AUDIO, p->last);
+        p->last = NULL;
+    } else {
+        frame = mp_pin_out_read(f->ppins[0]);
+
+        if (frame.type == MP_FRAME_AUDIO) {
+            last_dur = mp_aframe_duration(frame.data);
+            p->diff -= last_dur;
+            if (p->diff > last_dur / 2) {
+                MP_VERBOSE(f, "drop\n");
+                mp_frame_unref(&frame);
+                mp_filter_internal_mark_progress(f);
+            }
+        }
+    }
+
+    if (frame.type == MP_FRAME_AUDIO) {
+        struct mp_aframe *fr = frame.data;
+        talloc_free(p->last);
+        p->last = mp_aframe_new_ref(fr);
+        mp_aframe_mul_speed(fr, p->speed);
+        p->diff += mp_aframe_duration(fr);
+        mp_aframe_set_pts(p->last, mp_aframe_end_pts(fr));
+    } else if (frame.type == MP_FRAME_EOF) {
+        TA_FREEP(&p->last);
+    }
+    mp_pin_in_write(f->ppins[1], frame);
+}
+
+static bool af_drop_command(struct mp_filter *f, struct mp_filter_command *cmd)
+{
+    struct priv *p = f->priv;
+
+    switch (cmd->type) {
+    case MP_FILTER_COMMAND_SET_SPEED:
+        p->speed = cmd->speed;
+        return true;
+    }
+
+    return false;
+}
+
+static void af_drop_reset(struct mp_filter *f)
+{
+    struct priv *p = f->priv;
+
+    TA_FREEP(&p->last);
+    p->diff = 0;
+}
+
+static void af_drop_destroy(struct mp_filter *f)
+{
+    af_drop_reset(f);
+}
+
+static const struct mp_filter_info af_drop_filter = {
+    .name = "drop",
+    .priv_size = sizeof(struct priv),
+    .process = af_drop_process,
+    .command = af_drop_command,
+    .reset = af_drop_reset,
+    .destroy = af_drop_destroy,
+};
+
+static struct mp_filter *af_drop_create(struct mp_filter *parent, void *options)
+{
+    struct mp_filter *f = mp_filter_create(parent, &af_drop_filter);
+    if (!f) {
+        talloc_free(options);
+        return NULL;
+    }
+
+    mp_filter_add_pin(f, MP_PIN_IN, "in");
+    mp_filter_add_pin(f, MP_PIN_OUT, "out");
+
+    struct priv *p = f->priv;
+    p->speed = 1.0;
+
+    return f;
+}
+
+const struct mp_user_filter_entry af_drop = {
+    .desc = {
+        .description = "Change audio speed by dropping/repeating frames",
+        .name = "drop",
+        .priv_size = sizeof(struct priv),
+    },
+    .create = af_drop_create,
+};