add pitch-shifting feature

Uses resampling in tandem with a time-stretching audio filter to
change the audio's pitch while leaving its tempo intact.

Curly braces have been repurposed to increase/decrease the pitch,
and backspace will now reset the pitch and speed simultaneously.

DOCS/man/options.rst

@@ -216,6 +216,11 @@ Playback Control
     speed higher than normal automatically inserts the ``scaletempo2`` audio
     filter.
 
+``--pitch=<0.01-100>``
+    Raise or lower the audio's pitch by the factor given as parameter. Does not
+    affect playback speed. Playing with an altered pitch automatically inserts
+    the ``scaletempo2`` audio filter.
+
 ``--pause``
     Start the player in paused state.
 

etc/input.conf

@@ -70,9 +70,9 @@
 #Shift+PGDWN seek -600                  # seek 10 minutes backward
 #[ multiply speed 1/1.1                 # decrease the playback speed
 #] multiply speed 1.1                   # increase the playback speed
-#{ multiply speed 0.5                   # halve the playback speed
-#} multiply speed 2.0                   # double the playback speed
-#BS set speed 1.0                       # reset the speed to normal
+#{ multiply pitch 1/1.1                 # decrease the playback pitch
+#} multiply pitch 1.1                   # increase the playback pitch
+#BS set pitch 1.0 ; set speed 1.0       # reset the pitch & speed to normal
 #Shift+BS revert-seek                   # undo the previous (or marked) seek
 #Shift+Ctrl+BS revert-seek mark         # mark the position for revert-seek
 #q quit

etc/mplayer-input.conf

@@ -19,9 +19,9 @@ SHARP cycle audio           # switch audio streams
 - add audio-delay -0.100
 [ multiply speed 0.9091	# scale playback speed
 ] multiply speed 1.1
-{ multiply speed 0.5
-} multiply speed 2.0
-BS set speed 1.0	# reset speed to normal
+{ multiply pitch 0.9091	# scale playback pitch
+} multiply pitch 1.1
+BS set pitch 1.0 ; set speed 1.0	# reset pitch & speed to normal
 q quit
 ESC quit
 ENTER playlist-next force       # skip to next file

options/options.c

@@ -560,6 +560,7 @@ static const m_option_t mp_opts[] = {
     {"audio-channels", OPT_CHANNELS(audio_output_channels), .flags = UPDATE_AUDIO},
     {"audio-format", OPT_AUDIOFORMAT(audio_output_format), .flags = UPDATE_AUDIO},
     {"speed", OPT_DOUBLE(playback_speed), M_RANGE(0.01, 100.0)},
+    {"pitch", OPT_DOUBLE(playback_pitch), M_RANGE(0.01, 100.0)},
 
     {"audio-pitch-correction", OPT_BOOL(pitch_correction)},
 
@@ -1032,6 +1033,7 @@ static const struct MPOpts mp_default_opts = {
     .audio_display = 1,
     .audio_output_format = 0,  // AF_FORMAT_UNKNOWN
     .playback_speed = 1.,
+    .playback_pitch = 1.,
     .pitch_correction = true,
     .audiofile_auto = -1,
     .coverart_whitelist = true,

options/options.h

@@ -292,6 +292,7 @@ typedef struct MPOpts {
     int audio_output_format;
     int force_srate;
     double playback_speed;
+    double playback_pitch;
     bool pitch_correction;
     struct m_obj_settings *vf_settings, *vf_defs;
     struct m_obj_settings *af_settings, *af_defs;

player/audio.c

@@ -55,14 +55,16 @@ static void update_speed_filters(struct MPContext *mpctx)
         return;
 
     double speed = mpctx->opts->playback_speed;
-    double resample = mpctx->speed_factor_a;
+    double resample = mpctx->speed_factor_a * mpctx->opts->playback_pitch;
     double drop = 1.0;
 
     if (!mpctx->opts->pitch_correction) {
         resample *= speed;
         speed = 1.0;
     }
 
+    speed /= mpctx->opts->playback_pitch;
+
     if (mpctx->display_sync_active) {
         switch (mpctx->video_out->opts->video_sync) {
             case VS_DISP_ADROP:

player/command.c

@@ -404,6 +404,19 @@ static int mp_property_playback_speed(void *ctx, struct m_property *prop,
     return mp_property_generic_option(mpctx, prop, action, arg);
 }
 
+/// Playback pitch (RW)
+static int mp_property_playback_pitch(void *ctx, struct m_property *prop,
+                                      int action, void *arg)
+{
+    MPContext *mpctx = ctx;
+    if (action == M_PROPERTY_PRINT) {
+        double pitch = mpctx->opts->playback_pitch;
+        *(char **)arg = talloc_asprintf(NULL, "%.2f", pitch);
+        return M_PROPERTY_OK;
+    }
+    return mp_property_generic_option(mpctx, prop, action, arg);
+}
+
 static int mp_property_av_speed_correction(void *ctx, struct m_property *prop,
                                            int action, void *arg)
 {
@@ -3746,6 +3759,7 @@ static const struct m_property mp_properties_base[] = {
     // General
     {"pid", mp_property_pid},
     {"speed", mp_property_playback_speed},
+    {"pitch", mp_property_playback_pitch},
     {"audio-speed-correction", mp_property_av_speed_correction, .priv = "a"},
     {"video-speed-correction", mp_property_av_speed_correction, .priv = "v"},
     {"display-sync-active", mp_property_display_sync_active},
@@ -4158,6 +4172,7 @@ static const struct property_osd_display {
      .seek_bar = OSD_SEEK_INFO_BAR},
     {"hr-seek", "hr-seek"},
     {"speed", "Speed"},
+    {"pitch", "Pitch"},
     {"clock", "Clock"},
     {"edition", "Edition"},
     // audio
@@ -6895,7 +6910,8 @@ void mp_option_change_callback(void *ctx, struct m_config_option *co, int flags,
             vo_control(mpctx->video_out, VOCTRL_EXTERNAL_RESIZE, NULL);
     }
 
-    if (opt_ptr == &opts->playback_speed) {
+    if (opt_ptr == &opts->playback_speed ||
+        opt_ptr == &opts->playback_pitch) {
         update_playback_speed(mpctx);
         mp_wakeup_core(mpctx);
     }