command: add sub_seek input command

Essentially reuses the sub_step command, and is subject to the same
restrictions.

Seems to behave a bit strange sometimes, but generally works.

DOCS/man/en/input.rst

@@ -226,6 +226,15 @@ List of Input Commands
     ``<skip>`` subtitle events is displayed. ``<skip>`` can be negative to step
     backwards.
 
+``sub_seek <skip>``
+    Seek to the next (skip set to 1) or the previous (skip set to -1) subtitle.
+    This is similar to ``sub_step``, except that it seeks video and audio
+    instead of adjusting the subtitle delay.
+
+    Like with ``sub_step``, this works with external text subtitles only. For
+    embedded text subtitles (like with Matroska), this works only with subtitle
+    events that have already been displayed.
+
 ``osd [<level>]``
     Toggle OSD level. If ``<level>`` is specified, set the OSD mode
     (see ``--osd-level`` for valid values).

mpvcore/command.c

@@ -2211,6 +2211,7 @@ void run_command(MPContext *mpctx, mp_cmd_t *cmd)
     bool auto_osd = cmd->on_osd == MP_ON_OSD_AUTO;
     bool msg_osd = auto_osd || (cmd->on_osd & MP_ON_OSD_MSG);
     bool bar_osd = auto_osd || (cmd->on_osd & MP_ON_OSD_BAR);
+    bool msg_or_nobar_osd = msg_osd && !(auto_osd && opts->osd_bar_visible);
     int osdl = msg_osd ? 1 : OSD_LEVEL_INVISIBLE;
 
     if (!cmd->raw_args) {
@@ -2243,7 +2244,7 @@ void run_command(MPContext *mpctx, mp_cmd_t *cmd)
         }
         if (bar_osd)
             mpctx->add_osd_seek_info |= OSD_SEEK_INFO_BAR;
-        if (msg_osd && !(auto_osd && opts->osd_bar_visible))
+        if (msg_or_nobar_osd)
             mpctx->add_osd_seek_info |= OSD_SEEK_INFO_TEXT;
         break;
     }
@@ -2349,16 +2350,25 @@ void run_command(MPContext *mpctx, mp_cmd_t *cmd)
     }
 
     case MP_CMD_SUB_STEP:
+    case MP_CMD_SUB_SEEK:
         if (mpctx->osd->dec_sub) {
             double a[2];
             a[0] = mpctx->video_pts - mpctx->osd->video_offset + opts->sub_delay;
             a[1] = cmd->args[0].v.i;
             if (sub_control(mpctx->osd->dec_sub, SD_CTRL_SUB_STEP, a) > 0) {
-                opts->sub_delay += a[0];
+                if (cmd->id == MP_CMD_SUB_STEP) {
-
+                    opts->sub_delay += a[0];
-                osd_changed_all(mpctx->osd);
+                    osd_changed_all(mpctx->osd);
-                set_osd_tmsg(mpctx, OSD_MSG_SUB_DELAY, osdl, osd_duration,
+                    set_osd_tmsg(mpctx, OSD_MSG_SUB_DELAY, osdl, osd_duration,
-                             "Sub delay: %d ms", ROUND(opts->sub_delay * 1000));
+                                 "Sub delay: %d ms", ROUND(opts->sub_delay * 1000));
+                } else {
+                    queue_seek(mpctx, MPSEEK_RELATIVE, a[0], 1);
+                    set_osd_function(mpctx, (a[0] > 0) ? OSD_FFW : OSD_REW);
+                    if (bar_osd)
+                        mpctx->add_osd_seek_info |= OSD_SEEK_INFO_BAR;
+                    if (msg_or_nobar_osd)
+                        mpctx->add_osd_seek_info |= OSD_SEEK_INFO_TEXT;
+                }
             }
         }
         break;

mpvcore/input/input.c

@@ -157,6 +157,7 @@ static const mp_cmd_t mp_cmds[] = {
                       {"force", 1},             {"1", 1})),
   }},
   { MP_CMD_SUB_STEP, "sub_step", { ARG_INT } },
+  { MP_CMD_SUB_SEEK, "sub_seek", { ARG_INT } },
   { MP_CMD_OSD, "osd", { OARG_INT(-1) } },
   { MP_CMD_PRINT_TEXT, "print_text", { ARG_STRING } },
   { MP_CMD_SHOW_TEXT, "show_text", { ARG_STRING, OARG_INT(-1), OARG_INT(0) } },

mpvcore/input/input.h

@@ -43,6 +43,7 @@ enum mp_command_type {
     MP_CMD_PLAYLIST_REMOVE,
     MP_CMD_PLAYLIST_MOVE,
     MP_CMD_SUB_STEP,
+    MP_CMD_SUB_SEEK,
     MP_CMD_TV_SET_CHANNEL,
     MP_CMD_TV_LAST_CHANNEL,
     MP_CMD_TV_SET_FREQ,