options: turn --idx, --forceidx into --index

Also clarify the semantics.

It seems --idx didn't do anything. Possibly it used to change how the
now removed legacy demuxers like demux_avi used to behave. Or maybe
it was accidental.

--forceidx basically becomes --index=force. It's possible that new
index modes will be added in the future, so I'm keeping it
extensible, instead of e.g. creating --force-index.

DOCS/man/en/changes.rst

@@ -158,11 +158,13 @@ Command Line Switches
     ``-endpos``                 ``--length``
     ``-font``                   ``--osd-font``
     ``-forcedsubsonly``         ``--sub-forced-only``
+    ``-forceidx``               ``--index``
     ``-format``                 ``--audio-format``
     ``-fsmode-dontuse``         (removed)
     ``-fstype``                 ``--x11-netwm`` (changed semantics)
     ``-hardframedrop``          ``--framedrop=hard``
     ``-identify``               (removed; use TOOLS/mpv_identify.sh)
+    ``-idx``                    ``--index``
     ``-lavdopts ...``           ``--vd-lavc-...``
     ``-lavfdopts``              ``--demuxer-lavf-...``
     ``-lircconf``               ``--input-lirc-conf``

DOCS/man/en/options.rst

@@ -826,15 +826,6 @@ OPTIONS
     Display only forced subtitles for the DVD subtitle stream selected by e.g.
     ``--slang``.
 
-``--forceidx``
-    Force index rebuilding. Useful for files with broken index (A/V desync,
-    etc). This will enable seeking in files where seeking was not possible.
-
-    .. note::
-
-        This option only works if the underlying media supports seeking
-        (i.e. not with stdin, pipe, etc).
-
 ``--fps=<float>``
     Override video framerate. Useful if the original value is wrong or missing.
 
@@ -1129,11 +1120,13 @@ OPTIONS
     Mostly useful in slave mode, where mpv can be controlled through input
     commands (see also ``--slave-broken``).
 
-``--idx``
-    Rebuilds index of files if no index was found, allowing seeking. Useful
-    with broken/incomplete downloads or badly created files. Now this is done
-    automatically by the demuxers used for most video formats, meaning that
-    this switch has no effect in the typical case. See also ``--forceidx``.
+``--index=<mode>``
+    Controls how to seek in files. Note that if the index is missing from a
+    file, it will be built on the fly by default, so you don't need to change
+    this. But it might help with some broken files.
+
+    :default:   use an index if the file has one, or build it if missing
+    :recreate:  don't read or use the file's index
 
     .. note::
 

demux/demux_lavf.c

@@ -641,7 +641,7 @@ static int demux_open_lavf(demuxer_t *demuxer, enum demux_check check)
         parse_cryptokey(avfc, lavfdopts->cryptokey);
     if (lavfdopts->genptsmode)
         avfc->flags |= AVFMT_FLAG_GENPTS;
-    if (opts->index_mode == 0)
+    if (opts->index_mode != 1)
         avfc->flags |= AVFMT_FLAG_IGNIDX;
 
 #if LIBAVFORMAT_VERSION_MICRO >= 100

demux/demux_mkv.c

@@ -690,7 +690,7 @@ static int demux_mkv_read_cues(demuxer_t *demuxer)
 
     mkv_d->deferred_cues = 0;
 
-    if (opts->index_mode == 0 || opts->index_mode == 2) {
+    if (opts->index_mode != 1) {
         ebml_read_skip(demuxer->log, -1, s);
         return 0;
     }

options/m_config.c

@@ -981,5 +981,7 @@ static const char *const replaced_opts =
     "|autosub#--sub-auto"
     "|native-fs#--fs-missioncontrol"
     "|status-msg#--term-status-msg"
+    "|idx#--index"
+    "|forceidx#--index"
     "|"
 ;

options/options.c

@@ -186,9 +186,7 @@ const m_option_t mp_opts[] = {
     OPT_FLAG("pause", pause, M_OPT_FIXED),
     OPT_FLAG("keep-open", keep_open, 0),
 
-    // AVI and Ogg only: (re)build index at startup
-    OPT_FLAG_CONSTANTS("idx", index_mode, 0, -1, 1),
-    OPT_FLAG_STORE("forceidx", index_mode, 0, 2),
+    OPT_CHOICE("index", index_mode, 0, ({"default", 1}, {"recreate", 0})),
 
     // select audio/video/subtitle stream
     OPT_TRACKCHOICE("aid", audio_id),
@@ -628,7 +626,7 @@ const struct MPOpts mp_default_opts = {
 
     .hwdec_codecs = "h264,vc1,wmv3",
 
-    .index_mode = -1,
+    .index_mode = 1,
 
     .dvd_angle = 1,
 

options/options.h

@@ -189,7 +189,7 @@ typedef struct MPOpts {
     char *screenshot_template;
 
     double force_fps;
-    int index_mode; // -1=untouched  0=don't use index  1=use (generate) index
+    int index_mode;
 
     struct mp_chmap audio_output_channels;
     int audio_output_format;