options: remove --stereo

Whatever this was supposed to be originally, it doesn't have much value
anymore. It just forced ad_mpg123 to upmix mono to stereo by default
(the audio chain can do that). As an option, it was mostly useless and
misleading, so get rid of it.

DOCS/man/en/options.rst

@@ -1973,13 +1973,6 @@
 
     *NOTE*: without ``--hr-seek``, skipping will snap to keyframes.
 
---stereo=<mode>
-    Select type of MP2/MP3 stereo output.
-
-    :0: stereo
-    :1: left channel
-    :2: right channel
-
 --stop-xscreensaver
     (X11 only)
     Turns off xscreensaver at startup and turns it on again on exit. If your

audio/decode/ad_mpg123.c

@@ -46,10 +46,6 @@ LIBAD_EXTERN(mpg123)
 /* Switch for updating bitrate info of VBR files. Not essential. */
 #define AD_MPG123_MEAN_BITRATE
 
-/* Funny thing, that. I assume I shall use it for selecting mpg123 channels.
- * Please correct me if I guessed wrong. */
-extern int fakemono;
-
 struct ad_mpg123_context {
     mpg123_handle *handle;
 #ifdef AD_MPG123_MEAN_BITRATE
@@ -67,7 +63,7 @@ struct ad_mpg123_context {
  * parameters. */
 static int preinit(sh_audio_t *sh)
 {
-    int err, flag;
+    int err;
     struct ad_mpg123_context *con;
     /* Assumption: You always call preinit + init + uninit, on every file.
      * But you stop at preinit in case it fails.
@@ -83,13 +79,6 @@ static int preinit(sh_audio_t *sh)
     if (!con->handle)
         goto bad_end;
 
-    /* Guessing here: Default value triggers forced upmix of mono to stereo. */
-    flag = fakemono == 0 ? MPG123_FORCE_STEREO :
-           fakemono == 1 ? MPG123_MONO_LEFT    :
-           fakemono == 2 ? MPG123_MONO_RIGHT   : 0;
-    if (mpg123_param(con->handle, MPG123_ADD_FLAGS, flag, 0.0) != MPG123_OK)
-        goto bad_end;
-
     /* Basic settings.
      * Don't spill messages, enable better resync with non-seekable streams.
      * Give both flags individually without error checking to keep going with

audio/decode/dec_audio.c

@@ -39,8 +39,6 @@
 
 #include "audio/filter/af.h"
 
-int fakemono = 0;
-
 struct af_cfg af_cfg = {0}; // Configuration for audio filters
 
 static int init_audio_codec(sh_audio_t *sh_audio, const char *decoder)

core/options.c

@@ -45,9 +45,6 @@ extern char *lirc_configfile;
 extern int mp_msg_color;
 extern int mp_msg_module;
 
-/* from dec_audio, currently used for ac3surround decoder only */
-extern int fakemono;
-
 extern int dvd_speed; /* stream/stream_dvd.c */
 
 /* defined in demux: */
@@ -452,9 +449,6 @@ const m_option_t mp_opts[] = {
 
 // ------------------------- codec/vfilter options --------------------
 
-    // MP3-only: select stereo/left/right
-    {"stereo", &fakemono, CONF_TYPE_INT, CONF_RANGE, 0, 2, NULL},
-
     {"af*", &af_cfg.list, CONF_TYPE_STRING_LIST, 0, 0, 0, NULL},
 
     OPT_SETTINGSLIST("vf*", vf_settings, 0, (void *) &vf_obj_list),