core: allow changing filter filters at runtime

Add the "vf" command, which allows changing the video filter chain at
runtime. For example, the 'y' key could be bound to toggle deinterlacing
by adding 'y vf toggle yadif' to the input.conf.

Reconfiguring the video filter chain normally resets the VO, so that it
will be "stuck" until a new video frame is rendered. To mitigate this, a
seek to the current position is issued when the filter chain is changed.
This is done only if playback is paused, because normal playback will
show an actual new frame quickly enough.

If vdpau hardware decoding is used, filter insertion (whether it fails
or not) will break the video for a while. This is because vo_vdpau
resets decoding related things on vo_config().

7 files changed, 112 insertions, 12 deletions

diff --git a/DOCS/man/en/input.rst b/DOCS/man/en/input.rst
index bd62e65cd6..4acba49169 100644
--- a/DOCS/man/en/input.rst
+++ b/DOCS/man/en/input.rst
@@ -236,6 +236,37 @@ af_clr
     Remove all audio filters. (Conversion filters will be re-added
     automatically if needed.)
 
+vf set|add|toggle|del "filter1=params,filter2,..."
+    Change video filter chain.
+
+    The first argument decides what happens:
+
+    set
+        Overwrite the previous filter chain with the new one.
+
+    add
+        Append the new filter chain to the previous one.
+
+    toggle
+        Check if the given filter (with the exact parameters) is already
+        in the video chain. If yes, remove the filter. If no, add the filter.
+        (If several filters are passed to the command, this is done for
+        each filter.)
+
+    del
+        Remove the given filters from the video chain. Unlike in the other
+        cases, the second parameter is a comma separated list of filter names
+        or integer indexes. ``0`` would denote the first filter. Negative
+        indexes start from the last filter, and ``-1`` denotes the last
+        filter.
+
+    *EXAMPLE for input.conf*:
+
+    - ``a vf set flip`` turn video upside-down on the ``a`` key
+    - ``b vf set ""`` remove all video filters on ``b``
+    - ``c vf toggle lavfi=gradfun`` toggle debanding on ``c``
+
+
 Undocumented commands: tv_start_scan, tv_step_channel, tv_step_norm,
 tv_step_chanlist, tv_set_channel, tv_last_channel, tv_set_freq, tv_step_freq,
 tv_set_norm, dvb_set_channel, radio_step_channel, radio_set_channel,
diff --git a/core/command.c b/core/command.c
index ebc8d93485..9e16804e8a 100644
--- a/core/command.c
+++ b/core/command.c
@@ -1775,6 +1775,42 @@ static void show_playlist_on_osd(MPContext *mpctx)
     talloc_free(res);
 }
 
+static void change_video_filters(MPContext *mpctx, const char *cmd,
+                                 const char *arg)
+{
+    struct MPOpts *opts = &mpctx->opts;
+    struct m_config *conf = mpctx->mconfig;
+    struct m_obj_settings *old_vf_settings = NULL;
+    bool success = false;
+    bool need_refresh = false;
+    double refresh_pts = mpctx->last_vo_pts;
+
+    // The option parser is used to modify the filter list itself.
+    char optname[20];
+    snprintf(optname, sizeof(optname), "vf-%s", cmd);
+    const struct m_option *type = m_config_get_option(conf, bstr0(optname));
+
+    // Backup old settings, in case it fails
+    m_option_copy(type, &old_vf_settings, &opts->vf_settings);
+
+    if (m_config_set_option0(conf, optname, arg) >= 0) {
+        need_refresh = true;
+        success = reinit_video_filters(mpctx) >= 0;
+    }
+
+    if (!success) {
+        m_option_copy(type, &opts->vf_settings, &old_vf_settings);
+        if (need_refresh)
+            reinit_video_filters(mpctx);
+    }
+    m_option_free(type, &old_vf_settings);
+
+    // Try to refresh the video by doing a precise seek to the currently
+    // displayed frame.
+    if (need_refresh && opts->pause)
+        queue_seek(mpctx, MPSEEK_ABSOLUTE, refresh_pts, 1);
+}
+
 void run_command(MPContext *mpctx, mp_cmd_t *cmd)
 {
     struct MPOpts *opts = &mpctx->opts;
@@ -2289,6 +2325,7 @@ void run_command(MPContext *mpctx, mp_cmd_t *cmd)
             af_uninit(mpctx->mixer.afilter);
             af_init(mpctx->mixer.afilter);
         }
+        /* fallthrough */
     case MP_CMD_AF_ADD:
     case MP_CMD_AF_DEL: {
         if (!sh_audio)
@@ -2331,6 +2368,9 @@ void run_command(MPContext *mpctx, mp_cmd_t *cmd)
             af_reinit(sh_audio->afilter);
         }
         break;
+    case MP_CMD_VF:
+        change_video_filters(mpctx, cmd->args[0].v.s, cmd->args[1].v.s);
+        break;
     case MP_CMD_SHOW_CHAPTERS:
         show_chapters_on_osd(mpctx);
         break;
diff --git a/core/input/input.c b/core/input/input.c
index 7ba6b64cdc..116e963b93 100644
--- a/core/input/input.c
+++ b/core/input/input.c
@@ -198,6 +198,8 @@ static const mp_cmd_t mp_cmds[] = {
   { MP_CMD_AF_CLR, "af_clr", },
   { MP_CMD_AF_CMDLINE, "af_cmdline", { ARG_STRING, ARG_STRING } },
 
+  { MP_CMD_VF, "vf", { ARG_STRING, ARG_STRING } },
+
   { MP_CMD_SHOW_CHAPTERS, "show_chapters", },
   { MP_CMD_SHOW_TRACKS, "show_tracks", },
   { MP_CMD_SHOW_PLAYLIST, "show_playlist", },
diff --git a/core/input/input.h b/core/input/input.h
index 367abedfca..12823dd004 100644
--- a/core/input/input.h
+++ b/core/input/input.h
@@ -78,6 +78,9 @@ enum mp_command_type {
     MP_CMD_AF_CLR,
     MP_CMD_AF_CMDLINE,
 
+    /// Video filter commands
+    MP_CMD_VF,
+
     MP_CMD_SHOW_CHAPTERS,
     MP_CMD_SHOW_TRACKS,
     MP_CMD_SHOW_PLAYLIST,
diff --git a/core/mp_core.h b/core/mp_core.h
index 941396c48a..ce576273b4 100644
--- a/core/mp_core.h
+++ b/core/mp_core.h
@@ -298,6 +298,7 @@ double playing_audio_pts(struct MPContext *mpctx);
 struct track *mp_add_subtitles(struct MPContext *mpctx, char *filename,
                                float fps, int noerr);
 int reinit_video_chain(struct MPContext *mpctx);
+int reinit_video_filters(struct MPContext *mpctx);
 void pause_player(struct MPContext *mpctx);
 void unpause_player(struct MPContext *mpctx);
 void add_step_frame(struct MPContext *mpctx, int dir);
diff --git a/core/mplayer.c b/core/mplayer.c
index ac597beac1..a0b18cab62 100644
--- a/core/mplayer.c
+++ b/core/mplayer.c
@@ -2466,6 +2466,39 @@ static void update_fps(struct MPContext *mpctx)
 #endif
 }
 
+static void recreate_video_filters(struct MPContext *mpctx)
+{
+    struct MPOpts *opts = &mpctx->opts;
+    struct sh_video *sh_video = mpctx->sh_video;
+    assert(sh_video);
+
+    vf_uninit_filter_chain(sh_video->vfilter);
+
+    char *vf_arg[] = {
+        "_oldargs_", (char *)mpctx->video_out, NULL
+    };
+    sh_video->vfilter = vf_open_filter(opts, NULL, "vo", vf_arg);
+
+    sh_video->vfilter = append_filters(sh_video->vfilter, opts->vf_settings);
+
+    struct vf_instance *vf = sh_video->vfilter;
+    mpctx->osd->render_subs_in_filter
+        = vf->control(vf, VFCTRL_INIT_OSD, NULL) == VO_TRUE;
+}
+
+int reinit_video_filters(struct MPContext *mpctx)
+{
+    struct sh_video *sh_video = mpctx->sh_video;
+
+    if (!sh_video)
+        return -2;
+
+    recreate_video_filters(mpctx);
+    video_reinit_vo(sh_video);
+
+    return sh_video->vf_initialized > 0 ? 0 : -1;
+}
+
 int reinit_video_chain(struct MPContext *mpctx)
 {
     struct MPOpts *opts = &mpctx->opts;
@@ -2518,18 +2551,7 @@ int reinit_video_chain(struct MPContext *mpctx)
                        STREAM_CTRL_GET_ASPECT_RATIO, &ar) != STREAM_UNSUPPORTED)
         mpctx->sh_video->stream_aspect = ar;
 
-    {
-        char *vf_arg[] = {
-            "_oldargs_", (char *)mpctx->video_out, NULL
-        };
-        sh_video->vfilter = vf_open_filter(opts, NULL, "vo", vf_arg);
-    }
-
-    sh_video->vfilter = append_filters(sh_video->vfilter, opts->vf_settings);
-
-    struct vf_instance *vf = sh_video->vfilter;
-    mpctx->osd->render_subs_in_filter
-        = vf->control(vf, VFCTRL_INIT_OSD, NULL) == VO_TRUE;
+    recreate_video_filters(mpctx);
 
     init_best_video_codec(sh_video, opts->video_decoders);
 
diff --git a/video/decode/dec_video.c b/video/decode/dec_video.c
index 1dd83db8bd..5e55e78220 100644
--- a/video/decode/dec_video.c
+++ b/video/decode/dec_video.c
@@ -184,6 +184,7 @@ void uninit_video(sh_video_t *sh_video)
     mp_tmsg(MSGT_DECVIDEO, MSGL_V, "Uninit video.\n");
     sh_video->vd_driver->uninit(sh_video);
     vf_uninit_filter_chain(sh_video->vfilter);
+    sh_video->vfilter = NULL;
     talloc_free(sh_video->gsh->decoder_desc);
     sh_video->gsh->decoder_desc = NULL;
     sh_video->initialized = 0;