[FFmpeg-devel] [PATCH 3/3] lavfi/overlay: support timeline through the new system.

Clément Bœsch ubitux at gmail.com
Sat Apr 20 15:17:23 CEST 2013


On Sat, Apr 20, 2013 at 11:49:24AM +0200, Stefano Sabatini wrote:
> On date Friday 2013-04-19 00:28:54 +0200, Clément Bœsch encoded:
> > ---
> >  doc/filters.texi         | 15 +++---------
> >  libavfilter/vf_overlay.c | 64 +++++++++++++++++++++++++-----------------------
> >  2 files changed, 37 insertions(+), 42 deletions(-)
> [...]
> 
> I see two issues with this patch:
> - some variables are not supported in the generic enable expression
> - enable command is removed
> 
> The First problem should be mostly addressed by adding pos to the list
> of supported variables. You may ask, why is pos relevant? Well if you
> know the total size of a file pos can provide some hints about the
> position of the frame in the file (so you can roughly say: enable this
> if it is between 50% and 60% of the file).
> 

Interesting approach, why not, added. New patch attached.

> The second problem is more serious, indeed the enable command was the
> main reason for which I added that option.

Added another patch on top of this one to enable the enable command
injection, please comment.

-- 
Clément B.
-------------- next part --------------
From 7a5aa2e8bd93fa887ccb83fefb76b9eb96564e62 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20B=C5=93sch?= <ubitux at gmail.com>
Date: Mon, 8 Apr 2013 20:35:02 +0200
Subject: [PATCH 2/4] lavfi: add timeline support.

Flag added in a few simple filters. A bunch of other filters can likely
use the feature as well.
---
 Changelog                    |  1 +
 cmdutils.c                   |  2 ++
 doc/filters.texi             | 32 ++++++++++++++++++++++++++++
 libavfilter/af_volume.c      |  1 +
 libavfilter/avfilter.c       | 50 ++++++++++++++++++++++++++++++++++++++++++++
 libavfilter/avfilter.h       | 25 +++++++++++++++++++++-
 libavfilter/vf_boxblur.c     |  1 +
 libavfilter/vf_colormatrix.c |  1 +
 libavfilter/vf_cropdetect.c  |  1 +
 libavfilter/vf_curves.c      |  1 +
 libavfilter/vf_drawbox.c     |  1 +
 libavfilter/vf_edgedetect.c  |  1 +
 libavfilter/vf_gradfun.c     |  1 +
 libavfilter/vf_histeq.c      |  1 +
 libavfilter/vf_hqdn3d.c      |  2 +-
 libavfilter/vf_hue.c         |  1 +
 libavfilter/vf_lut.c         |  1 +
 libavfilter/vf_noise.c       |  1 +
 libavfilter/vf_pp.c          |  2 +-
 libavfilter/vf_smartblur.c   |  1 +
 libavfilter/vf_unsharp.c     |  2 +-
 21 files changed, 125 insertions(+), 4 deletions(-)

diff --git a/Changelog b/Changelog
index 7b2ae6b..dc871dc 100644
--- a/Changelog
+++ b/Changelog
@@ -28,6 +28,7 @@ version <next>:
 - The matroska demuxer can now output proper verbatim ASS packets. It will
   become the default at the next libavformat major bump.
 - decent native animated GIF encoding
+- timeline editing with filters
 
 
 version 1.2:
diff --git a/cmdutils.c b/cmdutils.c
index cc88697..b9985d6 100644
--- a/cmdutils.c
+++ b/cmdutils.c
@@ -1683,6 +1683,8 @@ static void show_help_filter(const char *name)
     if (f->priv_class)
         show_help_children(f->priv_class, AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_FILTERING_PARAM |
                                           AV_OPT_FLAG_AUDIO_PARAM);
+    if (f->flags & AVFILTER_FLAG_SUPPORT_TIMELINE)
+        printf("This filter has support for timeline through the 'enable' option.\n");
 #else
     av_log(NULL, AV_LOG_ERROR, "Build without libavfilter; "
            "can not to satisfy request\n");
diff --git a/doc/filters.texi b/doc/filters.texi
index 4c702a9..b443643 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -267,6 +267,36 @@ See the ``Quoting and escaping'' section in the ffmpeg-utils manual
 for more information about the escaping and quoting rules adopted by
 FFmpeg.
 
+ at chapter Timeline editing
+
+Some filters support a generic @option{enable} option. For the filters
+supporting timeline editing, this option can be set to an expression which is
+evaluated before sending a frame to the filter. If the evaluation is non-zero,
+the filter will be enabled, otherwise the frame will be sent unchanged to the
+next filter in the filtergraph.
+
+The expression accepts the following values:
+ at table @samp
+ at item t
+timestamp expressed in seconds, NAN if the input timestamp is unknown
+
+ at item n
+sequential number of the input frame, starting from 0
+
+ at item pos
+the position in the file of the input frame, NAN if unknown
+ at end table
+
+Like any other filtering option, the @option{enable} option follows the same
+rules.
+
+For example, to enable a denoiser filter (@ref{hqdn3d}) from 10 seconds to 3
+minutes, and a @ref{curves} filter starting at 3 seconds:
+ at example
+hqdn3d = enable='between(t,10,3*60)',
+curves = enable='gte(t,3)' : preset=cross_process
+ at end example
+
 @c man end FILTERGRAPH DESCRIPTION
 
 @chapter Audio Filters
@@ -2397,6 +2427,7 @@ indicates never reset and return the largest area encountered during
 playback.
 @end table
 
+ at anchor{curves}
 @section curves
 
 Apply color adjustments using curves.
@@ -3983,6 +4014,7 @@ ffplay -i input -vf histogram
 
 @end itemize
 
+ at anchor{hqdn3d}
 @section hqdn3d
 
 High precision/quality 3d denoise filter. This filter aims to reduce
diff --git a/libavfilter/af_volume.c b/libavfilter/af_volume.c
index 7d2b9ba..a55e1a3 100644
--- a/libavfilter/af_volume.c
+++ b/libavfilter/af_volume.c
@@ -296,4 +296,5 @@ AVFilter avfilter_af_volume = {
     .init           = init,
     .inputs         = avfilter_af_volume_inputs,
     .outputs        = avfilter_af_volume_outputs,
+    .flags          = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 43340d1..0c6f1f1 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -23,6 +23,7 @@
 #include "libavutil/avstring.h"
 #include "libavutil/channel_layout.h"
 #include "libavutil/common.h"
+#include "libavutil/eval.h"
 #include "libavutil/imgutils.h"
 #include "libavutil/opt.h"
 #include "libavutil/pixdesc.h"
@@ -483,12 +484,20 @@ static const AVClass *filter_child_class_next(const AVClass *prev)
     return NULL;
 }
 
+#define OFFSET(x) offsetof(AVFilterContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM
+static const AVOption filters_common_options[] = {
+    { "enable", "set enable expression", OFFSET(enable_str), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { NULL }
+};
+
 static const AVClass avfilter_class = {
     .class_name = "AVFilter",
     .item_name  = default_filter_name,
     .version    = LIBAVUTIL_VERSION_INT,
     .category   = AV_CLASS_CATEGORY_FILTER,
     .child_next = filter_child_next,
+    .option     = filters_common_options,
     .child_class_next = filter_child_class_next,
 };
 
@@ -618,9 +627,16 @@ void avfilter_free(AVFilterContext *filter)
     while(filter->command_queue){
         ff_command_queue_pop(filter);
     }
+    av_opt_free(filter);
+    av_expr_free(filter->enable);
+    filter->enable = NULL;
+    av_freep(&filter->var_values);
     av_free(filter);
 }
 
+static const char *const var_names[] = {   "t",   "n",   "pos",        NULL };
+enum                                   { VAR_T, VAR_N, VAR_POS, VAR_VARS_NB };
+
 static int process_options(AVFilterContext *ctx, AVDictionary **options,
                            const char *args)
 {
@@ -630,6 +646,8 @@ static int process_options(AVFilterContext *ctx, AVDictionary **options,
     const char *key;
     int offset= -1;
 
+    av_opt_set_defaults(ctx);
+
     if (!args)
         return 0;
 
@@ -665,6 +683,12 @@ static int process_options(AVFilterContext *ctx, AVDictionary **options,
         }
 
         av_log(ctx, AV_LOG_DEBUG, "Setting '%s' to value '%s'\n", key, value);
+
+        if (av_opt_find(ctx, key, NULL, 0, 0)) {
+            ret = av_opt_set(ctx, key, value, 0);
+            if (ret < 0)
+                return ret;
+        } else {
         av_dict_set(options, key, value, 0);
         if ((ret = av_opt_set(ctx->priv, key, value, 0)) < 0) {
             if (!av_opt_find(ctx->priv, key, NULL, 0, AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ)) {
@@ -675,11 +699,27 @@ static int process_options(AVFilterContext *ctx, AVDictionary **options,
             return ret;
             }
         }
+        }
 
         av_free(value);
         av_free(parsed_key);
         count++;
     }
+
+    if (ctx->enable_str) {
+        if (!(ctx->filter->flags & AVFILTER_FLAG_SUPPORT_TIMELINE)) {
+            av_log(ctx, AV_LOG_ERROR, "Timeline ('enable' option) not supported "
+                   "with filter '%s'\n", ctx->filter->name);
+            return AVERROR_PATCHWELCOME;
+        }
+        ctx->var_values = av_calloc(VAR_VARS_NB, sizeof(*ctx->var_values));
+        if (!ctx->var_values)
+            return AVERROR(ENOMEM);
+        ret = av_expr_parse((AVExpr**)&ctx->enable, ctx->enable_str, var_names,
+                            NULL, NULL, NULL, NULL, 0, ctx->priv);
+        if (ret < 0)
+            return ret;
+    }
     return count;
 }
 
@@ -852,6 +892,7 @@ static int default_filter_frame(AVFilterLink *link, AVFrame *frame)
 static int ff_filter_frame_framed(AVFilterLink *link, AVFrame *frame)
 {
     int (*filter_frame)(AVFilterLink *, AVFrame *);
+    AVFilterContext *dstctx = link->dst;
     AVFilterPad *dst = link->dstpad;
     AVFrame *out;
     int ret;
@@ -914,6 +955,15 @@ static int ff_filter_frame_framed(AVFilterLink *link, AVFrame *frame)
     }
 
     pts = out->pts;
+    if (dstctx->enable_str) {
+        int64_t pos = av_frame_get_pkt_pos(out);
+        dstctx->var_values[VAR_N] = link->frame_count;
+        dstctx->var_values[VAR_T] = pts == AV_NOPTS_VALUE ? NAN : pts * av_q2d(link->time_base);
+        dstctx->var_values[VAR_POS] = pos == -1 ? NAN : pos;
+        if (!av_expr_eval(dstctx->enable, dstctx->var_values, NULL))
+            filter_frame = dst->passthrough_filter_frame ? dst->passthrough_filter_frame
+                                                         : default_filter_frame;
+    }
     ret = filter_frame(link, out);
     link->frame_count++;
     link->frame_requested = 0;
diff --git a/libavfilter/avfilter.h b/libavfilter/avfilter.h
index 047208c..62b7c55 100644
--- a/libavfilter/avfilter.h
+++ b/libavfilter/avfilter.h
@@ -385,6 +385,19 @@ struct AVFilterPad {
     int needs_fifo;
 
     int needs_writable;
+
+    /**
+     * Passthrough filtering callback.
+     *
+     * If a filter supports timeline editing (AVFILTER_FLAG_SUPPORT_TIMELINE)
+     * then it can implement a custom passthrough callback to update its local
+     * context (for example to keep a frame reference, or simply send the
+     * filter to a custom outlink). The filter must not do any change to the
+     * frame in this callback.
+     *
+     * Input pads only.
+     */
+    int (*passthrough_filter_frame)(AVFilterLink *link, AVFrame *frame);
 };
 #endif
 
@@ -428,6 +441,12 @@ enum AVMediaType avfilter_pad_get_type(const AVFilterPad *pads, int pad_idx);
  * the options supplied to it.
  */
 #define AVFILTER_FLAG_DYNAMIC_OUTPUTS       (1 << 1)
+/**
+ * Some filters support a generic "enable" expression option that can be used
+ * to enable or disable a filter in the timeline. Filters supporting this
+ * option have this flag set.
+ */
+#define AVFILTER_FLAG_SUPPORT_TIMELINE      (1 << 16)
 
 /**
  * Filter definition. This defines the pads a filter contains, and all the
@@ -522,7 +541,7 @@ typedef struct AVFilter {
 
 /** An instance of a filter */
 struct AVFilterContext {
-    const AVClass *av_class;        ///< needed for av_log()
+    const AVClass *av_class;        ///< needed for av_log() and filters common options
 
     const AVFilter *filter;         ///< the AVFilter of which this is an instance
 
@@ -547,6 +566,10 @@ struct AVFilterContext {
     struct AVFilterGraph *graph;    ///< filtergraph this filter belongs to
 
     struct AVFilterCommand *command_queue;
+
+    char *enable_str;               ///< enable expression string
+    void *enable;                   ///< parsed expression (AVExpr*)
+    double *var_values;             ///< variable values for the enable expression
 };
 
 /**
diff --git a/libavfilter/vf_boxblur.c b/libavfilter/vf_boxblur.c
index 7589644..b010670 100644
--- a/libavfilter/vf_boxblur.c
+++ b/libavfilter/vf_boxblur.c
@@ -383,4 +383,5 @@ AVFilter avfilter_vf_boxblur = {
 
     .inputs    = avfilter_vf_boxblur_inputs,
     .outputs   = avfilter_vf_boxblur_outputs,
+    .flags     = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_colormatrix.c b/libavfilter/vf_colormatrix.c
index d25ce60..8db5fcf 100644
--- a/libavfilter/vf_colormatrix.c
+++ b/libavfilter/vf_colormatrix.c
@@ -385,4 +385,5 @@ AVFilter avfilter_vf_colormatrix = {
     .inputs        = colormatrix_inputs,
     .outputs       = colormatrix_outputs,
     .priv_class    = &colormatrix_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_cropdetect.c b/libavfilter/vf_cropdetect.c
index 3d109f8..cb170d0 100644
--- a/libavfilter/vf_cropdetect.c
+++ b/libavfilter/vf_cropdetect.c
@@ -233,4 +233,5 @@ AVFilter avfilter_vf_cropdetect = {
     .query_formats = query_formats,
     .inputs    = avfilter_vf_cropdetect_inputs,
     .outputs   = avfilter_vf_cropdetect_outputs,
+    .flags     = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_curves.c b/libavfilter/vf_curves.c
index 9f5d8bd..626b4ea 100644
--- a/libavfilter/vf_curves.c
+++ b/libavfilter/vf_curves.c
@@ -514,4 +514,5 @@ AVFilter avfilter_vf_curves = {
     .inputs        = curves_inputs,
     .outputs       = curves_outputs,
     .priv_class    = &curves_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_drawbox.c b/libavfilter/vf_drawbox.c
index edb77cc..c2ffbf3 100644
--- a/libavfilter/vf_drawbox.c
+++ b/libavfilter/vf_drawbox.c
@@ -181,4 +181,5 @@ AVFilter avfilter_vf_drawbox = {
     .query_formats   = query_formats,
     .inputs    = avfilter_vf_drawbox_inputs,
     .outputs   = avfilter_vf_drawbox_outputs,
+    .flags     = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_edgedetect.c b/libavfilter/vf_edgedetect.c
index f29c7ee..b4698a8 100644
--- a/libavfilter/vf_edgedetect.c
+++ b/libavfilter/vf_edgedetect.c
@@ -327,4 +327,5 @@ AVFilter avfilter_vf_edgedetect = {
     .inputs        = edgedetect_inputs,
     .outputs       = edgedetect_outputs,
     .priv_class    = &edgedetect_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_gradfun.c b/libavfilter/vf_gradfun.c
index 9e21560..48ac378 100644
--- a/libavfilter/vf_gradfun.c
+++ b/libavfilter/vf_gradfun.c
@@ -260,4 +260,5 @@ AVFilter avfilter_vf_gradfun = {
     .query_formats = query_formats,
     .inputs        = avfilter_vf_gradfun_inputs,
     .outputs       = avfilter_vf_gradfun_outputs,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_histeq.c b/libavfilter/vf_histeq.c
index 33cddaa..a4166c6 100644
--- a/libavfilter/vf_histeq.c
+++ b/libavfilter/vf_histeq.c
@@ -279,4 +279,5 @@ AVFilter avfilter_vf_histeq = {
     .inputs        = histeq_inputs,
     .outputs       = histeq_outputs,
     .priv_class    = &histeq_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_hqdn3d.c b/libavfilter/vf_hqdn3d.c
index a722d8f..003f175 100644
--- a/libavfilter/vf_hqdn3d.c
+++ b/libavfilter/vf_hqdn3d.c
@@ -355,6 +355,6 @@ AVFilter avfilter_vf_hqdn3d = {
     .query_formats = query_formats,
 
     .inputs    = avfilter_vf_hqdn3d_inputs,
-
     .outputs   = avfilter_vf_hqdn3d_outputs,
+    .flags     = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_hue.c b/libavfilter/vf_hue.c
index a1280be..9f63240 100644
--- a/libavfilter/vf_hue.c
+++ b/libavfilter/vf_hue.c
@@ -349,4 +349,5 @@ AVFilter avfilter_vf_hue = {
     .inputs          = hue_inputs,
     .outputs         = hue_outputs,
     .priv_class      = &hue_class,
+    .flags           = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_lut.c b/libavfilter/vf_lut.c
index 4c0cdfc..4313e77 100644
--- a/libavfilter/vf_lut.c
+++ b/libavfilter/vf_lut.c
@@ -350,6 +350,7 @@ static const AVFilterPad outputs[] = {
                                                                         \
         .inputs        = inputs,                                        \
         .outputs       = outputs,                                       \
+        .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE,                \
     }
 
 #if CONFIG_LUT_FILTER
diff --git a/libavfilter/vf_noise.c b/libavfilter/vf_noise.c
index ae64b76..996311a 100644
--- a/libavfilter/vf_noise.c
+++ b/libavfilter/vf_noise.c
@@ -471,4 +471,5 @@ AVFilter avfilter_vf_noise = {
     .inputs        = noise_inputs,
     .outputs       = noise_outputs,
     .priv_class    = &noise_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_pp.c b/libavfilter/vf_pp.c
index d2c1965..0571cfc 100644
--- a/libavfilter/vf_pp.c
+++ b/libavfilter/vf_pp.c
@@ -180,5 +180,5 @@ AVFilter avfilter_vf_pp = {
     .outputs         = pp_outputs,
     .process_command = pp_process_command,
     .priv_class      = &pp_class,
-
+    .flags           = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_smartblur.c b/libavfilter/vf_smartblur.c
index aed3fa6..4dd1664 100644
--- a/libavfilter/vf_smartblur.c
+++ b/libavfilter/vf_smartblur.c
@@ -301,4 +301,5 @@ AVFilter avfilter_vf_smartblur = {
     .inputs        = smartblur_inputs,
     .outputs       = smartblur_outputs,
     .priv_class    = &smartblur_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
diff --git a/libavfilter/vf_unsharp.c b/libavfilter/vf_unsharp.c
index 038ba4b..2d7aab2 100644
--- a/libavfilter/vf_unsharp.c
+++ b/libavfilter/vf_unsharp.c
@@ -299,6 +299,6 @@ AVFilter avfilter_vf_unsharp = {
     .query_formats = query_formats,
 
     .inputs    = avfilter_vf_unsharp_inputs,
-
     .outputs   = avfilter_vf_unsharp_outputs,
+    .flags     = AVFILTER_FLAG_SUPPORT_TIMELINE,
 };
-- 
1.8.2.1

-------------- next part --------------
From 60dbcae7054b2334b578c6d78e517ed051358840 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20B=C5=93sch?= <ubitux at gmail.com>
Date: Sat, 20 Apr 2013 14:11:21 +0200
Subject: [PATCH 3/4] lavfi: add 'enable' command injection to filters
 supporting timeline.

---
 doc/filters.texi       |  3 +++
 libavfilter/avfilter.c | 59 +++++++++++++++++++++++++++++++++++++++-----------
 2 files changed, 49 insertions(+), 13 deletions(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index b443643..e650f1d 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -287,6 +287,9 @@ sequential number of the input frame, starting from 0
 the position in the file of the input frame, NAN if unknown
 @end table
 
+Additionally, these filters support an @option{enable} command that can be used
+to re-define the expression.
+
 Like any other filtering option, the @option{enable} option follows the same
 rules.
 
diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 0c6f1f1..06d92b2 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -366,6 +366,49 @@ int ff_poll_frame(AVFilterLink *link)
     return min;
 }
 
+static const char *const var_names[] = {   "t",   "n",   "pos",        NULL };
+enum                                   { VAR_T, VAR_N, VAR_POS, VAR_VARS_NB };
+
+static int set_enable_expr(AVFilterContext *ctx, const char *expr)
+{
+    int ret;
+    char *expr_dup;
+    AVExpr *old = ctx->enable;
+
+    if (!(ctx->filter->flags & AVFILTER_FLAG_SUPPORT_TIMELINE)) {
+        av_log(ctx, AV_LOG_ERROR, "Timeline ('enable' option) not supported "
+               "with filter '%s'\n", ctx->filter->name);
+        return AVERROR_PATCHWELCOME;
+    }
+
+    expr_dup = av_strdup(expr);
+    if (!expr_dup)
+        return AVERROR(ENOMEM);
+
+    if (!ctx->var_values) {
+        ctx->var_values = av_calloc(VAR_VARS_NB, sizeof(*ctx->var_values));
+        if (!ctx->var_values) {
+            av_free(expr_dup);
+            return AVERROR(ENOMEM);
+        }
+    }
+
+    ret = av_expr_parse((AVExpr**)&ctx->enable, expr_dup, var_names,
+                        NULL, NULL, NULL, NULL, 0, ctx->priv);
+    if (ret < 0) {
+        av_log(ctx->priv, AV_LOG_ERROR,
+               "Error when evaluating the expression '%s' for enable\n",
+               expr_dup);
+        av_free(expr_dup);
+        return ret;
+    }
+
+    av_expr_free(old);
+    av_free(ctx->enable_str);
+    ctx->enable_str = expr_dup;
+    return 0;
+}
+
 void ff_update_link_current_pts(AVFilterLink *link, int64_t pts)
 {
     if (pts == AV_NOPTS_VALUE)
@@ -381,6 +424,8 @@ int avfilter_process_command(AVFilterContext *filter, const char *cmd, const cha
     if(!strcmp(cmd, "ping")){
         av_strlcatf(res, res_len, "pong from:%s %s\n", filter->filter->name, filter->name);
         return 0;
+    }else if(!strcmp(cmd, "enable")) {
+        return set_enable_expr(filter, arg);
     }else if(filter->filter->process_command) {
         return filter->filter->process_command(filter, cmd, arg, res, res_len, flags);
     }
@@ -634,9 +679,6 @@ void avfilter_free(AVFilterContext *filter)
     av_free(filter);
 }
 
-static const char *const var_names[] = {   "t",   "n",   "pos",        NULL };
-enum                                   { VAR_T, VAR_N, VAR_POS, VAR_VARS_NB };
-
 static int process_options(AVFilterContext *ctx, AVDictionary **options,
                            const char *args)
 {
@@ -707,16 +749,7 @@ static int process_options(AVFilterContext *ctx, AVDictionary **options,
     }
 
     if (ctx->enable_str) {
-        if (!(ctx->filter->flags & AVFILTER_FLAG_SUPPORT_TIMELINE)) {
-            av_log(ctx, AV_LOG_ERROR, "Timeline ('enable' option) not supported "
-                   "with filter '%s'\n", ctx->filter->name);
-            return AVERROR_PATCHWELCOME;
-        }
-        ctx->var_values = av_calloc(VAR_VARS_NB, sizeof(*ctx->var_values));
-        if (!ctx->var_values)
-            return AVERROR(ENOMEM);
-        ret = av_expr_parse((AVExpr**)&ctx->enable, ctx->enable_str, var_names,
-                            NULL, NULL, NULL, NULL, 0, ctx->priv);
+        ret = set_enable_expr(ctx, ctx->enable_str);
         if (ret < 0)
             return ret;
     }
-- 
1.8.2.1

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