lavfi/eq: rework expression evaluation

In particular, add support for t, pos, n, r parameters, and add an eval
mode option.

Also, partially reword option documentation.

With several major edit by Stefano Sabatini.

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>

3 files changed, 74 insertions, 47 deletions

diff --git a/libavfilter/version.h b/libavfilter/version.h
index b349aaf427..43b7ab9c03 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -31,7 +31,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  5
 #define LIBAVFILTER_VERSION_MINOR  13
-#define LIBAVFILTER_VERSION_MICRO 100
+#define LIBAVFILTER_VERSION_MICRO 101
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \
diff --git a/libavfilter/vf_eq.c b/libavfilter/vf_eq.c
index 520fd46188..f8b816038d 100644
--- a/libavfilter/vf_eq.c
+++ b/libavfilter/vf_eq.c
@@ -27,11 +27,6 @@
  * very simple video equalizer
  */
 
-/**
- * TODO:
- * - Add support to process_command
- */
-
 #include "libavfilter/internal.h"
 #include "libavutil/common.h"
 #include "libavutil/imgutils.h"
@@ -111,16 +106,16 @@ static void check_values(EQParameters *param, EQContext *eq)
 
 static void set_contrast(EQContext *eq)
 {
-    eq->var_values[VAR_CONTRAST] = av_clipf(av_expr_eval(eq->contrast_pexpr, eq->var_values, eq),-2.0, 2.0);
-    eq->param[0].contrast = eq->var_values[VAR_CONTRAST];
+    eq->contrast = av_clipf(av_expr_eval(eq->contrast_pexpr, eq->var_values, eq), -2.0, 2.0);
+    eq->param[0].contrast = eq->contrast;
     eq->param[0].lut_clean = 0;
     check_values(&eq->param[0], eq);
 }
 
 static void set_brightness(EQContext *eq)
 {
-    eq->var_values[VAR_BRIGHTNESS] =  av_clipf(av_expr_eval(eq->brightness_pexpr, eq->var_values, eq), -1.0, 1.0);
-    eq->param[0].brightness = eq->var_values[VAR_BRIGHTNESS];
+    eq->brightness = av_clipf(av_expr_eval(eq->brightness_pexpr, eq->var_values, eq), -1.0, 1.0);
+    eq->param[0].brightness = eq->brightness;
     eq->param[0].lut_clean = 0;
     check_values(&eq->param[0], eq);
 }
@@ -129,18 +124,18 @@ static void set_gamma(EQContext *eq)
 {
     int i;
 
-    eq->var_values[VAR_GAMMA]        =  av_clipf(av_expr_eval(eq->gamma_pexpr,        eq->var_values, eq),  0.1, 10.0);
-    eq->var_values[VAR_GAMMA_R]      =  av_clipf(av_expr_eval(eq->gamma_r_pexpr,      eq->var_values, eq),  0.1, 10.0);
-    eq->var_values[VAR_GAMMA_G]      =  av_clipf(av_expr_eval(eq->gamma_g_pexpr,      eq->var_values, eq),  0.1, 10.0);
-    eq->var_values[VAR_GAMMA_B]      =  av_clipf(av_expr_eval(eq->gamma_b_pexpr,      eq->var_values, eq),  0.1, 10.0);
-    eq->var_values[VAR_GAMMA_WEIGHT] =  av_clipf(av_expr_eval(eq->gamma_weight_pexpr, eq->var_values, eq),  0.0,  1.0);
+    eq->gamma        = av_clipf(av_expr_eval(eq->gamma_pexpr,        eq->var_values, eq), 0.1, 10.0);
+    eq->gamma_r      = av_clipf(av_expr_eval(eq->gamma_r_pexpr,      eq->var_values, eq), 0.1, 10.0);
+    eq->gamma_g      = av_clipf(av_expr_eval(eq->gamma_g_pexpr,      eq->var_values, eq), 0.1, 10.0);
+    eq->gamma_b      = av_clipf(av_expr_eval(eq->gamma_b_pexpr,      eq->var_values, eq), 0.1, 10.0);
+    eq->gamma_weight = av_clipf(av_expr_eval(eq->gamma_weight_pexpr, eq->var_values, eq), 0.0,  1.0);
 
-    eq->param[0].gamma = eq->var_values[VAR_GAMMA] * eq->var_values[VAR_GAMMA_G];
-    eq->param[1].gamma = sqrt(eq->var_values[VAR_GAMMA_B] / eq->var_values[VAR_GAMMA_G]);
-    eq->param[2].gamma = sqrt(eq->var_values[VAR_GAMMA_R] / eq->var_values[VAR_GAMMA_G]);
+    eq->param[0].gamma = eq->gamma * eq->gamma_g;
+    eq->param[1].gamma = sqrt(eq->gamma_b / eq->gamma_g);
+    eq->param[2].gamma = sqrt(eq->gamma_r / eq->gamma_g);
 
     for (i = 0; i < 3; i++) {
-        eq->param[i].gamma_weight = eq->var_values[VAR_GAMMA_WEIGHT];
+        eq->param[i].gamma_weight = eq->gamma_weight;
         eq->param[i].lut_clean = 0;
         check_values(&eq->param[i], eq);
     }
@@ -150,10 +145,10 @@ static void set_saturation(EQContext *eq)
 {
     int i;
 
-    eq->var_values[VAR_SATURATION] = av_clipf(av_expr_eval(eq->saturation_pexpr, eq->var_values, eq), 0.0, 3.0);
+    eq->saturation = av_clipf(av_expr_eval(eq->saturation_pexpr, eq->var_values, eq), 0.0, 3.0);
 
     for (i = 1; i < 3; i++) {
-        eq->param[i].contrast = eq->var_values[VAR_SATURATION];
+        eq->param[i].contrast = eq->saturation;
         eq->param[i].lut_clean = 0;
         check_values(&eq->param[i], eq);
     }
@@ -166,8 +161,7 @@ static int set_expr(AVExpr **pexpr, const char *expr, const char *option, void *
 
     if (*pexpr)
         old = *pexpr;
-    ret = av_expr_parse(pexpr, expr, var_names,
-                        NULL, NULL, NULL, NULL, 0, log_ctx);
+    ret = av_expr_parse(pexpr, expr, var_names, NULL, NULL, NULL, NULL, 0, log_ctx);
     if (ret < 0) {
         av_log(log_ctx, AV_LOG_ERROR,
                "Error when parsing the expression '%s' for %s\n",
@@ -200,10 +194,12 @@ static int initialize(AVFilterContext *ctx)
     if (ARCH_X86)
         ff_eq_init_x86(eq);
 
-    set_gamma(eq);
-    set_contrast(eq);
-    set_brightness(eq);
-    set_saturation(eq);
+    if (eq->eval_mode == EVAL_MODE_INIT) {
+        set_gamma(eq);
+        set_contrast(eq);
+        set_brightness(eq);
+        set_saturation(eq);
+    }
 
     return 0;
 }
@@ -222,6 +218,17 @@ static void uninit(AVFilterContext *ctx)
     av_expr_free(eq->gamma_b_pexpr);      eq->gamma_b_pexpr      = NULL;
 }
 
+static int config_props(AVFilterLink *inlink)
+{
+    EQContext *eq = inlink->dst->priv;
+
+    eq->var_values[VAR_N] = 0;
+    eq->var_values[VAR_R] = inlink->frame_rate.num == 0 || inlink->frame_rate.den == 0 ?
+        NAN : av_q2d(inlink->frame_rate);
+
+    return 0;
+}
+
 static int query_formats(AVFilterContext *ctx)
 {
     static const enum AVPixelFormat pixel_fmts_eq[] = {
@@ -239,12 +246,15 @@ static int query_formats(AVFilterContext *ctx)
     return ff_set_common_formats(ctx, fmts_list);
 }
 
+#define TS2T(ts, tb) ((ts) == AV_NOPTS_VALUE ? NAN : (double)(ts) * av_q2d(tb))
+
 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx = inlink->dst;
     AVFilterLink *outlink = inlink->dst->outputs[0];
     EQContext *eq = ctx->priv;
     AVFrame *out;
+    int64_t pos = av_frame_get_pkt_pos(in);
     const AVPixFmtDescriptor *desc;
     int i;
 
@@ -255,6 +265,17 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     av_frame_copy_props(out, in);
     desc = av_pix_fmt_desc_get(inlink->format);
 
+    eq->var_values[VAR_N]   = inlink->frame_count;
+    eq->var_values[VAR_POS] = pos == -1 ? NAN : pos;
+    eq->var_values[VAR_T]   = TS2T(in->pts, inlink->time_base);
+
+    if (eq->eval_mode == EVAL_MODE_FRAME) {
+        set_gamma(eq);
+        set_contrast(eq);
+        set_brightness(eq);
+        set_saturation(eq);
+    }
+
     for (i = 0; i < desc->nb_components; i++) {
         int w = inlink->w;
         int h = inlink->h;
@@ -283,7 +304,8 @@ static inline int set_param(AVExpr **pexpr, const char *args, const char *cmd,
     int ret;
     if ((ret = set_expr(pexpr, args, cmd, ctx)) < 0)
         return ret;
-    set_fn(eq);
+    if (eq->eval_mode == EVAL_MODE_INIT)
+        set_fn(eq);
     return 0;
 }
 
@@ -311,6 +333,7 @@ static const AVFilterPad eq_inputs[] = {
         .name = "default",
         .type = AVMEDIA_TYPE_VIDEO,
         .filter_frame = filter_frame,
+        .config_props = config_props,
     },
     { NULL }
 };
@@ -343,6 +366,9 @@ static const AVOption eq_options[] = {
         OFFSET(gamma_b_expr),      AV_OPT_TYPE_STRING, {.str = "1.0"}, CHAR_MIN, CHAR_MAX, FLAGS },
     { "gamma_weight", "set the gamma weight which reduces the effect of gamma on bright areas",
         OFFSET(gamma_weight_expr), AV_OPT_TYPE_STRING, {.str = "1.0"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "eval", "specify when to evaluate expressions", OFFSET(eval_mode), AV_OPT_TYPE_INT, {.i64 = EVAL_MODE_INIT}, 0, EVAL_MODE_NB-1, FLAGS, "eval" },
+         { "init",  "eval expressions once during initialization", 0, AV_OPT_TYPE_CONST, {.i64=EVAL_MODE_INIT},  .flags = FLAGS, .unit = "eval" },
+         { "frame", "eval expressions per-frame",                  0, AV_OPT_TYPE_CONST, {.i64=EVAL_MODE_FRAME}, .flags = FLAGS, .unit = "eval" },
     { NULL }
 };
 
diff --git a/libavfilter/vf_eq.h b/libavfilter/vf_eq.h
index fe9c09caca..8525048b3f 100644
--- a/libavfilter/vf_eq.h
+++ b/libavfilter/vf_eq.h
@@ -28,28 +28,20 @@
 #include "avfilter.h"
 #include "libavutil/eval.h"
 
-static const char * const var_names[] = {
-    "contrast",
-    "brightness",
-    "saturation",
-    "gamma",
-    "gamma_weight",
-    "gamma_r",
-    "gamma_g",
-    "gamma_b",
+static const char *const var_names[] = {
+    "n",   // frame count
+    "pos", // frame position
+    "r",   // frame rate
+    "t",   // timestamp expressed in seconds
     NULL
 };
 
 enum var_name {
-    VAR_CONTRAST ,
-    VAR_BRIGHTNESS ,
-    VAR_SATURATION ,
-    VAR_GAMMA ,
-    VAR_GAMMA_WEIGHT ,
-    VAR_GAMMA_R ,
-    VAR_GAMMA_G ,
-    VAR_GAMMA_B ,
-    VAR_VARS_NB ,
+    VAR_N,
+    VAR_POS,
+    VAR_R,
+    VAR_T,
+    VAR_NB
 };
 
 typedef struct EQParameters {
@@ -70,33 +62,42 @@ typedef struct {
 
     char   *contrast_expr;
     AVExpr *contrast_pexpr;
+    double  contrast;
 
     char   *brightness_expr;
     AVExpr *brightness_pexpr;
+    double  brightness;
 
     char   *saturation_expr;
     AVExpr *saturation_pexpr;
+    double  saturation;
 
     char   *gamma_expr;
     AVExpr *gamma_pexpr;
+    double  gamma;
 
     char   *gamma_weight_expr;
     AVExpr *gamma_weight_pexpr;
+    double  gamma_weight;
 
     char   *gamma_r_expr;
     AVExpr *gamma_r_pexpr;
+    double  gamma_r;
 
     char   *gamma_g_expr;
     AVExpr *gamma_g_pexpr;
+    double  gamma_g;
 
     char   *gamma_b_expr;
     AVExpr *gamma_b_pexpr;
+    double  gamma_b;
 
-    double var_values[VAR_VARS_NB];
+    double var_values[VAR_NB];
 
     void (*process)(struct EQParameters *par, uint8_t *dst, int dst_stride,
                     const uint8_t *src, int src_stride, int w, int h);
 
+    enum EvalMode { EVAL_MODE_INIT, EVAL_MODE_FRAME, EVAL_MODE_NB } eval_mode;
 } EQContext;
 
 void ff_eq_init_x86(EQContext *eq);