avfilter/vf_palettegen: add mode for generating palette for each input frame

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/vf_palettegen.c

@@ -53,6 +53,7 @@ struct hist_node {
 enum {
     STATS_MODE_ALL_FRAMES,
     STATS_MODE_DIFF_FRAMES,
+    STATS_MODE_SINGLE_FRAMES,
     NB_STATS_MODE
 };
 
@@ -80,9 +81,10 @@ typedef struct {
 static const AVOption palettegen_options[] = {
     { "max_colors", "set the maximum number of colors to use in the palette", OFFSET(max_colors), AV_OPT_TYPE_INT, {.i64=256}, 4, 256, FLAGS },
     { "reserve_transparent", "reserve a palette entry for transparency", OFFSET(reserve_transparent), AV_OPT_TYPE_BOOL, {.i64=1}, 0, 1, FLAGS },
-    { "stats_mode", "set statistics mode", OFFSET(stats_mode), AV_OPT_TYPE_INT, {.i64=STATS_MODE_ALL_FRAMES}, 0, NB_STATS_MODE, FLAGS, "mode" },
+    { "stats_mode", "set statistics mode", OFFSET(stats_mode), AV_OPT_TYPE_INT, {.i64=STATS_MODE_ALL_FRAMES}, 0, NB_STATS_MODE-1, FLAGS, "mode" },
         { "full", "compute full frame histograms", 0, AV_OPT_TYPE_CONST, {.i64=STATS_MODE_ALL_FRAMES}, INT_MIN, INT_MAX, FLAGS, "mode" },
         { "diff", "compute histograms only for the part that differs from previous frame", 0, AV_OPT_TYPE_CONST, {.i64=STATS_MODE_DIFF_FRAMES}, INT_MIN, INT_MAX, FLAGS, "mode" },
+        { "single", "compute new histogram for each frame", 0, AV_OPT_TYPE_CONST, {.i64=STATS_MODE_SINGLE_FRAMES}, INT_MIN, INT_MAX, FLAGS, "mode" },
     { NULL }
 };
 
@@ -480,8 +482,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx = inlink->dst;
     PaletteGenContext *s = ctx->priv;
-    const int ret = s->prev_frame ? update_histogram_diff(s->histogram, s->prev_frame, in)
-                                  : update_histogram_frame(s->histogram, in);
+    int ret = s->prev_frame ? update_histogram_diff(s->histogram, s->prev_frame, in)
+                            : update_histogram_frame(s->histogram, in);
 
     if (ret > 0)
         s->nb_refs += ret;
@@ -489,6 +491,21 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     if (s->stats_mode == STATS_MODE_DIFF_FRAMES) {
         av_frame_free(&s->prev_frame);
         s->prev_frame = in;
+    } else if (s->stats_mode == STATS_MODE_SINGLE_FRAMES) {
+        AVFrame *out;
+        int i;
+
+        out = get_palette_frame(ctx);
+        out->pts = in->pts;
+        av_frame_free(&in);
+        ret = ff_filter_frame(ctx->outputs[0], out);
+        for (i = 0; i < HIST_SIZE; i++)
+            av_freep(&s->histogram[i].entries);
+        av_freep(&s->refs);
+        s->nb_refs = 0;
+        s->nb_boxes = 0;
+        memset(s->boxes, 0, sizeof(s->boxes));
+        memset(s->histogram, 0, sizeof(s->histogram));
     } else {
         av_frame_free(&in);
     }
@@ -507,7 +524,7 @@ static int request_frame(AVFilterLink *outlink)
     int r;
 
     r = ff_request_frame(inlink);
-    if (r == AVERROR_EOF && !s->palette_pushed && s->nb_refs) {
+    if (r == AVERROR_EOF && !s->palette_pushed && s->nb_refs && s->stats_mode != STATS_MODE_SINGLE_FRAMES) {
         r = ff_filter_frame(outlink, get_palette_frame(ctx));
         s->palette_pushed = 1;
         return r;