Re: [FFmpeg-devel] [PATCH] Blackframe video filter now sets frame metadata accordingly.

[Stepan Bujnak]

On 11.07.2014 22:25, wm4 wrote:
On Fri, 11 Jul 2014 22:13:54 +0200
Stepan Bujnak <stepan.buj...@gmail.com> wrote:
the libavfilter/vf_blackframe.c filter now not only logs detected
values, but also sets frame metadata. The metadata have prefix
'lavfi.blackframe.*'.

Signed-off-by: Stepan Bujnak <stepan.buj...@gmail.com>
---
  libavfilter/vf_blackframe.c | 29 +++++++++++++++++++++++++----
  1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/libavfilter/vf_blackframe.c b/libavfilter/vf_blackframe.c
index 0eeda61..d89a25e 100644
--- a/libavfilter/vf_blackframe.c
+++ b/libavfilter/vf_blackframe.c
@@ -58,6 +58,10 @@ static int query_formats(AVFilterContext *ctx)
      return 0;
  }
  
+#define SET_META(key, format, value) \
+    snprintf(buf, sizeof(buf), format, value);  \
+    av_dict_set(metadata, key, buf, 0)
+
  static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
  {
      AVFilterContext *ctx = inlink->dst;
@@ -65,6 +69,10 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
      int x, i;
      int pblack = 0;
      uint8_t *p = frame->data[0];
+    AVDictionary **metadata;
+    double t = -1;
+    char type;
+    char buf[32];
  
      for (i = 0; i < frame->height; i++) {
          for (x = 0; x < inlink->w; x++)
@@ -76,12 +84,25 @@ static int filter_frame(AVFilterLink *inlink, AVFrame 
*frame)
          s->last_keyframe = s->frame;
  
      pblack = s->nblack * 100 / (inlink->w * inlink->h);
-    if (pblack >= s->bamount)
+    if (pblack >= s->bamount) {
+        metadata = avpriv_frame_get_metadatap(frame);
+        type = av_get_picture_type_char(frame->pict_type);
+
+        if (frame->pts != AV_NOPTS_VALUE) {
+            t = frame->pts * av_q2d(inlink->time_base);
+        }
+
          av_log(ctx, AV_LOG_INFO, "frame:%u pblack:%u pts:%"PRId64" t:%f "
                 "type:%c last_keyframe:%d\n",
-               s->frame, pblack, frame->pts,
-               frame->pts == AV_NOPTS_VALUE ? -1 : frame->pts * 
av_q2d(inlink->time_base),
-               av_get_picture_type_char(frame->pict_type), s->last_keyframe);
+               s->frame, pblack, frame->pts, t, type, s->last_keyframe);
+
+        SET_META("lavfi.blackframe.frame", "%u", s->frame);
+        SET_META("lavfi.blackframe.pblack", "%u", pblack);
+        SET_META("lavfi.blackframe.pts", "%"PRId64, frame->pts);
It shouldn't be needed to set the PTS - the frame already has it.

+        SET_META("lavfi.blackframe.t", "%f", t);
+        SET_META("lavfi.blackframe.type", "%c", type);
+        SET_META("lavfi.blackframe.last_keyframe", "%d", s->last_keyframe);
+    }
  
      s->frame++;
      s->nblack = 0;
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You are absolutely right. The same possibly applies to `t` and `type` 
values, but how about `s->frame` and `s->last_frame`? Are those necessary?
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