[FFmpeg-devel] [PATCH 5/5] lavfi/select: add support for concatdec_select option

[Marton Balint]

This option can be used to select useful frames from an ffconcat file which is
using inpoints and outpoints but where the source files are not intra frame
only.

Signed-off-by: Marton Balint <cus at passwd.hu>
---
 doc/filters.texi       | 17 +++++++++++++++++
 libavfilter/f_select.c | 20 ++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/doc/filters.texi b/doc/filters.texi
index 5a35bde..093eec5 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -13160,6 +13160,16 @@ value between 0 and 1 to indicate a new scene; a low value reflects a low
 probability for the current frame to introduce a new scene, while a higher
 value means the current frame is more likely to be one (see the example below)
 
+ at item concatdec_select
+The concat demuxer sets the @var{lavf.concat.start_time} and the
+ at var{lavf.concat.duration} packet metadata values which are also present in the
+decoded frames. These metadata entries contain the start_time and the duration
+of the respective file segments in the concatenated output.
+
+The @var{concatdec_select} variable is -1 if the frame pts is at least
+start_time but less than start_time + duration, 0 otherwise, and NaN if the
+mentioned metadata entires are not present.
+
 @end table
 
 The default value of the select expression is "1".
@@ -13234,6 +13244,13 @@ Send even and odd frames to separate outputs, and compose them:
 @example
 select=n=2:e='mod(n, 2)+1' [odd][even]; [odd] pad=h=2*ih [tmp]; [tmp][even] overlay=y=h
 @end example
+
+ at item
+Select useful frames from an ffconcat file which is using inpoints and
+outpoints but where the source files are not intra frame only.
+ at example
+ffmpeg -copyts -vsync 0 -i input.ffconcat -vf select=concatdec_select -af aselect=concatdec_select output.avi
+ at end example
 @end itemize
 
 @section selectivecolor
diff --git a/libavfilter/f_select.c b/libavfilter/f_select.c
index 2b926e1..d5f1470 100644
--- a/libavfilter/f_select.c
+++ b/libavfilter/f_select.c
@@ -82,6 +82,8 @@ static const char *const var_names[] = {
 
     "scene",
 
+    "concatdec_select",  ///< frame usefulness based on pts and frame metadata originating from the concat demuxer
+
     NULL
 };
 
@@ -132,6 +134,8 @@ enum var_name {
 
     VAR_SCENE,
 
+    VAR_CONCATDEC_SELECT,
+
     VAR_VARS_NB
 };
 
@@ -278,6 +282,21 @@ static double get_scene_score(AVFilterContext *ctx, AVFrame *frame)
     return ret;
 }
 
+static double get_concatdec_select(AVFrame *frame, int64_t pts)
+{
+    AVDictionary *metadata = av_frame_get_metadata(frame);
+    AVDictionaryEntry *e1 = av_dict_get(metadata, "lavf.concatdec.start_time", NULL, 0);
+    AVDictionaryEntry *e2 = av_dict_get(metadata, "lavf.concatdec.duration", NULL, 0);
+    if (e1 && e1->value && e2 && e2->value) {
+        int64_t start_time = strtoll(e1->value, NULL, 10);
+        int64_t duration = strtoll(e2->value, NULL, 10);
+        if (pts >= start_time && pts < start_time + duration)
+            return -1;
+        return 0;
+    }
+    return NAN;
+}
+
 #define D2TS(d)  (isnan(d) ? AV_NOPTS_VALUE : (int64_t)(d))
 #define TS2D(ts) ((ts) == AV_NOPTS_VALUE ? NAN : (double)(ts))
 
@@ -297,6 +316,7 @@ static void select_frame(AVFilterContext *ctx, AVFrame *frame)
     select->var_values[VAR_T  ] = TS2D(frame->pts) * av_q2d(inlink->time_base);
     select->var_values[VAR_POS] = av_frame_get_pkt_pos(frame) == -1 ? NAN : av_frame_get_pkt_pos(frame);
     select->var_values[VAR_KEY] = frame->key_frame;
+    select->var_values[VAR_CONCATDEC_SELECT] = get_concatdec_select(frame, av_rescale_q(frame->pts, inlink->time_base, AV_TIME_BASE_Q));
 
     switch (inlink->type) {
     case AVMEDIA_TYPE_AUDIO:
-- 
2.1.4