avfilter/filters: add ff_inlink_peek_frame and ff_inlink_queued_frames to...

avfilter/filters: add ff_inlink_peek_frame and ff_inlink_queued_frames to access frames in the inlink fifo
Signed-off-by: Marton Balint <cus@passwd.hu>

libavfilter/avfilter.c

@@ -1448,6 +1448,11 @@ int ff_inlink_acknowledge_status(AVFilterLink *link, int *rstatus, int64_t *rpts
     return 1;
 }
 
+size_t ff_inlink_queued_frames(AVFilterLink *link)
+{
+    return ff_framequeue_queued_frames(&link->fifo);
+}
+
 int ff_inlink_check_available_frame(AVFilterLink *link)
 {
     return ff_framequeue_queued_frames(&link->fifo) > 0;
@@ -1507,6 +1512,11 @@ int ff_inlink_consume_samples(AVFilterLink *link, unsigned min, unsigned max,
     return 1;
 }
 
+AVFrame *ff_inlink_peek_frame(AVFilterLink *link, size_t idx)
+{
+    return ff_framequeue_peek(&link->fifo, idx);
+}
+
 int ff_inlink_make_frame_writable(AVFilterLink *link, AVFrame **rframe)
 {
     AVFrame *frame = *rframe;

libavfilter/filters.h

@@ -60,6 +60,12 @@ int ff_inlink_process_commands(AVFilterLink *link, const AVFrame *frame);
  */
 int ff_inlink_evaluate_timeline_at_frame(AVFilterLink *link, const AVFrame *frame);
 
+/**
+ * Get the number of frames available on the link.
+ * @return the number of frames available in the link fifo.
+ */
+size_t ff_inlink_queued_frames(AVFilterLink *link);
+
 /**
  * Test if a frame is available on the link.
  * @return  >0 if a frame is available
@@ -102,6 +108,13 @@ int ff_inlink_consume_frame(AVFilterLink *link, AVFrame **rframe);
 int ff_inlink_consume_samples(AVFilterLink *link, unsigned min, unsigned max,
                             AVFrame **rframe);
 
+/**
+ * Access a frame in the link fifo without consuming it.
+ * The first frame is numbered 0; the designated frame must exist.
+ * @return the frame at idx position in the link fifo.
+ */
+AVFrame *ff_inlink_peek_frame(AVFilterLink *link, size_t idx);
+
 /**
  * Make sure a frame is writable.
  * This is similar to av_frame_make_writable() except it uses the link's