[FFmpeg-devel] [WIP] [PATCH 1/2] lavfi/framesync: support filters with multiple outputs

[Nicolas George <george@nsup.org>]

The filters will have to provide the logic to set the status
and check for a wanted frame.

Signed-off-by: Nicolas George <george@nsup.org>
---
 libavfilter/framesync.c | 46 ++++++++++++++++++++++++++++++-----------
 libavfilter/framesync.h | 28 +++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 12 deletions(-)


Untested yet.


diff --git a/libavfilter/framesync.c b/libavfilter/framesync.c
index c748262ba6..0923e8c22b 100644
--- a/libavfilter/framesync.c
+++ b/libavfilter/framesync.c
@@ -75,6 +75,10 @@ enum {
 
 static int consume_from_fifos(FFFrameSync *fs);
 
+static void default_on_eof(FFFrameSync *fs);
+
+static int default_on_miss(FFFrameSync *fs);
+
 void ff_framesync_preinit(FFFrameSync *fs)
 {
     if (fs->class)
@@ -83,28 +87,36 @@ void ff_framesync_preinit(FFFrameSync *fs)
     av_opt_set_defaults(fs);
 }
 
-int ff_framesync_init(FFFrameSync *fs, AVFilterContext *parent, unsigned nb_in)
+int ff_framesync_postinit(FFFrameSync *fs)
 {
-    /* For filters with several outputs, we will not be able to assume which
-       output is relevant for ff_outlink_frame_wanted() and
-       ff_outlink_set_status(). To be designed when needed. */
-    av_assert0(parent->nb_outputs == 1);
-
-    ff_framesync_preinit(fs);
-    fs->parent = parent;
-    fs->nb_in  = nb_in;
+    if (fs->parent->nb_outputs == 1) {
+        if (!fs->on_eof)
+            fs->on_eof = default_on_eof;
+        if (!fs->on_miss)
+            fs->on_miss = default_on_miss;
+    }
+    av_assert0(fs->on_eof);
+    av_assert0(fs->on_miss);
 
-    fs->in = av_calloc(nb_in, sizeof(*fs->in));
+    fs->in = av_calloc(fs->nb_in, sizeof(*fs->in));
     if (!fs->in)
         return AVERROR(ENOMEM);
     return 0;
 }
 
+int ff_framesync_init(FFFrameSync *fs, AVFilterContext *parent, unsigned nb_in)
+{
+    ff_framesync_preinit(fs);
+    fs->parent = parent;
+    fs->nb_in  = nb_in;
+    return ff_framesync_postinit(fs);
+}
+
 static void framesync_eof(FFFrameSync *fs)
 {
     fs->eof = 1;
     fs->frame_ready = 0;
-    ff_outlink_set_status(fs->parent->outputs[0], AVERROR_EOF, AV_NOPTS_VALUE);
+    fs->on_eof(fs);
 }
 
 static void framesync_sync_level_update(FFFrameSync *fs)
@@ -342,7 +354,7 @@ static int consume_from_fifos(FFFrameSync *fs)
         }
     }
     if (nb_miss) {
-        if (nb_miss == nb_active && !ff_outlink_frame_wanted(ctx->outputs[0]))
+        if (nb_miss == nb_active && !fs->on_miss(fs))
             return FFERROR_NOT_READY;
         for (i = 0; i < fs->nb_in; i++)
             if (!fs->in[i].have_next && fs->in[i].state != STATE_EOF)
@@ -422,3 +434,13 @@ int ff_framesync_dualinput_get_writable(FFFrameSync *fs, AVFrame **f0, AVFrame *
     }
     return 0;
 }
+
+static void default_on_eof(FFFrameSync *fs)
+{
+    ff_outlink_set_status(fs->parent->outputs[0], AVERROR_EOF, AV_NOPTS_VALUE);
+}
+
+static int default_on_miss(FFFrameSync *fs)
+{
+    return ff_outlink_frame_wanted(fs->parent->outputs[0]);
+}
diff --git a/libavfilter/framesync.h b/libavfilter/framesync.h
index 233f50a0eb..1957396c7f 100644
--- a/libavfilter/framesync.h
+++ b/libavfilter/framesync.h
@@ -193,6 +193,19 @@ typedef struct FFFrameSync {
      */
     int (*on_event)(struct FFFrameSync *fs);
 
+    /**
+     * Callback called when EOF is reached; can be NULL
+     * The default is to ff_outlink_set_status() on the single output.
+     */
+    void (*on_eof)(struct FFFrameSync *fs);
+
+    /**
+     * Callback called when no input can be produced to decide if input must
+     * be requested
+     * The default is ff_outlink_frame_wanted() on the singe output.
+     */
+    int (*on_miss)(struct FFFrameSync *fs);
+
     /**
      * Opaque pointer, not used by the API
      */
@@ -240,6 +253,21 @@ typedef struct FFFrameSync {
  */
 void ff_framesync_preinit(FFFrameSync *fs);
 
+/**
+ * Finish the initialization of a frame sync structure
+ *
+ * Use it in combination with ff_framesync_preinit() and set fields and
+ * options in between.
+ *
+ *   ff_framesync_preinit(fs);
+ *   fs->parent = parent;
+ *   fs->nb_in  = nb_in;
+ *   fs->field  = value;
+ *   ret = ff_framesync_postinit(fs);
+ *   if (ret < 0) ...
+ */
+int ff_framesync_postinit(FFFrameSync *fs);
+
 /**
  * Initialize a frame sync structure.
  *
-- 
2.39.2

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