vf_lavfi: recreate filter graph on seek

Resetting the filter graph helps dealing with filters which save state
between frames. This is important especially if they modify frame timing
or emit additional frames.

Unfortunately the libavfilter API doesn't have a way to do this
directly, so we have to use a dirty trick: we recreate the whole graph,
including format negotiation down and filter string parsing. ffplay does
this too. If libavfilter somehow decides to change output format or size
from what the first run in config() returned, mpv will explode. The same
applies to vf_next_query_format() return values (although this could be
mitigated, should it really happen).

1 files changed, 41 insertions, 14 deletions

diff --git a/video/filter/vf_lavfi.c b/video/filter/vf_lavfi.c
index 6889aa0595..6fb9ae0cd3 100644
--- a/video/filter/vf_lavfi.c
+++ b/video/filter/vf_lavfi.c
@@ -67,6 +67,7 @@ static void destroy_graph(struct vf_instance *vf)
 {
     struct vf_priv_s *p = vf->priv;
     avfilter_graph_free(&p->graph);
+    p->in = p->out = NULL;
 }
 
 // FFmpeg and Libav have slightly different APIs, just enough to cause us
@@ -101,9 +102,8 @@ static void dar_from_sar_par(int width, int height, AVRational par,
     }
 }
 
-static int config(struct vf_instance *vf, int width, int height,
-                  int d_width, int d_height, unsigned int flags,
-                  unsigned int fmt)
+static bool recreate_graph(struct vf_instance *vf, int width, int height,
+                           int d_width, int d_height, unsigned int fmt)
 {
     void *tmp = talloc_new(NULL);
     struct vf_priv_s *p = vf->priv;
@@ -111,7 +111,7 @@ static int config(struct vf_instance *vf, int width, int height,
 
     if (bstr0(p->cfg_graph).len == 0) {
         mp_msg(MSGT_VFILTER, MSGL_FATAL, "lavfi: no filter graph set\n");
-        return 0;
+        return false;
     }
 
     destroy_graph(vf);
@@ -187,8 +187,28 @@ static int config(struct vf_instance *vf, int width, int height,
 
     assert(out->nb_inputs == 1);
     assert(in->nb_outputs == 1);
-    AVFilterLink *l_out = out->inputs[0];
-    AVFilterLink *l_in = in->outputs[0];
+
+    talloc_free(tmp);
+    return true;
+
+error:
+    mp_msg(MSGT_VFILTER, MSGL_FATAL, "Can't configure libavfilter graph.\n");
+    avfilter_graph_free(&graph);
+    talloc_free(tmp);
+    return false;
+}
+
+static int config(struct vf_instance *vf, int width, int height,
+                  int d_width, int d_height, unsigned int flags,
+                  unsigned int fmt)
+{
+    struct vf_priv_s *p = vf->priv;
+
+    if (!recreate_graph(vf, width, height, d_width, d_height, fmt))
+        return 0;
+
+    AVFilterLink *l_out = p->out->inputs[0];
+    AVFilterLink *l_in = p->in->outputs[0];
 
     p->timebase_in = l_in->time_base;
     p->timebase_out = l_out->time_base;
@@ -198,15 +218,9 @@ static int config(struct vf_instance *vf, int width, int height,
     int dw, dh;
     dar_from_sar_par(l_out->w, l_out->h, l_out->sample_aspect_ratio, &dw, &dh);
 
-    talloc_free(tmp);
     return vf_next_config(vf, l_out->w, l_out->h, dw, dh, flags,
                           pixfmt2imgfmt(l_out->format));
 
-error:
-    mp_msg(MSGT_VFILTER, MSGL_FATAL, "Can't configure libavfilter graph.\n");
-    avfilter_graph_free(&graph);
-    talloc_free(tmp);
-    return 0;
 }
 
 static int query_format(struct vf_instance *vf, unsigned int fmt)
@@ -267,6 +281,20 @@ static int filter_ext(struct vf_instance *vf, struct mp_image *mpi)
     return 0;
 }
 
+static int control(vf_instance_t *vf, int request, void *data)
+{
+    struct vf_priv_s *p = vf->priv;
+    switch (request) {
+    case VFCTRL_SEEK_RESET:
+        if (p->graph) {
+            struct vf_format *f = &vf->fmt_in;
+            recreate_graph(vf, f->w, f->h, f->dw, f->dh, f->fmt);
+        }
+        break;
+    }
+    return vf_next_control(vf, request, data);
+}
+
 static void uninit(struct vf_instance *vf)
 {
     if (!vf->priv)
@@ -277,11 +305,10 @@ static void uninit(struct vf_instance *vf)
 
 static int vf_open(vf_instance_t *vf, char *args)
 {
-    //struct vf_priv_s *priv = vf->priv;
-
     vf->config = config;
     vf->filter_ext = filter_ext;
     vf->query_format = query_format;
+    vf->control = control;
     vf->uninit = uninit;
     return 1;
 }