video: pass through container fps to filters

This means vf_vapoursynth doesn't need a hack to work around the filter
code, and libavfilter filters now actually get the frame_rate field on
input pads set.

The libavfilter doxygen says the frame_rate field is only to be set if
the frame rate is known to be constant, and uses the word "must" (which
probably means they really mean it?) - but ffmpeg.c sets the field to
mere guesses anyway, and it looks like this normally won't lead to
problems.

filters/f_decoder_wrapper.c

@@ -358,6 +358,7 @@ static void process_video_frame(struct priv *p, struct mp_image *mpi)
         fix_image_params(p, &mpi->params);
 
     mpi->params = p->fixed_format;
+    mpi->nominal_fps = p->public.fps;
 
     mpi->pts = pts;
     p->pts = pts;

filters/f_lavfi.c

@@ -340,7 +340,8 @@ static bool is_vformat_ok(struct mp_image *a, struct mp_image *b)
 {
     return a->imgfmt == b->imgfmt &&
            a->w == b->w && a->h && b->h &&
-           a->params.p_w == b->params.p_w && a->params.p_h == b->params.p_h;
+           a->params.p_w == b->params.p_w && a->params.p_h == b->params.p_h &&
+           a->nominal_fps == b->nominal_fps;
 }
 static bool is_format_ok(struct mp_frame a, struct mp_frame b)
 {
@@ -483,6 +484,7 @@ static bool init_pads(struct lavfi *c)
             params->sample_aspect_ratio.num = fmt->params.p_w;
             params->sample_aspect_ratio.den = fmt->params.p_h;
             params->hw_frames_ctx = fmt->hwctx;
+            params->frame_rate = av_d2q(fmt->nominal_fps, 1000000);
             filter_name = "buffer";
         } else {
             assert(0);
@@ -680,6 +682,11 @@ static bool read_output_pads(struct lavfi *c)
                 mp_aframe_set_pts(aframe, c->in_pts +
                     (c->in_pts != MP_NOPTS_VALUE ? (out_time - in_time) : 0));
             }
+            if (frame.type == MP_FRAME_VIDEO) {
+                struct mp_image *vframe = frame.data;
+                vframe->nominal_fps =
+                    av_q2d(av_buffersink_get_frame_rate(pad->buffer));
+            }
             av_frame_unref(c->tmp_frame);
             if (frame.type) {
                 mp_pin_in_write(pad->pin, frame);

filters/f_output_chain.c

@@ -357,12 +357,6 @@ static double get_display_fps(struct mp_stream_info *i)
     return res;
 }
 
-static double get_container_fps(struct mp_stream_info *i)
-{
-    struct chain *p = i->priv;
-    return p->public.container_fps;
-}
-
 void mp_output_chain_set_vo(struct mp_output_chain *c, struct vo *vo)
 {
     struct chain *p = c->f->priv;
@@ -650,7 +644,6 @@ static void create_video_things(struct chain *p)
 
     p->stream_info.priv = p;
     p->stream_info.get_display_fps = get_display_fps;
-    p->stream_info.get_container_fps = get_container_fps;
 
     p->f->stream_info = &p->stream_info;
 

filters/filter.h

@@ -382,7 +382,6 @@ struct mp_stream_info {
     void *priv; // for use by whoever implements the callbacks
 
     double (*get_display_fps)(struct mp_stream_info *i);
-    double (*get_container_fps)(struct mp_stream_info *i);
 
     struct mp_hwdec_devices *hwdec_devs;
     struct osd_state *osd;

video/filter/vf_vapoursynth.c

@@ -103,7 +103,7 @@ static const struct mp_image dummy_img;
 static const struct mp_image dummy_img_eof;
 
 static void destroy_vs(struct priv *p);
-static int reinit_vs(struct priv *p);
+static int reinit_vs(struct priv *p, struct mp_image *input);
 
 struct script_driver {
     int (*init)(struct priv *p);                // first time init
@@ -368,7 +368,7 @@ static void vf_vapoursynth_process(struct mp_filter *f)
                 if (p->out_node)
                     destroy_vs(p);
                 p->fmt_in = mpi->params;
-                if (reinit_vs(p) < 0) {
+                if (reinit_vs(p, mpi) < 0) {
                     MP_ERR(p, "could not init VS\n");
                     mp_frame_unref(&frame);
                     return;
@@ -617,7 +617,7 @@ static void destroy_vs(struct priv *p)
     MP_DBG(p, "uninitialized.\n");
 }
 
-static int reinit_vs(struct priv *p)
+static int reinit_vs(struct priv *p, struct mp_image *input)
 {
     VSMap *vars = NULL, *in = NULL, *out = NULL;
     int res = -1;
@@ -665,11 +665,9 @@ static int reinit_vs(struct priv *p)
     p->vsapi->propSetInt(vars, "video_in_dh", d_h, 0);
 
     struct mp_stream_info *info = mp_filter_find_stream_info(p->f);
-    double container_fps = 0;
+    double container_fps = input->nominal_fps;
     double display_fps = 0;
     if (info) {
-        if (info->get_container_fps)
-            container_fps = info->get_container_fps(info);
         if (info->get_display_fps)
             display_fps = info->get_display_fps(info);
     }

video/mp_image.c

@@ -508,6 +508,7 @@ void mp_image_copy_attributes(struct mp_image *dst, struct mp_image *src)
     dst->params.color = src->params.color;
     dst->params.chroma_location = src->params.chroma_location;
     dst->params.spherical = src->params.spherical;
+    dst->nominal_fps = src->nominal_fps;
     // ensure colorspace consistency
     if (mp_image_params_get_forced_csp(&dst->params) !=
         mp_image_params_get_forced_csp(&src->params))

video/mp_image.h

@@ -105,6 +105,8 @@ typedef struct mp_image {
     double pts;
     /* only after decoder */
     double dts, pkt_duration;
+    /* container reported FPS; can be incorrect, or 0 if unknown */
+    double nominal_fps;
     /* for private use */
     void* priv;