filters: lavfi: allow hwdec_interop selection for filters

Today, lavfi filters are provided a hw_device from the first
hwdec_interop that was loaded, regardless of whether it's the right one
or not. In most situations where a hardware based filter is used, we
need more control over the device.

In this change, a `hwdec_interop` option is added to the lavfi wrapper
filter configuration and this is used to pick the correct hw_device to
inject into the filter or graph (in the case of a graph, all filters
get the same device).

Note that this requires the use of the explicit lavfi syntax to allow
for the extra configuration.

eg:

```
mpv --vf=hwupload
```

becomes

```
mpv --vf=lavfi=[hwupload]:hwdec_interop=cuda-nvdec
```

or

```
mpv --vf=lavfi-bridge=[hwupload]:hwdec_interop=cuda-nvdec
```

1 files changed, 2 insertions, 0 deletions

diff --git a/filters/f_lavfi.h b/filters/f_lavfi.h
index c6cf86f500..ec6990f68a 100644
--- a/filters/f_lavfi.h
+++ b/filters/f_lavfi.h
@@ -18,6 +18,7 @@ struct mp_lavfi {
 //  graph: a libavfilter graph specification
 struct mp_lavfi *mp_lavfi_create_graph(struct mp_filter *parent,
                                        enum mp_frame_type type, bool bidir,
+                                       char *hwdec_interop,
                                        char **graph_opts, const char *graph);
 
 // Unlike mp_lavfi_create_graph(), this creates a single filter, using explicit
@@ -26,6 +27,7 @@ struct mp_lavfi *mp_lavfi_create_graph(struct mp_filter *parent,
 // (which are applied with mp_set_avopts()).
 struct mp_lavfi *mp_lavfi_create_filter(struct mp_filter *parent,
                                         enum mp_frame_type type, bool bidir,
+                                        char *hwdec_interop,
                                         char **graph_opts,
                                         const char *filter, char **filter_opts);