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, 4 insertions, 4 deletions

diff --git a/video/filter/vf_vdpaupp.c b/video/filter/vf_vdpaupp.c
index 6de8671e39..de5caa3534 100644
--- a/video/filter/vf_vdpaupp.c
+++ b/video/filter/vf_vdpaupp.c
@@ -136,11 +136,11 @@ static struct mp_filter *vf_vdpaupp_create(struct mp_filter *parent, void *optio
 
     p->queue = mp_refqueue_alloc(f);
 
-    AVBufferRef *ref = mp_filter_load_hwdec_device(f, IMGFMT_VDPAU);
-    if (!ref)
+    struct mp_hwdec_ctx *hwdec_ctx =
+        mp_filter_load_hwdec_device(f, IMGFMT_VDPAU);
+    if (!hwdec_ctx || !hwdec_ctx->av_device_ref)
         goto error;
-    p->ctx = mp_vdpau_get_ctx_from_av(ref);
-    av_buffer_unref(&ref);
+    p->ctx = mp_vdpau_get_ctx_from_av(hwdec_ctx->av_device_ref);
     if (!p->ctx)
         goto error;