vf_vavpp: select best quality deinterlacing algorithm by default

This switches the default away from "bob" to the best algorithm reported
as supported by the driver. This is convenient for users, and there is
no reason to use something worse by default.

Untested.

DOCS/interface-changes.rst

@@ -75,6 +75,7 @@ Interface changes
     - make --deinterlace=yes always deinterlace, instead of trying to check
       certain unreliable video metadata. Also flip the defaults of all builtin
       HW deinterlace filters to always deinterlace.
+    - change vf_vavpp default to use the best deinterlace algorithm by default
  --- mpv 0.28.0 ---
     - rename --hwdec=mediacodec option to mediacodec-copy, to reflect
       conventions followed by other hardware video decoding APIs

DOCS/man/vf.rst

@@ -478,10 +478,14 @@ Available mpv-only filters are:
 
         no
             Don't perform deinterlacing.
+        auto
+             Select the best quality deinterlacing algorithm (default). This
+             goes by the order of the options as documented, with
+             ``motion-compensated`` being considered best quality.
         first-field
             Show only first field.
         bob
-            bob deinterlacing (default).
+            bob deinterlacing.
         weave, motion-adaptive, motion-compensated
             Advanced deinterlacing algorithms. Whether these actually work
             depends on the GPU hardware, the GPU drivers, driver bugs, and

video/filter/vf_vavpp.c

@@ -86,6 +86,7 @@ static void add_surfaces(struct priv *p, struct surface_refs *refs, int dir)
 }
 
 // The array items must match with the "deint" suboption values.
+// They're also sorted by quality.
 static const int deint_algorithm[] = {
     [0] = VAProcDeinterlacingNone,
     [1] = VAProcDeinterlacingBob, // first-field, special-cased
@@ -376,13 +377,26 @@ static bool initialize(struct mp_filter *vf)
         buffers[i] = VA_INVALID_ID;
     for (int i = 0; i < num_filters; i++) {
         if (filters[i] == VAProcFilterDeinterlacing) {
-            if (p->opts->deint_type < 1)
-                continue;
             VAProcFilterCapDeinterlacing caps[VAProcDeinterlacingCount];
             int num = va_query_filter_caps(vf, VAProcFilterDeinterlacing, caps,
                                            VAProcDeinterlacingCount);
             if (!num)
                 continue;
+            if (p->opts->deint_type < 0) {
+                for (int n = MP_ARRAY_SIZE(deint_algorithm) - 1; n > 0; n--) {
+                    for (int x = 0; x < num; x++) {
+                        if (caps[x].type == deint_algorithm[n]) {
+                            p->opts->deint_type = n;
+                            MP_VERBOSE(vf, "Selected deinterlacing algorithm: "
+                                       "%d\n", deint_algorithm[n]);
+                            goto found;
+                        }
+                    }
+                }
+                found: ;
+            }
+            if (p->opts->deint_type <= 0)
+                continue;
             VAProcDeinterlacingType algorithm =
                 deint_algorithm[p->opts->deint_type];
             for (int n=0; n < num; n++) { // find the algorithm
@@ -398,6 +412,8 @@ static bool initialize(struct mp_filter *vf)
                 MP_WARN(vf, "Selected deinterlacing algorithm not supported.\n");
         } // check other filters
     }
+    if (p->opts->deint_type < 0)
+        p->opts->deint_type = 0;
     p->num_buffers = 0;
     if (buffers[VAProcFilterDeinterlacing] != VA_INVALID_ID)
         p->buffers[p->num_buffers++] = buffers[VAProcFilterDeinterlacing];
@@ -456,8 +472,9 @@ error:
 #define OPT_BASE_STRUCT struct opts
 static const m_option_t vf_opts_fields[] = {
     OPT_CHOICE("deint", deint_type, 0,
-               // The values must match with deint_algorithm[].
-               ({"no", 0},
+               // The values >=0 must match with deint_algorithm[].
+               ({"auto", -1},
+                {"no", 0},
                 {"first-field", 1},
                 {"bob", 2},
                 {"weave", 3},
@@ -474,7 +491,7 @@ const struct mp_user_filter_entry vf_vavpp = {
         .name = "vavpp",
         .priv_size = sizeof(OPT_BASE_STRUCT),
         .priv_defaults = &(const OPT_BASE_STRUCT){
-            .deint_type = 2,
+            .deint_type = -1,
             .interlaced_only = 0,
             .reversal_bug = 1,
         },