stdin

diff --git a/configure b/configure
index 3ed7467252..06a4d3f485 100755
--- a/configure
+++ b/configure
@@ -3844,8 +3844,8 @@ host_cc_default="gcc"
 doxygen_default="doxygen"
 install="install"
 ln_s_default="ln -s -f"
-metalcc_default="xcrun metal"
-metallib_default="xcrun metallib"
+metalcc_default="xcrun -sdk macosx metal"
+metallib_default="xcrun -sdk macosx metallib"
 nm_default="nm -g"
 pkg_config_default=pkg-config
 ranlib_default="ranlib"
diff --git a/libavfilter/metal/utils.h b/libavfilter/metal/utils.h
index bd0319f63c..7350d42a35 100644
--- a/libavfilter/metal/utils.h
+++ b/libavfilter/metal/utils.h
@@ -20,16 +20,40 @@
 #define AVFILTER_METAL_UTILS_H
 
 #include <Metal/Metal.h>
+
+#include <AvailabilityMacros.h>
+
+// CoreVideo accidentally(?) preprocessor-gates Metal functionality
+// on MAC_OS_X_VERSION_MIN_REQUIRED >= 101100 (FB9816002).
+// There doesn't seem to be any particular reason for this,
+// so here we temporarily redefine it to at least that value
+// so CV will give us CVMetalTextureRef and the related functions.
+
+#if defined(MAC_OS_X_VERSION_MIN_REQUIRED) && (MAC_OS_X_VERSION_MIN_REQUIRED < 101100)
+#define ORIG_MAC_OS_X_VERSION_MIN_REQUIRED MAC_OS_X_VERSION_MIN_REQUIRED
+#undef MAC_OS_X_VERSION_MIN_REQUIRED
+#define MAC_OS_X_VERSION_MIN_REQUIRED 101100
+#endif
+
 #include <CoreVideo/CoreVideo.h>
 
+#ifdef ORIG_MAC_OS_X_VERSION_MIN_REQUIRED
+#undef MAC_OS_X_VERSION_MIN_REQUIRED
+#define MAC_OS_X_VERSION_MIN_REQUIRED ORIG_MAC_OS_X_VERSION_MIN_REQUIRED
+#undef ORIG_MAC_OS_X_VERSION_MIN_REQUIRED
+#endif
+
 void ff_metal_compute_encoder_dispatch(id<MTLDevice> device,
                                        id<MTLComputePipelineState> pipeline,
                                        id<MTLComputeCommandEncoder> encoder,
-                                       NSUInteger width, NSUInteger height);
+                                       NSUInteger width, NSUInteger height)
+                                       API_AVAILABLE(macos(10.11), ios(8.0));
 
 CVMetalTextureRef ff_metal_texture_from_pixbuf(void *avclass,
                                                CVMetalTextureCacheRef textureCache,
                                                CVPixelBufferRef pixbuf,
                                                int plane,
-                                               MTLPixelFormat format);
+                                               MTLPixelFormat format)
+                                               API_AVAILABLE(macos(10.11), ios(8.0));
+
 #endif /* AVFILTER_METAL_UTILS_H */
diff --git a/libavfilter/metal/utils.m b/libavfilter/metal/utils.m
index 759ebedfba..f365d3ceea 100644
--- a/libavfilter/metal/utils.m
+++ b/libavfilter/metal/utils.m
@@ -17,7 +17,7 @@
  */
 
 #include "libavutil/log.h"
-#include <libavfilter/metal/utils.h>
+#include "utils.h"
 
 void ff_metal_compute_encoder_dispatch(id<MTLDevice> device,
                                        id<MTLComputePipelineState> pipeline,
@@ -29,6 +29,8 @@ void ff_metal_compute_encoder_dispatch(id<MTLDevice> device,
     NSUInteger h = pipeline.maxTotalThreadsPerThreadgroup / w;
     MTLSize threadsPerThreadgroup = MTLSizeMake(w, h, 1);
     BOOL fallback = YES;
+    // MAC_OS_X_VERSION_10_15 is only defined on SDKs new enough to include its functionality (including iOS, tvOS, etc)
+#ifdef MAC_OS_X_VERSION_10_15
     if (@available(macOS 10.15, iOS 11, tvOS 14.5, *)) {
         if ([device supportsFamily:MTLGPUFamilyCommon3]) {
             MTLSize threadsPerGrid = MTLSizeMake(width, height, 1);
@@ -36,6 +38,7 @@ void ff_metal_compute_encoder_dispatch(id<MTLDevice> device,
             fallback = NO;
         }
     }
+#endif
     if (fallback) {
         MTLSize threadgroups = MTLSizeMake((width + w - 1) / w,
                                            (height + h - 1) / h,
diff --git a/libavfilter/metal/vf_yadif_videotoolbox.metal b/libavfilter/metal/vf_yadif_videotoolbox.metal
index 50783f2ffe..71328a9e5c 100644
--- a/libavfilter/metal/vf_yadif_videotoolbox.metal
+++ b/libavfilter/metal/vf_yadif_videotoolbox.metal
@@ -26,6 +26,15 @@
 
 using namespace metal;
 
+/*
+ * Shims
+ */
+
+#if __METAL_VERSION__ < 210
+#define max3(x, y, z) max(x, max(y, z))
+#define min3(x, y, z) min(x, min(y, z))
+#endif
+
 /*
  * Parameters
  */
@@ -44,7 +53,7 @@ struct deintParams {
  */
 
 #define accesstype access::sample
-const sampler s(coord::pixel);
+constexpr sampler s(coord::pixel);
 
 template <typename T>
 T tex2D(texture2d<float, access::sample> tex, uint x, uint y)
diff --git a/libavfilter/vf_yadif_videotoolbox.m b/libavfilter/vf_yadif_videotoolbox.m
index af83a73e89..455745817f 100644
--- a/libavfilter/vf_yadif_videotoolbox.m
+++ b/libavfilter/vf_yadif_videotoolbox.m
@@ -20,16 +20,18 @@
  */
 
 #include "internal.h"
+#include "metal/utils.h"
 #include "yadif.h"
-#include <libavutil/avassert.h>
-#include <libavutil/hwcontext.h>
-#include <libavutil/objc.h>
-#include <libavfilter/metal/utils.h>
+#include "libavutil/avassert.h"
+#include "libavutil/hwcontext.h"
+#include "libavutil/objc.h"
+
+#include <assert.h>
 
 extern char ff_vf_yadif_videotoolbox_metallib_data[];
 extern unsigned int ff_vf_yadif_videotoolbox_metallib_len;
 
-typedef struct YADIFVTContext {
+typedef struct API_AVAILABLE(macos(10.11), ios(8.0)) YADIFVTContext {
     YADIFContext yadif;
 
     AVBufferRef       *device_ref;
@@ -44,7 +46,12 @@ typedef struct YADIFVTContext {
     id<MTLBuffer> mtlParamsBuffer;
 
     CVMetalTextureCacheRef textureCache;
-} YADIFVTContext;
+} YADIFVTContext API_AVAILABLE(macos(10.11), ios(8.0));
+
+// Using sizeof(YADIFVTContext) outside of an availability check will error
+// if we're targeting an older OS version, so we need to calculate the size ourselves
+// (we'll statically verify it's correct in yadif_videotoolbox_init behind a check)
+#define YADIF_VT_CTX_SIZE (sizeof(YADIFContext) + sizeof(void*) * 10)
 
 struct mtlYadifParams {
     uint channels;
@@ -62,7 +69,7 @@ static void call_kernel(AVFilterContext *ctx,
                         id<MTLTexture> next,
                         int channels,
                         int parity,
-                        int tff)
+                        int tff) API_AVAILABLE(macos(10.11), ios(8.0))
 {
     YADIFVTContext *s = ctx->priv;
     id<MTLCommandBuffer> buffer = s->mtlQueue.commandBuffer;
@@ -93,7 +100,7 @@ static void call_kernel(AVFilterContext *ctx,
 }
 
 static void filter(AVFilterContext *ctx, AVFrame *dst,
-                   int parity, int tff)
+                   int parity, int tff) API_AVAILABLE(macos(10.11), ios(8.0))
 {
     YADIFVTContext *s = ctx->priv;
     YADIFContext *y = &s->yadif;
@@ -162,7 +169,7 @@ exit:
     return;
 }
 
-static av_cold void yadif_videotoolbox_uninit(AVFilterContext *ctx)
+static av_cold void do_uninit(AVFilterContext *ctx) API_AVAILABLE(macos(10.11), ios(8.0))
 {
     YADIFVTContext *s = ctx->priv;
     YADIFContext *y = &s->yadif;
@@ -188,7 +195,15 @@ static av_cold void yadif_videotoolbox_uninit(AVFilterContext *ctx)
     }
 }
 
-static av_cold int yadif_videotoolbox_init(AVFilterContext *ctx)
+
+static av_cold void yadif_videotoolbox_uninit(AVFilterContext *ctx)
+{
+    if (@available(macOS 10.11, iOS 8.0, *)) {
+        do_uninit(ctx);
+    }
+}
+
+static av_cold int do_init(AVFilterContext *ctx) API_AVAILABLE(macos(10.11), ios(8.0))
 {
     YADIFVTContext *s = ctx->priv;
     NSError *err = nil;
@@ -261,7 +276,19 @@ fail:
     return AVERROR_EXTERNAL;
 }
 
-static int config_input(AVFilterLink *inlink)
+static av_cold int yadif_videotoolbox_init(AVFilterContext *ctx)
+{
+    if (@available(macOS 10.11, iOS 8.0, *)) {
+        // Ensure we calculated YADIF_VT_CTX_SIZE correctly
+        static_assert(YADIF_VT_CTX_SIZE == sizeof(YADIFVTContext), "Incorrect YADIF_VT_CTX_SIZE value!");
+        return do_init(ctx);
+    } else {
+        av_log(ctx, AV_LOG_ERROR, "Metal is not available on this OS version\n");
+        return AVERROR(ENOSYS);
+    }
+}
+
+static int do_config_input(AVFilterLink *inlink) API_AVAILABLE(macos(10.11), ios(8.0))
 {
     AVFilterContext *ctx = inlink->dst;
     YADIFVTContext *s = ctx->priv;
@@ -283,7 +310,18 @@ static int config_input(AVFilterLink *inlink)
     return 0;
 }
 
-static int config_output(AVFilterLink *link)
+static int config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    if (@available(macOS 10.11, iOS 8.0, *)) {
+        return do_config_input(inlink);
+    } else {
+        av_log(ctx, AV_LOG_ERROR, "Metal is not available on this OS version\n");
+        return AVERROR(ENOSYS);
+    }
+}
+
+static int do_config_output(AVFilterLink *link) API_AVAILABLE(macos(10.11), ios(8.0))
 {
     AVHWFramesContext *output_frames;
     AVFilterContext *ctx = link->src;
@@ -347,6 +385,17 @@ exit:
     return ret;
 }
 
+static int config_output(AVFilterLink *link)
+{
+    AVFilterContext *ctx = link->src;
+    if (@available(macOS 10.11, iOS 8.0, *)) {
+        return do_config_output(link);
+    } else {
+        av_log(ctx, AV_LOG_ERROR, "Metal is not available on this OS version\n");
+        return AVERROR(ENOSYS);
+    }
+}
+
 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 #define CONST(name, help, val, unit) { name, help, 0, AV_OPT_TYPE_CONST, {.i64=val}, INT_MIN, INT_MAX, FLAGS, unit }
 
@@ -394,7 +443,7 @@ static const AVFilterPad yadif_videotoolbox_outputs[] = {
 AVFilter ff_vf_yadif_videotoolbox = {
     .name           = "yadif_videotoolbox",
     .description    = NULL_IF_CONFIG_SMALL("YADIF for VideoToolbox frames using Metal compute"),
-    .priv_size      = sizeof(YADIFVTContext),
+    .priv_size      = YADIF_VT_CTX_SIZE,
     .priv_class     = &yadif_videotoolbox_class,
     .init           = yadif_videotoolbox_init,
     .uninit         = yadif_videotoolbox_uninit,