hwcontext_vulkan: add APIs to get optional extensions

These provide a way for apps that initialize Vulkan themselves to know
which extensions we may be able to use without having to hardcode it.

Signed-off-by: Cameron Gutman <aicommander@gmail.com>

doc/APIchanges

@@ -2,6 +2,10 @@ The last version increases of all libraries were on 2025-03-28
 
 API changes, most recent first:
 
+2025-12-xx - xxxxxxxxxx - lavu 60.20.100 - hwcontext_vulkan.h
+  Add av_vk_get_optional_instance_extensions().
+  Add av_vk_get_optional_device_extensions().
+
 2025-12-xx - xxxxxxxxxx - lavc 62.22.101 - avcodec.h
   Add avcodec_receive_frame_flags().
   Add AV_CODEC_RECEIVE_FRAME_FLAG_SYNCHRONOUS.

libavutil/hwcontext_vulkan.c

@@ -693,6 +693,34 @@ static const VulkanOptExtension optional_device_exts[] = {
     { VK_KHR_VIDEO_DECODE_AV1_EXTENSION_NAME,                 FF_VK_EXT_VIDEO_DECODE_AV1       },
 };
 
+const char **av_vk_get_optional_instance_extensions(int *count)
+{
+    const char **exts = av_malloc_array(sizeof(*exts),
+                                        FF_ARRAY_ELEMS(optional_instance_exts));
+    if (!exts)
+        return NULL;
+
+    for (int i = 0; i < FF_ARRAY_ELEMS(optional_instance_exts); i++)
+        exts[i] = optional_instance_exts[i].name;
+
+    *count = FF_ARRAY_ELEMS(optional_instance_exts);
+    return exts;
+}
+
+const char **av_vk_get_optional_device_extensions(int *count)
+{
+    const char **exts = av_malloc_array(sizeof(*exts),
+                                        FF_ARRAY_ELEMS(optional_device_exts));
+    if (!exts)
+        return NULL;
+
+    for (int i = 0; i < FF_ARRAY_ELEMS(optional_device_exts); i++)
+        exts[i] = optional_device_exts[i].name;
+
+    *count = FF_ARRAY_ELEMS(optional_device_exts);
+    return exts;
+}
+
 static VkBool32 VKAPI_CALL vk_dbg_callback(VkDebugUtilsMessageSeverityFlagBitsEXT severity,
                                            VkDebugUtilsMessageTypeFlagsEXT messageType,
                                            const VkDebugUtilsMessengerCallbackDataEXT *data,

libavutil/hwcontext_vulkan.h

@@ -97,6 +97,8 @@ typedef struct AVVulkanDeviceContext {
      * each entry containing the specified Vulkan extension string to enable.
      * Duplicates are possible and accepted.
      * If no extensions are enabled, set these fields to NULL, and 0 respectively.
+     * av_vk_get_optional_instance_extensions() can be used to enumerate extensions
+     * that FFmpeg may use if enabled.
      */
     const char * const *enabled_inst_extensions;
     int nb_enabled_inst_extensions;
@@ -108,6 +110,8 @@ typedef struct AVVulkanDeviceContext {
      * If supplying your own device context, these fields takes the same format as
      * the above fields, with the same conditions that duplicates are possible
      * and accepted, and that NULL and 0 respectively means no extensions are enabled.
+     * av_vk_get_optional_device_extensions() can be used to enumerate extensions
+     * that FFmpeg may use if enabled.
      */
     const char * const *enabled_dev_extensions;
     int nb_enabled_dev_extensions;
@@ -375,4 +379,18 @@ AVVkFrame *av_vk_frame_alloc(void);
  */
 const VkFormat *av_vkfmt_from_pixfmt(enum AVPixelFormat p);
 
+/**
+ * Returns an array of optional Vulkan instance extensions that FFmpeg
+ * may use if enabled.
+ * @note Must be freed via av_free()
+ */
+const char **av_vk_get_optional_instance_extensions(int *count);
+
+/**
+ * Returns an array of optional Vulkan device extensions that FFmpeg
+ * may use if enabled.
+ * @note Must be freed via av_free()
+ */
+const char **av_vk_get_optional_device_extensions(int *count);
+
 #endif /* AVUTIL_HWCONTEXT_VULKAN_H */

libavutil/version.h

@@ -79,8 +79,8 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  60
-#define LIBAVUTIL_VERSION_MINOR  19
-#define LIBAVUTIL_VERSION_MICRO 101
+#define LIBAVUTIL_VERSION_MINOR  20
+#define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
                                                LIBAVUTIL_VERSION_MINOR, \